Battery cell, battery and electrical apparatus

Abstract

Disclosed in the present application are a battery cell, a battery and an electrical apparatus. The battery cell comprises a casing; at least one electrode component, the electrode component being arranged inside the casing; and at least one elastic buffer pad, the elastic buffer pad being arranged on at least part of the surface of the electrode component and / or inside the electrode component, the compression ratio of the elastic buffer pad in the thickness direction satisfying the following relationship: -5％≤P≤5％, the compression ratio of the elastic buffer pad under the pressure of 0.1 MPa being ≤20%, and the compression ratio thereof under the pressure of 0.5 MPa being ≤ 60%, or P＞5%, and the compression ratio of the elastic buffer pad under the pressure of 0.5 MPa being ≥50%, the at least one electrode component and the at least one elastic buffer pad being stacked in a first direction, and P being a ratio of a difference between the total distance of the electrode component in a fully-charged state and the total distance thereof in a fully-discharged state to the distance between the inner wall surfaces of the casing in the first direction.

Description

Battery cells, batteries and electrical devices Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to battery cells, batteries, and electrical devices. Background Art

[0002] Batteries, as energy storage devices, are widely used in various fields. Lithium-ion batteries, for example, are green, environmentally friendly, high-energy, and low-carbon. They are not only used in energy storage power systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, and ships, as well as in military equipment and aerospace. With the development of today's society, people's demands for batteries are also becoming increasingly higher.

[0003] Public content

[0004] In view of the technical problems existing in the background technology, the present application provides a battery cell, which aims to improve the effect of the buffer pad and reduce the risk of expansion, deformation or performance deterioration of the battery cell.

[0005] In order to achieve the above objectives, the first aspect of the present application provides a battery cell, comprising:

[0006] case;

[0007] at least one electrode assembly, the electrode assembly being disposed within the housing;

[0008] At least one elastic buffer pad, the elastic buffer pad being provided on at least a portion of the surface of the electrode assembly and / or inside the electrode assembly, wherein the compression rate of the elastic buffer pad along its thickness direction satisfies the following relationship:

[0009] -5%≤P≤5%, the compression rate of the elastic buffer pad under a pressure of 0.1 MPa is ≤20%, and the compression rate under a pressure of 0.5 MPa is ≤60%; or,

[0010] P>5%, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa is ≥50%;

[0011] In which, at least one of the electrode assemblies and at least one of the elastic buffer pads are stacked along a first direction, and P is the ratio of the difference between the total distance of the electrode assemblies 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 surface of the shell.

[0012] The battery cell of the first aspect of the present application has the following beneficial effects: it can be applied to battery cells of different expansion systems. For low expansion systems (-5% ≤ P ≤ 5%), the volume deformation of the electrode assembly during the charge and discharge process is relatively small. Selecting an elastic buffer pad whose compression rate along its thickness direction meets the given conditions can, on the one hand, buffer the volume expansion force generated by the electrode assembly during the charge and discharge process and suppress the deformation of the battery cell. On the other hand, it can also make the elastic buffer pad have a certain supporting strength. When the elastic buffer pad is not over-compressed, it is also beneficial to achieve direct adhesion between the electrode assembly and the inner wall of the shell or adhesion between the elastic buffer pad and the inner wall of the shell to achieve interaction force, which is beneficial to improving the force uniformity of the electrode piece and suppressing the shaking of the electrode assembly. For high expansion systems (P>5%), the volume deformation of the electrode assembly during the charge and discharge process is relatively large. Selecting an elastic buffer pad whose compression rate along its thickness direction meets the given conditions can be fully compressed during the expansion of the electrode assembly, transferring its 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, the elastic buffer pad can 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.

[0013] In some embodiments of the present application, the elastic buffer pad is provided between the electrode assembly and the housing, and / or between two adjacent electrode assemblies. Meeting the given conditions is conducive to improving the volume stability of the battery cell during long-term use.

[0014] In some embodiments of the present application, when -5% ≤ P ≤ 5%, the compression rate of the elastic cushion at a pressure of 0.1 MPa is ≤ 15%, and optionally ≤ 10%; and / or the compression rate of the elastic cushion at a pressure of 0.5 MPa is ≤ 55%, and optionally ≤ 50%. Meeting these conditions not only helps improve the volume stability of low-expansion battery cells during long-term use, but also helps improve the uniformity of force applied to the electrode sheets, reducing the risk of expansion, deformation, or performance deterioration of the battery cells.

[0015] In some embodiments of the present application, when P > 5%, the elastic cushion has a compression rate of ≥ 60% at a pressure of 0.5 MPa, and optionally ≥ 70%. Meeting this condition further helps reduce the expansion force exerted by the electrode assembly on the battery housing in high-expansion battery cells, thereby improving the volume stability of the battery cells during long-term use.

[0016] In some embodiments of the present application, the electrode assembly is a wound electrode assembly and includes a straight portion and a corner portion, and the elastic buffer pad is provided on at least a portion of the surface of the straight portion and / or the corner portion.

[0017] In some embodiments of the present application, the battery cell is a prismatic battery cell.

[0018] In some embodiments of the present application, the prismatic battery cell includes: at least one first elastic cushion and / or at least one second elastic cushion, wherein the first elastic cushion and the electrode assembly are stacked along the thickness of the battery cell, and / or the second elastic cushion and the electrode assembly are stacked along the length of the battery cell. Meeting these conditions helps reduce expansion forces generated by the electrode assembly during use.

[0019] In some embodiments of the present 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 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 walls of the shell, 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 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 walls of the shell, optionally 98% The length of the battery cell is such that the sum of the total thickness of the second elastic buffer in the free state and the length of the electrode assembly in the fully discharged state is 80% to 99% of the distance between the inner walls of the housing, optionally 85% to 98%, and optionally 90% to 95%; the length of the battery cell is such that the sum of the total thickness of the second elastic buffer in the free state and the length of the electrode assembly in the fully charged state is 95% to 110% of the distance between the inner walls of the housing, optionally 98% to 105%, and optionally 99% to 102%. Meeting these conditions facilitates the smooth insertion of the elastic buffer into the housing and / or improves the volume stability of the battery cell and the uniformity of force on the electrode sheets.

[0020] In some embodiments of the present application, the ratio of the total thickness of the first elastic buffer in a free state to the total thickness of the electrode assembly in a fully discharged state is 2% to 25%, optionally 5% to 20%, and further optionally 8% to 15%. Meeting these conditions is beneficial for maintaining the volume stability of the battery cell while also taking into account the energy density of the battery cell.

[0021] In some embodiments of the present application, when the first elastic buffer is in a free state, the ratio of the distance extended in the length direction of the electrode assembly to the length of the electrode assembly is 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05; and / or, when the first elastic buffer is in a free state, the ratio of the distance extended in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05. Meeting these conditions facilitates the elastic buffer covering a majority of the electrode assembly, which not only improves the volume stability of the battery cell but also further improves the force uniformity of the electrode sheet.

[0022] In some embodiments of the present application, the orthographic projection of the first elastic buffer on the electrode assembly is located in the region where the electrode assembly is located. Meeting the given conditions not only facilitates smooth insertion of the elastic buffer into the housing during assembly, but also helps to further balance the energy density of the battery.

[0023] In some embodiments of the present application, the battery cell is a cylindrical battery cell, at least one elastic buffer pad and the electrode assembly are stacked along the radial direction of the electrode assembly, and the distance between the inner walls of the shell is equal to the diameter of the shell inner cavity.

