Nicolas Villeneuve
email: nicolas.villeneuve@univ-reunion.fr

Patrick Bachèlery
email: p.bachelery@opgc.fr

Jacobus Kemp
email: jkemp@sun.ac.za

La Réunion Island: A Typical Example of a Basaltic Shield Volcano with Rapid Evolution

Keywords: Basaltic shield volcanoes, Volcanic geomorphology, Evolution, Natural hazard

Geographical and Geological Setting

.

. It is currently accepted that the Piton des Neiges built up in four main stages. The Piton de la Fournaise, on the southeastern part, is considered one of the most active volcanoes in the world with an average of 0.8 eruptions per year since 1998.

La Réunion is situated in the tropics, just north of the Tropic of Capricorn. This intertropical, oceanic setting gives the island a humid tropical climate, with an annual average humidity of between 70 and 80 %. Two main seasons can be distinguished: the southern winter and the southern summer, with winter bringing polar air closer to the island resulting in lowered temperatures.

During the summer months, specifi cally January to March, La Réunion is strongly affected by tropical depressions and cyclones. These systems sweep over La Réunion with

wind speeds that can reach 250 km/h and release enormous amounts of precipitation onto the island. In fact, La Réunion holds several world records for precipitation, being the place where the highest rainfalls for periods between 1 h (261.5 mm on 29 February 1964, Cyclone Giselle) and 15 days (6,083 mm between 14 and 28 January 1980, Cyclone Hyacinthe) have been recorded. Globally, cyclones are very well studied, followed and known. Nevertheless, in terms of risk on La Réunion, they are the most signifi cant factor responsible for deaths and injuries. They are also responsible for much damage to the infrastructure on which the community and local economy relies.

Outside the cyclone period, precipitation is highly variable in both time and space. The rainfall distribution on La Réunion is most strongly infl uenced by its topography. In winter, the southeasterly trade winds (known locally as Alizés ) carry humid air to higher elevations, causing adiabatic cooling and precipitation on the eastern mountain slopes. Mean annual precipitation for La Réunion ranges from around 750 mm on the sheltered west coast to more than 10,000 mm on the slopes of Piton de la Fournaise in the east (Fig. 25.2 ).

These signifi cant quantities of rainfall had dramatic implications for soil erosion and sediment transport by the island's rivers. With La Réunion's high rainfall, steep slopes and young reliefs, rates of erosion and sediment transport are huge and often considered some of the highest in the world [START_REF] Garcin | High rates of geomorphological processes in a tropical area: the Remparts River case study (Réunion Island, Indian Ocean)[END_REF].

Gross Morphology of La Réunion Complex

Around La Réunion Island, large amounts of debris avalanche deposits and numerous secondary submarine slope instabilities, resulting from the sliding and spreading of the submarine volcano fl anks, have been recognised [START_REF] Oehler | Growth and collapse of the Reunion Island volcanoes[END_REF][START_REF] Friant | A new model for the evolution of La Réunion volcanic complex from complete marine geophysical surveys[END_REF].

Several authors have proposed different interpretations of morphologies of La Réunion's bathymetry linked directly to onshore geological processes. Recently, high-resolution bathymetric acquisition during the FOREVER and ERODER cruises allowed very fi ne scale analyses and models that complement those of [START_REF] Oehler | Growth and collapse of the Reunion Island volcanoes[END_REF].

La Réunion, from the abyssal plain to the summit of the Piton des Neiges volcano, is a large 7 km high cone (Fig. 25.1a ) with a total volume of about 5.01•10 4 km 3 . Considering that the subaerial part has a volume of 2.1•10 3 km 3 , only 4 % of the volcanic complex is above sea level. The contact between La Réunion Island's volcanic products and the abyssal plain can be considered to lie at an average depth of 4,200 m.

The La Réunion Island volcanic complex is relatively well contained within a circle (radius 80-100 km) centred on the Piton des Neiges present summit (red circle,Fig. 25.1a ). This mainly corresponds to the slope transition between the abyssal plain and the cone of the volcanic complex, and Le [START_REF] Friant | A new model for the evolution of La Réunion volcanic complex from complete marine geophysical surveys[END_REF] explained the stretching towards the southeast as a consequence of a series of massive debris avalanches that occurred at Piton de la Fournaise (red oval,Fig. 25.1b ). These authors mainly proposed that fl ank destabilisation, onshore and offshore, would be less massive on Piton des Neiges than on Piton de la Fournaise.

Geomorphic Landscape of the Volcanic Island

A Very Rapid Evolution

La Réunion Island is characterised by a rapid landscape evolution resulting from a favourable geology combined with a tropical climate. Relationships between dramatic climatic events, small-scale and large-scale landslides, torrential transport of sediments and active volcanism lead to rapid evolution in terms of building, dismantling and/or refi lling of recently formed geomorphic features.

The most remarkable example occurred during the large 2007 eruption of the Piton de la Fournaise when the centre of Cratère Dolomieu dropped 350 m in height in only a few hours (Fig. 25.3a,b ) without signifi cantly modifying the crater contour (Fig. 25.3c ). Conversely, paleo-valleys on La Réunion have been infi lled by new lava fl ows, as can be observed in the upper reaches of the Rivière des Remparts (Fig. 25.4 ).

The coexistence of contrasted (building vs dismantling) and rapid evolution of the landforms in the same area, as highlighted by these two examples, certainly is one of the most interesting features of geomorphology concerning very active volcanoes.

Unstable cliffs and slopes are often sites of mass wasting such as collapses and debris avalanches, responsible for large to massive scale landforms like Cirques. The most massive landslide is the Saint-Gilles slide on the western fl ank of Piton des Neiges [START_REF] Bachèlery | Avalanches de débris sur le fl anc occidental du volcan-bouclier Piton des Neiges (Réunion)[END_REF]. The various breccia units cover an area of 16 km 2 . Bathymetric surveys show the offshore prolongation of "Saint-Gilles breccias" up to a depth of 2,500 m, allowing us to estimate the total area covered by the debris avalanche deposits at more than 500 km 2 .

The main river systems on La Réunion also drain the edifi ces of Piton des Neiges and Piton de la Fournaise in a generally radial pattern. Applying the [START_REF] Ollier | A volcaniclastic deep-sea fan off La Réunion Island (Indian Ocean)[END_REF] model to La Réunion, Piton de la Fournaise would be in the intact stage, while Piton des Neiges would be in the planeze stage .

Main Geomorphological Features of the Piton des Neiges Volcano

In terms of emerged surface extent, the Piton des Neiges volcano represents two-thirds of the total island area. At the The origin of these major depressions has been widely discussed. Several authors have assumed either a volcanotectonic or erosional origin, sometimes associated with massive debris avalanches. [START_REF] Oehler | Growth and collapse of the Reunion Island volcanoes[END_REF] proposed a multi-process origin, combining erosion, structural events and massive landslides. Except for the high cliffs surrounding the Cirques and some other rare reliefs inside, breccia deposits largely blanket the bottom of the three Cirques. It is quite diffi cult to recognise the source of the breccias and to distinguish between an erosional or tectonic origin for the landscape. The two processes were certainly acting together for millennia to build this spectacular relief. Currently, weathering can effi ciently proceed on breccia materials that compose the cirque fl oor, and the debris inside is very easily mobilised, supplying a strong transport of sediment off the island.

As already said, Piton des Neiges built up in four main stages. [START_REF] Salvany | Geomorphic evolution of the Piton des Neiges volcano (Réunion Island, Indian Ocean): competition between volcanic construction and erosion since 1.4 Ma[END_REF] assumed that the Cirques began to form with the lowering of the lava output rate of Piton des Neiges, around 180 Ka ago ( Phase I). Around 12,000 years ago [START_REF] Deniel | New 230Th-238U and 14C age determinations from Piton des Neiges volcano, Reunion -a revised chronology for the differentiated series[END_REF] ), all magma production on Piton des Neiges stopped, and only erosive mechanisms remained, which widened and deepened the Cirques to their current state, accounting for negative volumes of more than 101 ± 44 and 105 ± 41 km 3 for the Mafate and Cilaos Cirques. For Salazie cirque, Salvany et al. The Western Planeze, largely covered by recent lavas (Phase IV), is particularly smooth (Figs. 25.1 and 25.5 ). This is the result of both recent refi lling of erosion morphologies by lava fl ows and of its relative protection against weathering. For the Northern Planeze, the La Montagne edifi ce is much more eroded. This area has not been overfl owed by Phase III (partially) and Phase IV of the Piton des Neiges lava fl ows (Fig. 25.5 ). This signifi es that soils have been eroded during a long period estimated at least to 450 Ka.

