Battery cell, battery, and electric device

Abstract

The application discloses a battery cell, a battery and a power utilization device. The battery cell comprises a shell, at least one electrode assembly arranged in the shell, and at least one elastic buffer pad arranged on at least part of a surface of the electrode assembly and / or in the electrode assembly. The compression rate of the elastic buffer pad in the thickness direction of the elastic buffer pad satisfies the following relationship: -5%≤P≤5%, the compression rate of the elastic buffer pad under a pressure of 0.1 Mpa is ≤20%, and the compression rate of the elastic buffer pad under a pressure of 0.5 Mpa is ≤60%; or P>5%, and the compression rate of the elastic buffer pad under a pressure of 0.5 Mpa is ≥50%. The at least one electrode assembly and the at least one elastic buffer pad are arranged in a stack in a first direction, and P is the ratio of the difference between the total distance of the electrode assembly in a full charge state and the total distance of the electrode assembly in a full discharge state to the distance between the inner wall surface of the shell. Thus, the elastic buffer pad can play a good effect, and the risk of swelling deformation or performance deterioration of the battery cell can be reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and in particular relates to a battery monomer, a battery and a power utilization device. BACKGROUND

[0002] As an energy storage device, a battery is widely used in various fields. For example, a lithium ion battery has the characteristics of green, environmental protection, high energy, low carbon, etc., and is not only applied to energy storage power supply systems of hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles, ships and other electric vehicles, military equipment, aerospace and other fields. With the development of current society, people's requirements for batteries are also getting higher and higher. SUMMARY

[0003] In view of the technical problems in the background art, the present application provides a battery monomer, which aims to improve the effect of the buffer pad and reduce the risk of battery monomer swelling and deformation or performance deterioration.

[0004] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a battery monomer, which comprises:

[0005] a shell;

[0006] at least one electrode assembly disposed in the shell;

[0007] at least one elastic buffer pad provided on at least part of the surface of the electrode assembly and / or inside the electrode assembly, the compression rate of the elastic buffer pad along its thickness direction satisfies the following relationship:

[0008] -5%≤P≤5%, the compression rate of the elastic buffer pad under 0.1Mpa pressure is ≤20%, and the compression rate under 0.5Mpa pressure is ≤60%; or,

[0009] P>5%, the compression rate of the elastic buffer pad under 0.5Mpa pressure is ≥50%;

[0010] wherein the at least one electrode assembly and the at least one elastic buffer pad are stacked in a first direction, and P is the ratio of the difference between the total distance of the electrode assembly in the full charge state and the total distance in the full discharge state to the distance between the inner wall surface of the shell in the first direction.

[0011] The battery cell of the first aspect of this application has the following beneficial effects: it can be applied to battery cells with different expansion systems. For low expansion systems (-5% ≤ P ≤ 5%), the volume deformation of the electrode assembly during charging and discharging is relatively small. By selecting an elastic buffer pad with a compression ratio along its thickness direction that meets the given conditions, it can buffer the volume expansion force generated by the electrode assembly during charging and discharging, suppressing the deformation of the battery cell. On the other hand, it can also give the elastic buffer pad a certain supporting strength. When the elastic buffer pad is not over-compressed, it is also conducive to the direct contact between the electrode assembly and the inner wall of the casing, or the contact between the elastic buffer pad and the inner wall of the casing, to achieve interaction force. This is beneficial to both improving the uniformity of the force on the electrode sheet and suppressing the shaking of the electrode assembly. For high expansion systems (P > 5%), the volume deformation of the electrode assembly during charging and discharging is relatively large. By selecting an elastic buffer pad with a compression ratio along its thickness direction that meets the given conditions, it can be fully compressed during the expansion of the electrode assembly, giving up the space in its thickness direction to the electrode assembly and reducing the expansion force of the electrode assembly. Therefore, for battery cells with different expansion systems, it is beneficial to make the elastic buffer pad play a better role, improve the volume stability of the battery cell during long-term use, reduce the risk of expansion deformation or performance deterioration, and improve long-term performance.

[0012] In some embodiments of this application, the elastic buffer pad is provided between the electrode assembly and the housing, and / or the elastic buffer pad is provided between two adjacent electrode assemblies. Meeting the given conditions is beneficial for improving the volume stability of the battery cell during long-term use.

[0013] In some embodiments of this application, when -5% ≤ P ≤ 5%, the compression ratio of the elastic buffer pad under 0.1 MPa pressure is ≤15%, optionally ≤10%; and / or, the compression ratio of the elastic buffer pad under 0.5 MPa pressure is ≤55%, optionally ≤50%. Meeting the given conditions is beneficial for improving the volume stability of the battery cell in the low-expansion system during long-term use, and also beneficial for improving the stress uniformity of the electrode sheet, reducing the risk of battery cell expansion deformation or performance degradation.

[0014] In some embodiments of this application, when P > 5%, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa is ≥ 60%, optionally ≥ 70%. Meeting the given conditions further helps to reduce the expansion force generated by the electrode assembly on the casing in the battery cell of the high expansion system, and improves the volume stability of the battery cell during long-term use.

[0015] In some embodiments of this application, the electrode assembly is a wound electrode assembly, and includes a straight portion and a corner portion, wherein the elastic buffer pad is disposed on at least a portion of the surface of the straight portion and / or the corner portion.

[0016] In some embodiments of this application, the battery cell is a prismatic battery cell.

[0017] In some embodiments of this application, the prismatic battery cell includes: at least one first elastic buffer pad and / or at least one second elastic buffer pad, wherein the first elastic buffer pad and the electrode assembly are stacked along the thickness direction of the battery cell, and / or, the second elastic buffer pad and the electrode assembly are stacked along the length direction of the battery cell. Meeting the given conditions helps to reduce the expansion force generated by the electrode assembly during use.

[0018] In some embodiments of this application, the prismatic battery cell satisfies at least one of the following conditions: In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in its free state and the total thickness of the electrode assembly in its fully discharged state is 80% to 99% of the distance between the inner wall surfaces of the casing, optionally 85% to 98%, and further optionally 90% to 95%; In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in its free state and the total thickness of the electrode assembly in its fully charged state is 95% to 110% of the distance between the inner wall surfaces of the casing, optionally 98%. The thickness of the second elastic buffer pad in its free state is approximately 105%, and can be further selected as 99% to 102%. In the length direction of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully discharged state is 80% to 99% of the distance between the inner walls of the casing, optionally 85% to 98%, and further optionally 90% to 95%. In the length direction of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully charged state is 95% to 110% of the distance between the inner walls of the casing, optionally 98% to 105%, and further optionally 99% to 102%. Meeting the given conditions facilitates the smooth insertion of the elastic buffer pad into the casing and / or improves the volume stability of the battery cell and the uniformity of stress on the electrode sheets.

[0019] In some embodiments of this application, the ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 2% to 25%, optionally 5% to 20%, and further optionally 8% to 15%. Meeting the given conditions is beneficial for maintaining the volume stability of the battery cell while also taking into account the energy density of the battery cell.

[0020] In some embodiments of this application, the ratio of the extension distance of the first elastic buffer pad in the length direction of the electrode assembly to the length of the electrode assembly in its free state is 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05; and / or, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly in its free state is 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05. Meeting these conditions allows the elastic buffer pad to cover most of the electrode assembly, which is beneficial for improving the volume stability of the battery cell and further improving the uniformity of stress on the electrode sheet.

[0021] In some embodiments of this application, the orthographic projection of the first elastic buffer pad onto the electrode assembly is located within the region where the electrode assembly is situated. Meeting this condition facilitates the smooth insertion of the elastic buffer pad into the casing during assembly and also helps to further consider the energy density of the battery.

[0022] In some embodiments of this application, the battery cell is a cylindrical battery cell, at least one of the elastic buffer pads and the electrode assembly are stacked along the radial direction of the electrode assembly, and the distance between the inner wall surfaces of the housing is equal to the inner diameter of the housing cavity.

[0023] In some embodiments of this application, in the cylindrical battery cell, the sum of the total thickness of the elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 80% to 99% of the inner diameter of the housing, optionally 85% to 98%, and further optionally 90% to 95%; and / or, the sum of the total thickness of the elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully charged state is 85% to 110% of the inner diameter of the housing, optionally 98% to 105%, and further optionally 99% to 102%. Meeting these conditions facilitates the smooth insertion of the elastic buffer pad into the housing and / or improves the volume stability of the battery cell and the uniformity of stress on the electrode sheets.

[0024] In some embodiments of this application, in the cylindrical battery cell, the elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's extension distance in the circumferential direction of the electrode assembly to the circumference of the electrode assembly is 0.8–1.2, optionally 0.85–1.1, and further optionally 0.9–1.05; and / or, in its free state, the ratio of the elastic buffer pad's extension distance in the height direction of the electrode assembly to the height of the electrode assembly is 0.8–1.2, optionally 0.85–1.1, and further optionally 0.9–1.05. Meeting these conditions allows the elastic buffer pad to cover most of the electrode assembly, which is beneficial for improving the volume stability of the battery cell and further improving the uniformity of stress on the electrode sheets.

[0025] In some embodiments of this application, in the cylindrical battery cell, the elastic buffer pad, in its free state, extends circumferentially to a distance less than or equal to the circumference of the electrode assembly; and / or, in its free state, the elastic buffer pad extends circumferentially to a distance less than or equal to the height of the electrode assembly. Meeting these conditions facilitates the smooth insertion of the elastic buffer pad into the casing during assembly and also helps to further consider the energy density of the battery.

[0026] In some embodiments of this application, the thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state, optionally 5% to 10%. Meeting the given conditions is beneficial for maintaining the volume stability of the battery cell during its service life, especially in the later stages of use, while also taking into account the energy density of the battery cell.

