Buffer and its manufacturing or selection method, all-solid-state battery, battery module and battery pack

Abstract

The present invention discloses a buffer component and a method for making or selecting the same, an all-solid-state battery, a battery module, and a battery pack, belonging to the field of battery production technology. The method includes obtaining the effective expansion force of each battery cell in the SOC state, obtaining the effective expansion displacement of each battery cell in the SOC state, calculating the corresponding effective stress and effective strain of each battery SOC state buffer component based on the effective expansion force and effective expansion displacement of each battery cell in the SOC state, drawing a stress-strain diagram of the buffer component based on the corresponding effective stress and effective strain of each battery SOC state buffer component, and making or selecting the buffer component based on the stress-strain diagram of the buffer component. The buffer component provided by the present invention and the method for making or selecting the same can select a buffer component that has a better buffering effect on the charging expansion of the solid-state battery. When the battery cell is charged and expanded, the electrode group is expanded within a certain space, and good contact between the positive and negative electrode plates is ensured, thereby improving battery performance and reducing the maximum expansion of the entire battery cell.

Description

Technical Field

[0001] The present invention belongs to the field of battery production technology, and specifically relates to buffer components and methods for making or selecting same, all-solid-state batteries, battery modules and battery packs. Background Art

[0002] In recent years, the increasingly severe energy crisis and greenhouse effect have driven the global development of clean energy. Lithium-ion batteries have experienced rapid growth due to their superior properties, including high energy density, high output voltage, long service life, excellent cycle performance, low self-discharge rate, lack of memory effect, and environmental friendliness. They have been rapidly adopted in a wide range of fields, including electric vehicles and electronic products. However, with the increasing popularity of electric vehicles, battery technology is being updated at an increasingly rapid pace. Solid-state batteries are no longer competitive with traditional liquid batteries in terms of safety, weight, and volume, and are now the mainstream of development. At the China Electric Vehicle 100 Forum, it was noted that some core materials for solid-state batteries have entered mass production, and solid-state batteries are already being used in drones.

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

[0004] Chinese patent publication number: CN108063278A discloses an all-solid-state lithium-ion battery and its preparation method. 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 the solid-state battery, the movement of lithium ions and 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 address the above-mentioned deficiencies by providing a buffer component and a method for manufacturing or selecting the same, as well as an all-solid-state battery, a battery module, and a battery pack. These components can contain the electrode assembly within a defined space when the battery expands during charging, ensuring good contact between the positive and negative electrode sheets, thereby improving battery performance. Furthermore, they can reduce the maximum expansion of the entire battery, thereby buffering the expansion of the battery cell. To achieve the above-mentioned objectives, the present invention provides the following technical solutions:

[0009] A method for manufacturing or selecting a buffer member, wherein the buffer member 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 casing, comprising:

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

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

[0012] S3. Calculate the effective stress and effective strain of the buffer component at each battery SOC state based on the effective expansion force of the battery cell at each battery SOC state and the effective expansion displacement of the battery cell at each battery SOC state;

[0013] S4. Draw 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 based on 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.

[0016] Furthermore, in S2, by keeping the load in the thickness direction of the battery cell unchanged, the SOC state of the battery is changed, 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 battery cell surface 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 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 electrode group, and the area of ​​the battery cell surface formed by the electrode 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 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.

[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 cell formed by the electrode assembly is equal.

[0019] Furthermore, based on 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 electrode group when the buffer is not under force is obtained; the set target strain of the buffer is calculated based on 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 electrode group of the battery cell and the battery shell, and the set theoretical initial gap between the electrode group of the battery cell and the battery shell.

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

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

[0022] The effective stress and effective strain corresponding to the buffer component under each battery SOC state are calculated based on 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 battery cell surface 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 based on the expansion displacement of each divided area on the battery cell surface formed by the electrode group corresponding to the monitored battery SOC state.

[0025] Furthermore, the effective stress corresponding to the buffer component 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 electrode group, and the area of ​​the battery cell surface formed by the electrode group; the effective strain corresponding to the buffer component 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 component 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.

