Buffer and manufacturing or selecting method thereof, all-solid-state battery, battery module and battery pack

Abstract

The invention discloses a buffer piece and a manufacturing or selecting method thereof, an all-solid-state battery, a battery module and a battery pack, and belongs to the technical field of battery production. Comprising the steps of obtaining effective expansion force of each battery SOC state battery cell, obtaining effective expansion displacement of each battery SOC state battery cell, and calculating effective stress and effective strain corresponding to each battery SOC state buffer piece according to the effective expansion force of each battery SOC state battery cell and the effective expansion displacement of each battery SOC state battery cell. And drawing a buffer piece stress-strain diagram according to the effective stress and the effective strain corresponding to each battery SOC state buffer piece, and manufacturing or selecting the buffer piece according to the buffer piece stress-strain diagram. According to the buffer piece and the manufacturing or selecting method thereof provided by the invention, the buffer piece which plays a better role in buffering the charging expansion of the solid-state battery can be selected, when the battery cell is charged and expanded, the pole piece group is expanded in a certain space, good contact between the positive pole piece and the negative pole piece is ensured, the battery performance is improved, and the maximum expansion amount of the whole battery cell can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery production, and specifically relates to a buffer component and a method for making or selecting the same, an all-solid-state battery, a battery module and a battery pack. Background Art

[0002] In recent years, the increasingly serious energy crisis and greenhouse effect have prompted the development of clean energy around the world. Lithium-ion batteries have achieved rapid development due to their excellent characteristics such as high energy density, high output voltage, long service life, good cycle performance, low self-discharge rate, no memory effect and environmental friendliness, and have been rapidly applied to many fields such as electric vehicles and electronic products. However, with the popularization of electric vehicles, battery technology is being updated and iterated faster and faster. Traditional liquid batteries no longer have advantages over solid-state batteries in terms of safety, weight, volume, etc. Solid-state batteries are the mainstream direction of development. At the China Electric Vehicle Hundred People Forum, it was pointed out that some core materials of solid-state batteries have been mass-produced, and solid-state batteries have been used in drones.

[0003] All-solid-state batteries use solid electrolytes to replace the electrolytes and separators in liquid batteries, further improving the theoretical energy density of the battery while fundamentally avoiding electrolyte leakage and reducing or even avoiding battery safety accidents such as combustion and explosion.

[0004] Chinese Patent Publication No.: CN108063278A discloses an all-solid-state lithium-ion battery and a preparation method thereof. The all-solid-state lithium-ion battery has a layered structure, in which a negative electrode sheet, an inorganic ceramic solid electrolyte layer, a sulfide solid electrolyte layer, a positive electrode sheet, a sulfide solid electrolyte layer, an inorganic ceramic solid electrolyte layer, and a negative electrode sheet are stacked in sequence.

[0005] It can be seen that the main internal structure of a solid-state battery (hereinafter referred to as a battery cell) is composed of a stack of positive electrode sheets, solid electrolyte layers and negative electrode sheets. The movement of lithium ions mainly depends on the good contact between the positive electrode sheets and the negative electrode sheets. During the charging and discharging process of a solid-state battery, the movement of lithium ions, the absorption and deintercalation of lithium ions by the positive and negative electrode sheets will cause the thickness of the electrode group to change. When the battery is charging, the thickness of the battery electrode group gradually increases; when the battery is discharging, the thickness of the battery electrode group gradually decreases. During the change in the thickness of the battery electrode group, the pressure between the electrodes will also change, which will affect the good contact between the positive electrode sheet and the negative electrode sheet. Poor contact will lead to capacity attenuation and be accompanied by certain safety risks, affecting the performance of the battery.

[0006] For liquid batteries, although the battery will expand when charging, the electrolyte of the liquid battery is liquid, and the movement of lithium ions does not rely on good contact between the positive and negative electrodes as in solid-state batteries. The expansion of the battery does not affect the movement of lithium ions.