[0027] In some embodiments of this application, the thickness of a single elastic buffer pad in its free state is 0.2 mm to 10.5 mm. Meeting these conditions balances the compressibility of the elastic buffer pad and the energy density of the battery cell, while also ensuring the support layer has sufficient strength.

[0028] A second aspect of this application provides a battery comprising: the battery cell described in the first aspect of this application.

[0029] A third aspect of this application provides an electrical device comprising: the battery described in the second aspect of this application. Attached Figure Description

[0030] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0031] Figure 1 This is a schematic cross-sectional view of a prism-shaped battery cell according to one embodiment of this application.

[0032] Figure 2 This is a cross-sectional structural diagram of a prism-shaped battery cell according to another embodiment of this application.

[0033] Figure 3 This is a schematic cross-sectional view of a prism-shaped battery cell according to another embodiment of this application.

[0034] Figure 4 This is a schematic diagram of the cross-sectional structure of a prism-shaped battery cell according to another embodiment of this application.

[0035] Figure 5 This is a schematic diagram of the cross-sectional structure of a prism-shaped battery cell according to another embodiment of this application.

[0036] Figure 6 This is a schematic diagram of the cross-sectional structure of a prism-shaped battery cell according to another embodiment of this application.

[0037] Figure 7 This is a schematic diagram of the cross-sectional structure of a prism-shaped battery cell according to another embodiment of this application.

[0038] Figure 8 This is a schematic diagram of the cross-sectional structure of a prism-shaped battery cell according to another embodiment of this application.

[0039] Figure 9 This is a schematic cross-sectional view of a cylindrical battery cell according to one embodiment of this application.

[0040] Figure 10 This is a cross-sectional structural diagram of a cylindrical battery cell according to another embodiment of this application.

[0041] Figure 11 This is a schematic diagram of the structure of a battery cell according to an embodiment of this application.

[0042] Figure 12 This is a schematic diagram of the structure of a battery module according to an embodiment of this application.

[0043] Figure 13 This is a schematic diagram of the structure of a battery pack according to an embodiment of this application.

[0044] Figure 14 This is an exploded view of a battery pack according to an embodiment of this application.

[0045] Figure 15 This is a schematic diagram of one embodiment of an electrical device in which a battery is used as a power source, according to an embodiment of this application.

[0046] Figure label:

[0047] 11: Housing; 12: Electrode assembly; 13: Elastic buffer pad; 13a: First elastic buffer pad; 13b: Second elastic buffer pad; 1: Battery; 2: Battery module; 3: Battery pack; 4: Upper housing; 5: Lower housing. Detailed Implementation

[0048] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0049] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its preparation method, the positive electrode sheet, the battery, and the power device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this application is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit, which defines the boundary of the particular range. Ranges defined in this way may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined range, and any lower limit can be combined with other lower limits to form an undefined range. Similarly, any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value, or with other lower or upper limits, to form an undefined range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is expected that the ranges of 60–110 and 80–120 will also be understood. Furthermore, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are listed, then the following ranges can all be expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range “a–b” represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range “0–5” means that all real numbers between “0–5” have been listed herein, and “0–5” is merely a shortened representation of these numerical combinations. Additionally, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, indicating that the method may include steps S1 and S2 performed sequentially, or it may include steps S2 and S1 performed sequentially. For example, the method may also include step S3, indicating that step S3 may be added to the method in any order. For example, the method may include steps S1, S2, and S3, or it may include steps S1, S3, and S2, or it may include steps S3, S1, and S2, etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0055] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0056] Unless otherwise specified, in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0057] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0058] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion. Unless otherwise stated, the terms used in this application have their commonly understood meanings as understood by one of ordinary skill in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0059] With the continuous advancement of green and environmentally friendly themes, battery applications have penetrated into all aspects of life, including vehicles, electronic devices, and energy storage devices. However, as battery applications continue to expand, people's requirements for batteries are also increasing. Taking lithium-ion batteries as an example, lithium-ion batteries undergo volume changes during charge-discharge cycles and overcharging, and the expansion gradually increases with operating time. This not only easily leads to deformation of the battery casing under pressure, affecting the battery's volume stability, but also, if the electrodes expand excessively during charge-discharge cycles, it may affect the spacing between the electrodes and the separator, increasing the risk of lithium plating and affecting the battery's lifespan. To address this issue, there are currently solutions that place buffer pads between or within the cells. However, due to factors such as the type of active material on the electrode plates and the thickness of the active material layer, the amount and rate of expansion of the battery during charge-discharge will vary. Furthermore, the stress and strain requirements of the buffer pads located inside the cells differ for different expansion systems. Inappropriate matching is detrimental to the effectiveness of the buffer pads and may even lead to the deterioration of cell performance.

[0060] In this application, based on the different ratios of the distance difference between the electrode assembly in the fully charged state and the fully discharged state along the first direction and the distance between the inner wall surfaces of the casing along the first direction, different limits are made to the stress-strain relationship of the elastic buffer pad. Specifically, for low expansion systems, an elastic buffer pad with a compression ratio ≤20% in the thickness direction at 0.1 MPa pressure and ≤60% in the thickness direction at 0.5 MPa pressure is selected. This can buffer the volume expansion force generated by the electrode assembly during charging and discharging, and also have a certain supporting strength. Even when not over-compressed, it is beneficial to achieve direct contact between the electrode assembly and the inner wall of the casing, or contact between the electrode assembly and the inner wall of the casing through the elastic buffer pad, to realize the interaction force and improve the uniformity of the stress on the electrode sheet. For high expansion systems, an elastic buffer pad with a compression ratio ≥50% in the thickness direction at 0.5 MPa pressure is selected. This can ensure that the electrode assembly can be fully compressed during expansion, giving up the space in the thickness direction to the electrode assembly and reducing the expansion force of the electrode assembly. Therefore, for battery cells with different expansion systems, it is beneficial to make the elastic buffer pads perform better and reduce the risk of expansion deformation or performance degradation.

[0061] The battery cells and batteries disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0062] A first aspect of this application provides a battery cell comprising: a housing; at least one electrode assembly disposed within the housing; and at least one elastic buffer pad disposed on at least a portion of the surface and / or inside the electrode assembly, wherein the compression ratio of the elastic buffer pad along its thickness direction satisfies the following relationship: -5% ≤ P ≤ 5%, the compression ratio of the elastic buffer pad at 0.1 MPa pressure ≤ 20%, and the compression ratio at 0.5 MPa pressure ≤ 60%; or, P > 5%, the compression ratio of the elastic buffer pad at 0.5 MPa pressure ≥ 50%; wherein at least one electrode assembly and at least one elastic buffer pad are stacked along a first direction, and P is the ratio of the difference between the total distance of the electrode assembly in a fully charged state and the total distance in a fully discharged state in the first direction to the distance between the inner wall surfaces of the housing.

[0063] For example, refer to Figures 1-7Understood, the battery cell 1 of the first aspect of this application includes a housing 11, at least one electrode assembly 12, and at least one elastic buffer pad 13. The electrode assembly 12 is disposed within the housing 11, and the elastic buffer pad 13 may be disposed on at least a portion of the surface and / or inside the electrode assembly 12. Exemplarily, the elastic buffer pad 13 may be disposed between the electrode assembly 12 and the housing 11 (see reference). Figure 1 (understand), and / or located between two adjacent electrode assemblies 12 (refer to) Figure 2 (understand), and / or located inside the electrode assembly (see reference). Figure 3 (Understanding). The elastic buffer pad 13 can be disposed between the electrode assembly 12 and the housing 11. This can be understood as meaning it can be disposed in at least one of the following areas: between the electrode assembly 12 and the side wall of the housing 11, between the electrode assembly 12 and the bottom wall of the housing 11, and between the electrode assembly 12 and the top wall of the housing 11. Optionally, refer to... Figure 4 or Figure 5 It is understood that elastic buffer pads 13 can be simultaneously provided between the electrode assembly 12 and the housing 11 and between two adjacent electrode assemblies; alternatively, refer to Figure 1 , Figure 6 , Figure 7 It is understood that the elastic buffer pad 13 can be disposed between the electrode assembly 12 and the side wall of the housing 11. In actual operation, the elastic buffer pad 13 can be fitted to the electrode assembly 12 on both sides along its thickness direction (see reference). Figure 2 (Understanding), it can also be fitted to the electrode assembly 12 on one side and to the inner wall of the housing 11 on the other side.

[0064] As some specific examples, when the battery cell 1 includes only one electrode assembly 12, the number of elastic buffer pads 13 can be one or more. These pads can be disposed between the electrode assembly 12 and the housing 11, or inside the electrode assembly. Optionally, they can be disposed between the sidewalls of the electrode assembly 12 and the housing 11. As other specific examples, when the battery cell 1 includes at least two electrode assemblies 12, the number of elastic buffer pads 13 can be one or more. These elastic buffer pads 13 can be disposed only between the battery assemblies 12, only between the battery assembly 12 and the housing 11, or only inside the electrode assembly 12. They can also be partially disposed between the battery assemblies 12 and partially between the battery assembly 12 and the housing 11, etc. Optionally, the elastic buffer pad 13 disposed between the battery assembly 12 and the housing 11 can be disposed between the sidewalls of the electrode assembly 12 and the housing 11.

[0065] Optionally, the thickness direction of at least one elastic buffer pad 13 is the same as the thickness direction of the battery cell 1 (see reference). Figures 1-6(and 8 for understanding), and alternatively, at least one elastic buffer pad 13 has the same thickness direction as the battery cell 1 and the electrode assembly 12.