[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 cell formed by the electrode assembly is equal.

[0027] Furthermore, based on 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 electrode group is obtained when the buffer is not under force; the set target strain of the buffer is calculated based on 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 electrode group of the battery cell and the battery shell, and the set theoretical initial gap between the electrode group of the battery cell and the battery shell.

[0028] An all-solid-state battery comprises a battery cell formed by a battery casing and a pole piece group; the battery cell is placed in the battery casing; a buffer is provided between one or both sides of the pole piece group and the inner wall of the casing; 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 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, an all-solid-state battery, a battery module, and a battery pack, including the steps of obtaining the effective expansion force of a battery cell at each SOC state, obtaining the effective expansion displacement of a battery cell at each SOC state, obtaining the effective stress corresponding to the buffer component at each SOC state, obtaining the effective strain corresponding to the buffer component at each SOC state, 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 better buffers the expansion of a solid-state battery during charging. When the battery expands during charging, the electrode group expands within a certain space, ensuring good contact between the positive and negative electrode plates, improving 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 various parts of the battery cell of the present invention.

[0037] Figure 2 It is a structural schematic diagram of the present invention in which the surface of the battery cell 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 accompanying drawings: 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 with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0041] A solid-state battery is a battery that uses solid-state electrodes and solid-state electrolytes. The present invention exemplarily provides a solid-state battery solution, including a battery housing and a pole piece assembly disposed within the battery housing. The pole piece assembly includes a positive pole piece, a solid electrolyte layer, and a negative pole piece stacked together. 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 inherent working characteristics of battery materials, during high-power charging and discharging, both positive electrode materials (such as lithium iron phosphate and ternary materials) or negative electrode materials (such as silicon, graphite, and lithium metal) may shrink and expand. Solid electrolytes are fragile during this shrinkage and expansion process and may easily crack. Due to the accumulation of lithium dendrites, the solid electrolyte layer will begin to degrade, leading to battery short circuits and failure.

[0043] Example 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 core. The Mylar film 3 mainly plays an insulating role. 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 core 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 ideal state is that the electrode group 1 expands to a certain displacement, and the buffer 5 gives the electrode group 1 a reaction force to squeeze the expanded displacement back. However, the buffer 5 cannot be set to be completely rigid. In this way, 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 allow the electrode group 1 to move within a certain expansion space and allow the positive and negative electrodes to maintain a certain degree of good contact. 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 prone to bulging. 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 manufacturing or selecting a buffer component includes 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 component at each battery SOC state based on the effective expansion force and the effective expansion displacement of the battery cell at each battery SOC state, drawing a stress-strain diagram of the buffer component based on the effective stress and effective strain corresponding to the buffer component at each battery SOC state, and manufacturing or selecting a buffer component based on the stress-strain diagram of the buffer component.

[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 the effective expansion force of the battery cell can also be tested using a soft-pack battery with the same stacking method), the battery SOC is gradually increased through charging, and a high-precision displacement sensor, an acquisition system, a computer, and host software are used 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 reached by charging the battery is SOCn, and SOCn can be 100%, that is, the maximum SOC of the battery; n can take multiple values ​​of 2, 3...n, and then multiple battery SOC values ​​of SOC1, SOC2, SOC3...SOCn are taken as monitoring points. For the convenience of testing numerical values, the desirable 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. m can take multiple values ​​of 2, 3...m to obtain the expansion forces F on the m areas of 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, in the SOC1 state, the expansion forces F1(1), F2(1)...F on the m areas 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 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 on each m area, 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 SOC1, SOC2, ..., SOCn are:

[0059]

[0060] Choice of buffer material:

[0061] If a buffer is provided between the electrode group and the battery casing, and the buffer reaches a state of equilibrium with the electrode group while suppressing the expansion of the electrode group, then the effective expansion force and effective expansion displacement of the battery cell formed by the electrode 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 equivalent model establishment process. Then the effective expansion force and effective expansion displacement of the buffer surface are also: and