[0007] Therefore, for solid-state batteries, how to maintain good contact between the positive and negative electrodes and buffer the expansion of the battery is an urgent problem that needs to be solved. Summary of the invention

[0008] The purpose of the present invention is to provide a buffer and its manufacturing or selection method, all-solid-state battery, battery module and battery pack to address the above shortcomings, which can make the electrode group expand in a certain space when the battery is charged and expanded, and ensure good contact between the positive and negative electrode sheets, improve battery performance, and reduce the maximum expansion of the entire battery to buffer the expansion of the battery cell. To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A method for making or selecting a buffer, wherein the buffer is suitable for being arranged between one side or both sides of a battery cell formed by a pole piece group and the gap between the inner wall of a battery housing, comprising:

[0010] S1. Obtaining the effective expansion force of the battery cell under each battery SOC state;

[0011] S2. Obtaining the effective expansion displacement of the battery cell under each battery SOC state;

[0012] S3, calculating the corresponding effective stress and effective strain of the buffer under each battery SOC state according to the effective expansion force of the battery cell under each battery SOC state and the effective expansion displacement of the battery cell under each battery SOC state;

[0013] S4, drawing a stress-strain diagram of the buffer component according to the effective stress and effective strain corresponding to the buffer component under each battery SOC state;

[0014] S5. Make or select a buffer according to the stress-strain diagram of the buffer.

[0015] Furthermore, in S1, the SOC state of the battery is changed, and the effective expansion force of the battery cell corresponding to each battery SOC state is calculated according to the expansion force on each divided area on the surface of the battery cell formed by the electrode assembly corresponding to the monitored battery SOC state.

[0016] Furthermore, in S2, by keeping the load in the thickness direction of the battery cell unchanged and changing the SOC state of the battery, the effective expansion displacement of the battery cell corresponding to each battery SOC state is calculated based on the expansion displacement of each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state.

[0017] Furthermore, in S3, the effective stress corresponding to the buffer under each battery SOC state is calculated according to the corresponding effective expansion force of the battery cell under each battery SOC state, the number of divided areas on the battery cell surface formed by the pole piece group, and the area of ​​the battery cell surface formed by the pole piece group; the effective strain corresponding to the buffer under each battery SOC state is calculated according to the corresponding effective expansion displacement of the battery cell under each battery SOC state, the set theoretical initial compression amount when the buffer is located between the battery cell surface formed by the pole piece group and the battery shell, and the set theoretical initial gap between the battery cell surface formed by the pole piece group and the battery shell.

[0018] Furthermore, when the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the electrode assembly is equal.

[0019] Furthermore, according to the expansion displacement of the corresponding area when the battery SOC state is maximum and the set target strain, the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the pole piece group when the buffer is not subjected to force is obtained; the set target strain of the buffer is calculated according to the effective expansion displacement of the battery cell when the battery SOC state is maximum, the set theoretical initial compression amount when the buffer is located between the pole piece group of the battery cell and the battery shell, and the set theoretical initial gap between the pole piece group of the battery cell and the battery shell.

[0020] A buffer is arranged between one side or both sides of the battery cell formed by the electrode group and the gap between the inner wall of the battery housing, and has the stress-strain characteristics of the buffer stress-strain diagram;

[0021] The stress-strain diagram of the buffer component is drawn based on the effective stress and effective strain corresponding to the buffer component under each battery SOC state;

[0022] The effective stress and effective strain corresponding to the buffer under each battery SOC state are calculated according to the effective expansion force of the battery cell under each battery SOC state and the effective expansion displacement of the battery cell under each battery SOC state.

[0023] Furthermore, by changing the battery SOC state, the effective expansion force of the battery cell corresponding to each battery SOC state is calculated according to the expansion force on each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state.

[0024] Furthermore, by changing the battery SOC state, the effective expansion displacement of the battery cell corresponding to each battery SOC state is calculated according to the expansion displacement of each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state.

[0025] Furthermore, the effective stress corresponding to the buffer under each battery SOC state is calculated based on the effective expansion force of the battery cell corresponding to each battery SOC state, the number of divided areas on the battery cell surface formed by the pole piece group, and the area of ​​the battery cell surface formed by the pole piece group; the effective strain corresponding to the buffer under each battery SOC state is calculated based on the effective expansion displacement of the battery cell corresponding to each battery SOC state, the theoretical initial compression amount when the buffer is set between the battery cell surface formed by the pole piece group and the battery shell, and the theoretical initial gap between the battery cell surface formed by the pole piece group and the battery shell.

