A coupled battery thermal management system and an optimization design method thereof

Abstract

The application discloses a coupled battery thermal management system and an optimization design method thereof, and the system comprises a plurality of batteries, parallel flow channel liquid cooling plates, phase change materials and fire-retardant materials; the top or bottom of the battery is closely attached to the liquid cooling plate, and is arranged along the parallel flow channel direction and the vertical direction in the liquid cooling plate; the phase change material, the fire-retardant material or the mixture of the two is filled between adjacent batteries, and the density of the fire-retardant material is far lower than that of the phase change material. The optimization design method adjusts the thickness distribution of the phase change material and the fire-retardant material according to the temperature distribution of the battery under the given system volume, so that the temperature uniformity of the battery pack is improved, and the system is lightened. The system has the advantages of simple structure, reliable operation and the like, and the optimization design method has the advantages of simple implementation, rapid process, good effect, wide application range and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power battery thermal management, in particular to a coupled battery thermal management system and an optimization design method thereof. BACKGROUND

[0002] With the rapid development of global economy, energy crisis and environmental pollution problems are increasingly prominent. The country proposes to vigorously promote green and environmentally friendly low-carbon transportation, and new energy electric vehicles have developed rapidly. As one of the three components of electric vehicles, power batteries are the driving core of electric vehicles. The improvement of the power performance and the cruising range of electric vehicles means the improvement of the requirements of battery specific capacity and high-rate charge-discharge. The battery charge-discharge process is a heat generation process. If the generated heat cannot be dissipated in time, the battery temperature will rise, leading to thermal runaway. Therefore, the power battery needs to be thermally managed to ensure that the power battery works in a suitable temperature range, maintains the high performance of the electric vehicle and safely and stably operates. Among many thermal management methods, the coupled cooling method based on phase change material and liquid cooling plate can comprehensively utilize the advantages of high liquid cooling heat transfer coefficient and no energy consumption of phase change material, realize the improvement of system cooling performance and the reduction of energy consumption, and is a very promising composite thermal management method.

[0003] Previous studies mainly improve the thermal management ability of the system by adjusting the structural parameters of the phase change material coupled liquid-cooled battery thermal management system. Molaeimanesh et al. (Molaeimanesh G R, Nasiry S M, Dahmardeh M. Impact of configuration on the performance of a hybrid thermal management system including phase change material and water-cooling channels for Li-ion batteries [J]. Applied Thermal Engineering, 2020, 181.) changed the layout of the phase change material and multiple liquid cooling plates to cool the battery module under the condition of ensuring the volume of the system unchanged, reduced the maximum temperature of the battery pack and improved its temperature uniformity; Chen et al. (Chen X, Zhou F, Yang W, et al. A hybrid thermal management system with liquid cooling and composite phase change materials containing various expanded graphite contents for cylindrical lithium-ion batteries [J]. Applied Thermal Engineering, 2022, 200.) adjusted the content of expanded graphite (EG) in the phase change material along the flow direction of the cooling liquid, and finally obtained the optimal EG content segmentation layout, which reduced the temperature difference of the battery. The existing research mainly designs the parameters of the phase change material coupled liquid-cooled battery thermal management system through empirical adjustment and enumeration, which hinders the further improvement of the system performance. In addition, the design usually only considers the improvement of the thermal characteristics of the battery, and rarely pays attention to the reduction of the weight of the system. The popularity of electric vehicles and the improvement of the energy density of power batteries put forward higher requirements for the cooling performance and weight of the battery thermal management system, so it is necessary to design a phase change material coupled liquid-cooled battery thermal management system with wide application range, good cooling performance and simple and light. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a coupled battery thermal management system and an optimization design method thereof.

[0005] The present application is realized at least by one of the following technical solutions.

[0006] A coupled battery thermal management system, comprising a plurality of batteries, a liquid cooling plate, and a filling material; the top or bottom of each battery is tightly attached to the liquid cooling plate, and the plurality of batteries are arranged one by one along the parallel flow channel direction and the vertical direction of the liquid cooling plate, and the filling material is arranged between adjacent batteries.

