Battery monomer, battery pack and vehicle

Abstract

The embodiment of the invention relates to the technical field of vehicles, and discloses a single battery, a battery pack and a vehicle, the single battery comprises a battery shell provided with an accommodating cavity and a battery cell accommodated in the accommodating cavity, and a telescopic part is arranged on the battery shell, so that the battery shell can be telescopically deformed along a first direction along with the change of internal pressure of the accommodating cavity; the ratio of the total expansion amount of the battery cell in the first direction to the maximum telescopic displacement of the battery shell in the first direction is greater than or equal to 0.9 and less than or equal to 20. By applying the technical scheme provided by the invention, the problem that the telescopic part of the battery shell in the prior art is easy to be over-designed or under-designed can be solved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a battery cell, a battery pack, and a vehicle. Background Technology

[0002] During the charging and use of a battery cell, the cell thickness may increase, leading to increased internal expansion forces. This increased expansion force generates internal stress in the cell material, accelerating aging and affecting the cell's lifespan and reliability. To mitigate this issue, existing technologies incorporate telescopic sections on the battery casing. These sections expand and contract with the cell's growth, improving the cell's lifespan and reliability. However, improper design of these telescopic sections can result in over- or under-design. Over-designed sections increase the cell's volume, while under-designed sections fail to adequately release the expansion forces. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this application is to provide a battery cell, a battery pack and a vehicle, which aims to solve the problem that the telescopic part of the battery casing is prone to over-design or under-design in the prior art.

[0004] In a first aspect, embodiments of this application provide a battery cell, including a battery housing with a receiving cavity and a battery cell housed in the receiving cavity. The battery housing is provided with a telescopic part so that the battery housing can expand and contract along a first direction in response to changes in the internal pressure of the receiving cavity. The ratio of the total expansion of the battery cell in the first direction to the maximum expandable displacement of the battery housing in the first direction is greater than or equal to 0.9 and less than or equal to 20.

[0005] By adopting the above technical solution, by setting a telescopic part on the battery casing, the battery casing can deform in response to changes in the gas pressure inside the battery cell, thereby changing the actual volume of the accommodating cavity, releasing the internal pressure of the battery cell, maintaining pressure stability during the cell expansion process, and helping to improve the life and reliability of the battery cell.

[0006] By matching the total expansion of the battery cell with the maximum expandable displacement of the battery casing, it is possible to effectively prevent over-design or under-design of the battery casing's expansion and contraction parts. This can prevent the volume of the battery cell from increasing due to over-design or the expansion force from being insufficiently released due to under-design.

[0007] In some embodiments, the ratio of the total expansion of the battery cell in the first direction to the maximum expandable displacement of the battery casing in the first direction is greater than or equal to 1 and less than or equal to 1.1. A range greater than or equal to 1 and less than or equal to 1.1 is a preferred range for this ratio. Within this preferred range, the matching effect between the battery cell's cycle performance and the expandable portion is optimal, which can significantly release the expansion force during battery cell cycling, extend the number of battery cell cycles, and improve the cycle performance of the battery cell.

[0008] In some embodiments, the ratio of the dimension of the battery cell in the first direction to the dimension of the battery casing excluding the telescopic portion in the first direction is greater than or equal to 0.97. By employing the above technical solution, matching the size of the battery cell with the size of the rigid region of the battery casing, the energy density of the individual battery cells can be better guaranteed.

[0009] In some embodiments, the battery casing has telescopic portions at both ends in the first direction. By employing the above technical solution, having telescopic portions on both sides of the battery cell results in more uniform force distribution on the cell and better cell cycle performance.

[0010] In some embodiments, when the elongation of the battery casing in the first direction is half of the maximum expandable displacement, the internal pressure of the battery cell is greater than or equal to 0.5 MPa. By employing the above technical solution, the elastic deformation characteristics of the telescopic part can satisfy both the rigidity requirements of the battery casing and the requirement for the telescopic part to deform appropriately in response to changes in the internal gas pressure of the battery cell.

[0011] In some embodiments, the thickness direction of the battery cell is aligned with the first direction. The expansion of the battery cell is most pronounced in the thickness direction; aligning the thickness direction with the first direction ensures that the deformation of the expansion portion can effectively compensate for the expansion of the battery cell.

[0012] In some embodiments, the battery casing includes a casing body with an opening at one end and a top cover connected to the opening, the casing body and the top cover forming the receiving cavity, and the telescopic portion includes a first sub-telescopic portion disposed on the casing body and a second sub-telescopic portion disposed on the top cover. The above-described technical solution is easy to implement.