[0026] Furthermore, when the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the electrode assembly is equal.

[0027] Furthermore, according to the expansion displacement of the corresponding area when the battery SOC state is maximum and the set target strain, the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the pole piece group when the buffer is not subjected to force is obtained; the set target strain of the buffer is calculated according to the effective expansion displacement of the battery cell when the battery SOC state is maximum, the set theoretical initial compression amount when the buffer is located between the pole piece group of the battery cell and the battery shell, and the set theoretical initial gap between the pole piece group of the battery cell and the battery shell.

[0028] A fully solid-state battery comprises a battery shell and a battery cell formed by a pole piece group; the battery cell is placed in the battery shell; a buffer is provided between the gap between one side or both sides of the pole piece group and the inner wall of the shell; the pole piece group comprises a composite pole piece with a solid electrolyte, or a stacked positive pole piece, a negative pole piece and a solid electrolyte membrane arranged between the positive pole piece and the negative pole piece.

[0029] Furthermore, when the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the electrode assembly is equal.

[0030] Furthermore, when the buffer is not subjected to force, a protrusion is provided in the middle of the extrusion surface of the buffer corresponding to the surface of the battery cell formed by the electrode group; the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the electrode group is constructed as follows: the thickness of the protrusion gradually decreases from the center to the surrounding areas.

[0031] Furthermore, the buffer member adopts the above-mentioned buffer member.

[0032] A battery module comprises a battery box and a plurality of the above-mentioned all-solid-state batteries.

[0033] A battery pack comprises a battery thermal management module and the above-mentioned battery module; the battery thermal management module is electrically connected to a controller.

[0034] The beneficial effects of the present invention are:

[0035] The present invention discloses a buffer component and a method for making or selecting the same, a solid-state battery, a battery module and a battery pack, including steps of obtaining the effective expansion force of each battery SOC state battery cell, obtaining the effective expansion displacement of each battery SOC state battery cell, obtaining the effective stress corresponding to each battery SOC state buffer component, obtaining the effective strain corresponding to each battery SOC state buffer component, drawing a stress-strain diagram of the buffer component, and making or selecting the buffer component. The buffer component making or selecting method and the buffer component provided by the present invention can select a buffer component that has a better buffering effect on the charging expansion of the solid-state battery, and when the battery is charged and expanded, the electrode group is expanded within a certain space, and the positive and negative electrode plates are ensured to have good contact, thereby improving the battery performance and reducing the maximum expansion of the entire battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the components of the battery cell of the present invention.

[0037] Figure 2 It is a schematic diagram of the structure in which the surface of the battery cell of the present invention is divided into m areas of equal area.

[0038] Figure 3 It is the stress-strain diagram of the buffer material of the present invention.

[0039] In the attached figure: 1-electrode assembly, 2-battery housing, 3-Mylar film, 4-cover plate, 5-buffer. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods, but the present invention is not limited to the following embodiments.

[0041] A solid-state battery is a battery that uses solid electrodes and solid electrolytes. The present invention exemplarily provides a solution for a solid-state battery, including a battery housing and a pole piece group disposed in the battery housing. Among them, the pole piece group includes a positive pole piece, a solid electrolyte layer, and a negative pole piece stacked together. Among them, the solid electrolyte layer can be an independent solid electrolyte membrane, a solid electrolyte sheet, or a layer composited on the surface of the positive pole piece and / or the negative pole piece (forming a composite positive pole piece or a composite negative pole piece).

[0042] Due to the working characteristics of the battery materials themselves, during high-power charging and discharging, the positive electrode materials (such as lithium iron phosphate, ternary materials, etc.) or the negative electrode materials (such as silicon, graphite, lithium metal) may shrink and expand. Solid electrolytes are fragile during shrinkage and expansion, which may lead to easy cracking. Due to the accumulation of lithium dendrites, the solid electrolyte layer will begin to degrade, resulting in battery short circuit and failure.

[0043] Embodiment 1:

[0044] This embodiment is described using a square aluminum shell battery as an example. It should be understood that the design concept and principle of this solution are also applicable to hard shell batteries with long blade and short blade structures.