[0007] Further, the liquid cooling plate is a parallel flow channel liquid cooling plate, comprising an inlet section, an inlet manifold, a plurality of parallel flow channels, an outlet section, and an outlet manifold; the inlet section of the liquid cooling plate is connected to the inlet manifold, and the outlet section is connected to the outlet manifold; the inlet manifold and the outlet manifold are connected through the parallel flow channels.

[0008] Further, the filling material is a phase change material, a fire-retardant material, or a mixture of the two.

[0009] Further, the density of the fire-retardant material is much lower than that of the phase change material.

[0010] Further, the battery is a battery monomer or a battery pack; the battery pack is attached to the liquid cooling plate on one side, or on both sides.

[0011] Further, the battery monomer is a prismatic battery or a cylindrical battery.

[0012] An optimization design method for the coupled battery thermal management system is implemented, comprising the following steps:

[0013] S1, given the total volume V0 of the coupled system and the physical parameters of the filling material, set the filling material replacement temperature threshold to T b , the battery gap adjustment step to ΔL, the minimum value of the gap to L min , and the phase change rate threshold to

[0014] S2, assuming that the gaps between the batteries are the same at the initial time and all filled with phase change materials; calculate the battery gap according to the total volume V0 of the system, and along the parallel flow channel direction of the system, the gap distribution is recorded as L = [L1, L2, …, L k , …, L N , L N+1 ], where N is the number of batteries, and L k is the size of the kth gap;

[0015] S3, use a numerical simulation method to calculate the temperature field of the coupled system to obtain the monitoring temperature T k of each battery, and traverse the monitoring temperature T k of each battery in the direction of the parallel flow channel of the cold plate; when the monitoring temperature T k is lower than the material replacement temperature threshold T b , replace all the phase change materials on both sides of the battery with fire-retardant materials;

[0016] S4, calculate the temperature field of the coupled system using numerical simulation method, get the battery pack temperature difference ΔT, record the gap distribution at this time as the optimal distribution L opt , the corresponding battery pack temperature difference is the optimal temperature difference ΔT opt ;

[0017] S5, find the battery with the highest monitoring temperature, mark it as i, if i=N, increase L N+1 by ΔL; if i≠N, compare the monitoring temperatures T i-1 and T i+1 of the (i-1)th and (i+1)th batteries, if T i-1 ≥T i+1 , increase the gap L i of the ith battery by ΔL, if T i-1 <T i+1 , increase the gap L i+1 of the (i+1)th battery by ΔL; if the phase change rate of the selected gap adjustment region exceeds the phase change rate threshold , the region is not used as an adjustment region, continue to find the material adjustment region through step S5;

[0018] S6, find the battery with the lowest monitoring temperature, mark it as j, if j=1, decrease L1 by ΔL; if j≠1, compare the monitoring temperatures T j-1 and T j+1 of the (j-1)th and (j+1)th batteries, if T j-1 ≤T j+1 , decrease the gap L j of the jth battery by ΔL, if T j-1 >T j+1 , decrease the gap L j+1 of the (j+1)th battery by ΔL; if the selected gap adjustment region reaches the set minimum gap L min , the region is not used as an adjustment region, continue to find the material adjustment region through step S6;

[0019] S7, get the current battery gap distribution and the type of material filled therein through steps S5 and S6, calculate the monitoring temperature of each battery and the battery pack temperature difference ΔT in the current system using numerical simulation method again, if ΔT<ΔT opt , record the current gap distribution as the optimal distribution L opt , record the current temperature difference as the optimal temperature difference ΔT opt ; return to step S5 and repeat the above process until the battery pack temperature difference ΔT does not decrease with the increase of the adjustment step number, at this time stop the gap adjustment operation and go to step S8;

[0020] S8, according to the numerical simulation results of the current system, the melting condition of the filling material is obtained, the optimization design process is ended, and the current battery gap distribution and the type of the filling material therein are design results.

[0021] Further, the monitoring temperature of the battery is the average temperature T ave of the battery. max .

[0022] Further, the battery pack temperature difference is defined as the difference between the average temperatures of the batteries, and the expression is ΔT = max(T ave，i )-min(T ave，i ), wherein T ave，i is the average temperature of the i-th battery, and max(T ave，i ) and min(T ave，i ) are the maximum and minimum values of the average temperature of the battery, respectively.

