Buffer pad, battery cell, battery, and electric device having same

Abstract

A buffer pad (30), a battery cell (100), a battery (1000), and an electric device having same. The buffer pad (30) comprises a plurality of buffer regions, wherein the plurality of buffer regions is sequentially arranged along a first direction in the plane where the buffer pad (30) is located, and the electrolyte absorption rates of at least two buffer regions among the plurality of buffer regions are different.

Description

Buffer pad, battery cell, battery and electrical equipment having the same

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on the Chinese patent application with application number 2023225822090 and application date September 21, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a buffer pad, a battery cell, a battery, and an electrical device having the same. Background Art

[0004] Lithium-ion batteries offer advantages such as high volumetric and gravimetric energy density, long life, low self-discharge, and environmental friendliness. They are widely used in mobile communications devices, portable electronic devices such as laptops, and electric vehicles. However, during the charge and discharge cycles of lithium-ion batteries, the electrodes repeatedly expand. In the later stages of the battery cycle, as the electrode expansion force increases, the electrolyte decreases, is squeezed out, and the electrolyte reflow slows. This prevents some of the battery electrodes from being wetted in time, causing lithium deposition on the battery cell surface and impacting the battery cell's cycle life.

[0005] Application Contents

[0006] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a buffer pad that can balance the distribution of electrolyte, improve the wetting effect of the electrode assembly, reduce the occurrence of lithium deposition on the surface of the electrode assembly, and thus increase the cycle life of the battery cell.

[0007] The present application also provides a battery cell having the buffer pad.

[0008] The present application also provides a battery having the above-mentioned battery cell.

[0009] The present application also provides an electrical device having the battery.

[0010] According to the buffer pad of the first aspect of the present application, the buffer pad includes a plurality of buffer zones, the plurality of buffer zones are arranged sequentially along a first direction within the plane where the buffer pad is located, and at least two of the plurality of buffer zones have different liquid absorption rates.

[0011] According to the buffer pad of the present application, by setting multiple buffer zones, and at least two of the multiple buffer zones having different liquid absorption rates, the distribution of the electrolyte can be balanced, thereby improving the wetting effect of the electrode assembly and reducing the occurrence of lithium deposition on the surface of the electrode assembly, thereby improving the cycle life of the battery cell.

[0012] According to an example of the present application, in the first direction, the liquid absorption rate of the buffer pad gradually increases, gradually decreases, or first gradually increases and then gradually decreases.

[0013] In this embodiment, by setting the liquid absorption rate of the buffer pad to gradually increase, gradually decrease, or first gradually increase and then gradually decrease in the first direction, the adaptability of the electrolyte storage capacity in the buffer pad and the electrolyte consumption in the electrode assembly can be improved, the distribution uniformity of the electrolyte in the battery cell can be further improved, and the wetting effect of the electrode assembly can be improved, and the occurrence of lithium deposition on the surface of the electrode assembly can be reduced, thereby improving the cycle life of the battery.

[0014] According to an example of the present application, in the first direction, the liquid absorption rates of the plurality of buffer zones increase sequentially, decrease sequentially, or first increase and then decrease.

[0015] In this embodiment, by arranging the liquid absorption rates of the plurality of buffer zones in the first direction to increase sequentially, decrease sequentially, or increase first and then decrease, the difficulty of manufacturing the buffer pad can be reduced, thereby increasing the production rate of the buffer pad and reducing the production cost.

[0016] According to an example of the present application, the ratio of the liquid absorption rates of two adjacent buffer zones is greater than or equal to 1.05 and less than or equal to 1.1.

[0017] This embodiment sets the ratio of the liquid absorption rates of two adjacent buffer zones to be greater than or equal to 1.05 and less than or equal to 1.1, so that the liquid absorption rates of at least two buffer zones among the multiple buffer zones can be different, thereby balancing the distribution of the electrolyte inside the battery cell, thereby improving the wetting effect of the electrode assembly, reducing the occurrence of lithium deposition on the surface of the electrode assembly, and thus improving the cycle life of the battery cell.

[0018] According to an example of the present application, the plurality of buffer zones include a first region and a second region, and the difference between the liquid absorption rate of the first region and the liquid absorption rate of the second region is greater than or equal to 1.05 and less than or equal to 1.2.