[0013] In some embodiments, the telescopic portion includes one or more of a corrugated telescopic structure, a laminated telescopic structure, and an elastic membrane. The above-described technical solution is easy to implement.

[0014] Secondly, embodiments of this application provide a battery pack comprising any of the battery cells described above.

[0015] Thirdly, embodiments of this application provide a vehicle including any of the battery cells described above. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the background art, the accompanying drawings used in the embodiments of this application will be described below.

[0017] Figure 1 This is a schematic diagram of the vehicle structure disclosed in the embodiments of this application;

[0018] Figure 2 This is a schematic diagram of the battery pack structure disclosed in the embodiments of this application;

[0019] Figure 3 This is a schematic diagram of the structure of a single battery cell disclosed in an embodiment of this application;

[0020] Figure 4 This is a schematic diagram of the structure of the shell body disclosed in the embodiments of this application;

[0021] Figure 5 This is a schematic diagram of the top cover structure disclosed in an embodiment of this application;

[0022] Figure 6 This is a schematic diagram of the design scheme of a battery cell disclosed in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1-Vehicle; 2-Battery pack; 3-Controller; 4-Electric drive system;

[0025] 21-Battery cell; 22-Battery pack housing; 23-Battery pack housing cover;

[0026] 211-Housing body; 212-Battery cell; 213-Top cover; 214-Terminal post;

[0027] 2111-Cavity; 2112-First sidewall; 2113-Second sidewall; 2114-Third sidewall; 2115-Fourth sidewall; 2116-First sub-telescopic part;

[0028] 2131 - Second Sub-telescopic Section. Detailed Implementation

[0029] The terms "first," "second," etc., are used for descriptive purposes only and have no sequential or technical meaning, nor should they be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Directional terms used in this application, such as "x-direction," "y-direction," "z-direction," etc., are merely for reference to the orientation shown in the accompanying drawings. The use of directional terms is for better and clearer explanation and understanding of this application, and not for indicating the orientation of the referred device or component in a practical application scenario.

[0030] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the two parts can rotate relative to each other after connection. "Sliding connection" refers to a connection where the two parts can slide relative to each other after connection.

[0031] The embodiments of this application are described below with reference to the accompanying drawings.

[0032] The subject matter of this application is the battery cell 21, the battery pack 2, and the vehicle 1. The battery cell 21 is the inventive point of this application.

[0033] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of vehicle 1 disclosed in an embodiment of this application. Vehicle 1 can be, but is not limited to, a pure electric vehicle (PEV / BEV), a hybrid electric vehicle (HEV), a range-extended electric vehicle (REEV), a plug-in hybrid electric vehicle (PHEV), or a new energy vehicle.

[0034] In this embodiment, vehicle 1 includes a body, a battery pack 2, a controller 3, and an electric drive system 4. The battery pack 2 is fixedly mounted on the bottom of the body, and the electric drive system 4 is located at the front-wheel drive and / or rear-wheel drive position of the body, and is fixedly connected to the body. The battery pack 2 is electrically connected to the electric drive system 4 and supplies power to the electric drive system 4. The controller 3 controls the operation of the electric drive system 4. After receiving power, the electric drive system 4 converts electrical energy into mechanical energy to drive vehicle 1 to move.

[0035] Please see Figure 2, Figure 2 This is a schematic diagram of the battery pack 2 disclosed in an embodiment of this application. The battery pack 2 includes a battery pack housing, a thermal management component, and multiple battery cells 21. The battery pack housing encloses an accommodating space, and the thermal management component is disposed within the accommodating space and fixedly connected to the bottom plate of the battery pack housing. The multiple battery cells 21 are arranged in multiple rows and columns, and the multiple battery cells 21 are disposed on the surface of the thermal management component facing away from the bottom plate. The battery cells 21 generate heat during charging and discharging, and the thermal management component is used to dissipate heat from the battery cells 21. The battery pack housing typically includes a battery pack box 22 with an opening on the upper side and a battery pack box cover 23 installed on the upper side of the battery pack box 22, the battery pack box cover 23 closing the opening of the battery pack box 22.

[0036] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of a battery cell 21 disclosed in some embodiments of this application. The battery cell 21 includes a battery casing with a receiving cavity and a cell 212 housed in the receiving cavity. The battery casing is provided with a telescopic part so that the battery casing can expand and contract along a first direction as the internal pressure of the receiving cavity changes. The ratio of the total expansion of the cell 212 in the first direction to the maximum expandable displacement of the battery casing in the first direction is greater than or equal to 0.9 and less than or equal to 20.