The Le Dimitile edifi ce and patchwork on the Eastern Planeze have the same confi guration. This Planeze is very complex. First, its southeastern extent is limited by the Piton de la Fournaise formations. Secondly, the Bebour-Belouve area is a deep depression that is considered a paleo-cirque infi lled with recent lava fl ows.

Main Geomorphological Features of the Piton de la Fournaise Volcano

Piton de la Fournaise is composed of at least four different landscapes (Figs. 25.6 and 25.7 ): the Enclos Fouqué and Grand Brûlé structures, the northeast and southeast rift zones, the main rivers scars and the Saint Pierre-Les Plaines-Saint Benoit corridor.

The Enclos Fouqué and Grand Brûlé

This is a large uninhabited horseshoe structure of ~100 km 2 , open to sea on the eastern part of the island. Four main morphological units can be observed: (1) the summit area,

(2) the "Remparts", (3) the Grandes Pentes and the Plaine des Osmondes and (4) the Grand Brûlé. The main geomorphological features of the Enclos Fouqué are related to the volcanic and tectonic histories of the area associated with recent events. Presumably, the formations have been shaped by a series of events whose initial process is a combination of structural instabilities and local collapses linked with phreatomagmatic and phreatic explosions that could be paroxysmal. Morphologies are also linked to lava infi lling and smoothing. Bory (250 m × 350 m) and Dolomieu (750 m × 1,100 m) craters constitute the summit part of Piton de la Fournaise, as viewed from the west, where they top a 400 m high central cone. These landforms owe their origin to repeated collapses; though relatively rare, these collapse events usually occur in relation with high lava effusion rates. Michon et al. ( in press ) describe 14 events between 1791 and April 2007. Ten of these events are responsible for phreatic and/or phreatomagmatic activities. These events generate a real risk for summit hikers (~120,000/year) and Pas de Bellecombe visitors (~270,000/year). In April 2007, a ~90•10 6 m 3 caldera completely modifi ed the geometry inside the Cratère Dolomieu (Fig. 25.3a,b ).

The two summit craters are surrounded by high slopes with an average gradient of between 15° and 25°. They are relatively constant in all directions for 1.6 km from the centre of the Cratère Dolomieu. Several small eruptive vents are visible on the slope of the terminal cone. Between 30 and 50 cones per square kilometre can be counted in this area.

The western part of the Enclos Fouqué is relatively fl at. [START_REF] Lénat | Genèse du champ de lave de l'Enclos Fouqué: une eruption d'envergure exceptionnelle au Piton de la Fournaise (Réunion) au 18ème siècle[END_REF] named this area the "Champ de Lave de l'Enclos Fouqué". Pahoehoe lava mainly composes this large lava fi eld and is probably related to the late activity of the Cratère Bory during the seventeenth and eighteenth centuries.

The Enclos Fouqué/Grand Brûlé area is edged by ~35 km of cliffs, namely, the "Remparts". These are 100-200 m high subvertical cliffs. They are natural barriers that protected inhabited areas against lava fl ows coming from more frequent eruptions.

The Grandes Pentes correspond to ~25 % of the total area of the horseshoe depression. Here, the slope gradients range between 25° and 30°. Their formation is probably linked to landslides and/or spreading of the volcanic edifi ce.

The Plaine des Osmondes, localised northeast of the central cone, is a depressed area (2.5 × 4 km), edged on the north, the west and the south by the "Remparts", the Grandes Pentes and Le Piton de Crac, respectively. The eastern part opens this area towards the Grand Brûlé. [START_REF] Courteaud | Etudes des structures géologiques et hydrogéologiques du massif de La Fournaise par la méthode audiomagnétollurique[END_REF], from geophysical data, has interpreted the Plaine des Osmondes as the head of paleo-valley that could have been built during a long period of quiescence of the volcano, at least in this region.

The Grand Brûlé is a relatively fl at (4° to 8°) corridor between the Grandes Pentes and the coast. Its morphology is probably related to lava accumulation. Below the sea level, the Grand Brûlé stretches into the Chenal Vincent unit [START_REF] Oehler | Growth and collapse of the Reunion Island volcanoes[END_REF]. From Michon et al. ( submitted ), lava fl ows of about 28 eruptions have crossed the Grand Brûlé and reached the ocean since the beginning of the sixteenth century. The emplacement of lava fl ows crossing the coastal road (used daily by about 3,200 vehicles) and reaching the seashore occurs relatively often. Lava fl ows entering the sea are very impressive. Nevertheless, the difference in temperature generates explosions on the unstable platform built up by the progression of the lava fl ow, and acid plumes generated by seawater vaporisation can cause respiratory problems and/or environmental damage.

The Northeast and Southeast Rift Zones

Both rift zones are convex surfaces that stretch along steep slopes (Fig. 25.6 ). This morphology has been mapped below sea level up to depths of 1,800 and 2,000 m for the southern and northern zones, respectively. The rift zones correspond to areas of preferential magma ingestion for the volcano summit towards the outside fl anks. Between 1708 and 1998, seven eruptions (three on the northeast and four on the southeast rift zones) occurred in these areas. Their implication in terms of volcanologic risk is important. For instance, in 2012, 11,809 permanent residents lived in areas located within these rift zones.

The Main River Scars

On Piton de la Fournaise, 19 drainage basins have been identifi ed, but only Rivière de l'Est, Rivière Langevin and Rivière des Remparts have perennial fl ow. All three rivers are fed by springs resulting from rapid infi ltration due to the high permeability of the rocks and the high rainfall.

Four main hydrologic units are well identifi able on the Piton de la Fournaise edifi ce. Rivière de l'Est (24.5 km 2 ) is the only one cut into the north fl ank of the volcano. The Ravine Basse Vallée (9 km 2 ), the Rivière Langevin (23 km 2 ) and the Rivière des Remparts (56 km 2 ) drain the southern fl ank of the volcano. They are affected by different geomorphic processes (collapses and topographic inversion).

Erosion is clearly the main process involved in their formations, but a more complex history, with caldera and mass-wasting episodes, has been revealed by a detailed study of Rivière des Remparts and Rivière Langevin [START_REF] Merle | Calderas, landslides and paleo-canyons on Piton de la Fournaise volcano (La Réunion Island, Indian Ocean)[END_REF]. Rockfalls and landslides are common in these valleys. They result from (1) differential resistance of materials, (2) regressive erosion mechanisms and (3) hydrogeological erosion mechanisms as described by [START_REF] Fèvre | Mécanismes et vitesses d' érosion à l' échelle géologique sur une île volcanique jeune à relief élevé -La Réunion (Océan Indien)[END_REF]. In addition, several lava flows may also locally cover the riverbeds, showing that volcanic activity may continue after the erosion of the river.

The Saint Pierre-Les Plaines-Saint Benoit corridor

The Saint Pierre-Les Plaines-Saint Benoit corridor is a smooth surface that has been covered by relatively recent lava fl ows. These areas compose the morphological transition between the Piton de la Fournaise and Piton des Neiges volcanoes. The Plaine des Palmistes is the most complex area. It is a depression open to the sea, and its northern, western and southern cliff slopes are steep. The current morphology of this area certainly reveals the preponderance of erosional mechanisms.

Main Geomorphological Features of Coastlines

La Réunion Island is composed of 250 km of coastline that can be classifi ed into three main groups (Fig. 25.8 ):

-140 km of volcanic coastline -85 km of alluvial coastline -25 km of coral sand coastline The volcanic coastlines can be divided into two types: (1) low volcanic platforms and (2) volcanic cliff shorelines that can be also called wave-straightened cliffs in volcanic areas. The fi rst type has its origin in lava fl ows entering into the sea and can also be residual platforms. The second type develops under wave action at the bottom of cliffs that generates instabilities, such as rockfalls and landslides. From Grand Bois to Sainte Rose, on Piton de la Fournaise, the coastline is composed of 65 km of uninterrupted, generally high volcanic cliffs. The possible cliff collapses are a threat for the population. On Piton des Neiges, along "La Corniche" which is the highest and longest coastal cliff (~13 km long and 100-200 m high) and along the Cap La Houssaye cliff, very high-traffi c roads have been built at the foot of both cliffs. Several collapses have occurred, causing dramatic accidents, making these roads the most hazardous and at-risk areas. The alluvial coastlines include two types -(1) the black sand beaches and (2) the rolling stone beaches -directly linked to the transfer of fl uvial erosion products and grainsize sorting. Along the eastern coast (from Sainte Rose to Saint Denis), the 51 km long beach of rolling stones formed after hydraulic processes have washed away fi ne sediments. The same process occurred in small river deltas around La Réunion. In contrast, the Saint Paul and Etang Salé black sand beaches are mostly composed of fi ne sediments transported by marine currents. Here, strong winds have also transported fi ne particles to develop black sand dunes. In the Grand Brûlé area, two black sand beaches developed under a specifi c process: when the lava fl ows reached the sea, the contrast of temperature produced explosions generating volcaniclastic materials. The accumulation of these products usually builds non-permanent beaches.