[0063] Then the effective stress on 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 of each area (each of the m divided areas is small enough), where A is the projected area of ​​the buffer extrusion surface in the thickness direction of the battery cell. The battery cell surface 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 electrode group and the shell when the battery SOC state is SOC1. The theoretical initial gap is to allow the electrode group itself to have an expansion space. X0 is the theoretical initial compression amount when the buffer is set between the electrode group of the battery cell and the shell 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 between the shell and the electrode group. This can give the electrode group an initial preload force. The amount of compression is X0, and X0 can be a pre-given empirical value based on the total thickness of the battery cell formed by the electrode group, the electrode group, and the expansion force of the entire battery cell. Preferably, X0 is not less than 1mm. When the buffer is placed between the shell and the electrode group, the thickness of each area of ​​the buffer is equal. The thickness of the buffer at this time is not the actual thickness of the buffer, but the thickness of the m areas mentioned above when they are all in a compressed state.

[0065] The effective stress and effective strain are one-to-one corresponding. 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. These effective stress values ​​and effective strain values ​​are marked in the rectangular coordinate system. Then, these corresponding points can be fitted with data to obtain the stress-strain curve corresponding to the buffer, as shown in the following example: 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 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] Buffer design:

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

[0070] However, this buffer with constant thickness is not optimal, because the expansion bulge of the battery cell gradually decreases from the middle to the periphery. In a preferred embodiment, the thickness of the buffer can be gradually reduced from the middle to the periphery.

[0071] When the thickness of the buffer is different, the thickness of each area of ​​the buffer extrusion surface can be calculated according to Find, where X j ' is the expansion displacement of each region when the battery SOC state is SOCn, s' is the set target strain, and is given by 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 surface of the cell formed by the electrode group, This is the maximum effective expansion displacement of each area on the cell surface formed by the electrode assembly. The buffer thickness is calculated here based on the battery's maximum SOC (SOCn). This is because when the electrode assembly expands the most, the gap between the positive and negative electrodes is also the largest. When the gap between the positive and negative electrodes is largest, the force on the buffer surface is balanced, ensuring good contact between the positive and negative electrodes. This ensures good contact between the positive and negative electrodes at other battery SOC states. At the same time, the buffer can also reduce the maximum expansion of the entire battery, buffering the battery's expansion and reducing overall deformation.

[0072] Example 2:

[0073] A buffer component is placed between the gap between one or both sides of a battery cell formed by a pole piece group and the inner wall of a battery casing, and has stress-strain characteristics of a buffer component stress-strain diagram. The buffer component stress-strain diagram 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 component under each battery SOC state are calculated based on the effective expansion force and 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 calculating the expansion force on each divided area on the battery cell surface formed by the electrode group corresponding to 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 while keeping the load in the thickness direction of the battery cell unchanged, and calculating the expansion displacement of each divided area on the battery cell surface formed by the electrode group corresponding to each battery SOC state.

[0076] The effective stress corresponding to the buffer part under each battery SOC state is calculated based on the 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 electrode group, and the area of ​​the battery cell surface formed by the electrode group. The effective strain corresponding to the buffer part under each battery SOC state is calculated based on the effective expansion displacement of the battery cell under each battery SOC state, the theoretical initial compression amount when the buffer part 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.

[0077] When the buffer component is not subjected to force, the thickness of each region of the extrusion surface corresponding to the surface of the battery cell formed by the buffer component 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 electrode group when the buffer is not subjected to force is obtained based on 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 based on 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 electrode group of the battery cell and the battery shell, and the theoretical initial gap between the electrode group of the battery cell and the battery shell.

[0079] Example 3:

[0080] An all-solid-state battery comprises a cell formed by a housing and a pole piece assembly. The housing houses the cell, and a buffer is provided between one or both sides of the pole piece assembly and the inner wall of the housing. The pole piece assembly 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 disposed between the positive and negative pole pieces.