[0045] See attached Figure 1 . The solid-state battery of the square aluminum shell is mainly composed of a battery shell 2 with an upper opening and a pole piece group 1. A cover plate 4 is provided at the upper opening of the battery shell 2. The pole piece group 1 is placed in the battery shell 2. The pole piece group 1 is composed of a plurality of positive pole pieces, solid electrolytes and negative pole pieces stacked in sequence. A layer of Mylar film 3 is wrapped around the outside of the pole piece group 1 to form a battery cell. The Mylar film 3 mainly plays an insulating role, and the Mylar film 3 has no effect on the expansion of the pole piece group. There is a certain gap between the Mylar film 3 and the battery shell 2 (that is, there is a gap between the battery cell and the battery shell). The buffer 5 described in the present invention is arranged between the Mylar film 3 and the battery shell 2, and is located in the thickness direction of the pole piece group 1. The buffer 5 can be arranged on one side of the pole piece group 1, or on both sides of the pole piece group 1. The buffer 5 is mainly used to limit the expansion of the electrode group 1 of the battery cell. The most ideal state is that the electrode group 1 expands a certain displacement, and the buffer 5 gives the electrode group 1 a reaction force to squeeze the expanded displacement back, but the buffer 5 cannot be set to be completely rigid, so that the electrode group 1 cannot expand and move during charging, which ultimately affects the performance of the battery. Therefore, the buffer 5 reaches a balanced state with the electrode group 1 in the process of limiting the expansion of the electrode group 1, and does not completely limit the expansion of the electrode group 1. It can make the electrode group 1 move within a certain expansion space and keep the positive and negative electrodes in good contact to a certain extent. The good contact mentioned here means that after the buffer is set, the average force in each area on the expansion surface of the electrode group 1 is equal, so that the positive and negative electrodes are balanced on the entire surface. It can be imagined as two pieces of paper stacked together. When the force on the paper is uneven, the local part is easy to bulge out. When the force on the paper is uniform, the deformation of the two pieces of paper is uniform, and the contact is also good at this time.

[0046] See attached Figures 2-3 The method for making or selecting a buffer comprises obtaining an effective expansion force of a battery cell at each battery SOC state, obtaining an effective expansion displacement of a battery cell at each battery SOC state, calculating an effective stress and an effective strain corresponding to a buffer cell at each battery SOC state according to the effective expansion force of a battery cell at each battery SOC state and the effective expansion displacement of a battery cell at each battery SOC state, drawing a stress-strain diagram of the buffer cell according to the effective stress and effective strain corresponding to the buffer cell at each battery SOC state, and making or selecting a buffer cell according to the stress-strain diagram of the buffer cell.

[0047] Equivalent model establishment:

[0048] In obtaining the effective expansion force of the battery cell at each battery SOC state, an expansion force tester is used in an equivalent and simplified manner to monitor the expansion force on the battery surface (at this time, no buffer is set between the electrode group and the battery shell, and a soft-pack battery with the same stacking method can also be used to test the effective expansion force of the battery cell), the battery is fixed on a test fixture, charged, and the expansion force when the battery SOC changes is monitored by a force sensor; in obtaining the effective expansion displacement of each battery SOC state, a battery expansion displacement test system is used in an equivalent and simplified manner to monitor the expansion displacement of the battery surface (at this time, no buffer is set between the electrode group and the battery shell, and a soft-pack battery with the same stacking method can also be used to test the effective expansion force of the battery cell), the battery SOC is gradually increased by charging, and a high-precision displacement sensor and acquisition system are used in conjunction with a computer and host computer software to collect the change in displacement of the battery surface when the battery SOC changes. The state of charge of the battery gradually increases from SOC1 to SOCn, 0≤SOC1<SOCn≤100%. For the convenience of testing and calculation, SOC1 can be 0, that is, the SOC is zero when the battery cell is first placed in the shell; then the SOC amount reached by charging the battery is SOCn, and SOCn can be 100%, that is, the maximum SOC amount of the battery; n can take multiple values ​​of 2, 3...n, then take SOC1, SOC2, SOC3...SOCn multiple battery SOC amounts as monitoring points, for the convenience of testing values, it is desirable that SOC1, SOC2, SOC3...SOCn are preferably increased evenly, that is, the tolerances of SOC1, SOC2, SOC3...SOCn are equal.