The coral sand beaches are localised (1) from the south of Cap La Houssaye to La Souris Chaude in the Saint-Gilles area, (2) from La Pointe des Chateaux to La Pointe au Sel in the Saint Leu area, (3) from Ravine Blanche to Terre Sainte in the Saint Pierre area and (4) in the Grand Bois area. These have been built recently, less than 8,000 years ago [START_REF] Camoin | Holocene sea level changes and reef development in southwestern Indian Ocean[END_REF], by accumulation of the biodetritic elements from the reefs. The Saint-Gilles units are the largest ones. Around 12 linear kilometres are composed by the sand beach (160 m wide at its maximum), and sand dune accumulation is limited by old volcanic cliffs. The accumulation of sand can reach a maximum of 200 m in thickness.

Conclusion, Cultural Value and Touristic Promotion

Lava fl ows, landslides, fl oods and rockfalls have built La Réunion Island with its incredibly diverse landscapes. The high cliffs, steep valleys and variety of microclimates have allowed 236 endemic plant species and 92 endemic animal species (23 of which are extinct and 4 of which are threatened) to grow locally. For these reasons, 40 % of La Réunion Island is included in the UNESCO Nature World Heritage list. This international label covers the core of the National Park of La Réunion. This is not only a source of pride for residents but a true added value for the touristic promotion and the environment protection. The great paradox is that the magnifi cent morphologies and areas celebrated here are also those for which natural hazard and risk are the highest.

Fig. 25

 25 Fig. 25.1 ( a ) Slope gradient computed from FOREVER and ERODER1 swath bathymetry and IGN DEM (1997) for the aerial part. Brown lines corresponded to -4,000, -3,000, -2,000 -1,000 and -500 m isobath. The red circle shows the approximate boundary between La Réunion and the abyssal plain. ( b ) Shaded relief map of Réunion Island showing the location of Piton des Neiges (PDN), Piton de la Fournaise (PDF) volcanoes and place names. The red oval (AZ) corresponds to the hypovolcanic complex Les Alizés volcano as defi ned by Salvany et al. ( 2012 ). Read Roche Ecrite and Grand Bénare for RE and GB. Coordinates in metres (WGS84, UTM40S)

Fig. 25 . 2

 252 Fig. 25.2 Mean annual precipitation (between 1971 and 2000) overlain by the hydrologic network for La Réunion. Isohyets have a contours spacing of 500 mm (Data from Meteo-France)

  ( 2012 ) considered that it had been fi lled by lava 70 Ka ago. The same erosional volume has been obtained in only 70 Ka.The external slopes of Piton des Neiges volcano are less dismantled. With an almost triangular shape dissected by three rivers, they form large Planezes, stretching from Le Grand Bénare to the western coastline for the Western Planeze, from la Roche Ecrite to the northern coastline for the Northern Planeze and from the Piton des Neiges to the eastern coastline and to the Plaines area for the Eastern Planeze.

Fig. 25 . 3

 253 Fig. 25.3 Southeastern aerial photos of the Piton de la Fournaise summit before ( a ) and after ( b ) the collapse in April 2007. The mapping of the Dolomieu (foreground) and Bory (background) crater outlines from orthophotos acquired in 2003 and 2007 illustrates the relatively small change to Piton de la Fournaise in plan view compared to the extent of the vertical collapse ( c )

Fig. 25 . 4

 254 Fig. 25.4 Infi lling of a paleo-Rivière des Remparts on the northeastern side of Rivière des Remparts. ( a) Shaded relief of 5 m DEM (IGN); ( b ) slope gradient computed from the 5 m DEM, 1 and 2 on the north Rivière des Remparts head correspond to the possible extension of the river before infi lling; ( c ) a 3D surface (2012 orthophoto from IGN); ( d ) outcrop view from east (From Merle et al. 2010 )

Fig. 25. 7

 7 Fig. 25.7 Synthesis of different morphologies observable on the Piton de la Fournaise edifi ce. ( a ) Summit of the Piton de la Fournaise with the Cratère Dolomieu and the Cratère Bory; ( b ) Château Fort crater vent: a very typical scoriaceous cone shape; ( c ) pahoehoe lava fl ow overlapping an "aa" lava during the August 2006 event; ( d ) Rivière des Remparts viewed from north; ( e ) Plaine des Cafres and Rivière des Remparts ( left ); ( f ) lava fl ows from the Chisny eruption which had entered Rivière Langevin 1 Ka; ( g ) upper catchment of Rivière de l'Est called Savane Cimetière, viewed from north; ( h ) a lava lake enclosed within a scoriaceous cone during the August 2006 eruption

Fig. 25 . 8

 258 Fig. 25.8 Synthesis of different coastal morphologies observable around La Réunion. Coastline colour code: red for volcanic cliff, yellow for coral sand beaches, black for black sand beaches and grey for rolling stone beaches (*Courtesy of Olivier David)


Xinghui Zhang

Zhao Li

Lingai Luo
email: lingailuo@univ-nantes.fr

Yilin Fan

Zhengyu Du

A review on thermal management of lithiumion batteries for electric vehicles

Keywords: Lithium-ion battery, Battery thermal management system, Temperature Uniformity, Electric vehicles

In recent years, energy and environmental issues have become more and more prominent, and electric vehicles powered by lithium-ion battery have shown great potential and advantages in alleviating these issues. Compared with other batteries, lithium-ion batteries have the advantages of high specific energy, high energy density, long endurance, low self-discharge and long shelf life. However, temperature of the battery has become one of the most important parameters to be handled properly for the development and propagation of lithium-ion battery electric vehicles. Both the higher and lower temperature environments will seriously affect the battery capacity and the service life. Under high temperature environment, lithium-ion batteries may produce thermal runaway, resulting in short circuit, combustion, explosion and other safety problems. Lithium dendrites may appear in lithium-ion batteries at low temperature, causing short circuit, failure to start and other operational faults. In this paper, the used thermal management methods of lithium-ion batteries are introduced and their advantages and disadvantages are discussed and compared. At the same time, the prospect of future development is put forward.

Introduction

With the rapid development of China's economy, people's living standards are also improving, and private cars have gradually entered the family. However, traditional fossil fuel resources such as oil are limited, and their combustion will emit greenhouse gases (GHG) and harmful substances [START_REF] Leman | Emission Treatment towards Cold Start and Back Pressure in Internal Combustion Engine against Performance of Catalytic Converter: A Review[END_REF][START_REF] Alptekin | Emission, injection and combustion characteristics of biodiesel and oxygenated fuel blends in a common rail diesel engine[END_REF] and affect the environment and climate [START_REF] Zhi | Preparation and heat transfer characteristics of microencapsulated phase change material slurry: A review[END_REF] . A series of problems, such as energy shortage, environmental pollution and climate warming, brought by the traditional petrol-powered vehicles with oil or diesel as the main fuel, have also become the public concerns [START_REF] Azam | The effects of energy on investment, human health, environment and economic growth: empirical evidence from China[END_REF] . The transportation sector (fuel-powered automobiles) is one of the major consumers of fossil energies and thereby contributing a great part to the air pollutions and the GHG emissions. According to the 2017 China Motor Vehicle Environmental Management Annual Report [START_REF] Huang | Analysis Of Vehicle Contaminants Emission in China[END_REF] , the total emission of four pollutants (CO, NOx, carbureted hydrogen and particulate matter) from motor vehicles in China was 42.597 million tons. Facing these issues, a technology revolution of vehicles has quietly been emerging since the last century in Europe and now sweeping the world. Firstly, many countries have announced plans to ban the sale of petrol-powered vehicles from 10 to 40 years onwards. Secondly, cleaner and more environmentally friendly new energy vehicles also appear in the public's view, providing alternative choices for the majority of consumers. Electric vehicles (EVs) are the representative of clean and environmentally friendly vehicles.

A short history of EVs

The origin of EVs can be traced back to the 1830s. Thomas Davenport of the United States built the world's first tricycle powered by a non-rechargeable dry battery. In the 1880s, Gustave Trouve in France built the world's first rechargeable lead-acid battery-powered tricycle [START_REF] Fu-Qiang | Development status and research progress of power battery for pure electric vehicles[END_REF] . Frank Sprague designed and produced trams [START_REF] Chen | Modern electric vehicle technology[END_REF] . The iron and nickel battery invented by Thomas Edison provided the impetus for the development of EVs. At the end of the 19th century, many American and British companies began producing EVs. At the beginning of the 20th century, there were more than 30,000 EVs in operation in the United States [START_REF] Xue-Jie | Electric vehicles and Li-ion batteries[END_REF] , playing an important role in private transportation. At that time, EVs were a symbol of wealth, a vehicle for financial titans. After nearly a century of development, EVs have been driven by chemical power sources, from lead-acid batteries to nickel-metal hydride batteries and nickel-cadmium batteries. However, these batteries become more and more inadequate to meet the power requirements of pure EVs due to some technical constraints, such as battery volume, battery working environment and battery charging time. Combined with the rapid development of traditional diesel automobiles, the available global oil resources and other resources exploration and development, EVs were at a disadvantage in application.