[0019] In this embodiment, by setting the first area and the second area, and the ratio of the liquid absorption rate of the first area to the liquid absorption rate of the second area is greater than or equal to 1.05 and less than or equal to 1.2, the extrusion amount of the electrolyte in the first area can be greater than the extrusion amount in the second area, thereby increasing the wetting rate of the electrode at the corresponding position of the first area, and effectively preventing the occurrence of lithium plating at the interface.

[0020] According to an example of the present application, the first direction is along the up-down direction, and the first area is located above the second area; or the first direction is along the horizontal direction, and the second area includes two, and the two second areas are symmetrically arranged on the left and right sides of the first area.

[0021] In this embodiment, by arranging the buffer pad in the vertical direction in the first direction, the first region is located above the second region. This allows the electrolyte above the buffer pad to be squeezed out more under the action of the same expansion force, thereby allowing the upper portion of the electrode assembly to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the interface of the electrode piece in the upper portion of the electrode assembly, thereby increasing the cycle life of the battery. In addition, by arranging the first direction in the horizontal direction, the second region includes two, and the two second regions are symmetrically arranged on the left and right sides of the first region. This can increase the amount of electrolyte infiltration in the central region, thereby allowing the central region to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the interface of the electrode piece in the central region of the electrode assembly, thereby increasing the cycle life of the battery cell.

[0022] According to an example of the present application, a ratio of a total area of ​​the first region to a total area of ​​the buffer pad is greater than or equal to 0.3 and less than or equal to 0.7.

[0023] This embodiment can be used to limit the first area by setting the ratio of the total area of ​​the first area to the total area of ​​the buffer pad to be greater than or equal to 0.3 and less than or equal to 0.7, and thus can limit the total liquid storage capacity of the buffer pad, so that the electrolyte stored in the buffer pad can timely infiltrate the electrode without causing excessive electrolyte.

[0024] According to an example of the present application, the porosity of the first region is 40%-95%, and the porosity of the second region is 5%-60%.

[0025] In this embodiment, by setting the porosity of the first region to 40%-95% and the porosity of the second region to 5%-60%, the electrolyte storage capacity in the first region and the second region can meet the electrolyte replenishment required inside the battery cell, thereby solving the problem that some electrodes cannot be wetted in time.

[0026] According to an example of the present application, the porosity of the first region is 75%-90%, and the porosity of the second region is 10%-40%.

[0027] In this embodiment, by setting the porosity of the first area to 75%-90% and the porosity of the second area to 10%-40%, the liquid absorption rate of the first area can always be greater than the liquid absorption rate of the second area, thereby ensuring that the amount of electrolyte extruded in the first area is greater than the amount extruded in the second area, thereby solving the problem of uneven electrolyte distribution and some electrodes not being able to be wetted in time.

[0028] According to an example of the present application, the buffer pad is configured to have a compressibility of 5%-20% under a first preset pressure condition; and / or, the buffer pad is configured to have a compressibility of 40%-60% under a second preset pressure condition; and / or, the buffer pad is configured to have a compressibility of 60%-80% under a third preset pressure condition; and / or, the buffer pad is configured to have a compressibility greater than or equal to 80% under a fourth preset pressure condition, and the first preset pressure is less than the second preset pressure and less than the third preset pressure and less than the fourth preset pressure.

[0029] This embodiment sets the compressibility of the buffer pad to increase with the increase of the preset pressure, so that the buffer pad can match the expansion force of the electrode assembly throughout its life cycle, and can effectively absorb the expansion force of the electrode assembly, improve the wrinkling phenomenon of the electrode sheet, and thus improve the cycle capacity of the electrode assembly.

[0030] According to an example of the present application, the first preset pressure is 0-0.2 MPa, the second preset pressure is 0.2 MPa-0.5 MPa, the third preset pressure is 0.5 MPa-0.8 MPa, and the fourth preset pressure is 0.8 MPa-1 MPa.

[0031] In this embodiment, the first preset pressure is set to 0-0.2MPa, the second preset pressure is set to 0.2MPa-0.5MPa, the third preset pressure is set to 0.5MPa-0.8MPa, and the fourth preset pressure is set to 0.8MPa-1MPa. The compressibility of the buffer pad under the first preset pressure is 5%-20%; the compressibility under the second preset pressure is 40%-60%; the compressibility under the third preset pressure is 60%-80%; and the compressibility under the fourth preset pressure is greater than or equal to 80%. In this way, the buffer pad can match the expansion force of the electrode assembly throughout its life cycle, thereby effectively absorbing the expansion force of the electrode assembly, improving the wrinkling phenomenon of the electrode piece, and thus improving the cycle capacity of the electrode assembly.