[0024] In some embodiments of the present application, in the cylindrical battery cell, the sum of the total thickness of the elastic cushion in the free state and the total thickness of the electrode assembly in the fully discharged state is 80% to 99% of the diameter of the inner cavity of the housing, optionally 85% to 98%, and further optionally 90% to 95%; and / or the sum of the total thickness of the elastic cushion in the free state and the total thickness of the electrode assembly in the fully charged state is 85% to 110% of the diameter of the inner cavity of the housing, optionally 98% to 105%, and further optionally 99% to 102%. Meeting these conditions facilitates smooth insertion of the elastic cushion into the housing and / or improves the volume stability of the battery cell and the uniformity of force applied to the electrode sheets.

[0025] In some embodiments of the present application, in the cylindrical battery cell, the elastic buffer is disposed between the electrode assembly and the housing. In a free state, the ratio of the distance the elastic buffer extends in the circumferential direction of the electrode assembly to the circumference of the electrode assembly is 0.8 to 1.2, optionally 0.85 to 1.1, or further optionally 0.9 to 1.05; and / or, in a free state, the ratio of the distance the elastic buffer extends in the height direction of the electrode assembly to the height of the electrode assembly is 0.8 to 1.2, optionally 0.85 to 1.1, or further optionally 0.9 to 1.05. Meeting these conditions facilitates the elastic buffer covering a majority of the electrode assembly, thereby improving both the volume stability of the battery cell and further improving the uniformity of force applied to the electrode sheet.

[0026] In some embodiments of the present application, in the cylindrical battery cell, the elastic cushioning pad, when in a free state, extends circumferentially of the electrode assembly for a distance less than or equal to the circumference of the electrode assembly; and / or, the elastic cushioning pad, when in a free state, extends heightwise of the electrode assembly for a distance less than or equal to the height of the electrode assembly. Meeting these conditions not only facilitates smooth insertion of the elastic cushioning pad into the battery case during assembly, but also helps balance the battery's energy density.

[0027] In some embodiments of the present application, the thickness of a single elastic buffer pad in a free state is 2% to 15%, and optionally 5% to 10%, of the thickness of a single electrode assembly in a fully discharged state. Meeting this condition is beneficial for maintaining the volume stability of the battery cell during its life cycle, especially in the later stages of use, while also ensuring the energy density of the battery cell.

[0028] In some embodiments of the present application, the thickness of a single elastic buffer pad in a free state is 0.2 mm to 10.5 mm. Meeting the given conditions can not only take into account the compressible deformation of the elastic buffer pad and the energy density of the battery cell, but also ensure that the support layer has a certain strength.

[0029] A second aspect of the present application provides a battery, which includes: the battery cell described in the first aspect of the present application.

[0030] The third aspect of the present application provides an electrical device, which includes: the battery described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0032] FIG1 is a schematic cross-sectional view of a prismatic battery cell according to one embodiment of the present application.

[0033] FIG2 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0034] FIG3 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0035] FIG4 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0036] FIG5 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0037] FIG6 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0038] FIG7 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0039] FIG8 is a schematic cross-sectional view of a prismatic battery cell according to another embodiment of the present application.

[0040] FIG9 is a schematic cross-sectional view of a cylindrical battery cell according to one embodiment of the present application.

[0041] FIG10 is a schematic cross-sectional view of a cylindrical battery cell according to another embodiment of the present application.

[0042] FIG11 is a schematic structural diagram of a battery cell according to an embodiment of the present application.

[0043] FIG12 is a schematic structural diagram of a battery module according to an embodiment of the present application.

[0044] FIG13 is a schematic structural diagram of a battery pack according to an embodiment of the present application.

[0045] FIG14 is an exploded view of a battery pack according to one embodiment of the present application.

[0046] FIG15 is a schematic diagram of an embodiment of an electric device using a battery as a power source according to an embodiment of the present application.

[0047] Reference numerals: 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 case; 5: lower case. DETAILED DESCRIPTION

[0048] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0049] Below, with appropriate reference to the accompanying drawings, the embodiments of the positive electrode active material and its preparation method, the positive electrode sheet, the battery and the electric device of the present application are described in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] The "range" disclosed in this application is defined in the form of a lower limit and / or an upper limit, and a given range is defined by selecting a lower limit and / or an upper limit, and the selected lower limit and / or upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with other lower limits to form an unspecified range, and similarly any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an unspecified range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also contemplated. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this document, and "0-5" is just an abbreviation for these numerical combinations. In addition, when a parameter is expressed 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 the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

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

[0053] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, which means that the method may include steps S1 and S2 performed sequentially, or may include steps S2 and S1 performed sequentially. For example, the method may further include step S3, which means that step S3 may be added to the method in any order, for example, the method may include steps S1, S2, and S3, or may include steps S1, S3, and S2, or may include steps S3, S1, and S2, etc.

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

[0055] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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, the term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

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

[0058] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned description of the drawings and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0059] With the continued advancement of green environmental protection, battery applications have become increasingly ubiquitous in all aspects of life, including vehicles, electronic devices, and energy storage devices. However, as battery applications continue to expand, so too do people's expectations for batteries. Taking lithium-ion batteries as an example, lithium-ion batteries undergo volume changes during charge-discharge cycles and overcharge, and their expansion increases with operating time. This not only easily causes the battery casing to deform under compressive forces, affecting the battery's volume stability, but also excessive expansion of the electrode plates during charge-discharge cycles can affect the spacing between the electrode plates and the separator, increasing the risk of lithium plating and shortening the battery's service life. To address this issue, buffer pads are currently being installed between or within battery cells. However, the amount and rate of battery expansion during charge and discharge vary depending on factors such as the type of active material in the electrode plates and the thickness of the active material layer. Different expansion systems place varying stress and strain requirements on the buffer pads within the battery cells. Improper matching can hinder the effectiveness of the buffer pads and may even deteriorate battery cell performance.

[0060] In the present application, based on the different ratios of the distance difference between the electrode assembly in the battery cell in the fully charged state and the fully discharged state along the first direction to the distance between the inner wall surface of the shell along the first direction, different restrictions are made on the stress-strain relationship of the elastic buffer pad. That is, for a low expansion system, an elastic buffer pad with a compression rate of ≤20% in the thickness direction under a pressure of 0.1 MPa and a compression rate of ≤60% in the thickness direction under a pressure of 0.5 MPa is selected. This can not only buffer the volume expansion force generated by the electrode assembly during the charging and discharging process, but also have a certain supporting strength. Even in a state that is not over-compressed, it is conducive to achieving direct adhesion between the electrode assembly and the inner wall of the shell or adhesion between the electrode assembly and the inner wall of the shell through the elastic buffer pad, thereby achieving interaction force and improving the force uniformity of the electrode piece. For a high expansion system, an elastic buffer pad with a compression rate of ≥50% in the thickness direction under a pressure of 0.5 MPa is selected. This can achieve full compression during the expansion process of the electrode assembly, transfer its space in the thickness direction to the electrode assembly, and reduce the expansion force of the electrode assembly. Therefore, for battery cells with different expansion systems, the elastic buffer pad can play a better role and reduce the risk of expansion deformation or performance deterioration.

[0061] The battery cells and batteries disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or 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, battery-powered vehicles, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0062] The first aspect of the present application provides a battery cell, which includes: a shell; at least one electrode assembly, which is placed in the shell; at least one elastic buffer pad, which is arranged on at least part of the surface of the electrode assembly and / or inside the electrode assembly, and the compression rate of the elastic buffer pad along its thickness direction satisfies the following relationship: -5%≤P≤5%, the compression rate of the elastic buffer pad under a pressure of 0.1Mpa is ≤20%, and the compression rate under a pressure of 0.5Mpa is ≤60%; or, P>5%, the compression rate of the elastic buffer pad under a pressure of 0.5Mpa is ≥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 shell.