In the 21st century, with the rapid development of economy and human society, the demand for energy is fast increasing. How to reduce the energy consumption of the transport sector is a matter of concern. Electric cars are once again on the scene. EVs have significant advantages in energy conservation, emission reduction and environmental protection. The popularization and application of EVs are of great significance for alleviating environmental pollution, solving the oil crisis, ensuring national energy security and realizing the sustainable development of society and economy.

Batteries for EVs

With the continuous breakthrough of key technologies for EVs and the improvement of infrastructure, countries all over the world have joined the ranks of seizing the technology and market of EVs. There are four main types of EVs: hybrid electric vehicle (HEV), battery electric vehicle (BEV), fuel cell electric vehicle (FCEV) and other new energy EVs. The development of energy storage technologies has greatly accelerated the battery-driven trend in the automobile industry. EVs have three core components: power sources, motor and electronic control system. From the perspective of global new energy vehicle development, its power sources mainly include lithium-ion batteries (LIBs), nickel metal hydride batteries, fuel cells, lead-acid batteries, supercapacitors and so on. The working state of the power sources is closely related to temperature. LIBs have shown great potential in the application of EVs at room temperature. It has the advantages of high specific energy, high energy density [START_REF] Tarascon | Issues and challenges facing rechargeable lithium batteries[END_REF][START_REF] Nitta | Li ion Battery Materials: Present and Future[END_REF] , long service life, low self-discharge [START_REF] Jaguemont | A comprehensive review of lithium-ion batteries used in hybrid and electric vehicles at cold temperatures[END_REF] and long shelf life [START_REF] Aneke | Energy storage technologies and real life applications -A state of the art review[END_REF] . But for LIBs to be widely used in EVs, safety [START_REF] Basu | Coupled electrochemical thermal modelling of a novel Li-ion battery pack thermal management system[END_REF] , cost, energy efficiency, charging devices and other issues need to be considered. Among various influencing factors, the operating temperature plays an important role on the performance, life and safety of LIBs [START_REF] Zhang | Thermodynamic assessment of active cooling/heating methods for lithium-ion batteries of electric vehicles in extreme conditions[END_REF] . At too low or too high temperature, the charge-discharge performance of LIB is still a big problem [START_REF] Huang | The limits of low temperature performance of Li-ion cells[END_REF] .

Therefore, in view of the complex thermal characteristics of EVs under different external environmental conditions and driving conditions, it is necessary to develop the battery thermal management system (BTMS) [START_REF] Cen | Experimental investigation on using the electric vehicle air conditioning system for lithium-ion battery thermal management[END_REF] , which plays a decisive role in the future development of EVs.

Objectives of this review paper

At present, there are a lot of scholars studying the temperature management of EVs working in harsh environments. This topic has received increasing research attention, indicated by the significantly increasing number of yearly publications since 2000 (Fig. 1). Reviews papers related to LIBs for EVs have also been published. Raijmakers et al. [START_REF] Raijmakers | A review on various temperatureindication methods for Li-ion batteries[END_REF] have summarized various methods of temperature indication of LIBs and briefly introduced the working principle of LIBs. Xie et al. [START_REF] Xie | Novel Mesoscale Electrothermal Modeling for Lithium-Ion Batteries[END_REF][START_REF] Xie | An Enhanced Online Temperature Estimation for Lithium-Ion Batteries[END_REF] have studied the thermal simulation of LIBs and proposed a variety of electrothermal models to provide support for the thermal management of LIBs. Wu et al. [START_REF] Wu | The state of the art on preheating lithium-ion batteries in cold weather[END_REF] and Vidal et al. [START_REF] Vidal | XEV LI-ION BATTERY LOW TEMPERATURE EFFECTS -REVIEW[END_REF] have reviewed the heating technology of LIBs in cold weather. Jaguemont and Mierlo [START_REF] Jaguemont | A comprehensive review of future thermal management systems for battery-electrified vehicles[END_REF] have reviewed the current situation of BTMS and systematically introduced traditional cooling systems. Specifically, Landini et al. [START_REF] Landini | A Review of Phase Change Materials for the Thermal Management and Isothermalisation of Lithium-Ion Cells[END_REF] and Chen et al. [START_REF] Chen | Effects of different phase change material thermal management strategies on the cooling performance of the power lithium ion batteries: A review[END_REF] have analyzed and reviewed the applications of phase change materials (PCMs) in the thermal management of LIBs-EVs. Solyali and Akinlabi [START_REF] Solyali | Configuration, design, and optimization of air-cooled battery thermal management system for electric vehicles: A review[END_REF] have focused on the analysis of the air-cooled BTMS for EVs. Choudhari et al. [START_REF] Choudhari | A review on effect of heat generation and various thermal management systems for lithium ion battery used for electric vehicle[END_REF] have reviewed temperature control systems for different cooling technologies such as air convection, liquid convection, PCMs and their combinations. However, most of the reviews only focus on the heating or cooling of LIBs while a comprehensive overview of the thermal management for LIBs-EVs is still lacking.

Therefore, the main objective of this review paper is to summarize the efforts made by various researchers in the development of EV's BTMS using electric heating, air heating/cooling, liquid heating/cooling, and PCMs heating/cooling, as well as their advantages and challenges. The paper starts with a brief overview of the working principle of LIBs, the heat generation principles and possible consequences, providing the basic battery functioning knowledge to the readers. Then, various heating and cooling methods of LIBs under low and high temperature conditions are systematically summarized. Finally, the prospect of BTMS for lithium-ion EVs in the future is put forward.

The rest of the paper is organized as follows. Section 2 begins with the hazardous consequences of LIBs due to harsh temperatures. Section 3 introduces the common heating methods of LIBs. Section 4 describes the common cooling methods of LIBs. In section 5, the main conclusions are summarized and some prospects are proposed.

Temperature: the key factor impacting the performance of LIBs

A LIB consists of a positive electrode, a negative electrode, an electrolyte, a membrane through which only lithium-ions can pass freely, and a battery shell. LIBs use carbon material as the negative electrode and lithium-containing compounds as the positive electrode, such as LiFePO4, LiMn2O4 and Li(NiCoMn)O2. LIBs work mainly by moving lithium-ions between the positive and negative poles. For the discharging process, the lithium-ions detach from the negative electrode and pass through the electrolyte to penetrate into the positive electrode. The charging process is the reverse operation. Charging and discharging of LIBs involve thereby an electrochemical reaction, which takes time and is accompanied by the conversion of energy and heat. The electrode reaction in charge and discharge process is illustrated by an example of lithium iron phosphate battery [START_REF] Padhi | Phospho-Olivines as Positive-Electrode Materials for Rechargeable Lithium Batteries[END_REF] .

The positive electrode reaction equation for the discharging of LIB is: 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 4 → 𝐿𝐿𝐿𝐿 1-𝑥𝑥 𝐿𝐿𝐿𝐿𝐹𝐹𝐿𝐿 4 + 𝑥𝑥𝐿𝐿𝐿𝐿 + + 𝑥𝑥𝐿𝐿 - The negative reaction equation is:

6𝐶𝐶 + 𝑥𝑥𝐿𝐿𝐿𝐿 + + 𝑥𝑥𝐿𝐿 -→ 𝐿𝐿𝐿𝐿 𝑥𝑥 𝐶𝐶 6 The overall reaction equation is:

𝐿𝐿𝐿𝐿 𝑥𝑥 𝐶𝐶 6 + 𝐿𝐿𝐿𝐿 1-𝑥𝑥 𝐿𝐿𝐿𝐿𝐹𝐹𝐿𝐿 4 → 6𝐶𝐶 + 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 4 There are four main sources of heat inside a battery [START_REF] Saito | Thermal studies of a lithium-ion battery[END_REF] : the reaction heat from a reversible reaction; the by-reaction heat generated by electrolyte decomposition during overcharging or overdischarge; joule heat due to the internal resistance of the cell due to the Joule effect; and the heat of polarization generated by the polarization reaction. The larger the discharge current of the battery, the smaller the discharge capacity and the faster the voltage drop. When the charging current increases, the charging speed increases, and the more heat a battery generates. Based on the literature survey, the recommended operating temperature ranges of the battery pack are closely overlapping. The common operating temperature of LIBs is usually between 15 °C and 40 °C [START_REF] Wang | A critical review of thermal management models and solutions of lithium-ion batteries for the development of pure electric vehicles[END_REF][START_REF] Alkhulaifi | Improving the performance of thermal management system for electric and hybrid electric vehicles by adding an ejector[END_REF] . Adapted temperature is an important guarantee for the efficient operation of LIBs and also one of the key factors to improve the performance of the EV.