[0023] Further, the melting condition of the filling material is obtained according to the numerical simulation results of the current system, and the region of the un-melted phase change material is replaced by the fire-retardant material.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] 1. The coupling type battery thermal management system has the advantages of simple structure, reliable operation and good cooling effect. The phase change material is coupled with the liquid cooling plate, which combines the advantages of high heat exchange coefficient of liquid cooling and no energy consumption of phase change material. The liquid cooling plate is sealed and packaged and attached to the outside of the battery, reducing the risk of cooling liquid leakage. The phase change material is filled between the batteries to improve the temperature uniformity of the batteries and reduce energy consumption.

[0026] 2. The coupling type battery thermal management system optimization design method has the advantages of simple implementation and fast optimization speed. The optimization design method uses a numerical simulation method to calculate the battery pack temperature distribution, and gradually adjusts or replaces the thickness distribution of the phase change material and the fire-retardant material according to the current temperature distribution. There is no complex and tedious operation, and the proposed adjustment strategy can obtain convergent optimization results in a short time. Therefore, the optimization design equation has the advantages of simple process, easy implementation, and fast optimization speed.

[0027] 3. The coupling type battery thermal management system optimization design method has the advantage of good optimization effect. The adjustment and replacement strategy proposed by the optimization method distributes the thickness distribution of the phase change material and the fire-retardant material according to the current temperature distribution of the battery. This strategy can effectively reduce the temperature difference and hot spot temperature of the battery pack and reduce the weight of the system.

[0028] 4. The coupled battery thermal management system optimization design method provided by this invention has the advantage of wide applicability. This optimization design method is independent of system size, physical parameters of the cooling fluid, number of power batteries, and heat generation power. Therefore, the optimization method involved in this invention can be extended to the optimization design of other similar coupled thermal management systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a coupled battery thermal management system according to the present invention;

[0030] Figure 2 This is a flow chart of a coupled battery thermal management system optimization design method of the present invention;

[0031] Figure 3 This is a front view of a phase change material coupled liquid-cooled battery thermal management system according to an embodiment of the present invention;

[0032] Figure 4 This is a comparison diagram of the average temperature of the battery pack before and after optimization according to Example 2 of the present invention;

[0033] Figure 5 This is a comparison diagram of the average temperature of the battery pack before and after optimization in Example 3 of the present invention;

[0034] Among them, 1-liquid cooling plate, 2-filling material, 3-battery. DETAILED DESCRIPTION

[0035] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0036] Example 1:

[0037] like Figure 1 As shown, a phase change material coupled liquid-cooled battery thermal management system of this embodiment includes several batteries, a parallel flow channel liquid cooling plate 1, and a filling material 2; the top or bottom of the battery 3 is tightly attached to the liquid cooling plate, and is arranged one by one along the parallel flow channel direction and the vertical direction in the liquid cooling plate 1, and a filling material 2 is provided between adjacent batteries 3. The filling material is a phase change material, a flame retardant material, or a mixture of the two; the liquid cooling plate is attached to one side of the battery pack, or both sides.

[0038] The liquid cooling plate 1 includes an inlet section, an inlet manifold, several parallel flow channels, an outlet section, and an outlet manifold; the inlet section of the liquid cooling plate is connected to the inlet manifold, and the outlet section is connected to the outlet manifold; the inlet manifold and the outlet manifold are connected through parallel flow channels; the inlet section is perpendicular to the inlet manifold, the outlet section is perpendicular to the outlet manifold, and the parallel flow channels are perpendicular to the inlet manifold and the outlet manifold.

[0039] The system is operated under adiabatic condition, and the system is optimized by using the optimization design method, and the optimization process is as shown in Figure 2 The specific steps are as follows:

[0040] S1 gives the total volume V0 of the coupled system, and the physical parameters of the phase change material and the fire-retardant material, sets the material replacement temperature threshold to T b , the battery gap adjustment step is ΔL, the minimum value of the gap is L min , and the phase change rate threshold is

[0041] S2 assumes that the gap between the batteries is the same at the initial moment, and all the phase change materials are filled; the battery gap is calculated according to the total volume V0 of the system, and the gap distribution is recorded as L=[L1, L2, …, L k , …, L N , L N+1 ] along the parallel flow direction of the system, wherein N is the number of batteries, and L k is the size of the kth gap;