[0063] For example, referring to Figures 1 to 7 , it is understood that the battery cell 1 of the first aspect of the present application includes a housing 11, at least one electrode assembly 12, and at least one elastic buffer pad 13. The electrode assembly 12 is placed in the housing 11, and the elastic buffer pad 13 can be provided on at least a portion of the surface of the electrode assembly 12 and / or inside the electrode assembly 12. Exemplarily, the elastic buffer pad 13 can be provided between the electrode assembly 12 and the housing 11 (refer to Figure 1 for understanding), and / or between two adjacent electrode assemblies 12 (refer to Figure 2 for understanding), and / or inside the electrode assembly (refer to Figure 3 for understanding). Among them, the elastic buffer pad 13 can be provided between the electrode assembly 12 and the shell 11. It can be understood that it can be provided in at least one of the areas between the electrode assembly 12 and the side wall of the shell 11, between the electrode assembly 12 and the bottom wall of the shell 11, and between the electrode assembly 12 and the top wall of the shell 11. Optionally, with reference to Figure 4 or Figure 5, it is understood that the elastic buffer pad 13 can be provided between the electrode assembly 12 and the shell 11 and between two adjacent electrode assemblies at the same time; and more optionally, with reference to Figures 1, 6, and 7, it is understood that the elastic buffer pad 13 can be provided between the electrode assembly 12 and the side wall of the shell 11. In actual operation, both sides of the elastic buffer pad 13 along its thickness direction can be fitted with the electrode assembly 12 (refer to Figure 2 for understanding), or one side can be fitted with the electrode assembly 12 and the other side can be fitted with the inner wall of the shell 11.

[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, and they can be disposed between the electrode assembly 12 and the housing 11, or inside the electrode assembly. Optionally, they can be disposed between the electrode assembly 12 and the side wall of 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, and the one or more elastic buffer pads 13 can be disposed only between the battery assemblies 12, or only between the battery assembly 12 and the housing 11, or only inside the electrode assembly 12, or partially between the battery assemblies 12 and partially between the battery assembly 12 and the housing 11, etc. Optionally, the elastic buffer pads 13 disposed between the battery assembly 12 and the housing 11 can be disposed between the electrode assembly 12 and the side wall of 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 (refer to Figures 1 to 6 and 8 for understanding), and further optionally, the thickness direction of at least one elastic buffer pad 13 is the same as the thickness direction of the battery cell 1 and the electrode assembly 12.

[0066] In the battery cell of the present 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, and the distance between the inner wall surfaces of the shell 11 along the first direction is the inner cavity diameter of the shell.

[0067] In the battery cell of the present application, different requirements are placed on the stress-strain relationship of the elastic buffer pad 13 based on different expansion systems. That is, according to the different ratios 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 and the distance between the inner walls of the shell in the battery cell, different requirements are placed on the compressibility 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 ratio P (P = Δd / d0, Δd = d1-d2) of the difference Δd between the total thickness d1 of the electrode assembly in the fully charged state and the total thickness d2 of the electrode assembly in the fully discharged state to the distance d0 between the inner walls of the shell 11 in the thickness direction is different. The following requirements are placed on the compressibility of the elastic buffer pad 13 along its thickness direction:

[0068] When -5%≤P≤5%, an elastic buffer pad with a compression rate ≤20% under a pressure of 0.1 MPa and a compression rate ≤60% under a pressure of 0.5 MPa is selected. For example, the compression rate of the elastic buffer pad under a pressure of 0.1 MPa may be ≤20%, ≤18%, ≤16%, ≤14%, ≤12%, ≤10%, ≤8%, ≤6%, ≤4%, etc., or may be a range consisting of any of the above values; for another example, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa may be ≤60%, ≤55%, ≤50%, ≤45%, ≤40%, ≤35%, ≤30%, ≤25%, ≤20%, etc., or may be a range consisting of any of the above values. When -5%≤P≤5%, the expansion deformation of the battery cell during the charge and discharge process is relatively small, and the elastic buffer pad cannot be over-compressed. Selecting an elastic buffer pad whose compression rate along its thickness direction under a pressure of 0.1Mpa and under a pressure of 0.5Mpa meets the given conditions can not only buffer the volume expansion force generated by the electrode assembly during the charge and discharge process, but also give it a certain supporting strength. Even in a state that is not over-compressed, it is beneficial to achieve direct bonding between the electrode assembly and the inner wall of the shell or bonding with the inner wall of the shell through an elastic buffer pad or a mylar film (i.e., an insulating film) to achieve interaction force, which is beneficial to improving the force uniformity of the electrode piece and suppressing the shaking of the electrode assembly, thereby reducing the risk of wrinkles in local areas of the electrode assembly and the occurrence of abnormalities such as purple spots and lithium precipitation in the wrinkled area, which leads to a decrease in the utilization rate of active lithium.

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

[0070] Among them, the compression rate of the elastic buffer pad along its thickness direction under different stresses can be carried out with reference to GB / T 1041-92. The compression rate of the elastic buffer pad along its thickness direction is the ratio of the thickness change of the elastic buffer pad in the free state and under stress state to the thickness in the free state. The free state of the elastic buffer pad refers to the state in which the elastic buffer pad is not subjected to any external force, and the stress state of the elastic buffer pad refers to the state in which the elastic buffer pad is subjected to a certain compressive stress. The thickness test of the elastic buffer pad in the free state can be carried out using conventional instruments and conventional methods in this field, such as a Mitutoyo ID-C112MX micrometer thickness gauge (or similar instrument), and the test can be carried out under a test force less than or equal to 1.8N. Multiple points (such as 5, 10, etc.) are randomly measured and the average value is taken. The thickness test of the elastic buffer pad under stress state can be carried out using two parallel flat plates, with the elastic buffer pad located in the middle of the flat plates, and a preset pressure is applied to the elastic buffer pad using the flat plates and the distance between the flat plates is measured. The instruments used to measure the distance between the flat plates may include but are not limited to conventional instruments such as vernier calipers.

[0071] A fully charged state refers to a state in which the battery cell is charged at room temperature at a constant current of 0.33C of the rated capacity of the battery cell to the upper limit of the cut-off voltage, and then charged at a constant voltage until the current reaches 0.05C, or a state in which the battery SOC no longer changes under these conditions. A fully discharged state refers to a state in which the battery cell is discharged at room temperature at a constant current of 0.33C of the rated capacity of the battery cell to the lower limit of the cut-off voltage. In a battery cell, the total distance of the electrode assemblies in the first direction refers to the cumulative value of the distances of all electrode assemblies in the battery cell 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 generally extends along the thickness direction of the battery cell. The total thickness of the electrode assembly in the fully charged state refers to the cumulative value of the thickness of all electrode assemblies in the battery cell in the fully charged state at room temperature. With reference to FIG2 , a battery cell 1 has two electrode assemblies 12. The total thickness of the electrode assembly in the fully charged state refers to the sum of the thicknesses of the two electrode assemblies 12 in the battery cell in the fully charged state at room temperature. Accordingly, the total thickness of the electrode assembly in the fully discharged state refers to the cumulative value of the thicknesses of all electrode assemblies in the battery cell in the fully discharged state at room temperature. The thickness of the electrode assembly in the fully charged or fully discharged state can also be measured using conventional methods and instruments in the art. For example, the following method can be used: two parallel plates are used, with the electrode assembly positioned between them. A pressure of 0.1 MPa is applied to the electrode assembly using the plates. The thickness of the electrode assembly is measured by measuring the distance between the plates. The Yinghaoda PPG1200 battery thickness gauge can be used for this test. The distance between the inner walls of the housing in the first direction can be measured using conventional instruments and methods in the art.