LIBs at low temperature

The performance of LIBs can be problematic at low temperatures (e.g., < 15 °C). Both the charging and discharging performance will be affected because the electrochemical reaction cannot be carried out normally [START_REF] Zhang | Charging optimization in lithium-ion batteries based on temperature rise and charge time[END_REF] . When the temperature is too low, the diffusion rate of lithium-ions in the electrolyte decreases seriously due to the increase of electrolyte viscosity, resulting in significant increase of the internal resistance. The number of lithium-ions participating in the reaction decreases, which will directly affects the electricity storage and release, leading to the attenuation of battery capacity and power characteristics [START_REF] Jaguemont | Thermal Management of a Hybrid Electric Vehicle in Cold Weather[END_REF] . Under extreme conditions, the electrolyte freezes, preventing the battery from discharging and the car from starting. For the charging of LIBs at low temperature, lithium dendrites may pierce the film, forming an internal short circuit and threatening the safety of use [START_REF] Yu-Tao | Research Development of Battery Thermal Management at Low Temperature[END_REF] . Fig. 2 shows the relationship between charging capacity and charging voltage at different temperatures. In constant current charging, the charging voltage increases continuously and rapidly to the cut-off voltage as the temperature drops. Studies show that LIBs can only be charged at -10 °C with 10 A constant current charging capacity of only 60 % of the rated capacity [START_REF] Lei | A study on the low-temperature performance of lithium-ion battery for electric vehicles[END_REF] . This irreversible capacity reduction is also related to the number of battery uses. Finally, significant temperature difference may occur in different areas (cells) of the battery pack. The uneven temperature distribution inside the battery pack will cause local degradation [START_REF] Rao | A review of power battery thermal energy management[END_REF] , accelerating the battery aging and reducing the battery lifetime.

LIBs at high temperature

LIBs can also have performance problems at high temperatures (e.g., > 40 °C) [START_REF] Chen | Temperature rise prediction of lithium-ion battery suffering external short circuit for all-climate electric vehicles application[END_REF][START_REF] Joris | Combining an Electrothermal and Impedance Aging Model to Investigate Thermal Degradation Caused by Fast Charging[END_REF] . On one hand, lithium is chemically very reactive and burns easily. LIB pack is composed of many single LIBs in series or in parallel, so that the heat generated by the electrochemical reaction of the battery itself cannot be released in time due to the high environment temperature when the battery pack undergoes charging or discharging. A single battery cell may be overheated, resulting in the combustion, the explosion, or the escape of toxic gases (e.g., CO, C2H4, H2S, HF) [START_REF] Ouyang | A Review on the Thermal Hazards of the Lithium-Ion Battery and the Corresponding Countermeasures[END_REF][START_REF] Xiaoqing | Review of Thermal Runaway and Safety Management for Lithium-ion Traction Batteries in Electric Vehicles[END_REF] . Moreover, the short circuit may occur at high temperature due to the complicated internal power circuit structure of LIB pack [START_REF] Santoli | An overview on safety issues related to hydrogen and methane blend applications in domestic and industrial use[END_REF][START_REF] Wu | A critical review of battery thermal performance and liquid based battery thermal management[END_REF][START_REF] Lei | Thermal runaway characteristics on NCM lithium-ion batteries triggered by local heating under different heat dissipation conditions[END_REF] . On the other hand, high temperatures also affect the capacity of LIBs. Studies have shown that LIBs lose nearly 70% of their capacity after 500 cycles of discharging at 55 °C [43] . This effect greatly shortens the life of LIBs [START_REF] Al-Zareer | A novel phase change based cooling system for prismatic lithium ion batteries[END_REF] , not to mention the runaway heat that seriously threatens the human life.

All these problems of LIBs in harsh weather due to poor heating or cooling will seriously hinder the massive deployment and propagation of EVs. Finding appropriate thermal management solutions for better temperature control of LIB pack is therefore essential. The common heating and cooling methods of LIBs are described in the following sections.

Heating methods for LIBs

In order to augment the performance of EV LIBs at low temperature, the LIBs must be heated and insulated. According to different heating forms, the heating methods for LIBs can be divided into the following categories: electric heating, air heating, liquid heating, PCM heating, and other heating methods (such as Peltier effect and heat pipe).

Electrical heating

At low temperature, the viscosity of electrolyte and the internal resistance increase. Taking advantage of this property by sending an electric current through a resistance, the resulting joule effect will heat the LIBs up and make them work.

Li et al. [START_REF] Li | Researches on heating low-temperature lithium-ion power battery in electric vehicles[END_REF] have improved the performance of LIB at low temperature by heating an aluminum sheet with positive temperature coefficient (PTC) resistance wire winding. LiMn2O4 power battery with nominal voltage of 3.7 V and capacity of 35 Ah was selected as the research object. It was placed at -40 °C for 10 hours. The battery is charged by 1/3 C constant current and constant voltage at normal temperature. After charging, the battery was placed at 20 °C and -20 °C respectively to discharge at a certain rate until the discharge voltage of a single battery reached 3 V. Both simulation and experimental results indicated that the PTC heating method, can greatly improve the performance of battery at low temperature.

Lei et al. [START_REF] Lei | Preheating method of lithium-ion batteries in an electric vehicle[END_REF] have proposed the method of heating the battery by placing two wide wire metal films on the two largest surfaces of the battery. One side of the wide wire metal film was a rectangular copper film, and the other side was a certain width of continuous copper wire. A battery pack (consisting of three 35 Ah@3.7 V LiMn2O4 battery cells) with a wide wire metal film was placed in the battery box. The battery box was placed at -40 °C for 5-8 hours to achieve the thermal balance, and then the low-temperature discharge performance was tested. Heating at -40 °C and 120 W for 15 minutes was shown to be equivalent to charging and discharging at 0 °C. Jaguemont et al. [START_REF] Boulon | Characterization and Modeling of a Hybrid-Electric-Vehicle Lithium-Ion Battery Pack at Low Temperatures[END_REF] has proposed an effective LIB model suitable for thermal management of HEVs. The cells were placed in a climate chamber to recreate the climate at -20 °C, -10 °C, 0.0 °C, and +25 °C respectively. Experimental results showed that the improved electrothermal model worked well at low temperatures. Whether the high current value could accelerate the cell degeneration or not remained to be studied. The model was also applicable for the battery pack of HEVs.

Jin et al. [START_REF] Xin | Researches on Modeling and Experiment of Li-ion Battery PTC Self-heating in Electric Vehicles[END_REF] have put forward the PTC self-heating method of battery and conducted experimental tests. The slotted aluminum plate was placed between the two batteries and the PTC resistance belt was embedded into the slotted aluminum plate. The heat generated by the PTC can be quickly transferred to the battery for its heating in cold weather e.g., -36.4 °C. After the heating for 34.2 minutes, the average temperature of the battery pack raised to -20.7 °C. Nevertheless, the PTC self-heating device would increase the weight of the battery body and make the battery structure more complex. Further improvement is thus needed.

Lei et al. [START_REF] Lei | Improving temperature uniformity of a lithium-ion battery by intermittent heating method in cold climate[END_REF] have established a 3D finite element model and analyzed the temperature gradient of self-heating lithium-ion battery (SHLB). The intermittent SHLB heating method has been put forward. Their experimental results indicated that 0.1 VS 0.3 intermittent SHLB heating method (heating for 0.1 s and stopping heating for 0.3 s) could heat the LIBs well. However, the optimal interval time remained to be further studied.

Jiang et al. [START_REF] Jiang | A low-temperature internal heating strategy without lifetime reduction for large-size automotive lithium-ion battery pack[END_REF] have proposed the coupling of direct current and alternating current to heat LIBs. Firstly, the LIB pack was placed in a climate box at -20 °C for more than 10 hours to simulate the working environment of the battery in winter conditions. Then, direct current and alternating current generated by the soft switch resonant circuit were used to heat the battery. After 600 times of repeated experiments, the best heating effect was found to be achieved with AC frequency at about 754 Hz. However, the optimal ratio between the DC and AC still needs to be determined. How to maximize the heat production rate while reducing the risk of lithium-ion deposition is another research direction.