[0032] According to an example of the present application, the buffer pad is a polyethylene piece, a polypropylene piece, a polyethylene terephthalate piece, an aerogel piece, a foam material piece and / or a silicone rubber piece.

[0033] In this embodiment, by configuring the buffer pad to be a polyethylene part, a polypropylene part, a polyethylene terephthalate part, an aerogel part, a foam material part and / or a silicone rubber part, the possibility of the buffer pad being corroded or crushed by the electrolyte can be reduced, the reliability of the buffer pad throughout the life cycle of the battery cell can be improved, and the service life of the buffer pad can be increased; at the same time, the production cost of the buffer pad can be reduced, and thus the production cost of the battery can be reduced.

[0034] According to the second aspect of the present application, the battery cell includes: a shell having a accommodating cavity filled with an electrolyte; an electrode assembly, the electrode assembly being arranged in the accommodating cavity; and a buffer pad according to the first aspect of the present application, the buffer pad being arranged between the electrode assembly and the inner wall surface of the accommodating cavity, and / or the buffer pad being arranged between two adjacent electrode assemblies.

[0035] According to the battery cell of the present application, by setting the buffer pad of the first aspect mentioned above, using the different liquid absorption rates of at least two buffer zones in the buffer pad, when the electrode assembly expands, the expansion force of the electrode assembly can squeeze the buffer member provided inside the shell, and part of the electrolyte stored in the buffer pad can be squeezed out under the action of the expansion force. At the same time, the amount of electrolyte squeezed out of different buffer zones is different. Therefore, the buffer pad of the present application can increase the distribution of the electrolyte inside the battery cell, thereby improving the wetting effect of the electrode assembly, reducing the occurrence of lithium deposition on the surface of the electrode assembly, and thus improving the cycle life of the battery cell.

[0036] According to an example of the present application, the electrode assembly is a vertically arranged wound electrode assembly, the first direction is along the up and down direction, a pole ear is formed on the top of the electrode assembly, and the liquid absorption rate of the buffer pad increases in the direction from bottom to top.

[0037] In this embodiment, the electrode assembly is arranged as a vertically wound electrode assembly, and the liquid absorption rate of the buffer pad is increased in the direction from bottom to top, so that the upper part of the electrode assembly can be replenished with electrolyte in time, thereby effectively reducing the probability of lithium deposition at the interface of the upper electrode plate of the electrode assembly, thereby increasing the cycle life of the battery cell.

[0038] According to an example of the present application, the electrode assembly is a horizontally arranged wound electrode assembly, the first direction is along the horizontal direction, the electrode assembly has pole ears formed at both ends in the horizontal direction, and the liquid absorption rate of the buffer pad increases in the direction from the two ends toward the middle of the electrode assembly.

[0039] In this embodiment, the electrode assembly is arranged as a horizontally wound electrode assembly, and the liquid absorption rate of the buffer pad is increased in the direction from the two ends toward the middle of the electrode assembly. This can increase the electrolyte infiltration amount in the central area of ​​the electrode assembly, and then enable the central area to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the electrode interface in the central area of ​​the electrode assembly, thereby increasing the cycle life of the battery cell.

[0040] A battery according to a third aspect of the present application includes the battery cell according to the second aspect of the present application.

[0041] According to the battery of the present application, the battery cell according to the second aspect is provided, thereby improving the overall performance of the battery.

[0042] The electrical device according to the fourth aspect of the present application includes the battery according to the third aspect of the present application, and the battery is used to provide electrical energy.

[0043] According to the electric device of the present application, the battery according to the third aspect is provided, thereby improving the overall performance of the electric device.

[0044] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a schematic diagram of a vehicle according to an embodiment of the present application;

[0046] FIG2 is a schematic diagram of a battery according to an embodiment of the present application;

[0047] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0048] FIG4 is a schematic diagram of a cushion according to an embodiment of the present application;

[0049] FIG5 is a schematic diagram of a cushion according to another embodiment of the present application;

[0050] FIG6 is a cross-sectional view of a battery cell according to an embodiment of the present application;

[0051] FIG7 is a cross-sectional view of a battery cell according to an embodiment of the present application from another angle;

[0052] FIG8 is a cross-sectional view of a battery cell according to another embodiment of the present application;

[0053] FIG9 is a cross-sectional view of a battery cell according to another embodiment of the present application from another angle;

[0054] FIG10 is a cross-sectional view of a battery cell according to another embodiment of the present application;

[0055] FIG11 is a cross-sectional view of a battery cell according to another embodiment of the present application from another angle.