[0072] The battery cell of the first aspect of the present application has the following beneficial effects: it can be applicable to battery cells with different expansion systems, and for battery cells with different expansion systems, it is beneficial for the elastic buffer pad to play a better effect, 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 use performance.

[0073] It can be understood that in the embodiments of the present application, battery cells include but are not limited to shells, electrode assemblies and elastic buffer pads. For example, battery cells may also include electrolytes; in the embodiments of the present application, battery cells include but are not limited to secondary battery cells, primary battery cells, etc.; in the embodiments of the present application, battery cells include but are not limited to lithium-ion battery cells, sodium-ion battery cells, magnesium-ion battery cells, etc.; in the embodiments of the present application, battery cells include but are not limited to hard battery cells, soft-pack battery cells, etc., and hard battery cells include but are not limited to metal battery shell cells, etc.

[0074] Furthermore, the battery cell of the first aspect of the present application, in addition to satisfying the above conditions, can further improve the performance of the battery cell by controlling the compression rate of the elastic cushion along its thickness direction under specific stress, the relationship between the elastic cushion and the electrode assembly and / or 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 can also be optionally satisfied.

[0075] In some embodiments of the present application, an elastic buffer pad 13 is provided between the electrode assembly 12 and the shell 11, and / or an elastic buffer pad 13 is provided between two adjacent electrode assemblies 12. This can be understood with reference to Figures 1, 2, and 4. Meeting the given conditions is further conducive to improving the volume stability of the battery cell during long-term use and reducing the risk of its expansion deformation or performance deterioration. Optionally, an elastic buffer pad 13 can be provided only between the electrode assembly 12 and the shell 11 and / or between two adjacent electrode assemblies 12, which is beneficial to the molding of the electrode assembly and also helps to reduce the expansion force generated by the electrode assembly on the shell.

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

[0077] Exemplarily, when -5%≤P≤5%, the compression rate of the elastic buffer pad along its thickness direction under a pressure of 0.1 MPa may be ≤15%, ≤14%, ≤13%, ≤12%, ≤11%, ≤10%, ≤9%, ≤8%, ≤7%, ≤6%, ≤5%, and the like; and / or, the compression rate of the elastic buffer pad along its thickness direction under a pressure of 0.5 MPa may be ≤55%, ≤53%, ≤51%, ≤50%, ≤48%, ≤45%, ≤42%, ≤40%, and the like. Selecting an elastic buffer pad that meets the given conditions is beneficial for buffering the expansion force generated by the electrode assembly during use, and is also beneficial for further realizing direct adhesion between the electrode assembly and the inner wall of the shell under a low expansion system, or adhesion between the electrode assembly and the inner wall of the shell through an elastic buffer pad or a mylar film, thereby realizing interaction force, which is further beneficial for improving the force uniformity of the electrode piece, reducing the risk of wrinkles in local areas of the electrode assembly, and the occurrence of abnormalities such as purple spots and lithium precipitation in the wrinkled area, which may lead to a decrease in the utilization rate of active lithium.

[0078] Selecting an elastic buffer pad that meets the given conditions is beneficial to improving the volume stability of the battery cell of the low expansion system during long-term use, and is also beneficial to improving the force uniformity of the electrode and reducing the risk of expansion deformation or performance deterioration of the battery cell.

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

[0080] For example, when P > 5%, the compression rate of the elastic cushion along its thickness direction under a pressure of 0.5 MPa may be ≥60%, ≥62%, ≥65%, ≥68%, ≥70%, ≥72%, ≥75%, ≥78%, ≥80%, etc. Selecting an elastic cushion that meets the given conditions further helps reduce the expansion force exerted by the electrode assembly on the battery housing in high-expansion battery cells, improves the volume stability of the battery cells during long-term use, and reduces the risk of expansion deformation or performance deterioration.

[0081] In some embodiments of the present application, the electrode assembly 12 may be a wound electrode assembly and include 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 the present application, the electrode assembly can be a laminated electrode assembly or a wound electrode assembly; the wound electrode assembly can be used in a prismatic shell or a cylindrical shell. Among them, during the charge and discharge process of the wound electrode assembly, the risk of uneven force on the pole pieces is relatively high, especially for prismatic battery cells with wound electrode assemblies. Combining the wound electrode assembly with the elastic buffer pad can help alleviate the problem of uneven force on the pole pieces in the wound electrode assembly, reduce polarization differences, and improve volume stability and long-term cycle performance. Optionally, the electrode assembly 12 can be a wound electrode assembly and include a straight portion and a corner portion. The elastic buffer pad 13 can be provided on at least part of the surface of the straight portion and / or the corner portion, thereby helping to further alleviate the problem of uneven force on the pole pieces in the prismatic battery cell. It is understandable that prismatic battery cells include but are not limited to square 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 the present application, with reference to Figures 1 to 8 , it can be understood that the battery cell 1 may be a prismatic battery cell.

[0084] In some embodiments of the present application, a prismatic battery cell may include: at least one first elastic buffer pad 13a and / or at least one second elastic buffer pad 13b, 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] Referring to Figure 8 , taking a prismatic battery cell as an example, in the given structural design, the thickness of the first elastic buffer 13a can extend along the thickness direction of the battery cell, and the thickness of the second elastic buffer 13b can extend along the length direction of the battery cell. The provision of both the first elastic buffer 13a, 13b, and the second elastic buffer help reduce the expansion force generated by the electrode assembly during use. Optionally, the battery cell can include at least one first elastic buffer 13a. In the housing 11 of a prismatic battery cell, the two sidewalls facing each other in the thickness direction of the battery cell typically have a larger area. Providing the first elastic buffer between these two sidewalls helps increase the contact area between the elastic buffer and the electrode assembly, thereby further reducing the expansion force that may be generated by the electrode assembly during use and further alleviating the uneven force that may be applied to the electrode sheets in a wound electrode assembly. Alternatively, a prismatic battery cell can include only the first elastic buffer 13a. Meeting these conditions not only helps reduce the expansion force of the electrode assembly and alleviate the uneven force that may be applied to the electrode sheets, but also omitting the second elastic buffer can simplify the battery cell structure and increase the energy density of the battery cell.

[0086] In some embodiments of the present application, in a 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 shell 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 shell 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0087] With reference to FIG8 , for example, a square battery cell can be taken as an example. The sum of the total thickness d of the first elastic buffer pad 13a in the free state and the total thickness d2 of the electrode assembly 12 in the fully discharged state can be 80% to 99% of the distance d0 between the two inner wall surfaces of the shell 11 that are oppositely arranged along the thickness direction thereof. For example, The value of can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99%, etc., or can be a range consisting of any of the above values. Meeting the given conditions can make a gap between the elastic buffer pad and the electrode assembly before they are inserted into the shell, which is conducive to the smooth insertion of the elastic buffer pad and the electrode assembly into the shell and facilitates the assembly of the battery cell. Optionally, Alternatively, Meeting the given conditions is further conducive to the smooth insertion of the elastic buffer pad and the electrode assembly into the shell. At the same time, it is also conducive to achieving direct or indirect contact between the electrode assembly and the inner wall of the shell after charging, thereby improving the force uniformity of the electrode piece.