Yang et al. [START_REF] Yang | Innovative heating of large-size automotive Li-ion cells[END_REF] have proposed the concept of a full climate LIBs, as shown in Fig. 3. In addition to the usual anode, cathode and electrolyte, an activation terminal consisting of 50 micron nickel foil and insulating layer was included. The temperature of the battery pack was controlled by switching between the activation terminal and the negative terminal [START_REF] Wang | Lithium-ion battery structure that self-heats at low temperatures[END_REF] , and the heating process was monitored and characterized by the infrared thermography [START_REF] Zhang | Visualization of self-heating of an all climate battery by infrared thermography[END_REF] . An electric current was sent to pass through the nickel foil so as to generate heat. Compared with some conventional electric heating methods such as PTC, the power of the external heater must be increased in order to accelerate the heating. However, for large-sized thick batteries, local overheating may occur. At the same time, in the actual operation of EVs, the output current of the battery depends on the power demand of the driver. In this regard, it is unrealistic to heat the traditional battery with high current discharge [START_REF] Yang | Fast charging of lithium-ion batteries at all temperatures[END_REF][START_REF] Yang | Computational design and refinement of self-heating lithium ion batteries[END_REF] . Fig. 3. Schematic illustration of a conventional Li-ion cell and a self-heating Li-ion battery with multiple Ni foils inserted [START_REF] Yang | Innovative heating of large-size automotive Li-ion cells[END_REF] Ji and Wang [START_REF] Ji | Heating strategies for Li-ion batteries operated from subzero temperatures[END_REF] have proposed a method of pulse mutual heating. The entire battery pack was divided into two equal sized packs, one undergone discharging while the other charged. Their experimental results showed that the LIBs could be heated from -20 °C to 20 °C, with a capacity loss of only 5%.

Air heating

The principle of the air heating method is shown in Fig. 4. The temperature of the electric heating wire is firstly raised by the power supply from the battery. Then the electric heating wire at high temperature heats up the surrounding air by convection. The hot air enters into the battery box by the fan and exchanges heat with the battery monomer to heat the low-temperature battery to the appropriate temperature. Ji and Wang [START_REF] Ji | Heating strategies for Li-ion batteries operated from subzero temperatures[END_REF] have proposed a convection heating strategy, as shown in Fig. 5. External heating used the power output of the battery to convert electrical energy into heat through the resistance heater. The fan generated convection air flow to enhance the heat transfer between the heater and the air, and from the air to the battery. The advantage of the convective heating strategy lies in its high efficiency, but the heat conduction inside the battery pack may become a limiting factor due to the thickness of the battery cell, leading to a larger temperature gradient inside the battery. Fig. 5. Convection heating strategy [START_REF] Ji | Heating strategies for Li-ion batteries operated from subzero temperatures[END_REF] Mahamud and Park [START_REF] Mahamud | Reciprocating air flow for Li-ion battery thermal management to improve temperature uniformity[END_REF] have proposed a new method for thermal management of cylindrical LIBs by means of reciprocating airflow. Two-dimensional computational fluid dynamics (CFD) model, lumped capacitive heat model and flow network model were developed and compared. The experimental results showed that the network model was in good agreement with the 2D CFD results, which could effectively manage the temperature of the battery. The shorter the reciprocating period, the lower the temperature difference and maximum unit temperature of the system. The influence of different battery spacing on the thermal management effect remained to be further studied.

Liquid heating

Similar to air heating, the electric heating wire is firstly heated by a power source to raise its temperature, as shown in Fig. 6. The high-temperature electric wire heats then a liquid, which flows between the heating wire and the battery monomer through reserved flow channels to heat the lowtemperature battery up to an appropriate temperature. The commonly used heat transfer mediums include water, oil, glycol, acetone and so on [START_REF] Rao | A review of power battery thermal energy management[END_REF] . Compared with air heating, liquid heating has great advantages due to its higher specific heat capacity and higher heat transfer coefficient. The battery pack could therefore be more compact. It must be pointed out that the liquid heating also has some technological barriers to overcome, such as the liquid leakage problem and the design of the efficient flow network [START_REF] Xia | A review on battery thermal management in electric vehicle application[END_REF] . Fig. 6. Schematic of liquid heating Nelson et al. [START_REF] Nelson | Modeling thermal management of lithium-ion PNGV batteries[END_REF] have proposed a method of heating or cooling the battery with silicone variable pressure fluid, which is a better heat transfer fluid than air. Its thermal conductivity is greater than air, and its heat capacity per unit volume is also higher than air. However, due to the temperature difference between the heating and cooling battery, the size design of fluid channel is particularly important in order to realize the whole process of summer cooling and winter heating simultaneously.

PCM heating

PCMs include hydrated salts, stearic acid, polyethylene glycol, paraffin, graphene and phase change composites based on them. As shown in Fig. 7, PCMs can be filled inside a framework to form a new kind of composite phase change material (CPCM) in a modular manner. During battery discharge, the CPCM absorbs the heat released by the battery, rapidly reducing the battery temperature. Zhang et al. [START_REF] Zhang | Thermodynamic assessment of active cooling/heating methods for lithium-ion batteries of electric vehicles in extreme conditions[END_REF] have proposed using pentadecane (C15H31) as microencapsulated PCM slurry for battery heating. Phase change slurry cycle having high latent heat capacity is a commonly used heat transfer medium in the heat transfer process. Microencapsulated PCM slurry can be used for heating applications of EVs. The melting temperature of pentadecane is 9.9 °C. Their experimental results showed that the active heating system could keep the temperature of the battery box above 0 °C, and the battery could work at 5-10 °C. Octadecane and pentadecane are used in combination to meet summer and winter conditions respectively.

Other methods

Other methods have been used to heat LIBs, by using the Peltier effect elements or the heat pipe.

The Peltier effect or the second thermoelectric effect is known as two different semiconductors formed into a cycle. After passing through the direct current, the connection of two conductors produces heat absorption or exothermic phenomenon, forming high and low temperature areas. The Peltier element based on the Peltier effect can transfer heat from the higher end of the free electron count to the lower end. The direction of heat transfer can be changed by changing the direction of current. Troxler et al. [START_REF] Troxler | The effect of thermal gradients on the performance of lithium-ion batteries[END_REF] have used the Peltier elements to control the temperature of LIBs, as shown in Fig. 8. One end of the Peltier element was in contact with the battery, and the other end was connected with a water cooled heat sink. The battery was heated by the movement of free electrons within the Peltier elements. In order to make the heating effect more uniform, copper plate was inserted between the Peltier element and the battery. Experiments were carried out in the range of -13 °C to 55 °C. Since the Peltier effect requires a large temperature gradient, how to improve its thermal efficiency is the focus of the future research. [START_REF] Troxler | The effect of thermal gradients on the performance of lithium-ion batteries[END_REF] Heat pumps and heat pipes are also used to heat LIBs. Parekh [START_REF] Parekh | Development and Evaluation of Active Thermal Management System for Lithium-Ion Batteries using Solid-State Thermoelectric Heat Pump and Heat Pipes with Electric Vehicular Applications[END_REF] has studied three methods of thermal management for LIBs, including the simple electric heating, the heat pipe heating and the composite solid-state thermoelectric heat pump and heat pipe heating. The operating conditions of the battery from -10 °C to 10 °C have been tested. The heating effect of composite solid-state thermoelectric heat pump and heat pipe system was found to be better than that of simple electric heating or heat pipe heating. The heat pipe could make the heat distribution more uniform. However, the operating temperature range of the battery is limited. The design of thermal resistance, bypass flow and inefficient spacing still needs further study.

Short summary Table 1

Short summary of different heating methods

Author Method Condition

Heatup time

Result Notes

Li et al. [START_REF] Li | Researches on heating low-temperature lithium-ion power battery in electric vehicles[END_REF] battery cell, PTC resistance wire winding 35 W, -40 °C 25 min 0 °C poor temperature uniformity Lei et al. [START_REF] Lei | Preheating method of lithium-ion batteries in an electric vehicle[END_REF] battery pack, wide wire metal film 90 W, -40 °C 15 min the same as working at 0 °C the structure of the heating device is simple Jaguemont et al. [START_REF] Boulon | Characterization and Modeling of a Hybrid-Electric-Vehicle Lithium-Ion Battery Pack at Low Temperatures[END_REF] battery cell, high current heating Lei et al. [START_REF] Lei | Improving temperature uniformity of a lithium-ion battery by intermittent heating method in cold climate[END_REF] battery pack, intermittent self-heating heating for 0.1 s stopping heating for 0.3 s last 30 s ∆T=2-3 °C good temperature uniformity Jiang et al. [START_REF] Jiang | A low-temperature internal heating strategy without lifetime reduction for large-size automotive lithium-ion battery pack[END_REF] battery cell, direct current and alternating current 754 Hz, -20 °C 10 min 2.1 °C the structure of the heating device is complex Yang et al. [START_REF] Yang | Innovative heating of large-size automotive Li-ion cells[END_REF] battery pack, an active terminal added nickel foil heating elements added 10 s Tmax=50 °C Tmin=-28 °C rapid temperature rise local overheating poor temperature uniformity Ji and Wang [START_REF] Ji | Heating strategies for Li-ion batteries operated from subzero temperatures[END_REF] battery cell, convection heating 60 Hz, -20 °C 3 min 20 °C rapid temperature rise Complex device system By comparing different heating methods of lithium-ion batteries, it can be found that the scholars have made contributions to ensuring the normal operation of LIBs of EVs at low temperatures from multiple perspectives, such as energy consumption, heating temperature, heating rate, temperature uniformity inside the battery, simplicity of heating device structure. Table 1 briefly summarizes the various heating methods used for LIBs. It can be found that the intermittent Self Heating LB (SHLB) method has the best temperature uniformity inside the LIBs, which is promising.