[0056] Reference numerals: vehicle 1; battery 1000; battery cell 100; housing 10; accommodating chamber 101; electrode assembly 20; buffer pad 30; first buffer region 31; second buffer region 32; end cap 40; insulating film 50; adapter 60; housing 200; controller 2000; motor 3000. DETAILED DESCRIPTION

[0057] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0060] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0061] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0062] In the description of the embodiments of the present application, the term "plurality" refers to more than two (including two).

[0063] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the embodiments of the present application.

[0064] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0065] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0066] During the battery cycle, the positive and negative electrodes are constantly expanding and contracting. As the cycle progresses, the positive electrode particles are easily broken, resulting in a higher thickness expansion. The negative electrode will also have a very large thickness expansion as the SEI film is continuously repaired and the graphite particles become loose. The repeated expansion will eventually cause the shell to bulge and deform. At the same time, repeated deformation will cause the tightness between the electrodes to change, and the contact between the positive and negative electrodes and the diaphragm will gradually become loose and uneven, and even dead zones will appear, thereby affecting the movement of ions inside the battery, resulting in increased internal resistance of the battery, interface wrinkling and interface lithium deposition, etc., which will reduce the cycle life of the battery and reduce the safety performance. In addition, during the recycling process of lithium-ion batteries, the electrolyte will gradually become less, thereby affecting the transfer of lithium ions in the battery, and the cycle performance of the battery will gradually deteriorate.

[0067] To address the problem of expansion of the electrode assembly causing the shell to bulge and deform, resulting in increased internal resistance and reduced electrolyte, the current solution is to add a buffer between the shell and the electrode assembly. The buffer has compressibility and liquid storage capacity. This allows the electrode assembly to expand during battery cycling, squeezing the buffer layer and compressing it. The expanded electrode assembly can occupy the compressed space of the buffer layer, and the buffer layer can provide a certain restraining force to limit further expansion of the electrode assembly, thereby reducing the expansion of the electrode assembly shell. At the same time, as the expansion force increases, the electrolyte in the buffer can be squeezed out, thereby replenishing the consumed electrolyte. However, as the electrolyte decreases, it generally accumulates at the bottom of the battery under the action of its own gravity, and the electrolyte reflux rate is slow in the later stages of the cycle. Even if the buffer can replenish the consumed electrolyte, it will still cause the electrode sheets on the top of the electrode assembly to not be wetted in time.

[0068] Based on the above considerations, in order to solve the problem of uneven distribution of electrolyte and the inability of some electrodes to be wetted in time, a buffer pad is designed. The buffer pad includes multiple buffer zones, and at least two of the multiple buffer zones have different liquid absorption rates. In this way, the buffer zone with a relatively high liquid absorption rate can be arranged at a position with less electrolyte distribution, and the buffer zone with a relatively low liquid absorption rate can be arranged at a position with a larger electrolyte capacity. In this way, the distribution of electrolyte inside the battery cell can be balanced, the wetting effect of the electrode assembly can be improved, and the occurrence of lithium deposition on the surface of the electrode assembly can be reduced, thereby improving the cycle life of the battery.

[0069] After the buffer part of the present application is applied to the battery cell, since the liquid absorption rates of at least two buffer zones in the buffer pad are different, when the electrode assembly expands, the expansion force of the electrode assembly can squeeze the buffer part provided inside the shell, and part of the electrolyte stored in the buffer pad can be squeezed out under the action of the expansion force. At the same time, the amount of electrolyte squeezed out of different buffer zones is different. The amount of electrolyte squeezed out of the buffer zone with a higher liquid absorption rate is larger, and the amount of electrolyte squeezed out of the buffer zone with a lower liquid absorption rate is relatively small. Furthermore, buffer zones with different liquid absorption rates can be arranged accordingly according to the distribution of the electrolyte inside the battery cell. Therefore, the buffer pad of the present application can improve the distribution of the electrolyte inside the electrode cell, thereby improving the wetting effect of the electrode assembly, reducing the occurrence of lithium deposition on the surface of the electrode assembly, and thus improving the cycle life of the battery.