[0088] Taking a square battery cell as an example, the sum of the total thickness d of the first elastic buffer pad 13a in the free state and the total thickness d1 of the electrode assembly 12 in the fully charged state can be 95% to 110% of the distance d0 between the two inner wall surfaces of the shell 11 arranged opposite to each other along the thickness direction thereof, that is, For example, The value of can be 95%, 97%, 99%, 100%, 102%, 104%, 106%, 108%, 110%, etc., or can be a range consisting of any of the above values. Meeting the given conditions is further beneficial for the battery cell to directly fit the electrode assembly to the inner wall of the shell or fit it to the inner wall of the shell through an elastic buffer pad (or mylar film) during use, thereby realizing interaction force, which is beneficial to further improve the force uniformity of the pole piece, reduce the risk of wrinkles in local areas of the electrode assembly and the occurrence of purple spots and lithium precipitation in the wrinkled area, which may cause 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 force uniformity of the electrode piece while further reducing the expansion force that the electrode assembly may generate on the shell.

[0089] Meeting the given conditions is not only beneficial to the assembly of battery cells, but also beneficial to improving the volume stability of the battery cells and the force uniformity of the pole pieces, thereby helping to reduce the risk of expansion, deformation or performance deterioration of the battery cells.

[0090] In some embodiments of the present application, in a prismatic battery cell, in the length direction of the 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 can be 80% to 99% of the distance between the inner wall surfaces of the shell 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 shell 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0091] For example, referring to FIG8 , taking a square battery cell as an example, 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 can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99%, etc. of the distance between the two inner wall surfaces of the shell 11 arranged opposite to each other along its length direction, or can be a range consisting of any of the above values. Among them, the length direction of the electrode assembly 12 in the fully discharged state and the length direction of the shell cavity are shown in FIG8 . In this application, the length of the electrode assembly 12 can be the maximum extension distance in the length direction of the battery cell. If the given conditions are met, a gap can be created between the elastic buffer pad and the electrode assembly before they are inserted into the shell, which is conducive to the smooth insertion of the elastic buffer pad and the electrode assembly into the shell and facilitates the assembly 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 discharged state can be 85% to 98% of the distance between the two inner wall surfaces of the shell 11 arranged opposite to each other along its length direction, and can be further optionally 90% to 95%. Meeting the given conditions is further conducive to the smooth insertion of the elastic buffer pad and the electrode assembly into the shell. At the same time, it is also conducive to achieving direct or indirect contact between the electrode assembly and the inner wall of the shell after charging, thereby improving the force uniformity of the electrode piece.

[0092] For example, referring to FIG8 , taking a square battery cell as an example, the sum of the total thickness of the second elastic buffer pad 13b in a free state and the length of the electrode assembly 12 in a 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 shell 11 disposed opposite each other along its length, or can be a range consisting of any of the above values. Meeting the given conditions further facilitates the electrode assembly to be directly bonded to the inner wall of the shell or bonded to the inner wall of the shell through the elastic buffer pad (or mylar film) during use, thereby achieving an interaction force, which in turn helps to further improve the force uniformity of the electrode piece, reduce the risk of wrinkles in local areas of the electrode assembly, and reduce the risk of abnormalities such as purple spots and lithium deposition in the wrinkled areas that lead to a decrease in active lithium utilization, thereby improving 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 shell 11 arranged opposite to each other along its length direction, and can be further optionally 99% to 102%. Meeting the given conditions can further reduce the expansion force that the electrode assembly may generate on the shell while improving the uniformity of the force on the electrode piece.

[0093] Meeting the given conditions is not only beneficial to the assembly of battery cells, but also beneficial to improving the volume stability of the battery cells and the force uniformity of the pole pieces, thereby helping to reduce the risk of expansion, deformation or performance deterioration of the battery cells.

[0094] In some embodiments of the present 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] Referring to Figure 8 , the ratio of the total thickness d of the first elastic cushion 13a in the free state to the total thickness d2 of the electrode assembly 12 in the 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%, or any range thereof. Increasing the value of d / d2 improves the elastic cushion's ability to absorb the expansion deformation and force generated by the electrode assembly, further suppressing expansion deformation of the battery cell. A d / d2 value that meets the given conditions not only helps maintain the volume stability of the battery cell throughout its life cycle, especially in its later stages, but also balances the energy density of the battery cell. Alternatively, the value of d / d2 can be 5% to 20%, or even 8% to 15%. Meeting the given conditions further balances the volume stability and energy density of the battery cell throughout its life cycle, especially in its later stages.

[0096] Meeting the given conditions is beneficial to maintaining the volume stability of the battery cell while also taking into account the energy density of the battery cell.

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

[0098] With reference to FIG8 , it can be understood that the ratio of the extension distance of the first elastic buffer 13a in the length direction of the electrode assembly 12 in the free state 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 consisting 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 the fully charged state. The length of the electrode assembly and the extension distance of the first elastic buffer in the free state along the length direction of the electrode assembly can be measured by conventional methods and conventional instruments.

[0099] With reference to FIG8 , it can be understood that the ratio of the extension distance of the first elastic buffer 13a in the height direction of the electrode assembly 12 in the free state to the height of the electrode assembly 12 can be 0.8 to 1.2, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, etc., or can be any range consisting 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 the fully charged state. The height of the electrode assembly and the extension distance of the first elastic buffer in the free state in the height direction of the electrode assembly can be measured by conventional methods and conventional instruments.

[0100] The dimensions of the first elastic buffer pad and the electrode assembly meet the given conditions, which is conducive to the elastic buffer pad covering most areas of the electrode assembly, thereby improving the volume stability of the battery cell, further improving the force uniformity of the electrode sheet, and reducing the risk of deterioration of the battery cell performance.

[0101] In some embodiments of the present application, as will be understood with reference to FIG8 , the orthographic projection of the first elastic buffer 13a on the electrode assembly 12 may be located within the region where the electrode assembly 12 is located. The first elastic buffer meeting the given conditions facilitates smooth insertion of the elastic buffer into the battery case during assembly and further balances the energy density of the battery.

[0102] In some embodiments of the present application, as understood with reference to Figures 9 and 10 , the battery cell 1 can be a cylindrical battery cell, with at least one elastic cushion 13 and the electrode assembly 12 stacked along the radius of the electrode assembly 12, and the distance between the inner walls of the housing 11 equal to the inner diameter of the housing 11. That is, the thickness of the electrode assembly 12 can extend along its radius, and the distance between the inner walls 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 walls of the housing 11 and the inner diameter of the housing 11 can be less than or equal to 2%, and optionally less than or equal to 1%. Cylindrical battery cells typically include only one wound electrode assembly. The elastic cushion can be positioned within the wound electrode assembly, with the electrode assembly laminated unit initially wound around the cushion; and / or the elastic cushion can be positioned 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 housing's inner cavity.

[0103] In some embodiments of the present application, in a cylindrical battery cell, the sum of the total thickness of the elastic buffer pad 13 in a free state and the total thickness of the electrode assembly 12 in a fully discharged state may be 80% to 99% of the inner cavity diameter of the shell 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 a free state and the total thickness of the electrode assembly 12 in a fully charged state may be 85% to 110% of the inner cavity diameter of the shell 11, optionally 98% to 105%, and further optionally 99% to 102%.

[0104] For example, referring to FIG9 , 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; in FIG10 , 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 elastic buffer pad 13 plus twice the thickness of the electrode assembly. In this application, the inner cavity diameter of the shell 11 can be understood as the average diameter of the inner cavity of the shell, which can be measured using conventional methods and conventional instruments.