Cooling methods for LIBs

EV LIBs at high temperature must be cooled to augment the performance. Different methods have been proposed, including the air cooling, the liquid cooling and the PCM cooling technologies.

Air cooling

Air cooling is the most widely used heat dissipation method for battery packs, by directly using the wind around the moving car to conduct natural convection, or by generating forced airflow through the fan operation (Fig. 9). Natural convection has the obvious advantages of simplicity and low cost, while it also has the disadvantage of weak heat dissipation capacity due to uncontrollable wind. The forced convection by fan is more reliable and easier to maintain than the natural convection, therefore becoming a more common battery cooling method. However, a common problem for forced convection is the temperature uniformity within the cell. Researchers in various countries have conducted different optimizations to improve the temperature uniformity by taking the inconsistencies of the cell into account [START_REF] Peng | Thermal performance investigation of an air-cooled lithium-ion battery pack considering the inconsistency of battery cells[END_REF] . But due to the characteristics of air itself, its cooling effect has certain limitations. Sun and Dixon [START_REF] Sun | Development of cooling strategy for an air cooled lithium-ion battery pack[END_REF] have established a 3D battery pack thermal model based on the simplified electrode theory and combined with the experiments design model. It has been found that the geometric shape of the inlet and outlet channel plays an important role in the flow uniformity of the cooling channel, which significantly affects the temperature uniformity of LIBs. Based on the baseline z-type flow, the cooling surface area of the channel was increased by inserting ripples between the cooling plates in the battery pack (Fig. 10), thereby improving the temperature uniformity of the battery pack. The cooling efficiency of the flow channel can be increased to approximately 93%. Fig. 10. Z-flow air cooling with corrugated sheets [START_REF] Sun | Development of cooling strategy for an air cooled lithium-ion battery pack[END_REF] Chen et al. [START_REF] Chen | Cooling efficiency improvement of air-cooled battery thermal management system through designing the flow pattern[END_REF] have improved the efficiency of the air-cooled BTMS by designing the air flow circuit. In their study, the influence of the location of the inlet and outlet areas on the cooling effect was examined (Fig. 11). Their numerical results showed that the symmetrical air-cooled cooling system with the inlet and outlet located in the middle of the static chamber had higher cooling efficiency than conventional Z-type flow circuit. Further experimental validation is still needed. Fig. 11. Z-flow air cooling at different inlet and outlet locations [START_REF] Chen | Cooling efficiency improvement of air-cooled battery thermal management system through designing the flow pattern[END_REF] Chekuri et al. [START_REF] Chekuri | Three dimensional numerical validation and investigation on air cooling system of Li-ion battery used in hybrid electric vehicles[END_REF] have improved the temperature uniformity by using forced convection. The introduction of tapering inlet and outlet could reduce the battery temperature through 3D simulation of a LIB cooling system for hybrid cars. The optimization of conical inlet and outlet needs further study.

Behi et al. [START_REF] Behi | A new concept of thermal management system in Li-ion battery using air cooling and heat pipe for electric vehicles[END_REF] have proposed a method of combining air cooling with heat pipe to improve the temperature uniformity of LIB. The experimental test and simulation verification of 24 cylindrical LIBs have shown that the new method could improve the battery temperature uniformity by about 70 %.

Xie et al. [START_REF] Xie | Improving the Air-Cooling Performance for Battery Packs via Electro-Thermal Modelling and Particle Swarm Optimization[END_REF] have proposed a novel design optimization method for air passage with varying cell spacing. Different air passages between each row and each column were used instead of evenly spaced air passages. The purpose is to reduce the resistance of the local channel and improve the uneven temperature of each cell in the battery pack. By optimizing the 3P4S battery pack (three strings in parallel and four cells in each string), the maximum temperature difference can be reduced by 2 °C. However, for other combined forms of battery packs, optimization is still to be studied.

Liquid cooling

Liquid cooling is another commonly used method for the cooling of LIBs. Its principle is shown in Fig. 12. Compared with air cooling, liquid cooling is more efficient due to higher heat transfer coefficient of water [START_REF] Kim | Review on battery thermal management system for electric vehicles[END_REF] . Liquid cooling can be classified into direct cooling and indirect cooling. Direct cooling (such as liquid immersion cooling) can cool the entire battery surface, which greatly contributes to the temperature uniformity of LIBs. Direct contact liquid cooling [START_REF] Dincer | Thermal Management of Electric Vehicle Battery Systems[END_REF][START_REF] Xia | A review on battery thermal management in electric vehicle application[END_REF][START_REF] Yang | A Review of Lithium-Ion Battery Thermal Management System Strategies and the Evaluate Criteria[END_REF] is not common in automobile battery cooling system due to its high requirement on the waterproof performance of battery system, and electrical short circuit and electrochemical reaction may occur. Indirect liquid cooling (such as tube cooling, cold plate cooling with mini/micro channels, jacket cooling, etc.) has attracted the attention of many scholars due to its advantages of easier implementation and higher safety. The liquid cooling devices of cylindrical LIB [START_REF] Yates | Analysing the performance of liquid cooling designs in cylindrical lithium-ion batteries[END_REF][START_REF] Hu | A Comparative Study of Control-Oriented Thermal Models for Cylindrical Li-Ion Batteries[END_REF][START_REF] Tang | Numerical analysis of temperature uniformity of a liquid cooling Configurations for Automotive Battery Pack Thermal Management[END_REF] and plate LIB [75,76] have been proposed and studied. Usually, the cooling device is developed to be compact and light [77] , and new materials [78][79][80] are used to improve the cooling channel. Preheating is also used for liquid cooling [81] . In addition, liquid cooling can also be combined with other methods such as air cooling [82] or heat pipes [83] to create better results. At present, most of the researches focus on the optimization of cooling plates through simulation or experimental methods [84][85][86][87] . Fig. 12. Schematic of liquid cooling Shen et al. [88] have improved the air-conditioning system of traditional automobiles. A parallel plate (cold plate) was arranged on the evaporator side of the traditional automobile air conditioning system. After the refrigerant was throttled and decompressed in the expansion valve, it was directly introduced into the cooling pipe in the battery pack, and the battery directly exchanged heat with the refrigerant. The battery could be cooled from 44 °C to about 30 °C. This kind of structure doesn't change much the initial structure of EVs, and the system is relatively simple. Compared with water cooling, the refrigerant has lower thermal conductivity, thus reducing the damage to the battery caused by coolant leakage. The efficiency of the experimental research system has a higher energy efficiency ratio, but there is still some room for improvement.

Mohammadian et al. [89] have conducted a transient numerical simulation study to compare the internal and external cooling of LIBs. Internal cooling referred to the use of electrolyte as coolant to cool LIBs in the rectangular microchannels of positive and negative electrodes. External cooling referred to the cooling of LIBs with refrigerants through microchannels outside the cell. The maximum temperature and standard deviation of the internal temperature field did not decrease significantly by the external cooling. However, increasing the pumping power during internal cooling could significantly reduce the maximum temperature inside the battery and improve the temperature uniformity.

Jin et al. [90] have designed an ultra-thin minichannel liquid cold plate (LCP) to improve the traditional straight channel LCP design. In conventional straight channel LCP designs, the development of the hydrodynamic boundary layer lead to the rise of the maximum temperature and a significant increase in the temperature gradient. The ultra-thin minichannel LCP redivided the boundary layer. The discontinuity of the downstream fins caused the hydrodynamic boundary layer to redevelop at the leading edge of the downstream segment. The inclined LCP was able to maintain the battery surface temperature below 50 °C under the condition of 1240 W and flow rate smaller than 0.9 L min -1 . However, there was still some distance from the optimal working temperature of LIBs.