[0049] The expansion force and expansion displacement of different areas on the battery surface are different, such as Figure 2 As shown, the surface of the battery to be tested is divided into m areas of equal area for monitoring, and m can take 2, 3, ... m multiple values ​​to obtain the expansion forces F of m areas on the battery surface under n battery SOC conditions. j (i) and each expansion displacement X j (i), i is 1, 2, 3...n, j is 1, 2, 3...m.

[0050] For example, at SOC1, the expansion forces F1(1), F2(1)...F on the m regions of the battery surface m (1), the expansion displacement is X1(1), X2(1)...X m (1);

[0051] At SOC2, the expansion forces F1(2), F2(2)...F on the m regions of the battery surface are m (2), the expansion displacement is X1(2), X2(2)…X m (2);

[0052] And so on; in the SOCn state, each expansion force F1(n), F2(n)...F m (n), the expansion displacement is X1(n),

[0053] X2(n)……X m (n).

[0054] From the previous analysis, we can know that good contact between the pole pieces is to make the average force of each area on the expansion surface of the pole piece group equal. Here, each area refers to the m areas with equal force, so when we get the expansion force F of each area on m j (i) and each expansion displacement X j (i) After that, a root mean square mathematical model is used to make the expansion force F j (i) and expansion displacement X j (i) is equivalent to the balanced force and balanced expansion displacement of each area on the surface of the battery cell, that is, the effective expansion force and effective expansion displacement, respectively.

[0055]

[0056] Then the effective expansion forces corresponding to the multiple battery SOC states of SOC1, SOC2, ..., SOCn are

[0057]

[0058] The effective expansion displacements corresponding to multiple battery SOC states of SOC1, SOC2, ..., SOCn are:

[0059]

[0060] Choice of buffer material:

[0061] If a buffer is provided between the pole piece group and the battery casing, and the buffer reaches a state of equilibrium with the pole piece group in the process of suppressing the expansion of the pole piece group, then the effective expansion force and effective expansion displacement of the battery cell formed by the pole piece group reflected on the buffer should be the same.

[0062] The surface of the buffer is also divided into m regions of equal area, which correspond one-to-one to the regions of the cell surface formed by the electrode group in the process of establishing the equivalent model. Then the effective expansion force and effective expansion displacement of the buffer surface are also: and

[0063] Then, the effective stress of the buffer component at each battery SOC state can be obtained. and effective strain The effective stress and effective strain of the buffer here can be regarded as the average value in each area (each of the m divided areas is small enough), where A is the projected area of ​​the extrusion surface of the buffer in the thickness direction of the battery cell, and the surface of the battery cell is divided into m areas of equal area, A is the total area of ​​each m area, and A / m is the area of ​​each small area. h' is the theoretical initial gap between the pole piece group and the shell when the battery SOC state is SOC1. The theoretical initial gap is to allow the pole piece group itself to have an expansion space. X0 is the theoretical initial compression amount when the buffer is set between the pole piece group of the battery cell and the shell of the battery cell when the battery SOC state is SOC1.

[0064] It should be understood that when the battery SOC state is SOC1, the buffer can be placed in a compressed state in the shell when placed between the shell and the pole piece group, so that an initial preload force can be given to the pole piece group. This compression amount is X0, and X0 can be a comprehensive reference to the total thickness of the battery cell formed by the pole piece group, the pole piece group and the expansion force of the entire battery cell. An empirical value given in advance. Preferably, X0 is not less than 1mm. When the buffer is placed between the shell and the pole piece group, the thickness of each area of ​​the buffer is equal. The thickness of the buffer at this time is not the thickness of a real buffer, but when the above-mentioned m areas are all in a compressed state.

[0065] The effective stress and effective strain correspond one to one. Under multiple battery SOC states, such as SOC1, SOC2, ..., SOCn, the effective stress and effective strain are: i is 1, 2, 3, ..., n, and and and

[0066] After obtaining the effective stress and effective strain of the buffer corresponding to n battery SOC states, a rectangular coordinate system is drawn with effective stress as the ordinate and effective strain as the abscissa, and these effective stress values ​​and effective strain values ​​are marked in the rectangular coordinate system. Then, these corresponding points can be fitted to obtain the stress-strain curve corresponding to the buffer, such as Figure 3 shown.