[0066] In the battery cell of this application, at least one electrode assembly 12 and at least one elastic buffer pad 13 are stacked along a first direction. Optionally, the first direction can be the thickness direction of the electrode assembly 12. When the electrode assembly 12 is a wound electrode assembly and includes a straight portion and a corner portion, the first direction can be the thickness direction of the straight portion. When the electrode assembly 12 is cylindrical, the first direction is the radial direction of the electrode assembly. The distance between the inner wall surfaces of the housing 11 along the first direction is the inner diameter of the housing cavity.

[0067] In the battery cell of this application, based on different expansion systems, there are different requirements for the stress-strain relationship of the elastic buffer pad 13. That is, depending on the ratio of the difference between the total distance of the electrode assembly in the fully charged state and the total distance in the fully discharged state in the first direction of the battery cell to the distance between the inner wall surfaces of the casing, there are different requirements for the compression ratio of the elastic buffer pad along its thickness direction. Taking the thickness direction of the electrode assembly as the first direction and the thickness direction of the battery cell being consistent with the thickness direction of the electrode assembly as an example: In the battery cell, the different ratios of the difference Δd between the total thickness d1 and the total thickness d2 of the electrode assembly in the fully charged state and the distance d0 between the inner wall surfaces of the casing 11 in the thickness direction, and the ratio of P (P=Δd / d0, Δd=d1-d2), result in the compression ratio of the elastic buffer pad 13 along its thickness direction as follows:

[0068] When -5% ≤ P ≤ 5%, select an elastic cushioning pad with a compression ratio ≤ 20% at 0.1 MPa pressure and a compression ratio ≤ 60% at 0.5 MPa pressure. For example, the compression ratio of the elastic cushioning pad at 0.1 MPa pressure can be ≤ 20%, ≤ 18%, ≤ 16%, ≤ 14%, ≤ 12%, ≤ 10%, ≤ 8%, ≤ 6%, ≤ 4%, etc., or can be any range of the above values; as another example, the compression ratio of the elastic cushioning pad at 0.5 MPa pressure can be ≤ 60%, ≤ 55%, ≤ 50%, ≤ 45%, ≤ 40%, ≤ 35%, ≤ 30%, ≤ 25%, ≤ 20%, etc., or can be any range of the above values. When -5% ≤ P ≤ 5%, the expansion deformation of the battery cell during charging and discharging is relatively small. The elastic buffer pad cannot be over-compressed. The elastic buffer pad with a compression ratio along its thickness direction that meets the given conditions at 0.1 MPa and 0.5 MPa pressure can not only buffer the volume expansion force generated by the electrode assembly during charging and discharging, but also give it a certain supporting strength. Even in the state of not being over-compressed, it is conducive to the direct bonding of the electrode assembly to the inner wall of the shell, or bonding with the inner wall of the shell through the elastic buffer pad or Mylar film (i.e., insulating film), so as to realize the interaction force. This is beneficial to improve the uniformity of the force on the electrode sheet, suppress the shaking of the electrode assembly, and reduce the risk of wrinkles in local areas of the electrode assembly and abnormalities such as purple spots and lithium plating in the wrinkled areas, which lead to a decrease in the utilization rate of active lithium.

[0069] When P > 5%, the compression ratio of the elastic buffer pad 13 under 0.5 MPa pressure is ≥ 50%, for example, it can be ≥ 50%, ≥ 55%, ≥ 60%, ≥ 65%, ≥ 70%, ≥ 75%, ≥ 80%, ≥ 85%, etc., or it can be any range of the above values. When P > 5%, the expansion deformation of the battery cell during charging and discharging is relatively large. Selecting an elastic buffer pad with a compression ratio along its thickness direction that meets the given conditions under 0.5 MPa pressure allows it to be fully compressed during the expansion of the electrode assembly, transferring its thickness space to the electrode assembly and reducing the expansion force of the electrode assembly.

[0070] The compressibility of the elastic cushioning pad along its thickness under different stresses can be determined according to GB / T 1041-92. The compressibility of the elastic cushioning pad along its thickness is the ratio of the thickness change of the elastic cushioning pad in the free state and under stress state to its thickness in the free state. The free state of the elastic cushioning pad refers to the state where the elastic cushioning pad is not subjected to any external force, while the stress state refers to the state where the elastic cushioning pad is subjected to a certain compressive stress. The thickness of the elastic cushioning pad in the free state can be tested using conventional instruments and methods in this field, such as a Mitutoyo ID-C112MX micrometer thickness gauge (or a similar instrument), with a test force less than or equal to 1.8N, randomly measuring multiple points (e.g., 5, 10, etc.) and taking the average value. The thickness of the elastic cushioning pad under stress state can be tested using two parallel plates, with the elastic cushioning pad positioned between the plates. A preset pressure is applied to the elastic cushioning pad using the plates, and the distance between the plates is measured. The instruments used to measure the distance between the plates can include, but are not limited to, conventional instruments such as vernier calipers.

[0071] Full charge refers to the state of charging a battery cell at room temperature using a constant current of 0.33C (of its rated capacity) to the upper limit of the cutoff voltage, followed by constant voltage charging until the current reaches 0.05C, or charging to the point where the battery's SOC no longer changes. Full discharge refers to the state of discharging a battery cell at room temperature using a constant current of 0.33C (of its rated capacity) to the lower limit of the cutoff voltage. In a battery cell, the total distance of the electrode assembly in the first direction refers to the sum of the distances of all electrode assemblies in the first direction. Taking the thickness direction of the electrode assembly as the first direction as an example, the thickness of the electrode assembly typically extends along the thickness direction of the battery cell. The total thickness of the electrode assembly in a fully charged state refers to the sum of the thicknesses of all electrode assemblies in the battery cell at room temperature under full charge conditions. (Reference) Figure 2 It is understood that the battery cell 1 has two electrode assemblies 12. The total thickness of the electrode assemblies in a fully charged state refers to the sum of the thicknesses of the two electrode assemblies 12 in the battery cell at room temperature during full charging. Correspondingly, the total thickness of the electrode assemblies in a fully discharged state refers to the cumulative thickness of all electrode assemblies in the battery cell at room temperature during full discharge. The thickness of the electrode assemblies in fully charged or fully discharged states can also be measured using conventional methods or instruments in the art. For example, it can be tested using the following method: using two parallel plates, placing the electrode assembly between the plates, applying a pressure of 0.1 MPa to the electrode assembly using the plates, and measuring the distance between the plates to obtain the thickness of the electrode assembly. An Innolux PPG1200 battery thickness measuring instrument can be used for this test. The distance between the inner wall surfaces of the casing in the first direction can be measured using conventional instruments and methods in the art.

[0072] The battery cell of the first aspect of this application has the following beneficial effects: it can be applied to battery cells with different expansion systems. For battery cells with different expansion systems, it is beneficial to make the elastic buffer pad play a better role, improve the volume stability of the battery cell during long-term use, reduce the risk of its expansion deformation or performance deterioration, and improve long-term performance.

[0073] It is understood that, in the embodiments of this application, the battery cell includes, but is not limited to, a casing, electrode assembly, and elastic buffer pad. For example, the battery cell may also include an electrolyte. In the embodiments of this application, the battery cell includes, but is not limited to, a secondary battery cell, a primary battery cell, etc. In the embodiments of this application, the battery cell includes, but is not limited to, a lithium-ion battery cell, a sodium-ion battery cell, a magnesium-ion battery cell, etc. In the embodiments of this application, the battery cell includes, but is not limited to, a rigid battery cell, a pouch battery cell, etc., and the rigid battery cell includes, but is not limited to, a metal battery casing cell, etc.

[0074] Furthermore, in addition to satisfying the above conditions, the battery cell of the first aspect of this application can further improve its performance by controlling the compressibility of the elastic buffer pad along its thickness direction under specific stress, the relationship between the elastic buffer pad and the electrode assembly and / or the housing dimensions, and the arrangement for different battery cell types. That is, in addition to satisfying the above conditions, one or more of the following conditions may also be satisfied.

[0075] In some embodiments of this application, an elastic buffer pad 13 is provided between the electrode assembly 12 and the housing 11, and / or an elastic buffer pad 13 is provided between two adjacent electrode assemblies 12. See also... Figure 1 , Figure 2 and Figure 4 Understood. Meeting the given conditions further improves the volume stability of the battery cells during long-term use, reducing the risk of expansion, deformation, or performance degradation. Optionally, elastic buffer pads 13 can be provided only between the electrode assembly 12 and the housing 11 and / or between two adjacent electrode assemblies 12, which is beneficial for both electrode assembly forming and reducing the expansion force exerted by the electrode assembly on the housing.

[0076] In some embodiments of this application, when -5% ≤ P ≤ 5%, the compression rate of the elastic buffer pad 13 under 0.1 MPa pressure can be ≤ 15%, optionally ≤ 10%; and / or, the compression rate of the elastic buffer pad 13 under 0.5 MPa pressure is ≤ 55%, optionally ≤ 50%.

[0077] For example, when -5% ≤ P ≤ 5%, the compression ratio of the elastic cushioning pad along its thickness direction under a pressure of 0.1 MPa can be ≤15%, ≤14%, ≤13%, ≤12%, ≤11%, ≤10%, ≤9%, ≤8%, ≤7%, ≤6%, ≤5%, etc.; and / or, the compression ratio of the elastic cushioning pad along its thickness direction under a pressure of 0.5 MPa can be ≤55%, ≤53%, ≤51%, ≤50%, ≤48%, ≤45%, ≤42%, ≤40%, etc. Choosing an elastic buffer pad that meets the given conditions is beneficial for buffering the expansion force generated during the use of the electrode assembly. It also facilitates the direct bonding of the electrode assembly to the inner wall of the housing or the bonding of the electrode assembly to the inner wall of the housing through the elastic buffer pad or Mylar film in a low expansion system, thereby realizing the interaction force. This further helps to improve the uniformity of the stress on the electrode sheet and reduce the risk of wrinkles in local areas of the electrode assembly and abnormalities such as purple spots and lithium plating in wrinkled areas, which lead to a decrease in the utilization rate of active lithium.