Darcovich et al. [91] have made experimental measurements by selecting the smaller battery and used numerical simulations to compare two liquid-channel cooling plate structures, one for an ice plate (flush with battery face) placed between each cell of the battery pack and the other for a cold plate (bottom surface of battery) placed below the battery. Experiments and simulations showed that the vertical temperature difference existed in the cold plate system while the ice plate system generally performed better, allowing the battery to be cooled to 37 °C. But the ice disk system is relatively more complex. How to simplify the design and ensure the performance is particularly important in practical applications.

Zhen et al. [START_REF] Zhen | Thermal performance of lithium-ion battery thermal management system by using mini-channel cooling[END_REF] have proposed a liquid cooling method based on micro-channel cold plate, A 3D numerical model of the method was established to analyze the influences of channel number, inlet mass flow, flow direction and channel width on the thermal performance of battery pack. The results showed that the mini-channel cold plate BTMS provided good cooling efficiency at 5C discharge. Increasing the number of channels and the mass flow at the inlet could reduce the maximum temperature and improve the temperature uniformity of LIBs.

Krüger et al. [START_REF] Krüger | Energy Consumption Of Battery Cooling In Hybrid Electric Vehicles[END_REF] have studied the indirect evaporative cooling of automobile batteries under different climatic conditions using different refrigerants (R134a and R1234yf). But the energy consumption has been greatly affected by weather and driving cycle.

PCM cooling

PCM cooling method is similar to that of heating LIBs. Appropriate PCMs should be selected according to different requirements of phase change temperature. PCMs have the advantage of requiring no extra energy and the disadvantages of relatively complex cooling structures. Many scholars have carried out numerical simulation for the cooling method of PCM to improve its cooling uniformity [START_REF] Parhizi | Analytical Modeling and Optimization of Phase Change Thermal Management of a Li-ion Battery Pack[END_REF][START_REF] Cao | Delayed liquid cooling strategy with phase change material to achieve high temperature uniformity of Li-ion battery under high-rate discharge[END_REF][START_REF] Hong | Thermal performance of direct two-phase refrigerant cooling for lithium-ion batteries in electric vehicles[END_REF] . The storage device of PCMs is also the research focus. Choudhari et al. [START_REF] Choudhari | Numerical analysis of different fin structures in phase change material module for battery thermal management system and its optimization -ScienceDirect[END_REF] have studied the influence of fin structure on the temperature uniformity of cylindrical LIBs. The structure of fin, battery and PCM is shown in Fig. 13. Simulation results showed that the i-shaped fins could have better heat transfer effect. Landini et al. [START_REF] Landini | Passive Cooling of Li-Ion Cells with Direct-Metal-Laser-Sintered Aluminium Heat Exchangers filled with Phase Change Materials[END_REF] have studied the influence of Direct-Metal-Laser-Sintered aluminum heat exchangers on the temperature uniformity of battery. PCM cooling can also be combined with liquid cooling [START_REF] Cao | Liquid cooling with phase change materials for cylindrical Li-ion batteries: An experimental and numerical study[END_REF]100] or heat pipes [101,102] to achieve better cooling performance. Fig. 13. The structure of fin, battery and PCM [START_REF] Choudhari | Numerical analysis of different fin structures in phase change material module for battery thermal management system and its optimization -ScienceDirect[END_REF] Bai et al. [103] have designed the PCM/water-cooled plate battery module from the perspective of energy saving and fluid mechanics. The factors that affect the performance of the cooling module, such as the mass flow and flow direction of the inlet, thermal conductivity, PCM melting point, were analyzed numerically. The results showed that the PCM/water-cooled plate structure could effectively cool the LIBs. The average battery temperature could be maintained at 38.5 °C. But there was still a temperature difference of more than 10 °C inside the battery pack.

Yu et al. [104] have proposed a BTMS using PCMs and cooling water as the cooling device to control the temperature of LIBs. Specially, the graphite sheets were adopted to improve the thermal conductivity of the PCMs, leading to a better temperature uniformity. The effectiveness of this BTMS was verified by a 3D numerical simulation of LIB module. The maximum temperature difference could meet the demand only when 3 water cooling tubes worked together. A temperature difference of 6-8 °C still existed at both ends of the battery pack.

Lei et al. [105] have proposed a BTMS integrating PCM, heat pipe and spray cooling, which can maintain the thermal stability of LIBs in different environment. A battery pack is formed by two LIBs connected in parallel, and a sintered copper-water heat pipe is sandwiched between them. The battery pack was placed in an acrylic box and the chamber was filled with PCM. The battery heat generated during the day would be stored in the PCM. When the battery temperature continued to rise, the battery heat would be transferred via a heat pipe from battery surfaces to its condensation end, and the water spray was carried out intermittently. When the temperature was cold at night, the latent heat stored in the PCM would be released, protecting LIB from low-temperature degradation in its performance and damages in its materials. The method could significantly improve the working temperature environment of LIBs, but the cooperation of multiple systems made the structure of the LIBs huge and complex. Sun and Dixon [START_REF] Sun | Development of cooling strategy for an air cooled lithium-ion battery pack[END_REF] battery pack, improve the cold plate different materials for cold plate Tmax=33.8 °C ∆T=1.9 °C Z type corrugated sheets better Chen et al. [START_REF] Chen | Cooling efficiency improvement of air-cooled battery thermal management system through designing the flow pattern[END_REF] battery It can be found that researchers have made contributions to ensuring the normal operation of LIBs of EVs at high temperatures from multiple perspectives, such as cooling temperature, cooling rate, temperature uniformity inside the battery, and the matching of cooling device with the air conditioning system of EVs. Table 2 provides a brief summary of commonly used cooling methods for LIBs. The combination of PCM and cold plate cooling method is promising. It can not only maintain the temperature of LIBs in the operating range, but also improve the temperature uniformity of the LIBs.

Short summary

Conclusion and prospects

The problem of low/high temperature of LIB must be solved for the better development of EVs. Since EVs need to be used steadily throughout the year and the climate environment varies greatly in different regions, the working environment of LIBs for EVs is quite complex. A way to maintain the operating temperature of LIBs for all climates is particularly needed. In the current study, different methods proposed to improve the low temperature performance of LIBs have been summarized including the air heating, the liquid heating, the electric heating, the PCM heating and other heating methods. On the other hand, different methods have also been proposed to improve the high temperature performance of LIBs based on air cooling, liquid cooling and PCM cooling. The air heating/cooling method requires fans, air ducts and other accessories. The whole system is relatively large and the heat transfer efficiency is low. Liquid heating/cooling avoids the installation of the fan, air duct, but requires pumps, pipes and other accessories instead. The use of liquid greatly improves the heat transfer efficiency, but the liquid leakage is always a big risk. Electric heating is relatively simple and efficient, and therefore becomes the most common heating method. However, it may lead to uneven battery pack temperature and reduce its lifetime. In addition, PCMs are also a good choice for the thermal management of LIBs, for both winter heating and summer cooling if appropriate PCMs are employed.

A number of prospects could then be summarized as the directions of future research: 1. Adapted methods to maintain the stable and uniform temperature of the battery pack.

2. Compatible heating and cooling system of the battery with the air conditioning system of the vehicle, and the unified thermal management of the vehicle with rational use of resources.

3. Modification of the electrolyte of LIBs to change its electrolyte composition, so as to fundamentally improve the low-temperature performance of LIBs.

4. The aging effect of battery by the thermal management still needs to be studied.

Fig. 1 .

 1 Fig. 1. Number of publications on the LIBs for EVs (source: Scopus; keyword: LIBs for EVs, thermal management system; date: 20 January 2021)

Fig. 2 .

 2 Fig. 2. Charging curve at 10 A constant current and constant voltage at different temperature

Fig. 4 .

 4 Fig. 4. Principle of air heating

Fig. 7 .

 7 Fig. 7. Schematic diagrams of the CPCM-based battery pack

Fig. 8 .

 8 Fig.8. Structure diagram of Peltier effect heating[START_REF] Troxler | The effect of thermal gradients on the performance of lithium-ion batteries[END_REF]

Fig. 9 .

 9 Fig. 9. Traditional Z-flow air cooling

battery module composed of

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Table 2

 2 Short summary of different cooling methods

	Author	Method	Condition	Result	Notes

Acknowledgement

This work is supported by the Key Research and Development (R&D) Projects of Shanxi Province (201803D31035), the National Key Research and Development Program (Grant No.2016YFE0133300-04) and European project H2020-MSCA-RISE-2016: Low Energy Dew Point Cooling for Computing Data Centers (DEW-COOL-4CDC).

List of abbreviations


Fotios Pitoulis

Raquel Nunez-Toldra

Ke Xiao

Worrapong Kit-Anan

Saskia Mitzka

Richard Jabbour

Sian Harding

Filippo Perbellini

Thomas Thum

Pieter De Tombe

Remodelling of adult cardiac tissue subjected to physiological and pathological mechanical load in vitro

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