[0067] Finally, according to the stress-strain curve, designers can select buffers that conform to the stress-strain curve, where the error can be set within 10%. Any buffer that conforms to the stress-strain curve with an error within 10% is acceptable. Of course, the closer the buffer is to the stress-strain curve, the more uniform the force can be during the expansion of the pole piece group.

[0068] Design of buffer:

[0069] In one embodiment, the thickness of each region of the buffer may be equal, and when the buffer is not subjected to force, the thickness of each region of the extrusion surface of the buffer is X0+h'.

[0070] However, such a buffer with equal thickness is not optimal, because the expansion bulge of the battery cell gradually decreases from the middle to the surrounding areas. In a preferred embodiment, the thickness of the buffer may gradually decrease from the middle to the surrounding areas.

[0071] When the thickness of the buffer is different, the thickness of each area of ​​the buffer extrusion surface when the buffer is not under force can be based on Find, where X j ' is the expansion displacement of each region when the battery SOC state is SOCn, s' is the set target strain, Get it here is the maximum effective expansion displacement of the electrode group. When the battery SOC state is SOCn, X' m The maximum expansion displacement of each area on the cell surface formed by the pole piece group, The maximum effective expansion displacement of each area on the cell surface formed by the electrode group. Here, the thickness of the buffer is calculated by the battery SOC state at the maximum SOCn, because when the corresponding electrode group is the largest expansion, the gap between the corresponding positive and negative electrode sheets is also the largest. When the gap between the positive and negative electrode sheets is the largest, the force on the buffer surface can be balanced, so that the positive and negative electrode sheets are in good contact. Then, the positive and negative electrode sheets can also be in good contact at other battery SOC states. At the same time, the buffer can also reduce the maximum expansion of the entire battery, buffer the expansion of the battery, and reduce the deformation of the entire battery.

[0072] Embodiment 2:

[0073] A buffer is placed between the gap between one side or both sides of a battery cell formed by a pole piece group and the inner wall of a battery shell, and has stress-strain characteristics of a buffer stress-strain diagram. The buffer stress-strain diagram is drawn according to the corresponding effective stress and effective strain of the buffer under each battery SOC state. The corresponding effective stress and effective strain of the buffer under each battery SOC state are calculated according to the effective expansion force of the battery cell under each battery SOC state and the effective expansion displacement of the battery cell under each battery SOC state.

[0074] The effective expansion force of the battery cell corresponding to each battery SOC state is calculated by gradually increasing the battery SOC state while keeping the battery cell thickness unchanged, and by the expansion force on each divided area on the battery cell surface formed by the corresponding electrode group under each monitored battery SOC state.

[0075] The effective expansion displacement of the battery cell corresponding to each battery SOC state is calculated by gradually increasing the battery SOC state by keeping the load in the thickness direction of the battery cell unchanged, and calculating the expansion displacement of each divided area on the surface of the battery cell formed by the corresponding electrode group under each battery SOC state.

[0076] The effective stress corresponding to the buffer under each battery SOC state is calculated based on the corresponding effective expansion force of the battery cell under each battery SOC state, the number of divided areas on the battery cell surface formed by the pole piece group, and the area of ​​the battery cell surface formed by the pole piece group. The effective strain corresponding to the buffer under each battery SOC state is calculated based on the corresponding effective expansion displacement of the battery cell under each battery SOC state, the set theoretical initial compression when the buffer is located between the battery cell surface formed by the pole piece group and the battery shell, and the set theoretical initial gap between the battery cell surface formed by the pole piece group and the battery shell.

[0077] When the buffer is not subjected to force, the thickness of each area of ​​the extrusion surface corresponding to the surface of the cell formed by the buffer and the electrode assembly is equal.