[0105] With reference to Figures 9 and 10 , it can be understood that in a cylindrical battery cell, the sum of the total thickness of the elastic buffer pad 13 in a free state and the total thickness of the electrode assembly 12 in a fully discharged state can be 80%, 82%, 85%, 87%, 89%, 91%, 95%, 97%, 99%, etc., of the inner cavity diameter of the shell 11, or can be a range consisting of any of the above values. If the given conditions are met, a gap can be created between the elastic buffer pad and the electrode assembly before they are inserted into the shell, which is beneficial for the smooth insertion of the elastic buffer pad and the electrode assembly into the shell and facilitates the assembly of the 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 charged state can be 95%, 97%, 99%, 100%, 102%, 104%, 106%, 108%, 110% of the inner cavity diameter of the shell 11, or can be a range composed of any of the above values. Meeting the given conditions is further beneficial for the electrode assembly to be directly bonded to the inner wall of the shell or to be bonded to the inner wall of the shell through the elastic buffer pad (or mylar film) during the use of the battery cell to achieve interaction force, which is beneficial to further improve the force uniformity of the electrode piece, reduce the risk of wrinkles in local areas of the electrode assembly and the occurrence of abnormalities such as purple spots and lithium precipitation in the wrinkled area, which leads to a decrease in the utilization rate of active lithium, and improve the capacity retention rate of the battery cell.

[0106] Meeting the given conditions is not only beneficial to the assembly of battery cells, but also beneficial to improving the volume stability of the battery cells and the force uniformity of the pole pieces, thereby helping to reduce the risk of expansion, deformation or performance deterioration of the battery cells.

[0107] In some embodiments of the present application, in a cylindrical battery cell, the elastic buffer pad 13 can be arranged between the electrode assembly 12 and the shell 11, and when the elastic buffer pad 13 is in a 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 can be 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05; and / or, when the elastic buffer pad 13 is in a free state, the ratio of the extension distance in the height direction of the electrode assembly 12 to the height of the electrode assembly 12 can be 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05.

[0108] With reference to FIG9 , it can be understood that the ratio of the distance that the elastic buffer pad 13 extends in the circumferential direction of the electrode assembly 12 in the free state 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 can be a range consisting 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 the fully charged state. The ratio of the distance that the elastic buffer pad 13 extends in the height direction of the electrode assembly 12 in the free state 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 can be a range consisting 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 direction of the battery cell in the fully charged state. In the present application, the circumference and height of the electrode assembly, as well as the extension distance of the elastic buffer pad 13 in the circumferential direction or height of the electrode assembly in a free state can be measured by conventional methods and conventional instruments.

[0109] The dimensions of the first elastic buffer pad and the electrode assembly meet the given conditions, which is conducive to the elastic buffer pad covering most areas of the electrode assembly, thereby improving the volume stability of the battery cell, further improving the force uniformity of the electrode sheet, and reducing the risk of deterioration of the battery cell performance.

[0110] In some embodiments of the present application, in a cylindrical battery cell, the elastic cushioning pad 13, when in a free state, extends a distance in the circumferential direction of the electrode assembly 12 that is less than or equal to the circumference of the electrode assembly 12; and / or, the elastic cushioning pad 13, when in a free state, extends a distance in the height direction of the electrode assembly 12 that is less than or equal to the height of the electrode assembly 12. Meeting these conditions for the elastic cushioning pad not only facilitates smooth insertion of the cushioning pad into the battery case during assembly, but also helps to further balance the energy density of the battery.

[0111] In some embodiments of the present application, the thickness of a single elastic buffer pad 13 in a free state may be 2% to 15%, or optionally 5% to 10%, of the thickness of a single electrode assembly 12 in a fully discharged state. For example, the thickness of a single elastic buffer pad 13 in a free state may be 2%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, or the like, of the thickness of a single electrode assembly 12 in a fully discharged state, or may be a range consisting of any 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, while also taking into account the energy density of the battery cell.

[0112] In some embodiments of the present application, the thickness of a single elastic buffer pad 13 in the free state can be 0.2 mm to 10.5 mm. For example, the thickness of a single elastic buffer pad 13 in the 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 consisting of the above values. Meeting the given conditions can not only take into account the compressible deformation of the elastic buffer pad and the energy density of the battery cell, but also ensure that the support layer has a certain strength.

[0113] It can be understood that in the battery cell of the first aspect of the present application, the structure and material of the elastic buffer pad are not particularly limited, as long as its compression rate along its thickness direction under a 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 rates of the elastic buffer pad along its thickness direction under a preset pressure.

[0114] Exemplarily, the elastic buffer pad may be a single-layer structure, and its material may include but is not limited to at least one of foamed polyethylene, polypropylene, polyurethane, silicone rubber, etc.

[0115] Exemplarily, 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 provided on at least one of the two sides of the elastic buffer layer along its thickness direction. Exemplarily, 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 smaller than that of the support layer, and / or, under the same pressure, the compressibility of the elastic buffer layer along its thickness direction is greater than that of the support layer along its thickness direction, and / or, the porosity of the elastic buffer layer can be greater than that 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, polymethacrylate, polyethylene terephthalate, and polytetrafluoroethylene. Alternatively, 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; and the elastic buffer layer and the support layer may be bonded together. The use of a composite support layer and elastic buffer layer can provide support for the elastic buffer layer, not only suppressing thermal shrinkage of the elastic buffer layer (such as thermal shrinkage during vacuum baking), but also optionally using the support layer to suppress thermal shrinkage of the elastic buffer layer in a two-dimensional direction perpendicular to its thickness, thereby improving the problem of the elastic buffer layer losing its original function due to thermal shrinkage. It can also improve the problem of material damage caused by mechanical stress in the later stages of battery use. Furthermore, placing the elastic buffer pad inside the battery cell can further improve the volume stability of the battery during long-term use and enhance long-term performance.

[0116] In some embodiments of the present application, the electrode assembly 12 may include a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet, the negative electrode sheet, and the separator may be wound together to form the electrode assembly. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrode sheets. The separator is disposed between the positive and negative electrode sheets to provide isolation.

[0117] [Positive electrode]

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

[0119] In the present application, the specific type of positive electrode active material is not limited, and active materials that can be used for battery positive electrodes known in the art can be used, and those skilled in the art can choose according to actual needs. For example, the positive electrode active material may include but is not limited to lithium transition metal oxides and / or olivine structure lithium phosphate positive electrode active materials, 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, the olivine structure lithium phosphate may include undoped and / or optionally doped modified olivine structure lithium phosphates, uncoated and / or coated modified olivine structure lithium phosphates. The positive electrode active materials within the given range can be obtained either by preparation or by commercial channels.

[0120] In some specific embodiments of the present application, the positive electrode active material layer may also 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]

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

[0123] In some embodiments of the present application, the battery cell of the first aspect of the present application may be a lithium-ion battery cell. In this case, the specific type of negative electrode active material is not limited, and active materials known in the art that can be used for battery negative electrodes may be used. Those skilled in the art may 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. Alternatively, the silicon-based material may include one or more of elemental silicon, silicon oxide compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Alternatively, the tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode active material within the given range can be obtained either by preparation or through commercial channels.

[0124] In some specific embodiments of the present 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 (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.

[0125] In some embodiments of the present application, the isolation membrane 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 multiple polymers.