[0037] By adopting the above technical solution, by setting a telescopic part on the battery casing, the battery casing can deform in response to changes in the gas pressure inside the battery cell 21, thereby changing the actual volume of the accommodating cavity, releasing the internal pressure of the battery cell 21, and maintaining the pressure stability during the expansion process of the cell 212, which helps to improve the life and reliability of the battery cell 21.

[0038] By matching the total expansion of the battery cell 212 with the maximum expandable displacement of the battery casing, it is possible to effectively prevent over-design or under-design of the battery casing expansion section. This can prevent the volume of the battery cell 21 from increasing due to over-design or the expansion force from being insufficiently released due to under-design.

[0039] In practice, the cavity typically contains a battery cell 212 and an electrolyte. The battery cell 212 can be composed of multiple cores, and the thickness direction of the battery cell 212 is consistent with the thickness direction of the battery cell 21.

[0040] Please see Figure 6 , Figure 6This is a schematic diagram of the design scheme of the battery cell 21 disclosed in some embodiments of this application. In this application, the total expansion of the cell 212 in the first direction is defined as follows: In the early stage of the cell 212's lifespan or in a brand-new state, when the cell 212 is fully charged, the thickness of the cell 212 in the first direction is N; in the late stage of the cell 212's lifespan or at the end of its lifespan, when the cell 212 is fully charged, the rebound thickness increase rate of the cell 212 is k; the total expansion of the cell 212 in the first direction is N*k. Typically, 0.05 ≤ k ≤ 0.2.

[0041] The maximum expandable displacement of the battery casing in the first direction is defined as follows: In the initial state where the battery casing is not deformed, the telescopic parts are in an unstretched initial state, and the sum of the lengths of all telescopic parts on the battery casing in the first direction is the initial length. When the internal pressure of the battery cell 21 rises to a preset pressure relief threshold or safety limit, the sum of the lengths of all telescopic parts on the battery casing in the first direction is the maximum length, and the maximum expandable displacement of the battery casing in the first direction is the difference between the maximum length and the initial length. Obviously, when there is one telescopic part on the battery casing, all the telescopic parts on the battery casing are that one telescopic part; when there are multiple telescopic parts on the battery casing, all the telescopic parts on the battery casing are those multiple telescopic parts.

[0042] In specific implementation, the battery cell 21 can be a lithium-ion secondary battery, a lithium-ion primary battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery, or a magnesium-ion battery.

[0043] In some embodiments, the ratio of the total expansion of the cell 212 in the first direction to the maximum expandable displacement of the battery casing in the first direction is greater than or equal to 1 and less than or equal to 1.1. A range greater than or equal to 1 and less than or equal to 1.1 is a preferred range for this ratio. Within this preferred range, the cycle performance of the cell 212 and the matching effect of the expandable portion are optimal, effectively releasing the expansion force of the battery cell 21 during cycling, extending the number of cycles of the battery cell 21, and improving the cycle performance of the battery cell 21.

[0044] In some embodiments, the ratio of the dimension of the cell 212 in the first direction to the dimension of the battery casing excluding the telescopic portion in the first direction is greater than or equal to 0.97 and less than or equal to 1. By adopting the above technical solution, by matching the dimension of the cell 212 with the dimension of the rigid portion of the battery casing, the energy density of the battery cell 21 can be better guaranteed.

[0045] Please see Figure 6 The area of ​​the battery casing excluding the telescopic part is the rigid part of the battery casing. The length of the rigid part of the battery casing in the first direction is L, and the thickness of the battery cell 212 in the first direction is N, 0.97≤N / L≤1.

[0046] In practical implementation, the dimension of cell 212 in the first direction is usually the thickness of cell 212.

[0047] Please see Figure 3 and Figure 6 In some embodiments, the battery casing has telescopic portions at both ends in the first direction. By employing the above technical solution, telescopic portions are provided on both sides of the cell 212, resulting in more uniform force distribution on the cell 212 and better cycle performance.

[0048] In some embodiments, when the elongation of the battery casing in the first direction is half of the maximum expandable displacement, the internal pressure of the battery cell 21 is greater than or equal to 0.5 MPa. By employing the above technical solution and rationally setting the elastic deformation characteristics of the telescopic portion, the telescopic portion can meet both the rigidity requirements of the battery casing and the requirement for appropriate deformation in response to changes in the internal gas pressure of the battery cell 21. This also helps to reduce the possibility of over- or under-design in the battery casing telescopic portion.