[0078] Choosing an elastic buffer pad that meets the given conditions is beneficial for improving the volume stability of battery cells in low-expansion systems during long-term use, as well as improving the uniformity of stress on the electrode sheets and reducing the risk of battery cell expansion, deformation, or performance degradation.

[0079] In some embodiments of this application, when P > 5%, the compression rate of the elastic buffer pad 13 under a pressure of 0.5 MPa can be ≥ 60%, and optionally ≥ 70%.

[0080] For example, when P > 5%, the compression ratio of the elastic buffer pad along its thickness direction under a pressure of 0.5 MPa can be ≥60%, ≥62%, ≥65%, ≥68%, ≥70%, ≥72%, ≥75%, ≥78%, ≥80%, etc. Selecting an elastic buffer pad that meets the given conditions further helps to reduce the expansion force generated by the electrode components on the casing in the battery cell of a high-expansion system, improves the volume stability of the battery cell during long-term use, and reduces the risk of its expansion deformation or performance degradation.

[0081] In some embodiments of this application, the electrode assembly 12 may be a wound electrode assembly, and includes a straight portion and a corner portion, and the elastic buffer pad 13 may be provided on at least a portion of the surface of the straight portion and / or the corner portion.

[0082] In the battery cell of this application, the electrode assembly can be a stacked electrode assembly or a wound electrode assembly; the wound electrode assembly can be used in a prismatic housing or a cylindrical housing. Among these, the wound electrode assembly has a relatively high risk of uneven stress on the electrode sheets during charging and discharging, especially in prismatic battery cells with wound electrode assemblies. Combining the wound electrode assembly with an elastic buffer pad helps alleviate the problem of uneven stress on the electrode sheets in the wound electrode assembly, reduces polarization differences, and improves volume stability and long-term cycle performance. Optionally, the electrode assembly 12 can be a wound electrode assembly, including a straight portion and a corner portion, and the elastic buffer pad 13 can be disposed on at least a portion of the surface of the straight portion and / or the corner portion, thereby further helping to alleviate the problem of uneven stress on the electrode sheets in the prismatic battery cell. It is understood that prismatic battery cells include, but are not limited to, prismatic battery cells. Optionally, the straight portion of the wound electrode assembly can be provided with an elastic buffer pad 13.

[0083] In some embodiments of this application, reference is made to Figures 1-8 It is understood that battery cell 1 can be a prismatic battery cell.

[0084] In some embodiments of this application, the prismatic battery cell may include at least one first elastic buffer pad 13a and / or at least one second elastic buffer pad 13b, wherein the first elastic buffer pad 13a and the electrode assembly 12 may be stacked along the thickness direction of the battery cell, and / or the second elastic buffer pad 13b and the electrode assembly 12 may be stacked along the length direction of the battery cell.

[0085] refer to Figure 8 To illustrate, taking a square battery cell as an example, in the given structural design, the thickness of the first elastic buffer pad 13a can extend along the thickness direction of the battery cell, and the thickness of the second elastic buffer pad 13b can extend along the length direction of the battery cell. Both the first elastic buffer pad 13a and the second elastic buffer pad 13b help reduce the expansion force generated by the electrode assembly during use. Optionally, the battery cell may include at least one first elastic buffer pad 13a. In the housing 11 of the square battery cell, the areas of the two sidewalls opposite each other in the thickness direction of the battery cell are usually large. Providing a first elastic buffer pad between these two sidewalls helps increase the contact area between the elastic buffer pad and the electrode assembly, thereby further reducing the expansion force that may be generated by the electrode assembly during use and further alleviating the problem of uneven stress on the electrode sheets in the wound electrode assembly. Alternatively, a prismatic battery cell may only include the first elastic buffer pad 13a, satisfying the given conditions to reduce the expansion force of the electrode assembly, improve the problem of uneven stress on the electrode sheets, and eliminate the need for the second elastic buffer pad, which also simplifies the battery cell structure and increases the energy density of the battery cell.

[0086] In some embodiments of this application, in the prismatic battery cell, in the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad 13a in the free state and the total thickness of the electrode assembly 12 in the fully discharged state can be 80% to 99% of the distance between the inner wall surfaces of the housing 11, optionally 85% to 98%, and further optionally 90% to 95%; and / or, the sum of the total thickness of the first elastic buffer pad 13a in the free state and the total thickness of the electrode assembly 12 in the fully charged state can be 95% to 110% of the distance between the inner wall surfaces of the housing 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0087] refer to Figure 8 To understand, taking a square battery cell as an example, the sum of the total thickness d of the first elastic buffer pad 13a in its free state and the total thickness d2 of the electrode assembly 12 in its fully discharged state can be 80% to 99% of the distance d0 between the two inner wall surfaces of the housing 11 that are arranged opposite each other along its thickness direction, that is... For example, The value can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99%, etc., or a range of any of the above values. Meeting the given conditions ensures a gap between the elastic buffer pad and the electrode assembly and the housing before insertion, facilitating the smooth insertion of the elastic buffer pad and electrode assembly and simplifying the assembly of the battery cells. Optionally, Alternatively, Meeting the given conditions further facilitates the smooth insertion of the elastic buffer pad and electrode assembly into the housing. At the same time, it also helps to achieve direct or indirect contact between the electrode assembly and the inner wall of the housing after charging, thus improving the uniformity of force on the electrode sheet.

[0088] Taking a square battery cell as an example, the sum of the total thickness d of the first elastic buffer pad 13a in its free state and the total thickness d1 of the electrode assembly 12 in its fully charged state can be 95% to 110% of the distance d0 between the two inner wall surfaces of the housing 11 that are arranged opposite each other along its thickness direction, that is... For example, The value can be 95%, 97%, 99%, 100%, 102%, 104%, 106%, 108%, 110%, etc., or a range of any of the above values. Meeting the given conditions further facilitates the direct contact between the electrode assembly and the inner wall of the casing during battery cell use, or through an elastic buffer pad (or Mylar film), achieving interaction forces. This, in turn, helps to further improve the uniformity of stress on the electrode sheets, reduce the risk of wrinkles in localized areas of the electrode assembly and abnormalities such as purple spots and lithium plating in wrinkled areas that lead to a decrease in the utilization rate of active lithium, and improve the capacity retention rate of the battery cell. Optionally, Alternatively, Meeting the given conditions can improve the uniformity of force distribution on the electrode plates and further reduce the expansion force that the electrode assembly may exert on the housing.

[0089] Meeting the given conditions is beneficial not only for the assembly of battery cells, but also for improving the volume stability of battery cells and the uniformity of stress on the electrodes, thereby reducing the risk of battery cell expansion, deformation or performance degradation.

[0090] In some embodiments of this application, in the prismatic battery cell, the sum of the total thickness of the second elastic buffer pad 13b in the free state and the length of the electrode assembly 12 in the fully discharged state along the length direction of the battery cell can be 80% to 99% of the distance between the inner wall surfaces of the housing 11, optionally 85% to 98%, and further optionally 90% to 95%; and / or, the sum of the total thickness of the second elastic buffer pad 13b in the free state and the length of the electrode assembly 12 in the fully charged state can be 85% to 110% of the distance between the inner wall surfaces of the housing 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0091] For example, refer to Figure 8 To understand, taking a square battery cell as an example, the sum of the total thickness of the second elastic buffer pad 13b in its free state and the length of the electrode assembly 12 in its fully discharged state can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99%, etc., of the distance between the two inner wall surfaces of the housing 11 arranged opposite each other along its length direction, or it can be a range of any of the above values. Wherein, the length direction of the electrode assembly 12 in its fully discharged state and the length direction of the housing cavity are as follows... Figure 8 As shown in this application, the length of the electrode assembly 12 can be the maximum extension distance in the length direction of the battery cell. Meeting the given conditions allows for a gap between the elastic buffer pad and the battery housing before insertion, facilitating the smooth insertion of the elastic buffer pad and electrode assembly and simplifying battery cell assembly. Optionally, the sum of the total thickness of the second elastic buffer pad 13b in its free state and the length of the electrode assembly 12 in its fully discharged state can be 85% to 98% of the distance between the two inner wall surfaces of the housing 11 arranged opposite each other along its length direction, and can also be 90% to 95%. Meeting the given conditions further facilitates the smooth insertion of the elastic buffer pad and electrode assembly into the housing, and also helps to achieve direct or indirect contact between the electrode assembly and the inner wall of the housing after charging, improving the uniformity of force on the electrode sheets.

[0092] For example, refer to Figure 8To illustrate, taking a square battery cell as an example, the sum of the total thickness of the second elastic buffer pad 13b in its free state and the length of the electrode assembly 12 in its fully charged state can be 95%, 97%, 99%, 100%, 102%, 104%, 106%, 108%, 110%, etc., of the distance between the two inner wall surfaces of the housing 11 arranged opposite each other along its length direction, or it can be any range of the above values. Meeting the given conditions further facilitates direct contact between the electrode assembly and the inner wall of the housing during use, or contact between the electrode assembly and the inner wall of the housing via the elastic buffer pad (or Mylar film), achieving interaction forces. This further improves the uniformity of force on the electrode sheets, reduces the risk of wrinkles in local areas of the electrode assembly and abnormalities such as purple spots and lithium plating in wrinkled areas that lead to a decrease in the utilization rate of active lithium, and improves the capacity retention rate of the battery cell. Optionally, the sum of the total thickness of the second elastic buffer pad 13b in the free state and the length of the electrode assembly 12 in the fully charged state can be 98% to 105% of the distance between the two inner wall surfaces of the housing 11 that are arranged opposite each other along its length direction, or more preferably 99% to 102%. Satisfying the given conditions can improve the uniformity of the force on the electrode sheet and further reduce the expansion force that the electrode assembly may generate on the housing.