[0042] S3 uses a numerical simulation method to calculate the temperature field of the coupled system, obtains the monitoring temperature T k of each battery, traverses the monitoring temperature T k of each battery in the direction of the parallel flow channel of the cold plate, and when the monitoring temperature T k is lower than the material replacement temperature threshold T b , all the phase change materials on both sides of the battery are replaced by fire-retardant materials;

[0043] S4 uses a numerical simulation method to calculate the temperature field of the coupled system, obtains the battery pack temperature difference ΔT, and records the gap distribution of the battery pack at this time as the optimal distribution L opt , and the corresponding battery pack temperature difference is the optimal temperature difference ΔT opt ;

[0044] S5 finds the battery with the highest monitoring temperature, which is marked as i, if i=N, L N+1 is increased by ΔL; if i≠N, the monitoring temperatures T i-1 and T i+1 of the i-1th battery and the i+1th battery are compared, if T i-1 ≥T i+1 , the i-th gap L i is increased by ΔL, if T i-1 <T i+1 , the i+1th gap L i+1 is increased by ΔL; if the phase change rate of the selected gap adjustment region exceeds , the region is not used as an adjustment region, and the material adjustment region is continued to be searched through step S5;

[0045] S6 find the battery with the lowest monitoring temperature, mark as j, if j = 1, reduce L1 by ΔL; if j≠1, compare the monitoring temperature T of the j-1th battery with that of the j+1th battery j-1 and T j+1 , if T j-1 ≤T j+1 , reduce the jth gap L j by ΔL, if T j-1 >T j+1 , reduce the j+1th gap L j+1 by ΔL; if the selected gap adjustment region reaches the set minimum gap L min , the region is not used as an adjustment region, continue to find the material adjustment region through step S6;

[0046] S7 through steps S5 and S6, get the current battery gap distribution and the type of material filled therein, and then use the numerical simulation method to calculate the monitoring temperature of each battery and the battery pack temperature difference ΔT in the current system, if ΔT<ΔT opt , record the current gap distribution as the best distribution L opt , and record the current temperature difference as the best temperature difference ΔT opt ; return to step S5 and repeat the above process until ΔT does not decrease with the increase of the adjustment step number, at which time the gap adjustment operation is stopped, and step S8 is entered;

[0047] S8 according to the numerical simulation results of the current system, get the melting situation of the phase change material, replace the region of the phase change material that has not melted with the fire-retardant material, and the optimization design process is ended, and the current battery gap distribution and the type of material filled therein are the design results.

[0048] Example 2:

[0049] As shown in Figure 3 , the phase change material coupled liquid-cooled battery thermal management system of the embodiment includes 8×2 prismatic batteries, parallel flow channel liquid-cooled plates, phase change materials, and fire-retardant materials; the top and bottom of the battery are tightly attached to the liquid-cooled plate, and are arranged one by one along the parallel flow channel direction and the vertical direction in the liquid-cooled plate, and the phase change material, the fire-retardant material, or a mixture of the two is filled between adjacent batteries.

[0050] The battery size is 18mm×65mm×90mm, the specific heat capacity of the battery is 950J / (kg·K), the density is 2335kg / m 3 , the thermal conductivity is anisotropic, and is 1.05, 21.1, and 21.1W / (m·K) respectively;

[0051] The liquid-cooled plate material is aluminum, and the density is 2702kg / m 3The specific heat capacity is 903 J / (kg·K), the thermal conductivity is 237 W / (m·K), the length of the inlet section and the length of the outlet section are both 65 mm, the thickness of the liquid cooling plate is 2 mm, the depth of the flow channel is 0.6 mm, and the width of the flow channel is 12 mm; the cooling working medium is water, the inlet water temperature is 303.15 K, and the flow rate is 5 g / s;

[0052] The phase change material is a composite phase change material, the density is 950 kg / m 3 , the thermal conductivity is 7.654 W / (m·K), the specific heat capacity is 3000 J / (kg·K), the phase change enthalpy is 141.7 kJ / kg, and the phase change temperature interval is 315.15-317.15 K;

[0053] The flame-retardant material is aerogel, the density is 160 kg / m 3 , the thermal conductivity is 0.02 W / (m·K), and the specific heat capacity is 549 J / (kg·K).