[0049] In some embodiments, the thickness direction of the battery cell 212 is aligned with the first direction. Using the above technical solution, the expansion of the battery cell 212 is most prominent in the thickness direction. By aligning the thickness direction of the battery cell 212 with the first direction, it is ensured that the deformation of the expansion portion can effectively compensate for the expansion of the battery cell 212.

[0050] In some embodiments, the battery casing includes a casing body 211 with an opening at one end and a top cover 213 connected to the opening. The casing body 211 and the top cover 213 form a receiving cavity. The telescopic portion includes a first sub-telescopic portion 2116 disposed on the casing body 211 and a second sub-telescopic portion 2131 disposed on the top cover 213. Using the above technical solution, the battery casing is assembled from the casing body 211 and the top cover 213, which is easy to manufacture and implement.

[0051] Please see Figure 4 , Figure 4This is a schematic diagram of the structure of the housing body 211 disclosed in an embodiment of this application. As a specific example, the housing body 211 is surrounded by a bottom wall, a first side wall 2112, a second side wall 2113, a third side wall 2114, and a fourth side wall 2115. The third side wall 2114 and the fourth side wall 2115 are arranged opposite to each other in a first direction. The first side wall 2112 and the second side wall 2113 are arranged opposite to each other in a second direction perpendicular to the first direction. The bottoms of the first side wall 2112, the second side wall 2113, the third side wall 2114, and the fourth side wall 2115 are respectively connected to the bottom wall. The bottom wall, the first side wall 2112, the second side wall 2113, the third side wall 2114, and the fourth side wall 2115 define a cavity 2111. A first sub-telescopic portion 2116 is provided on the side of the first sidewall 2112, the second sidewall 2113, and the bottom wall adjacent to the third sidewall 2114; a first sub-telescopic portion 2116 is also provided on the side of the first sidewall 2112, the second sidewall 2113, and the bottom wall adjacent to the fourth sidewall 2115. The portion of the housing body 211 excluding the two first sub-telescopic portions 2116 constitutes the first rigid portion. The first rigid portion of the housing body and the first sub-telescopic portions 2116 can be sealed together by laser welding or integral molding. The tops of the first sidewall 2112, the second sidewall 2113, the third sidewall 2114, and the fourth sidewall 2115 form an opening in the housing body 211, and the opening is positioned opposite the bottom wall in a third-order direction.

[0052] As a specific example, the first direction is the x-axis, the second direction is the y-axis, and the third direction is the z-axis.

[0053] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of the top cover 213 disclosed in the embodiment of this application. The top cover 213 is provided with a second sub-telescopic part 2131 at both ends in the first direction. The part of the top cover 213 other than the two second sub-telescopic parts 2131 is a second rigid part. The second rigid part and the second sub-telescopic parts 2131 can be sealed together by laser welding or integral molding.

[0054] In practice, the pole post 214 is extended from the second rigid part of the top cover 213.

[0055] In practical implementation, the top cover 213 and the housing body 211 can be connected by an elastic connector. The first rigid part of the housing body 211 and the second rigid part of the top cover 213 constitute the rigid part of the battery housing. As the battery cell is used, the telescopic part gradually extends as gas is generated inside the battery cell 21, which not only ensures the safety of the battery cell 21, but also facilitates the release of the internal expansion force of the battery cell 21, thus helping to improve the life of the battery cell 21.

[0056] In some embodiments, the telescopic part includes a corrugated telescopic structure. Using the above-described technical solution, the corrugated telescopic structure has good telescopicity and pressure resistance, and is easy to implement.

[0057] In some embodiments, the telescopic portion includes a laminated telescopic structure. Using the above-described technical solution, the laminated structure can provide deformation through interlayer displacement, and is easy to implement.

[0058] In some embodiments, the telescopic portion includes an elastic membrane. Using the above-described technical solution, the elastic membrane can provide uniform deformation over a large area and is easy to implement.

[0059] In practical implementation, the expansion joint can be made of metal or polymer materials, such as stainless steel or silicone rubber. For example, a corrugated expansion structure can be made of metal, or an elastic membrane can be made of polymer materials.

[0060] To more clearly demonstrate the performance advantages of the proposed battery cell 21, the following comparative analysis and explanation will be conducted using a total of twenty-seven test cases.