[0093] Meeting the given conditions is beneficial not only for the assembly of battery cells, but also for improving the volume stability of battery cells and the uniformity of stress on the electrodes, thereby reducing the risk of battery cell expansion, deformation or performance degradation.

[0094] In some embodiments of this application, the ratio of the total thickness of the first elastic buffer pad 13a in the free state to the total thickness of the electrode assembly 12 in the fully discharged state can be 2% to 25%, optionally 5% to 20%, and further optionally 8% to 15%.

[0095] refer to Figure 8It is understood that the ratio of the total thickness d of the first elastic buffer pad 13a in its free state to the total thickness d2 of the electrode assembly 12 in its fully discharged state can be 2% to 25%, i.e., 2% ≤ d / d2 ≤ 25%. For example, the value of d / d2 can be 2%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, etc., or any range of the above values. Increasing the value of d / d2 is beneficial to improving the elastic buffer pad's ability to absorb the expansion deformation and expansion force generated by the electrode assembly, and is beneficial to further suppressing the expansion deformation of the battery cells. The value of d / d2, satisfying the given conditions, is beneficial to maintaining the volume stability of the battery cells during their service life, especially in the later stages of use, while also taking into account the energy density of the battery cells. Optionally, the value of d / d2 can be 5% to 20%, and more specifically 8% to 15%, satisfying the given conditions to further take into account the volume stability and energy density of the battery cells during their service life, especially in the later stages of use.

[0096] Meeting the given conditions is beneficial for maintaining the volume stability of individual battery cells while also taking into account their energy density.

[0097] In some embodiments of this application, the ratio of the extension distance of the first elastic buffer pad 13a in the length direction of the electrode assembly 12 to the length of the electrode assembly 12 in the free state can be 0.8 to 1.2, optionally 0.85 to 1.1, or even more optionally 0.9 to 1.05; and / or, the ratio of the extension distance of the first elastic buffer pad 13a in the height direction of the electrode assembly 12 to the height of the electrode assembly 12 in the free state can be 0.8 to 1.2, optionally 0.85 to 1.1, or even more optionally 0.9 to 1.05.

[0098] refer to Figure 8 It is understood that, in its free state, the ratio of the extension distance of the first elastic buffer pad 13a along the length direction of the electrode assembly 12 to the length of the electrode assembly 12 can be 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc., or can be a range of any of the above values. In this ratio, the length of the electrode assembly refers to the maximum extension distance of the electrode assembly along the length direction of the battery cell in a fully charged state. The length of the electrode assembly and the extension distance of the first elastic buffer pad in the free state along the length direction of the electrode assembly can be measured using conventional methods and instruments.

[0099] refer to Figure 8It is understood that, in its free state, the ratio of the extension distance of the first elastic buffer pad 13a in the height direction of the electrode assembly 12 to the height of the electrode assembly 12 can be 0.8 to 1.2, such as 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, or any range of the above values. In this ratio, the height of the electrode assembly refers to the maximum extension distance of the electrode assembly along the height direction of the battery cell in a fully charged state. The height of the electrode assembly and the extension distance of the first elastic buffer pad in the height direction of the electrode assembly in its free state can be measured using conventional methods and instruments.

[0100] The dimensions of the first elastic buffer pad and the electrode assembly meet the given conditions, which is beneficial for the elastic buffer pad to cover most of the electrode assembly. This is beneficial for improving the volume stability of the battery cell and further improving the uniformity of stress on the electrode sheet, thus reducing the risk of battery cell performance degradation.

[0101] In some embodiments of this application, reference is made to Figure 8 It is understood that the orthogonal projection of the first elastic buffer pad 13a onto the electrode assembly 12 can be located within the area where the electrode assembly 12 is situated. The first elastic buffer pad satisfies the given conditions, which is beneficial for the elastic buffer pad to be smoothly inserted into the casing during assembly, and also helps to further consider the energy density of the battery.

[0102] In some embodiments of this application, reference is made to Figure 9 and Figure 10 It is understood that the battery cell 1 can be a cylindrical battery cell, with at least one elastic buffer pad 13 and an electrode assembly 12 stacked along the radial direction of the electrode assembly 12, and the distance between the inner wall surfaces of the housing 11 is equal to the inner diameter of the housing 11. That is, the thickness of the electrode assembly 12 can extend along its radial direction, and the distance between the inner wall surfaces of the housing 11 can be equal to or slightly less than the inner diameter of the housing 11. For example, the difference between the distance between the inner wall surfaces of the housing 11 and the inner diameter of the housing 11 can be less than or equal to 2%, optionally less than or equal to 1%. A cylindrical battery cell typically includes only one wound electrode assembly. The elastic buffer pad can be disposed inside the wound electrode assembly, allowing the stacked units of the electrode assembly to begin winding around the elastic buffer pad; and / or, the elastic buffer pad can be disposed between the wound electrode assembly and the housing. In this application, the inner diameter of the housing 11 can be understood as the average diameter of the inner cavity of the housing.

[0103] In some embodiments of this application, in a cylindrical battery cell, the sum of the total thickness of the elastic buffer pad 13 in the free state and the total thickness of the electrode assembly 12 in the fully discharged state can be 80% to 99% of the inner diameter of the housing 11, optionally 85% to 98%, and further optionally 90% to 95%; and / or, the sum of the total thickness of the elastic buffer pad 13 in the free state and the total thickness of the electrode assembly 12 in the fully charged state can be 85% to 110% of the inner diameter of the housing 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0104] For example, refer to Figure 9 It can be understood that the total thickness of the elastic buffer pad 13 in the free state and the total thickness of the electrode assembly 12 in the fully discharged state (or fully discharged state) can be understood as the average diameter of the electrode assembly plus twice the thickness of the single-layer elastic buffer pad 13 in the free state. Figure 10 In this context, the total thickness of the elastic buffer pad 13 in its free state and the total thickness of the electrode assembly 12 in its fully discharged state (or under full discharge conditions) can be understood as the average diameter of the elastic buffer pad 13 plus twice the thickness of the electrode assembly. In this application, the inner diameter of the housing 11 can be understood as the average diameter of the inner cavity of the housing, which can be measured using conventional methods and instruments.

[0105] refer to Figure 9 and Figure 10 It is understood that in a cylindrical battery cell, the sum of the total thickness of the elastic buffer pad 13 in the free state and the total thickness of the electrode assembly 12 in the fully discharged state can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99% of the inner diameter of the housing 11, or any range of the above values. Satisfying the given conditions can ensure that there is a gap between the elastic buffer pad and the electrode assembly and the housing before they are inserted into the housing, which is conducive to the smooth insertion of the elastic buffer pad and the electrode assembly into the housing and facilitates the assembly of the battery cell. The sum of the total thickness of the elastic buffer pad 13 in its free state and the total thickness of the electrode assembly 12 in its fully charged state can be 95%, 97%, 99%, 100%, 102%, 104%, 106%, 108%, 110% of the inner diameter of the housing 11, or any of the above values. Meeting the given conditions further facilitates the direct contact between the electrode assembly and the inner wall of the housing or the contact between the electrode assembly and the inner wall of the housing through the elastic buffer pad (or Mylar film) during the use of the battery cell, thereby realizing the interaction force. This further improves the uniformity of the force on the electrode sheet, reduces the risk of wrinkles in local areas of the electrode assembly and abnormalities such as purple spots and lithium plating in the wrinkled areas that lead to a decrease in the utilization rate of active lithium, and improves the capacity retention rate of the battery cell.

[0106] Meeting the given conditions is beneficial not only for the assembly of battery cells, but also for improving the volume stability of battery cells and the uniformity of stress on the electrodes, thereby reducing the risk of battery cell expansion, deformation or performance degradation.

[0107] In some embodiments of this application, in a cylindrical battery cell, an elastic buffer pad 13 may be disposed between the electrode assembly 12 and the housing 11. In the free state, the ratio of the extension distance of the elastic buffer pad 13 in the circumferential direction of the electrode assembly 12 to the circumference of the electrode assembly 12 may be 0.8 to 1.2, optionally 0.85 to 1.1, or even more optionally 0.9 to 1.05; and / or, in the free state, the ratio of the extension distance of the elastic buffer pad 13 in the height direction of the electrode assembly 12 to the height of the electrode assembly 12 may be 0.8 to 1.2, optionally 0.85 to 1.1, or even more optionally 0.9 to 1.05.

[0108] refer to Figure 9 It is understood that, in its free state, the ratio of the extension distance of the elastic buffer pad 13 along the circumference of the electrode assembly 12 to the circumference of the electrode assembly 12 can be 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc., or a range of any of the above values. In this ratio, the circumference of the electrode assembly refers to the average circumference of the electrode assembly in a fully charged state. Similarly, in its free state, the ratio of the extension distance of the elastic buffer pad 13 along the height of the electrode assembly 12 to the height of the electrode assembly 12 can be 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc., or a range of any of the above values. In this ratio, the height of the electrode assembly refers to the maximum extension distance of the electrode assembly along the height of the battery cell in a fully charged state. In this application, the circumference and height of the electrode assembly, as well as the extension distance of the elastic buffer pad 13 along the circumference or height of the electrode assembly in its free state, can all be measured using conventional methods and instruments.

[0109] The dimensions of the first elastic buffer pad and the electrode assembly meet the given conditions, which is beneficial for the elastic buffer pad to cover most of the electrode assembly. This is beneficial for improving the volume stability of the battery cell and further improving the uniformity of stress on the electrode sheet, thus reducing the risk of battery cell performance degradation.