[0078] The thickness of each area of ​​the extrusion surface corresponding to the battery cell surface formed by the buffer and the pole piece group when the buffer is not subjected to force is obtained according to the expansion displacement of the corresponding area when the battery SOC state is maximum and the set target strain; the set target strain is calculated according to the effective expansion displacement of the battery cell when the battery SOC state is maximum, the theoretical initial compression amount when the buffer is set between the pole piece group of the battery cell and the battery shell, and the theoretical initial gap between the pole piece group of the battery cell and the battery shell.

[0079] Embodiment three:

[0080] An all-solid-state battery comprises a battery cell formed by a shell and a pole piece group, wherein the battery cell formed by the pole piece group is placed in the shell, and a buffer is provided between the gap between one side or both sides of the pole piece group and the inner wall of the shell. The pole piece group is a composite pole piece with a solid electrolyte layer or comprises a stacked positive pole piece, a negative pole piece, and a solid electrolyte membrane arranged between the positive pole piece and the negative pole piece.

[0081] The buffer can be of equal thickness, but such a buffer of equal thickness is not optimal, because the expansion bulge of the battery cell gradually decreases from the middle to the periphery. In a preferred embodiment, a bulge is provided in the middle of the side of the battery cell formed by the electrode assembly, and the thickness of the bulge gradually decreases from the center to the periphery. Such a buffer can effectively suppress the bulge in the middle of the battery cell formed by the electrode assembly.

[0082] When the thickness of each area of ​​the buffer is uneven, the buffer adopts the buffer described in Example 2. At this time, the buffer has a better buffering effect on the expansion of the battery cell formed by the electrode group. When the battery expands during charging and discharging, the positive and negative electrode sheets are ensured to have good contact, thereby improving battery performance.

[0083] Embodiment 4:

[0084] A battery module includes a battery box and the all-solid-state battery of embodiment 3. The buffer member arranged in the battery buffers the expansion of the battery core formed by the electrode group, and ensures good contact between the positive and negative electrode sheets when the battery expands during charging, thereby improving the battery performance.

[0085] Embodiment five:

[0086] A battery pack includes a battery thermal management module and a battery module of Embodiment 4; the battery thermal management module is electrically connected to a controller. If the operating temperature of the battery exceeds a reasonable temperature range, thermal runaway may occur, leading to safety problems. Therefore, electric vehicles are equipped with a power battery thermal management system to monitor the operating temperature and other conditions of the battery, and to promptly alarm and handle abnormalities.

[0087] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for making or selecting a buffer, It is characterized in that The buffer is suitable for being arranged between one side or both sides of the battery cell formed by the electrode group and the gap between the inner wall of the battery housing, and includes: S1. Obtaining the effective expansion force of the battery cell under each battery SOC state; S2. Obtaining the effective expansion displacement of the battery cell under each battery SOC state; S3, calculating the corresponding effective stress and effective strain of the buffer under each battery SOC state according to the effective expansion force of the battery cell under each battery SOC state and the effective expansion displacement of the battery cell under each battery SOC state; S4, drawing a stress-strain diagram of the buffer component according to the effective stress and effective strain corresponding to the buffer component under each battery SOC state; S5. Make or select a buffer according to the buffer stress-strain diagram.

2. A method for making or selecting a buffer according to claim 1, It is characterized in that In S1, the SOC state of the battery is changed, and the effective expansion force of the battery cell corresponding to each battery SOC state is calculated according to the expansion force on each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state.

3. A method for making or selecting a buffer according to claim 2, It is characterized in that In S2, the SOC state of the battery is changed by keeping the load in the thickness direction of the battery cell unchanged, and the effective expansion displacement of the battery cell corresponding to each battery SOC state is calculated based on the expansion displacement of each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state.

4. A method for making or selecting a buffer according to claim 3, It is characterized in that In S3, the effective stress corresponding to the buffer under each battery SOC state is calculated according to the corresponding effective expansion force of the battery cell under each battery SOC state, the number of divided areas on the battery cell surface formed by the pole piece group, and the area of ​​the battery cell surface formed by the pole piece group. The effective strain corresponding to the buffer under each battery SOC state is calculated according to the corresponding effective expansion displacement of the battery cell under each battery SOC state, the theoretical initial compression amount when the buffer is set between the battery cell surface formed by the pole piece group and the battery shell, and the theoretical initial gap between the battery cell surface formed by the pole piece group and the battery shell.