[0061] The battery cell for Test 1 can be prepared according to the following steps:

[0062] Lithium iron phosphate (LiFePO4), carbon black conductive agent, and polyvinylidene fluoride (PVDF) binder were mixed at a mass ratio of 96.8:1.2:2. N-methylpyrrolidone solvent was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated onto aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the positive electrode sheets were obtained.

[0063] The negative electrode active material graphite or a mixture of graphite and other active materials in different mass ratios, carbon black conductive agent, sodium carboxymethyl cellulose thickener, and styrene-butadiene rubber binder are mixed in a mass ratio of 96.1:0.8:1.3:1.8. Deionized water is added as a solvent, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on copper foil, dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the negative electrode sheet is obtained.

[0064] Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0065] Using a separator with a 7μm base film + 3μm coating + 3μm coating, the positive electrode, separator, and negative electrode are stacked together and wound into multiple turns. After winding, they are flattened to prepare a core. Two cores are installed into the housing body, and then the top cover and housing body are welded together. After processes such as liquid injection, settling, formation, and shaping, a single battery cell is obtained.

[0066] A single battery cell was prepared according to the above preparation steps and charged at a rate of 0.33C until fully charged. After full charging, the battery cell was disassembled, and the cell's dimensions in the thickness direction under full charge were measured using calipers. After dimensional measurement, the cell was further disassembled, and the interface state of the negative electrode was observed. After measurement and calculation, the cell's thickness dimension N was found to be 49.5 mm, the cell's rebound thickness increase rate k was 0.05, and the maximum extendable displacement M of the telescopic part was designed to be 5.5 mm.

[0067] Repeat the above preparation steps to install the battery cell into the casing body, then weld the top cover and casing body, and go through processes such as liquid injection, settling, formation, and shaping to obtain the battery cell.

[0068] The interface testing and cycle performance testing process is as follows: The battery cell is fixed to a fixture, which clamps the large surface of the cell from both sides, applying a clamping force of 3000N. The fixture is equipped with a pressure sensor to detect the pressure F between the large surface of the cell and the fixture in real time. Under normal temperature conditions, the battery cell is charged and discharged at a 1C rate for a full charge-discharge cycle test until the cell's capacity decays to 70% of its initial capacity. During the cycle, the state of the battery cell is monitored in real time. When the cell's capacity decays to 70% of its initial capacity, the number of cycles is recorded, and the increase in the cell's expansion force, ΔF, is calculated: ΔF = F - 3000N. Simultaneously, the tested cell is reverse-engineered to confirm the cell's thickness and interface state at the end of its lifespan or when fully charged.

[0069] Test Example 2: The preparation and testing methods of the battery cell in Test Example 2 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 2.75 mm.

[0070] Test Example 3: The preparation and testing methods of the battery cell in Test Example 3 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 2.48 mm.

[0071] Test Example 4: The preparation and testing methods of the battery cell in Test Example 4 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 2.25 mm.

[0072] Test Example 5: The preparation and testing methods of the battery cell in Test Example 5 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 1.65 mm.

[0073] Test Example 6: The preparation and testing methods of the battery cell in Test Example 6 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 1.24 mm.

[0074] Test Example 7: The preparation and testing methods of the battery cell in Test Example 7 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 0.25 mm.

[0075] Test Example 8: The preparation and testing methods of the battery cell in Test Example 8 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 0.12 mm.

[0076] Test Example 9: The preparation and testing methods of the battery cell in Test Example 9 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 22mm.

[0077] Test Example 10: The preparation and testing methods of the battery cells in Test Example 10 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 11mm.

[0078] Test Example 11: The preparation and testing methods of the battery cell in Test Example 11 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 9.9 mm.

[0079] Test Example Twelve: The preparation and testing methods of the battery cells in Test Example Twelve are the same as those in Test Example One. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 9mm.

[0080] Test Example 13: The preparation and testing methods of the battery cell in Example 13 are the same as those in Test Example 1, except that the negative electrode formulation was adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 6.6 mm.

[0081] Test Example 14: The preparation and testing methods of the battery cell in Test Example 14 are the same as in Example 1, except that the negative electrode formulation was adjusted, k is 0.2, and the maximum expandable displacement M of the telescopic part is 4.95 mm.

[0082] Test Example 15: The preparation and testing methods of the battery cell in Test Example 15 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum expandable displacement M of the telescopic part is 0.99mm.