[0110] In some embodiments of this application, in the cylindrical battery cell, the elastic buffer pad 13, in its free state, extends circumferentially to a distance less than or equal to the circumference of the electrode assembly 12; and / or, in its free state, the elastic buffer pad 13 extends circumferentially to a distance less than or equal to the height of the electrode assembly 12. The elastic buffer pad satisfies these conditions, which not only facilitates its smooth insertion into the casing during assembly but also helps to further consider the energy density of the battery.

[0111] In some embodiments of this application, the thickness of a single elastic buffer pad 13 in its free state can be 2% to 15% of the thickness of a single electrode assembly 12 in its fully discharged state, and optionally 5% to 10%. For example, the thickness of a single elastic buffer pad 13 in its free state can be 2%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, etc., of the thickness of a single electrode assembly 12 in its fully discharged state, or can be any range of the above values. Meeting the given conditions is beneficial for maintaining the volume stability of the battery cell during its service life, especially in the later stages of use, and also takes into account the energy density of the battery cell.

[0112] In some embodiments of this application, the thickness of a single elastic buffer pad 13 in its free state can be from 0.2 mm to 10.5 mm. For example, the thickness of a single elastic buffer pad 13 in its free state can be 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 10.5 mm, etc., or can be any range of the above values. By satisfying the given conditions, both the compressibility deformation of the elastic buffer pad and the energy density of the battery cell can be considered, while also ensuring that the support layer has a certain strength.

[0113] It is understood that the structure and material of the elastic buffer pad in the battery cell of the first aspect of this application are not particularly limited, as long as its compression ratio along its thickness direction under the preset pressure can meet the given requirements. For example, at least one of the material, porosity and pore size of the elastic buffer pad can be adjusted to obtain elastic buffer pads with different stress-strain relationships, so as to achieve different compression ratios of the elastic buffer pad along its thickness direction under the preset pressure.

[0114] For example, the elastic cushioning pad can be a single-layer structure, and its material can be at least one of foamed polyethylene, polypropylene, polyurethane, silicone rubber, etc.

[0115] For example, the elastic buffer pad can be a multi-layer structure, specifically including an elastic buffer layer and a support layer. The support layer can be disposed on at least one side of the elastic buffer layer along its thickness direction. For example, in a battery cell, at least one elastic buffer pad includes one elastic buffer layer and one support layer, and / or, at least one elastic buffer pad includes one elastic buffer layer and two support layers. Optionally, the elastic modulus of the elastic buffer layer is less than the elastic modulus of the support layer, and / or, under the same pressure, the compressibility of the elastic buffer layer along its thickness direction is greater than the compressibility of the support layer along its thickness direction, and / or, the porosity of the elastic buffer layer can be greater than the porosity of the support layer. For example, the porosity of the elastic buffer layer 31 can be 40% to 95%, optionally 55% to 90%, and further optionally 70% to 85%, and the porosity of the support layer 32 can be less than or equal to 5%. Alternatively, the elastic buffer layer may include at least one of foamed polyethylene, polypropylene, polyurethane, and silicone rubber, and the support layer may include, but is not limited to, at least one of high-density polyethylene, polymethyl methacrylate, polyethylene terephthalate, and polytetrafluoroethylene. Further, at least one of the following conditions may be met: the thickness of the elastic buffer layer may be greater than the thickness of the support layer; in a single elastic buffer pad, the ratio of the total thickness of the support layer to the free thickness of the elastic buffer layer may be 0.005 to 0.1, such as 0.02 to 0.05; the thickness of the elastic buffer layer in its natural state may be 0.2 mm to 10 mm, and the thickness of a single support layer may be 30 μm to 200 μm; the elastic buffer layer and the support layer may be bonded together. The composite structure of a support layer and an elastic buffer layer provides support to the elastic buffer layer, which not only suppresses thermal shrinkage (such as during vacuum baking) but also, through the support layer, inhibits thermal shrinkage in the two-dimensional direction perpendicular to its thickness, thus mitigating the problem of loss of function due to thermal shrinkage. Furthermore, it also addresses the issue of material damage caused by mechanical stress in the later stages of battery use. Moreover, placing this elastic buffer pad inside the battery cell further improves the battery's volume stability during long-term use and enhances its long-term performance.

[0116] In some embodiments of this application, the electrode assembly 12 may include a positive electrode, a negative electrode, and a separator. The positive electrode, negative electrode, and separator can be formed into the electrode assembly through a winding process. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode. The separator is disposed between the positive and negative electrode to provide isolation.

[0117] [Positive electrode plate]

[0118] In a battery, the positive electrode typically includes a positive current collector and a layer of positive active material disposed on the positive current collector, the positive active material layer comprising the positive active material. The positive current collector can be a conventional metal foil or a composite current collector (a composite current collector can be formed by depositing metal material on a polymer substrate). As an example, the positive current collector can be aluminum foil.

[0119] In this application, the specific type of positive electrode active material is not limited; any active material known in the art that can be used for battery positive electrodes can be used, and those skilled in the art can select according to actual needs. For example, the positive electrode active material may include, but is not limited to, positive electrode active materials containing lithium transition metal oxides and / or lithium phosphates with olivine structures. The lithium transition metal oxides may include undoped and / or optionally doped modified lithium transition metal oxides, uncoated and / or coated modified lithium transition metal oxides, and the lithium phosphates with olivine structures may include undoped and / or optionally doped modified lithium phosphates, uncoated and / or coated modified lithium phosphates. The positive electrode active materials within the given range can be prepared or obtained commercially.

[0120] In some specific embodiments of this application, the positive electrode active material layer may optionally include a binder, a conductive agent, and other optional additives. As an example, the conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers. As an example, the binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0121] [Negative electrode plate]

[0122] In a battery, the negative electrode typically includes a negative current collector and a layer of negative active material disposed on the negative current collector, the negative active material layer comprising a negative active material. The negative current collector can be a conventional metal foil or a composite current collector (for example, a composite current collector can be formed by depositing metal material on a polymer substrate). As an example, the negative current collector can be copper foil.

[0123] In some embodiments of this application, the battery cell of the first aspect of this application can be a lithium-ion battery cell. In this case, the specific type of negative electrode active material is not limited, and any active material known in the art that can be used for the negative electrode of a battery can be used. Those skilled in the art can flexibly select according to actual needs. As an example, the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. Optionally, silicon-based materials may include one or more of elemental silicon, silicon oxide compounds (e.g., silicon suboxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Further optionally, tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode active materials within the given range can be prepared or obtained commercially.

[0124] In some specific embodiments of this application, the negative electrode active material layer may optionally include a binder, a conductive agent, and other optional additives. As an example, the conductive agent may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). As an example, other optional additives may include, but are not limited to, thickeners and dispersants (e.g., sodium carboxymethyl cellulose CMC-Na), and PTC thermistor materials.

[0125] In some embodiments of this application, the separator in the battery may include, but is not limited to, a polyethylene porous membrane, a polypropylene porous membrane, a polyimide porous membrane, and a porous membrane formed by a composite of various polymers.

[0126] A second aspect of this application provides a battery comprising: the battery cell described in the first aspect of this application. Optionally, the battery can be a secondary battery, such as a lithium-ion secondary battery.

[0127] In some embodiments of this application, the battery can be either a single battery cell 1 (see reference 1) Figure 11 (Understanding), or it can be a battery module 2 composed of individual battery cells 1 (refer to) Figure 12 (Understanding) or battery pack 3 (Reference) Figure 13 understand).

[0128] In some implementations, the battery can be a battery module, and the number of individual battery cells contained in the battery module can be one or more, the specific number of which can be adjusted according to the application and capacity of the battery module. For example... Figure 12This is battery module 2 as an example. (See reference...) Figure 12 In battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 1 can be secured with fasteners. Optionally, battery module 2 may also include a housing with a receiving space in which the multiple battery cells 1 are received.

[0129] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. (See reference...) Figure 13 or Figure 14 ( Figure 13 and Figure 14 As an example, a battery pack 3 may include a battery compartment and multiple battery modules 2 disposed within the battery compartment. The battery compartment may include an upper housing 4 and a lower housing 5, with the upper housing 4 covering the lower housing 5 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 may be arranged in any manner within the battery compartment.

[0130] In some embodiments, the battery may include a first battery cell assembly and at least two second battery cell assemblies. The first battery cell assembly includes at least one battery cell 1 according to the first aspect of this application, and the second battery cell assembly includes at least two second battery cells. The at least two second battery cells are disposed on both sides of the first battery cell assembly along its thickness direction, and the thickness direction of the first battery cell assembly is consistent with the thickness direction of the battery cell 1. Optionally, the battery cell of the first aspect of this application is a prismatic battery cell with a wound electrode assembly. By combining the prismatic housing, the wound electrode assembly, and the elastic buffer pad, the problem of uneven stress on the electrode sheets in the prismatic wound battery can be alleviated, and the stability of the battery cell can be improved. The battery can be either a battery module or a battery pack. For example, taking the length direction of the first battery cell assembly as a row and the thickness direction of the first battery cell assembly as a column, in the battery module or the battery pack, the first battery cell assembly may include multiple battery cells 1 arranged in rows and / or columns, and / or, multiple second battery cells arranged in rows and / or columns may be independently provided on both sides of the first battery cell assembly along its thickness direction. Optionally, at least two second battery cells may be symmetrically arranged on both sides of the first battery cell assembly along its thickness direction. Further optionally, in the battery module or the battery pack, based on the total number of battery cells 1 and second battery cells, the proportion of battery cells 1 may be 30% to 70%. A battery typically comprises multiple individual cells, which are stacked along their thickness. In this case, the cells located in the center of the battery often experience the most significant expansion and the greatest expansion force during use. By incorporating a first elastic buffer pad only in the first cell located in the center, and omitting the elastic buffer pads in the second cells located on either side of the first cell assembly's thickness direction, the battery can absorb the volume expansion of the cells that experience more significant expansion and greater expansion force, reducing the expansion force in the central cells and improving the battery's volume stability. Furthermore, this approach helps mitigate the problem of stress concentration in the central cells caused by cell volume expansion during later battery use, which can lead to lithium plating and a drop in battery performance. Simultaneously, it also ensures high energy density for the battery.