[0054] The system is operated under adiabatic conditions, and the system is optimized by using the optimization design method.

[0055] In this example, at the initial moment, the gap is completely filled with the phase change material, and the gap distribution is L=[2, 4, 4, 4, 4, 4, 4, 4, 2]; the material replacement temperature threshold is set to 315 K, the battery gap adjustment step is 1 mm, the minimum value of the gap is 1 mm, and the phase change rate threshold is 10%; the battery monitoring temperature of this embodiment is the average temperature (T ave ) of the battery, and the temperature difference is the temperature difference between the average temperatures of the batteries, expressed as ΔT=max(T ave，i )-min(T ave，i ), wherein T ave，i is the average temperature of the i th battery, max(T ave，i ) and min(T ave ) are the maximum value and the minimum value of the average temperature of the battery, respectively.

[0056] The coupled battery thermal management system is designed by using the optimization design method, the system performance before and after optimization is evaluated by numerical simulation, and the results are shown in Figure 4 . The highest value of the average temperature of the battery, the temperature difference of the battery pack, and the weight of the gap filling material before optimization are 318.9 K, 4.9 K, and 355.7 g, respectively; the highest value of the average temperature of the battery, the temperature difference of the battery pack, and the weight of the gap filling material after optimization are 317.7 K, 2.2 K, and 272.4 g, respectively, which are reduced by 1.2 K, 55%, and 23% compared with before optimization, respectively. It can be seen that the thermal management system and the optimization design method significantly reduce the temperature and the temperature difference of the battery pack and reduce the weight of the system. The example verifies the effectiveness of the application.

[0057] Example 3:

[0058] Figure 3 A phase change material coupled liquid-cooled battery thermal management system is shown in this example. The system composition, system operating parameters, material physical parameters of this example are the same as those of Example 2, but the battery gap adjustment step size, gap minimum value and phase change rate threshold of the adjustment process are different.

[0059] In this example, at the initial moment, the gap is completely filled with phase change material, and the gap distribution L = [2, 4, 4, 4, 4, 4, 4, 4, 2]; the material replacement temperature threshold is 315K, the battery gap adjustment step size is 2mm, the minimum value of the gap is 2mm, and the phase change rate threshold is 20%; the battery monitoring temperature of this example is the average temperature of the battery (T ave ), and the temperature difference is the temperature difference between the average temperatures of the batteries, expressed as ΔT = max(T ave，i )-min(T ave，i ), where T ave，i is the average temperature of the i-th battery, and max(T ave，i ) and min(T ave，i ) are the maximum and minimum values of the average temperature of the batteries, respectively.

[0060] The battery thermal management system is designed using the optimization design method of the present application, and the system performance before and after optimization is evaluated by numerical simulation, and the results are shown in Figure 5 . The highest value of the average temperature of the battery, the temperature difference of the battery pack, and the weight of the gap filling material before optimization are 318.9K, 4.9K, and 355.7g, respectively; and the highest value of the average temperature of the battery, the temperature difference of the battery pack, and the weight of the gap filling material after optimization are 317.9K, 2.7K, and 245.6g, respectively, which are 1K, 45%, and 31% lower than before optimization, respectively. It can be seen that the thermal management system and the optimization design method of the present application significantly reduce the temperature and temperature difference of the battery pack and reduce the weight of the system. This example verifies the effectiveness of the present application.

[0061] The above describes only the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent substitutions or changes within the scope disclosed by the present application according to the technical solutions and inventive concepts of the present application, which are within the protection scope of the present application.