[0126] The second aspect of the present application provides a battery, comprising: the battery cell described in the first aspect of the present application. Optionally, the battery may be a secondary battery, for example, a lithium-ion secondary battery.

[0127] In some embodiments of the present application, the battery may be either a battery cell 1 (refer to FIG11 for understanding), or a battery module 2 (refer to FIG12 for understanding) or a battery pack 3 (refer to FIG13 for understanding) composed of battery cells 1.

[0128] In some embodiments, the battery may be a battery module, and the number of battery cells contained in the battery module may be one or more, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 12 is a battery module 2 as an example. Referring to Figure 12, in the battery module 2, a plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. The plurality of battery cells 1 may further be fixed by fasteners. Optionally, the battery module 2 may further include a housing having a housing space, and the plurality of battery cells 1 are accommodated in the housing space.

[0129] In some embodiments, the above-mentioned battery modules 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. Referring to Figure 13 or Figure 14 (Figures 13 and 14 are battery packs 3 as an example), the battery pack 3 may include a battery box and a plurality of battery modules 2 disposed in the battery box. The battery box may include an upper box body 4 and a lower box body 5. The upper box body 4 can be covered on the lower box body 5 and form an enclosed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0130] In some embodiments, a battery may include a first battery cell assembly and at least two second battery cell assemblies, wherein the first battery cell assembly includes at least one battery cell 1 according to the first aspect of the present application, and the second battery cell assembly includes at least two second battery cells, wherein the at least two second battery cells are arranged on both sides of the first battery cell assembly along the thickness direction of the first battery cell assembly, 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 the present application is a prismatic battery cell having a wound electrode assembly. By combining a prismatic shell, a wound electrode assembly, and an elastic buffer pad, the problem of uneven force on the electrode sheets in the prismatic wound battery can be alleviated, thereby improving the stability of the battery cell. The battery may be either a battery module or a battery pack. Illustratively, with 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 a plurality of battery cells 1 arranged in rows and / or columns, and / or the first battery cell assembly may be independently provided with a plurality of second battery cells arranged in rows and / or columns on both sides 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 the 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 number of battery cells 1 may account for 30% to 70%. A battery usually includes multiple battery cells, and the stacking method of the multiple battery cells includes stacking them along the thickness direction of the battery cells. In the thickness direction of the battery cells, the battery cells located in the middle of the battery are often the parts that swell most severely and have the largest expansion force during use. By only building a first elastic buffer pad into the first battery cell located in the middle, and not providing an elastic buffer pad in the second battery cells located on both sides of the thickness direction of the first battery cell assembly, it is not only beneficial to absorb the volume expansion of the battery cells that swell relatively more severely and have relatively larger expansion force in the battery, reduce the expansion force of the battery cells in the middle of the battery, and improve the volume stability of the battery, but also beneficial to alleviate the problem of stress concentration in the battery cells located in the middle of the battery due to the volume expansion of the battery cells in the later stage of battery use, thereby causing lithium deposition and diving in the battery cells in the middle; at the same time, it can also take into account the high energy density of the battery.

[0131] In addition, the present application also provides an electric device, which includes: the battery of the second aspect of the present application. The battery, such as a battery cell, a battery module or a battery pack, can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include but is not limited to mobile devices (such as mobile phones, laptops), electric vehicles (such as 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. With reference to Figure 15, as a specific example, the electric device can be a vehicle. The electric device can select the specific type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0132] As an example, the electric device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery pack or battery module may be used.

[0133] As another example, the electrical device may be a mobile phone, a tablet computer, or a laptop computer. The electrical device is generally required to be lightweight and thin, and may use a battery cell as a power source.

[0134] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0135] Example 1

[0136] (1) Preparation of lithium secondary batteries

[0137] (1) Preparation of positive electrode sheet

[0138] The positive electrode active material LiNi 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, and solvent N-methylpyrrolidone was added. The mixture was stirred thoroughly to obtain a positive electrode slurry, which was then coated on both surfaces of a 13 μm thick positive electrode current collector aluminum foil. The coating density of the positive electrode slurry on one side of the aluminum foil was 20 mg / cm 2 , then dried and cold pressed to obtain the positive electrode sheet.

[0139] (2) Preparation of negative electrode sheet

[0140] The negative electrode active material artificial graphite, conductive agent Super P, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were mixed in a weight ratio of 96:0.5:2:1.5, and deionized water was added as a solvent. The mixture was stirred and mixed thoroughly to obtain a negative electrode slurry, which was then coated on both surfaces of a 6 μm thick negative electrode current collector copper foil. The coating thickness of the negative electrode slurry on one side of the copper foil was 100 μm, and the coating surface density of the negative electrode slurry on one side of the copper foil was 11 mg / cm 2 , then 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 ratio of 1:1:1, and then fully dried lithium salt LiPF6 is dissolved in the above mixed organic solvents. After stirring evenly, an electrolyte is obtained, in which the concentration of LiPF6 is 1 mol / L.

[0143] (4) Preparation of isolation membrane

[0144] A polyethylene porous membrane with a thickness of 7 μm was used as the separator.

[0145] (5) Preparation of elastic cushion

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

[0147] (6) Preparation of lithium secondary batteries

[0148] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrode sheets to provide separation. The electrodes are then wound and formed into an electrode assembly. The two electrode assemblies and an elastic cushioning pad are placed in a battery casing (with a distance d0 of 60 mm between the two opposing inner walls along the thickness direction), with an elastic cushioning pad sandwiched between the two electrode assemblies. The prepared electrolyte is then injected and packaged to produce a lithium-ion secondary battery.

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

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

[0151] (2) Battery testing method

[0152] (a) Test the size of the battery and electrode assembly and the compression rate of the elastic buffer pad

[0153] Two parallel sets of secondary battery samples were taken. After standing at 25°C for 5 minutes, both sets were charged at a constant current of 0.33C to 4.4V. They were then charged at a constant voltage of 4.4V to 0.05C 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 was tested for thickness, length L1, and height h1 (the length and height of the electrode assembly matched the length and height of the secondary battery casing, respectively; note: the length of the cylindrical battery electrode assembly and the secondary battery is measured by circumference). The other set of secondary batteries was discharged at a constant current of 0.33C to 2.8V and allowed to stand for 5 minutes. The secondary batteries were then disassembled to obtain the electrode assembly. After cleaning and drying, the electrode assembly was tested for thickness. The testing method involves placing the electrode assembly between two parallel plates. A pressure of 0.1MPa was applied to the electrode assembly using the plates. The thickness of the electrode assembly was measured by measuring the distance between the plates. The total thickness d1 of the electrode assembly in the secondary battery in a fully charged state and the total thickness d2 of the electrode assembly in a fully discharged state are calculated.

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

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

[0156] Take multiple parallel samples of secondary batteries, let the secondary batteries rest at 25°C for 5 minutes, then charge them at a constant current of 0.5C to 4.4V, then charge them at a constant voltage of 4.4V to 0.05C, let them rest for 5 minutes, then discharge the secondary batteries at a constant current of 0.33C to 2.8V, let them rest for 5 minutes, and record the discharge capacity C0. Repeat the above operation and calculate the battery capacity retention rate by the following formula: Capacity retention rate of 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] After the secondary battery was left at rest for 5 minutes at 25°C, 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 left to rest for 5 minutes. The secondary battery was then discharged to 2.8V at a constant current of 0.33C and left to rest for 5 minutes. Six pressure sensors were set at different positions on one side in the thickness direction. The battery 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 left to rest for 5 minutes. The expansion force displayed by the pressure sensors at different positions of the secondary battery in the fully charged state was recorded, and the average value of the expansion force under different charging states was calculated. The range of the rate of change of each expansion force under different charging states compared to the average value was calculated based on the average value.