[0131] Additionally, this application provides an electrical device comprising: a battery according to the second aspect of this application. The battery, such as a single cell, battery module, or battery pack, can serve as both a power source and an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, and energy storage systems. (Reference) Figure 15 To illustrate, as a specific example, the electrical device could be a vehicle. The specific type of battery can be selected based on the device's usage requirements, such as individual battery cells, battery modules, or battery packs.

[0132] As an example, the electrical device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery, a battery pack or battery module can be used.

[0133] As another example, the device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use battery cells as their power source.

[0134] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0135] Example 1

[0136] (I) Preparation of lithium secondary batteries

[0137] (1) Preparation of positive electrode sheet

[0138] LiNi, the positive electrode active material 0.6 Co 0.1 Mn 0.3 O2, conductive agent Super P, and binder PVDF were mixed in a weight ratio of 96:2:2. N-methylpyrrolidone solvent was added, and the mixture was thoroughly stirred to obtain a positive electrode slurry. This slurry was then coated onto both surfaces of a 13μm thick aluminum foil for the positive electrode current collector. The surface density of the positive electrode slurry on one side of the aluminum foil was 20 mg / cm³. 2 Then, it is dried and cold-pressed to obtain the positive electrode sheet.

[0139] (2) Preparation of negative electrode sheet

[0140] Artificial graphite (negative electrode active material), Super P (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed in a weight ratio of 96:0.5:2:1.5. Deionized water was added as a solvent, and the mixture was stirred thoroughly to obtain a negative electrode slurry. This slurry was then coated onto both surfaces of a 6 μm thick copper foil current collector. The coating thickness of the negative electrode slurry on one side of the copper foil was 100 μm, and the surface density of the negative electrode slurry on one side of the copper foil was 11 mg / cm³. 2 Then, it is dried and cold-pressed to obtain the negative electrode sheet.

[0141] (3) Preparation of electrolyte

[0142] In an argon atmosphere glove box with a water content of <10ppm, solvents EC (ethylene carbonate), PC (propylene carbonate), and DMC (dimethyl carbonate) are mixed in a 1:1:1 ratio. Then, fully dried lithium salt LiPF6 is dissolved in the above mixed organic solvent and stirred evenly to obtain an electrolyte, wherein the concentration of LiPF6 is 1mol / L.

[0143] (4) Preparation of the separating membrane

[0144] A 7μm thick porous polyethylene membrane was used as the separator.

[0145] (5) Preparation of elastic cushioning pad

[0146] Polypropylene with a thickness of 3 mm in its free state is used as an elastic buffer layer.

[0147] (6) Preparation of lithium secondary batteries

[0148] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound and shaped to form an electrode assembly. Two electrode assemblies and an elastic buffer pad are placed in the battery casing (the distance d0 between the two opposing inner wall surfaces along its thickness direction is 60 mm), with an elastic buffer pad sandwiched between the two electrode assemblies. The prepared electrolyte is injected and the casing is then encapsulated to obtain a lithium-ion secondary lithium battery.

[0149] Examples 2-22 and Comparative Examples 1-7

[0150] The differences between Examples 2-22 and Comparative Example 7 and Example 1 are detailed in Table 1. In Examples 1-22 and Comparative Examples 1-7, the elastic buffer pads are all porous structures. The different compression rates of elastic buffer pads made of the same material under the same stress are due to the different porosity and pore size of the elastic buffer pads.

[0151] (II) Battery Testing Methods

[0152] (a) Testing the dimensions of the battery and electrode assembly and the compressibility of the elastic cushioning pad.

[0153] Two sets of parallel secondary battery samples were taken. After resting at 25℃ for 5 minutes, both sets were charged to 4.4V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 4.4V, and allowed to stand for 5 minutes. One set of secondary batteries was disassembled to obtain the electrode assembly. After cleaning and drying the electrode assembly, its thickness, length L1, and height h1 were measured (the length and height of the electrode assembly are matched in the length and height directions of the secondary battery casing, respectively; note: the length of the cylindrical battery electrode assembly and the secondary battery are measured by circumference). The other set of secondary batteries was discharged to 2.8V with a constant current of 0.33C, allowed to stand for 5 minutes, and then disassembled to obtain the electrode assembly. After cleaning and drying the electrode assembly, its thickness was measured. The testing method was as follows: the electrode assembly was placed between two parallel flat plates, and a pressure of 0.1MPa was applied to the electrode assembly using the plates. The thickness of the electrode assembly was obtained by measuring the distance between the plates. Calculate the total thickness d1 of the electrode assembly in the secondary battery under full charge and the total thickness d2 of the electrode assembly under full discharge.

[0154] The thickness of the elastic buffer pad in its free state was measured using a Mitutoyo ID-C112MX micrometer thickness gauge under a test force of less than or equal to 1.8N. Multiple points (e.g., 5, 10, etc.) were randomly measured, and the average value was taken to calculate the total thickness d of the elastic buffer pad in the free state of the secondary battery. The length L2 and height h2 of the elastic buffer pad were also measured (the length and height of the elastic buffer pad are matched in the length and height directions of the electrode assembly, respectively). The elastic buffer pad was placed between two parallel plates, and pressures of 0.1MPa and 0.5MPa were applied to the elastic buffer pad using the plates. The distance between the plates was measured to obtain the thickness of the electrode assembly under compressive stress. The compression rate of the elastic buffer pad along its thickness under compressive stress was calculated as the ratio of the thickness change of the elastic buffer pad in the free state to the thickness in the compressive stress state multiplied by 100%.

[0155] (b) Testing the capacity retention of the secondary battery

[0156] Take multiple parallel samples of secondary batteries. After allowing the batteries to stand at 25°C for 5 minutes, charge them to 4.4V with a constant current of 0.5C, then charge them to 0.05C with a constant voltage of 4.4V, let them stand for 5 minutes, and then discharge them to 2.8V with a constant current of 0.33C, let them stand for 5 minutes, and record the discharge capacity C0. Repeat the above operation and calculate the battery capacity retention rate using the following formula: Capacity retention rate (%) of the secondary battery after n cycles = C n / C0×100%. Record the battery capacity retention rate after n cycles.

[0157] (c) Battery cell expansion force test

[0158] The secondary battery was left to stand at 25°C for 5 minutes, then charged at a constant current of 0.5C to 4.4V, followed by a constant voltage charge of 4.4V to 0.05C, and left to stand for 5 minutes. The secondary battery was then discharged at a constant current of 0.33C to 2.8V, and left to stand for 5 minutes. Six pressure sensors were placed at different locations on one side of the thickness direction. The battery was charged at a constant current of 0.5C to 4.4V, followed by a constant voltage charge of 4.4V to 0.05C, and left to stand for 5 minutes. The expansion force displayed by the pressure sensors at different locations was recorded when the secondary battery was fully charged. The average value of the expansion force under different charging conditions was calculated, and the range of the rate of change of each expansion force relative to the average value under different charging conditions was calculated based on this average value.

[0159] (d) Lithium plating drop test

[0160] After allowing the secondary battery to stand at 25°C for 5 minutes, it was charged to 4.4V at a constant current of 0.5C, then charged to 0.05C at a constant voltage of 4.4V, and allowed to stand for 5 minutes. Next, the secondary battery was discharged to 2.8V at a constant current of 0.33C, and allowed to stand for 5 minutes. This charge-discharge cycle was repeated until the secondary battery capacity showed significant decay. After the charge-discharge cycle test was completed, the secondary battery was disassembled, and the presence of lithium plating on the negative electrode was observed.

[0161] Relevant tests were conducted on Examples 1-20 and Comparative Examples 1-7, and the test results are detailed in Table 2.

[0162]

[0163]

[0164] in conclusion:

[0165] As can be seen from Examples 1-20, Comparative Examples 1-7, and Tables 1-2, the solutions of the above embodiments of this application are beneficial to improving the volume stability and stress uniformity of battery cells during long-term use, and reducing the risk of expansion, deformation, or performance degradation. Furthermore, for battery cells with P > 5%, an elastic buffer pad with a compression ratio ≥ 60% or ≥ 70% at 0.5 MPa pressure can be selected; for battery cells with -5% ≤ P ≤ 5%, an elastic buffer pad with a compression ratio ≤ 15% or ≤ 10% at 0.1 MPa pressure, and / or a compression ratio ≤ 55% or ≤ 50% at 0.5 MPa pressure can be selected. In addition, by further adjusting the ratio of the sum of the total thickness d of the elastic buffer pad in its free state and the total thickness d1 (d2) of the electrode assembly in its fully charged (discharged) state to the distance d0 between the two inner wall surfaces of the casing arranged opposite each other along its thickness direction, and by adjusting the size of the elastic buffer pad relative to the electrode assembly, it is also beneficial to further improve the volume stability and stress uniformity of battery cells during long-term use, and reduce the risk of expansion, deformation, or performance degradation.

[0166] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, include: case; At least one electrode assembly, said electrode assembly being disposed within the housing; At least one elastic buffer pad is disposed on at least a portion of the surface of the electrode assembly and / or inside the electrode assembly, and the compressibility of the elastic buffer pad along its thickness direction satisfies the following relationship: -5%≤P≤5%, the compression rate of the elastic buffer pad is ≤20% under 0.1 MPa pressure and ≤60% under 0.5 MPa pressure; or, P > 5%, the compression rate of the elastic buffer pad under 0.5 MPa pressure is ≥ 50%; Wherein, at least one of the electrode components and at least one of the elastic buffer pads are stacked along a first direction, where P is the ratio of the difference between the total distance of the electrode components in the fully charged state and the total distance in the fully discharged state in the first direction to the distance between the inner wall surfaces of the housing.