5. A method for making or selecting a buffer according to claim 4, Features: When the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the cell formed by the electrode assembly is equal.

6. A method for making or selecting a buffer according to claim 4, Features: According to the expansion displacement of the corresponding area when the battery SOC state is maximum and the set target strain, the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the pole piece group when the buffer is not under force is obtained; according to the effective expansion displacement of the battery cell when the battery SOC state is maximum, the set theoretical initial compression amount when the buffer is located between the pole piece group of the battery cell and the battery shell, and the set theoretical initial gap between the pole piece group of the battery cell and the battery shell, the set target strain of the buffer is calculated.

7. A buffer member, Features: It is arranged between one side or both sides of the battery cell formed by the electrode group and the gap between the inner wall of the battery housing, and has the stress-strain characteristics of the stress-strain diagram of the buffer; The stress-strain diagram of the buffer component is drawn based on the effective stress and effective strain corresponding to the buffer component under each battery SOC state; The effective stress and effective strain corresponding to the buffer under each battery SOC state are calculated according to the effective expansion force of the battery cell under each battery SOC state and the effective expansion displacement of the battery cell under each battery SOC state.

8. A buffer member according to claim 7, Features: By changing the battery SOC state, according to the expansion force on each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state, the effective expansion force of the battery cell corresponding to each battery SOC state is calculated.

9. A buffer member according to claim 8, Features: By changing the battery SOC state, according to the expansion displacement of each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state, the effective expansion displacement of the battery cell corresponding to each battery SOC state is calculated.

10. A buffer member according to claim 9, Features: According to the effective expansion force of the battery cell corresponding to each battery SOC state, the number of divided areas on the battery cell surface formed by the electrode assembly, and the area of ​​the battery cell surface formed by the electrode assembly, the effective stress corresponding to the buffer component under each battery SOC state is calculated; The effective strain corresponding to the buffer under each battery SOC state is calculated according to the corresponding effective expansion displacement of the battery cell under each battery SOC state, the theoretical initial compression amount when the buffer is set between the battery cell surface formed by the electrode group and the battery shell, and the theoretical initial gap between the battery cell surface formed by the electrode group and the battery shell.

11. A buffer member according to claim 10, Features: When the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the cell formed by the electrode assembly is equal.

12. A buffer member according to claim 10, Features: According to the expansion displacement of the corresponding area when the battery SOC state is maximum and the set target strain, the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the pole piece group when the buffer is not under force is obtained; the set target strain of the buffer is calculated according to the effective expansion displacement of the battery cell when the battery SOC state is maximum, the set theoretical initial compression amount when the buffer is located between the pole piece group of the battery cell and the battery shell, and the set theoretical initial gap between the pole piece group of the battery cell and the battery shell.

13. An all-solid-state battery, Features: The invention relates to a battery cell formed by a battery shell and a pole piece group; the battery cell is placed in the battery shell; a buffer is provided between the gap between one side or both sides of the pole piece group and the inner wall of the shell; the pole piece group comprises a composite pole piece with a solid electrolyte, or a stacked positive pole piece, a negative pole piece and a solid electrolyte membrane arranged between the positive pole piece and the negative pole piece.

14. The all-solid-state battery according to claim 13, Features: When the buffer is not subjected to force, the thickness between the back surface of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the cell formed by the electrode assembly is equal.

15. The all-solid-state battery according to claim 13, Features: When the buffer is not subjected to force, a protrusion is provided in the middle of the extrusion surface of the buffer corresponding to the surface of the battery cell formed by the electrode group; the thickness between the back side of the buffer corresponding to the battery and the extrusion surface corresponding to the surface of the battery cell formed by the electrode group is constructed as follows: the thickness of the protrusion gradually decreases from the center to the surrounding areas.

16. The all-solid-state battery according to claim 13, Features: The buffer member adopts the buffer member described in any one of claims 7 to 12.

17. A battery module, Features: It comprises a battery box and a plurality of all-solid-state batteries as claimed in any one of claims 13 to 16.

18. A battery pack, Features: It comprises a battery thermal management module and a battery module as claimed in claim 17; the battery thermal management module is electrically connected to a controller.

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