[0159] (d) Lithium deposition test

[0160] After standing at 25°C for 5 minutes, charge the battery at a constant current of 0.5C to 4.4V. Then, charge it at a constant voltage of 4.4V to 0.05C and let it stand for 5 minutes. Then, discharge the battery at a constant current of 0.33C to 2.8V and let it stand for 5 minutes. Repeat this charge-discharge cycle until the battery capacity shows significant degradation. After the charge-discharge cycle test is complete, disassemble the battery and inspect the negative electrode for lithium deposition.

[0161] Relevant tests were performed on Examples 1 to 20 and Comparative Examples 1 to 7. The test results are shown in Table 2.

[0162]

[0163]

[0164] in conclusion:

[0165] Based on Examples 1-20, Comparative Examples 1-7, and Tables 1-2, it can be seen that the implementation of the above-described embodiments of the present application is beneficial for improving the volume stability and force uniformity of battery cells during long-term use, reducing the risk of expansion, deformation, or performance deterioration. Furthermore, for battery cells with P > 5%, an elastic cushion with a compression rate of ≥ 60% or ≥ 70% at 0.5 MPa can be further selected; for battery cells with -5% ≤ P ≤ 5%, an elastic cushion with a compression rate of ≤ 15% or ≤ 10% at 0.1 MPa, and / or a compression rate of ≤ 55% or ≤ 50% at 0.5 MPa can be further selected. Furthermore, by further controlling the ratio of the sum of the total thickness d of the elastic cushion in the free state and the total thickness d1 (d2) of the electrode assembly in the fully charged (discharged) state to the distance d0 between the two inner walls of the housing disposed opposite each other along its thickness direction, as well as the size of the elastic cushion relative to the electrode assembly, it is also beneficial to further improve the volume stability and force uniformity of the battery cells during long-term use, reducing the risk of expansion, deformation, or performance deterioration.

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

Claims

1. A battery cell, wherein: include: case; at least one electrode assembly, the electrode assembly being disposed within the housing; At least one elastic buffer pad, the elastic buffer pad is arranged on at least a portion of the surface of the electrode assembly and / or inside the electrode assembly, and the compression rate of the elastic buffer pad along the thickness direction satisfies the following relationship: -5%≤P≤5%, the compression rate of the elastic buffer pad under a pressure of 0.1Mpa is ≤20%, and the compression rate under a pressure of 0.5Mpa is ≤60%; or, P>5%, the compression rate of the elastic buffer pad under a pressure of 0.5Mpa is ≥50%; Among them, at least one of the electrode assemblies and at least one of the elastic buffer pads are stacked along a first direction, and P is the ratio of the difference between the total distance of the electrode assemblies 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 surface of the shell.

2. The battery cell according to claim 1, wherein: The elastic buffer pad is arranged between the electrode assembly and the shell, and / or the elastic buffer pad is arranged between two adjacent electrode assemblies.

3. The battery cell according to claim 1 or 2, wherein: When -5%≤P≤5%, the compression rate of the elastic buffer pad under a pressure of 0.1Mpa is ≤15%, optionally ≤10%, and / or the compression rate of the elastic buffer pad under a pressure of 0.5Mpa is ≤55%, optionally ≤50%; or, When P>5%, the compression rate of the elastic buffer pad under a pressure of 0.5 MPa is ≥60%, and can be optionally ≥70%.

4. The battery cell according to any one of claims 1 to 3, wherein: The electrode assembly is a wound electrode assembly and includes a straight portion and a corner portion, and the elastic buffer pad is arranged on at least a portion of the surface of the straight portion and / or the corner portion.

5. The battery cell according to any one of claims 1 to 4, wherein: The battery cell is a prismatic battery cell.

6. The battery cell according to claim 5, wherein: The battery cell includes: at least one first elastic buffer pad and / or at least one second elastic buffer pad, 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.

7. The battery cell according to claim 6, wherein: At least one of the following conditions is met: In the thickness direction of the battery cell, the sum of the total thickness of the first elastic buffer pad in a free state and the total thickness of the electrode assembly in a fully discharged state is 80% to 99% of the distance between the inner walls of the shell, 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 a free state and the total thickness of the electrode assembly in a fully charged state is 95% to 110% of the distance between the inner walls of the shell, optionally 98% to 105%, and further optionally 99% to 102%; In the length direction of the battery cell, the sum of the total thickness of the second elastic buffer pad in a free state and the length of the electrode assembly in a fully discharged state is 80% to 99% of the distance between the inner walls of the shell, 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 a free state and the length of the electrode assembly in a fully charged state is 95% to 110% of the distance between the inner walls of the shell, optionally 98% to 105%, and further optionally 99% to 102%.

8. The battery cell according to claim 6 or 7, wherein: The ratio of the total thickness of the first elastic buffer pad in a free state to the total thickness of the electrode assembly in a fully discharged state is 2% to 25%, optionally 5% to 20%, and further optionally 8% to 15%.

9. The battery cell according to any one of claims 6 to 8, wherein: 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 a 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 first elastic buffer pad, in a free state, has an extension distance in the height direction of the electrode assembly equal to the height of the electrode assembly. The ratio is 0.8 to 1.2, which can be selected as 0.85 to 1.1, and further selected as 0.9 to 1.

05.

10. The battery cell according to any one of claims 6 to 9, wherein: The orthographic projection of the first elastic buffer pad on the electrode assembly is located in the area where the electrode assembly is located.

11. The battery cell according to any one of claims 1 to 3, wherein: 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 shell is equal to the diameter of the inner cavity of the shell.

12. The battery cell according to claim 11, wherein: The sum of the total thickness of the elastic buffer pad in a free state and the total thickness of the electrode assembly in a fully discharged state is 80% to 99% of the diameter of the inner cavity of the shell, optionally 85% to 98%, and further optionally 90% to 95%; and / or, The sum of the total thickness of the elastic buffer pad in a free state and the total thickness of the electrode assembly in a fully charged state is 85% to 110% of the diameter of the inner cavity of the shell, and can be optionally 98% to 105%, and further optionally 99% to 102%.

13. The battery cell according to claim 11 or 12, wherein: The elastic buffer pad is arranged between the electrode assembly and the shell, and the ratio of the extension distance of the elastic buffer pad in the circumferential direction of the electrode assembly to the circumference of the electrode assembly in a free state is 0.8 to 1.2, optionally 0.85 to 1.1, and further optionally 0.9 to 1.05; and / or, When the elastic buffer pad is in a 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, and can be optionally 0.85 to 1.1, and can further be optionally 0.9 to 1.

05.

14. The battery cell according to claim 13, wherein: When the elastic buffer pad is in a free state, the extension distance in the circumferential direction of the electrode assembly is less than or equal to the circumference of the electrode assembly; and / or, when the elastic buffer pad is in a free state, the extension distance in the height direction of the electrode assembly is less than or equal to the height of the electrode assembly.

15. The battery cell according to any one of claims 1 to 14, wherein: The thickness of a single elastic buffer pad in a free state is 2% to 15%, and optionally 5% to 10%, of the thickness of a single electrode assembly in a fully discharged state; and / or, The thickness of a single elastic buffer pad in a free state is 0.2 mm to 10.5 mm.

16. A battery, wherein: A battery cell comprising the battery cell according to any one of claims 1 to 15.

17. An electrical device, wherein: Comprising the battery of claim 16.

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