2. The battery cell according to claim 1, characterized in that, The elastic buffer pad is provided between the electrode assembly and the housing, and / or the elastic buffer pad is provided between two adjacent electrode assemblies.

3. The battery cell according to claim 1 or 2, characterized in that, When -5% ≤ P ≤ 5%, the compression ratio of the elastic buffer pad under 0.1 MPa pressure is ≤ 15%, and / or, the compression ratio of the elastic buffer pad under 0.5 MPa pressure is ≤ 55%; or, When P > 5%, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa is ≥ 60%.

4. The battery cell according to claim 3, characterized in that, When -5%≤P≤5%, the compression rate of the elastic buffer pad under 0.1Mpa pressure is ≤10%.

5. The battery cell according to claim 3, characterized in that, When -5%≤P≤5%, the compression rate of the elastic buffer pad under 0.5Mpa pressure is ≤50%.

6. The battery cell according to claim 3, characterized in that, When P > 5%, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa is ≥ 70%.

7. The battery cell according to claim 1 or 2, characterized in that, The electrode assembly is a wound electrode assembly, and includes a straight portion and a corner portion, wherein the elastic buffer pad is disposed on at least a portion of the surface of the straight portion and / or the corner portion.

8. The battery cell according to claim 3, characterized in that, The electrode assembly is a wound electrode assembly, and includes a straight portion and a corner portion, wherein the elastic buffer pad is disposed on at least a portion of the surface of the straight portion and / or the corner portion.

9. The battery cell according to claim 1 or 2, characterized in that, The battery cell is a prismatic battery cell.

10. The battery cell according to claim 3, characterized in that, The battery cell is a prismatic battery cell.

11. The battery cell according to claim 7, characterized in that, The battery cell is a prismatic battery cell.

12. The battery cell according to claim 9, characterized in that, The battery cell includes at least one first elastic buffer pad and / or at least one second elastic buffer pad, wherein the first elastic buffer pad and the electrode assembly are stacked along the thickness direction of the battery cell, and / or the second elastic buffer pad and the electrode assembly are stacked along the length direction of the battery cell.

13. The battery cell according to claim 12, characterized in that, At least one of the following conditions must be met: In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 80% to 99% of the distance between the inner wall surfaces of the housing; In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully charged state is 95% to 110% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully discharged state is 80% to 99% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully charged state is 95% to 110% of the distance between the inner walls of the housing.

14. The battery cell according to claim 13, characterized in that, At least one of the following conditions must be met: In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 85% to 98% of the distance between the inner wall surfaces of the housing; In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully charged state is 98% to 105% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully discharged state is 85% to 98% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully charged state is 98% to 105% of the distance between the inner walls of the housing.

15. The battery cell according to claim 14, characterized in that, At least one of the following conditions must be met: In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 90% to 95% of the distance between the inner wall surfaces of the housing; In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully charged state is 99% to 102% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully discharged state is 90% to 95% of the distance between the inner wall surfaces of the housing; Along the length of the battery cell, the sum of the total thickness of the second elastic buffer pad in its free state and the length of the electrode assembly in its fully charged state is 99% to 102% of the distance between the inner walls of the housing.

16. The battery cell according to claim 12, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 2% to 25%.

17. The battery cell according to claim 16, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 5% to 20%.

18. The battery cell according to claim 17, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 8% to 15%.

19. The battery cell according to claim 13, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 2% to 25%.

20. The battery cell according to claim 19, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 5% to 20%.

21. The battery cell according to claim 20, characterized in that, The ratio of the total thickness of the first elastic buffer pad in the free state to the total thickness of the electrode assembly in the fully discharged state is 8% to 15%.

22. The battery cell according to claim 12, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.8 to 1.2; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.

2.

23. The battery cell according to claim 22, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.85 to 1.1; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.85 to 1.

1.

24. The battery cell according to claim 23, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.9 to 1.05; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.9 to 1.

05.

25. The battery cell according to claim 13, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.8 to 1.2; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.

2.

26. The battery cell according to claim 25, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.85 to 1.1; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.85 to 1.

1.

27. The battery cell according to claim 26, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.9 to 1.05; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.9 to 1.

05.

28. The battery cell according to claim 16, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.8 to 1.2; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.

2.

29. The battery cell according to claim 28, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.85 to 1.1; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.85 to 1.

1.

30. The battery cell according to claim 29, characterized in that, In its free state, the ratio of the extension distance of the first elastic buffer pad along the length of the electrode assembly to the length of the electrode assembly is 0.9 to 1.05; and / or, In its free state, the ratio of the extension distance of the first elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.9 to 1.

05.

31. The battery cell according to claim 12, characterized in that, The orthographic projection of the first elastic buffer pad onto the electrode assembly lies within the area where the electrode assembly is located.

32. The battery cell according to claim 13, characterized in that, The orthographic projection of the first elastic buffer pad onto the electrode assembly lies within the area where the electrode assembly is located.

33. The battery cell according to claim 16, characterized in that, The orthographic projection of the first elastic buffer pad onto the electrode assembly lies within the area where the electrode assembly is located.

34. The battery cell according to claim 22, characterized in that, The orthographic projection of the first elastic buffer pad onto the electrode assembly lies within the area where the electrode assembly is located.

35. The battery cell according to claim 1 or 2, characterized in that, The battery cell is a cylindrical battery cell, and at least one of the elastic buffer pads and the electrode assembly are stacked along the radial direction of the electrode assembly. The distance between the inner wall surfaces of the housing is equal to the inner diameter of the housing cavity.

36. The battery cell according to claim 3, characterized in that, The battery cell is a cylindrical battery cell, and at least one of the elastic buffer pads and the electrode assembly are stacked along the radial direction of the electrode assembly. The distance between the inner wall surfaces of the housing is equal to the inner diameter of the housing cavity.

37. The battery cell according to claim 35, characterized in that, The sum of the total thickness of the elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 80% to 99% of the inner diameter of the housing cavity; and / or, The sum of the total thickness of the elastic buffer pad in its free state and the total thickness of the electrode assembly in its fully charged state is 85% to 110% of the inner diameter of the housing cavity.

38. The battery cell according to claim 37, characterized in that, The sum of the total thickness of the elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 85% to 98% of the inner diameter of the housing cavity; and / or, The sum of the total thickness of the elastic buffer pad in its free state and the total thickness of the electrode assembly in its fully charged state is 98% to 105% of the inner diameter of the housing cavity.

39. The battery cell according to claim 38, characterized in that, The sum of the total thickness of the elastic buffer pad in the free state and the total thickness of the electrode assembly in the fully discharged state is 90% to 95% of the inner diameter of the housing cavity; and / or, The sum of the total thickness of the elastic buffer pad in its free state and the total thickness of the electrode assembly in its fully charged state is 99% to 102% of the inner diameter of the housing cavity.

40. The battery cell according to claim 35, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.8 to 1.2; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.

2.

41. The battery cell according to claim 40, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.85 to 1.1; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.85 to 1.

1.

42. The battery cell according to claim 41, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.9 to 1.05; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.9 to 1.

05.

43. The battery cell according to claim 37, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.8 to 1.2; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.

2.

44. The battery cell according to claim 43, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.85 to 1.1; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.85 to 1.

1.

45. The battery cell according to claim 44, characterized in that, The elastic buffer pad is disposed between the electrode assembly and the housing. In its free state, the ratio of the elastic buffer pad's circumferential extension distance to the circumference of the electrode assembly is 0.9 to 1.05; and / or, In its free state, the ratio of the extension distance of the elastic buffer pad in the height direction of the electrode assembly to the height of the electrode assembly is 0.9 to 1.

05.

46. ​​The battery cell according to claim 40, characterized in that, In its free state, the elastic buffer pad extends in the circumferential direction of the electrode assembly at a distance less than or equal to the circumference of the electrode assembly; and / or, in its free state, the elastic buffer pad extends in the height direction of the electrode assembly at a distance less than or equal to the height of the electrode assembly.

47. The battery cell according to claim 1 or 2, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

48. The battery cell according to claim 47, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

49. The battery cell according to claim 3, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

50. The battery cell according to claim 49, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

51. The battery cell according to claim 7, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

52. The battery cell according to claim 51, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

53. The battery cell according to claim 9, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

54. The battery cell according to claim 53, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

55. The battery cell according to claim 12, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

56. The battery cell according to claim 55, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

57. The battery cell according to claim 13, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

58. The battery cell according to claim 57, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

59. The battery cell according to claim 16, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

60. The battery cell according to claim 59, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

61. The battery cell according to claim 22, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

62. The battery cell according to claim 61, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

63. The battery cell according to claim 31, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

64. The battery cell according to claim 63, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

65. The battery cell according to claim 35, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

66. The battery cell according to claim 65, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

67. The battery cell according to claim 37, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

68. The battery cell according to claim 67, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

69. The battery cell according to claim 40, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

70. The battery cell according to claim 69, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

71. The battery cell according to claim 46, characterized in that, The thickness of a single elastic buffer pad in its free state is 2% to 15% of the thickness of a single electrode assembly in its fully discharged state; and / or, The thickness of a single elastic cushioning pad in its free state is 0.2 mm to 10.5 mm.

72. The battery cell according to claim 71, characterized in that, The thickness of a single elastic buffer pad in the free state is 5% to 10% of the thickness of a single electrode assembly in the fully discharged state.

73. A battery, characterized in that, Includes the battery cell according to any one of claims 1 to 72.

74. An electrical device, characterized in that, Includes the battery as described in claim 73.

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