[0083] Test Example 16: The preparation and testing methods of the battery cells in Test Example 16 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.2, and the maximum extensible displacement M of the telescopic part is 0.5mm.

[0084] Test Example 17: The preparation and testing methods of the battery cell in Test Example 17 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 11mm.

[0085] Test Example 18: The preparation and testing methods of the battery cell in Test Example 18 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 5.5mm.

[0086] Test Example 19: The preparation and testing methods of the battery cell in Test Example 19 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum expandable displacement M of the telescopic part is 4.95mm.

[0087] Test Example 20: The preparation and testing methods of the battery cells in Test Example 20 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 4.5 mm.

[0088] Test Example 21: The preparation and testing methods of the battery cell in Test Example 21 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 3.3 mm.

[0089] Test Example 22: The preparation and testing methods of the battery cell in Test Example 22 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 2.48 mm.

[0090] Test Example 23: The preparation and testing methods of the battery cell in Test Example 23 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 0.5mm.

[0091] Test Example 24: The preparation and testing methods of the battery cell in Test Example 24 are the same as those in Test Example 1. The difference is that the negative electrode formulation has been adjusted, k is 0.1, and the maximum extensible displacement M of the telescopic part is 0.25mm.

[0092] Test Example 25: The preparation and testing methods of the battery cell in Test Example 25 are the same as those in Test Example 1, except that the maximum expandable displacement M of the telescopic part is 0 mm.

[0093] Test Example 26: The preparation and testing methods of the battery cell in Test Example 26 are the same as those in Test Example 9, except that the maximum expandable displacement M of the telescopic part is 0 mm.

[0094] Test Example 27: The preparation and testing methods of the battery cell in Test Example 27 are the same as those in Test Example 17, except that the maximum expandable displacement M of the telescopic part is 0 mm.

[0095] The evaluation results of the above twenty-seven test cases are shown in Table 1.

[0096]

[0097] Comparing the results of the above twenty-seven test cases, those with N*k / M values ​​between 0.9 and 20 showed advantages in cycle performance compared to other test cases. Furthermore, limiting N*k / M values ​​between 1 and 1.1 optimized the cell cycle performance and the utilization of the expansion joint, significantly reducing the expansion force generated during cycling, extending the number of cycles per cell, and improving the cycle performance of the cell.

[0098] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art can understand that implementing all or part of the processes of the above embodiments and making equivalent changes according to the claims of this application still fall within the scope of this application.

Claims

1. A battery cell, characterized in that, The battery includes a battery housing with a receiving cavity and a battery cell (212) housed in the receiving cavity. The battery housing is provided with a telescopic part so that the battery housing can expand and contract along a first direction as the internal pressure of the receiving cavity changes. The ratio of the total expansion of the battery cell (212) in the first direction to the maximum expandable displacement of the battery housing in the first direction is greater than or equal to 0.9 and less than or equal to 20.

2. The battery cell as described in claim 1, characterized in that, The ratio of the total expansion of the battery cell (212) in the first direction to the maximum expandable displacement of the battery casing in the first direction is greater than or equal to 1 and less than or equal to 1.

1.

3. The battery cell as described in claim 1, characterized in that, The ratio of the dimension of the cell (212) in the first direction to the dimension of the area of ​​the battery casing excluding the telescopic portion in the first direction is greater than or equal to 0.

97.

4. The battery cell as described in claim 1, characterized in that, The battery casing has telescopic portions at both ends in the first direction.

5. The battery cell as described in claim 1, characterized in that, When the elongation of the battery casing in the first direction is half of the maximum retractable displacement, the internal pressure of the battery cell (21) is greater than or equal to 0.5 MPa.

6. The battery cell as described in claim 1, characterized in that, The thickness direction of the battery cell (212) is consistent with the first direction.

7. The battery cell as described in claim 1, characterized in that, The battery housing includes a housing body (211) with an opening at one end and a top cover (213) connected to the opening. The housing body (211) and the top cover (213) form the receiving cavity. The telescopic part includes a first sub-telescopic part (2116) disposed on the housing body (211) and a second sub-telescopic part (2131) disposed on the top cover (213).

8. The battery cell as described in claim 1, characterized in that, The telescopic part includes one or more of the following: a corrugated telescopic structure, a laminated telescopic structure, and an elastic membrane.

9. A battery pack, characterized in that, Includes the battery cell (21) as described in any one of claims 1-8.

10. A vehicle, characterized in that, Includes the battery cell (21) as described in any one of claims 1-8.

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