[0081] The buffer can be of uniform thickness, but this is not optimal because the expansion bulge of the battery cell gradually decreases from the center to the periphery. In a preferred embodiment, the buffer is provided with a bulge in the middle of the side of the battery cell facing the electrode assembly, and the thickness of the bulge gradually decreases from the center to the periphery. This arrangement of the 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] Example 4:

[0084] A battery module includes a battery box and the all-solid-state battery of Example 3. The buffer provided in the battery buffers the expansion of the battery cell formed by the electrode assembly, ensuring good contact between the positive and negative electrode sheets when the battery expands during charging, thereby improving battery performance.

[0085] Embodiment 5:

[0086] A battery pack includes a battery thermal management module and the battery module of Example 4; the battery thermal management module is electrically connected to a controller. If the battery's operating temperature exceeds a reasonable range, thermal runaway may occur, leading to safety issues. Therefore, electric vehicles are equipped with power battery thermal management systems to monitor the battery's operating temperature and other conditions, and promptly issue alarms and address any 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 description 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, characterized in that: The buffer member 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. Obtain the effective expansion displacement of the battery cell under each battery SOC state; S3. Calculate the effective stress and effective strain of the buffer component at each battery SOC state based on the effective expansion force of the battery cell at each battery SOC state and the effective expansion displacement of the battery cell at each battery SOC state; S4. Draw 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 stress-strain diagram of the buffer; 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 based on the expansion force of each divided area on the surface of the battery cell formed by the electrode group corresponding to the monitored battery SOC state; 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; In S3, 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 electrode group, and the area of ​​the battery cell surface formed by the electrode 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 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.

2. A method for making or selecting a buffer according to claim 1, characterized in that: 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.

3. A method for manufacturing or selecting a buffer according to claim 1, characterized in that: 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 electrode 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 theoretical initial compression amount when the buffer is set between the electrode group of the battery cell and the battery shell, and the theoretical initial gap between the electrode group of the battery cell and the battery shell, the set target strain of the buffer is calculated.

4. A buffer component, comprising the method for manufacturing or selecting a buffer component according to any one of claims 1 to 3, characterized in that: 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 shell, and has the stress-strain characteristics of the stress-strain diagram of the buffer part; The stress-strain diagram of the buffer component is drawn based on the effective stress and effective strain of the buffer component at each battery SOC state; The effective stress and effective strain corresponding to the buffer component under each battery SOC state are calculated based on 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.

5. A buffer according to claim 4, characterized in that: By changing the battery SOC state, according to the expansion force on each divided area on the battery cell surface 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.

6. The buffer according to claim 5, characterized in that: 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 battery cell surface formed by the electrode group corresponding to the monitored battery SOC state.

7. The buffer according to claim 6, characterized in that: Calculate the effective stress of the buffer component at each battery SOC state based on the effective expansion force of the battery cell corresponding to each battery SOC state, the number of areas divided 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 strain corresponding to the buffer component under each battery SOC state is calculated based on the corresponding effective expansion displacement of the battery cell under each battery SOC state, the theoretical initial compression amount when the buffer component is located 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.

8. The buffer according to claim 7, characterized in that: 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.

9. The buffer according to claim 7, characterized in that: 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 electrode group is obtained when the buffer is not under force; 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 theoretical initial compression amount when the set buffer is located between the electrode group of the battery cell and the battery shell, and the theoretical initial gap between the electrode group of the battery cell and the battery shell.

10. An all-solid-state battery, characterized in that: A battery cell comprising a battery shell and a pole piece group; the battery cell is placed in the battery shell; a buffer member according to any one of claims 5 to 9 is provided 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.

11. The all-solid-state battery according to claim 10, characterized in that: 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. The all-solid-state battery according to claim 10, characterized in that: 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 area.

13. A battery module, characterized in that: It comprises a battery box and several all-solid-state batteries as claimed in claim 11 or 12.

14. A battery pack, characterized in that: It comprises a battery thermal management module and the battery module as claimed in claim 13; the battery thermal management module is electrically connected to a controller.

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