Claims

1. A method for optimal design of a coupled battery thermal management system, characterized in that, The coupled battery thermal management system comprises a plurality of batteries, a liquid cooling plate and a filling material; the top or bottom of each battery is tightly attached to the liquid cooling plate, and the plurality of batteries are arranged one by one along the parallel flow channel direction and the vertical direction in the liquid cooling plate, and the filling material is arranged between adjacent batteries. The optimization design method of the coupled battery thermal management system comprises the following steps: S1, set the filling material replacement temperature threshold to T given the total volume V0 of the coupling system and the physical parameters of the filling material b , the battery gap adjustment step is ΔL, and the minimum value of the gap is L min , the phase change rate threshold is φ lim ; S2. Assume that the gaps between batteries are the same at the initial moment and are all filled with phase change materials; calculate the battery gap based on the total volume V0 of the system, and the gap distribution along the parallel flow direction of the system is recorded as L = [L1, L2, ······, L k ,······,L N , L N+1 ], where N is the number of batteries, L k is the size of the kth gap; S3, using a numerical simulation method to calculate the temperature field of the coupled system, obtaining the monitoring temperature T of each battery k , traversing the monitoring temperature T of each battery in the direction of the parallel flow channel of the cold plate k , when the monitoring temperature T k is lower than the material replacement temperature threshold T b , replace the phase change material on both sides of the battery with fire-retardant material S4, using a numerical simulation method to calculate the temperature field of the coupling system, obtaining the battery pack temperature difference ΔT, recording the battery gap distribution at this time as the optimal distribution L opt , the corresponding battery pack temperature difference is the optimal temperature difference ΔT opt ; S5. Find the battery with the highest monitored temperature, mark it as i, if i=N, set L N+1 Increase ΔL; if i≠N, compare the monitored temperature T of the i-1th battery and the i+1th battery i-1 and T i+1 , if T i-1 ≥T i+1 , the i-th gap L i Increase ΔL, if T i-1 <T i+1 , the i+1th gap L i+1 Increase ΔL; if the phase change rate of the selected gap adjustment area exceeds the phase change rate threshold φ lim , then the area is not used as the adjustment area, and the search for the material adjustment area continues in step S5; S6, find the battery with the lowest monitoring temperature, mark as j, if j=1, decrease L1 by ΔL; if j≠1, compare the monitoring temperature T of the j-1th battery with that of the j+1th battery j-1 and T j+1 , if T j-1 ≤T j+1 , decrease the jth gap L j by ΔL, if T j-1 >T j+1 , decrease the j+1th gap L j+1 by ΔL; if the selected gap adjustment region reaches the set minimum gap L min , the region is not used as the adjustment region, continue to find the material adjustment region through step S6; S7, using the current cell gap distribution and the type of material filled therein obtained by step S5 and step S6, the monitoring temperature of each cell in the current system and the cell stack temperature difference AT are calculated again using the numerical simulation method, if AT < AT opt , the current gap distribution is recorded as the optimal distribution L opt , the current temperature difference is recorded as the optimal temperature difference AT opt ; return to step S5, repeat the above process until the cell stack temperature difference AT does not decrease with the increase of the adjustment step number, at which time the gap adjustment operation is stopped, and step S8 is turned to; S8, according to the numerical simulation result of the current system, the melting condition of the filling material is obtained, the optimization design process is ended, and the current battery gap distribution and the type of the filling material therein are the design results.

2. The method of claim 1, wherein, The liquid cooling plate is a parallel flow channel liquid cooling plate, comprising an inlet section, an inlet manifold, a plurality of parallel flow channels, an outlet section and an outlet manifold; the inlet section of the liquid cooling plate is connected with the inlet manifold, and the outlet section is connected with the outlet manifold; the inlet manifold and the outlet manifold are connected through the parallel flow channels.

3. The method of claim 1, wherein, The filling material is a phase change material, a fire-retardant material or a mixture of the two.

4. The method of claim 3, wherein, The density of the fire-retardant material is much lower than that of the phase change material.

5. The method of claim 1, wherein, The battery is a battery monomer or a battery pack; one side of the battery pack is attached to the liquid cooling plate, or both sides are attached to the liquid cooling plate.

6. The method of claim 5, wherein, The battery monomer is a prismatic battery or a cylindrical battery.

7. The method of claim 1, wherein, The monitoring temperature of the battery is the average temperature T of the battery ave or the maximum temperature T max .

8. The method of claim 1, wherein, The battery pack temperature difference is defined as the difference between the average temperatures of the batteries, expressed as ΔT = max(T ave,i )-min(T ave,i ), where T ave,i is the average temperature of the i-th battery, and max(T ave,i ) and min(T ave,i ) are the maximum and minimum values of the average temperatures of the batteries, respectively.

9. The method of claim 1, wherein, After stopping the gap adjustment operation, according to the numerical simulation result of the current system, the melting condition of the filling material is obtained, and the area of the non-melting phase change material is replaced by the fire-retardant material.

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