[0070] The buffer member disclosed in the embodiments of the present application can be applied to battery cells, which 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 vehicles, ships, spacecraft, and the like. Electric toys may include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric airplane toys, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, among others.

[0071] For the convenience of description, the following embodiments are described by taking a vehicle 1 as an example of an electrical device according to an embodiment of the present application.

[0072] Referring to Figure 1, Figure 1 is a schematic diagram of a vehicle 1 provided in some embodiments of the present application. The vehicle 1 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 1000 is provided inside the vehicle 1, and the battery 1000 can be provided at the bottom, head or tail of the vehicle 1. The battery 1000 can be used to power the vehicle 1. For example, the battery 1000 can serve as an operating power source for the vehicle 1. The vehicle 1 can also include a controller 2000 and a motor 3000. The controller 2000 is used to control the battery 1000 to power the motor 3000, for example, for starting, navigating and operating power requirements of the vehicle 1 during driving.

[0073] In some embodiments of the present application, the battery 1000 can serve not only as an operating power source for the vehicle 1 , but also as a driving power source for the vehicle 1 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1 .

[0074] In this application, the battery 1000 refers to a single physical module that includes one or more battery cells 100 to provide higher voltage and capacity. For example, the battery 1000 mentioned in this application may include a battery module or a battery pack. Some batteries 1000 may include a box 200 for encapsulating one or more battery cells 100 or multiple battery modules. The box 200 can effectively prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells 100. Of course, some batteries 1000 may not include the above-mentioned box 200 and are directly installed in the battery 1000 installation compartment of the electrical device.

[0075] 2 is a schematic diagram of a battery 1000 according to some embodiments of the present invention. The battery 1000 includes a housing 200 and a battery cell 100. The housing 200 has a cavity, and the battery cell 100 is accommodated in the cavity of the housing 200.

[0076] In the battery 1000, there may be multiple battery cells 100, and the multiple battery cells 100 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 100. The multiple battery cells 100 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 100 may be housed within the housing 200. Of course, the battery 1000 may also be a battery module formed by first connecting multiple battery cells 100 in series, in parallel, or in a hybrid connection, and then the multiple battery modules are further connected in series, in parallel, or in a hybrid connection to form an entire battery cell, and then housed within the housing 200. The battery 1000 may also include other structures, for example, the battery 1000 may also include a busbar component for electrically connecting the multiple battery cells 100.

[0077] Each battery cell 100 may be a secondary battery or a primary battery; it may also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 100 may be cylindrical, flat, rectangular, or in other shapes.

[0078] Referring to Figure 3, Figure 3 is an exploded view of a battery cell 100 according to some embodiments of the present application. As shown in Figure 3, the battery cell 100 according to this embodiment may include a housing 10, an end cap 40, an electrode assembly 20, an electrolyte, and a buffer pad 30. The housing 10 has a housing 101 formed therein for accommodating the electrode assembly 20, the electrolyte, and the buffer pad 30.

[0079] The shell 10 and the end cap 40 can be independent components. An opening can be provided on the shell 10, and the internal environment of the battery 1000 can be formed by covering the opening with the end cap 40. Without limitation, the end cap 40 and the shell 10 can also be integrated. Specifically, the end cap 40 and the shell 10 can form a common connection surface before other components are put into the shell. When the interior of the shell 10 needs to be encapsulated, the end cap 40 is covered with the shell 10. The shell 10 can be of various shapes and sizes, including but not limited to cylindrical, hexagonal, etc. Specifically, the shape of the shell 10 can be determined according to the specific shape and size of the electrode assembly 20. The material of the shell 10 can be various, including but not limited to: copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. According to an example of the present application, an insulating film 50 is also provided on the inner side of the shell 10. The insulating film 50 is wrapped around the outer surface of the electrode assembly 20 to isolate the electrode assembly 20 from the shell 10 to reduce the risk of short circuit.

[0080] The end cap 40 refers to a component that covers the opening of the shell 10 to isolate the internal environment of the battery 1000 from the external environment. Without limitation, the shape of the end cap 40 can be adapted to the shape of the shell 10 to match the shell 10. Optionally, the end cap 40 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 40 is not easily deformed when squeezed or collided, so that the battery 1000 can have a higher structural strength and improved safety performance. The material of the end cap 40 can also be various, including but not limited to: copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. According to an example of the present application, an insulating member can also be provided on the inner side of the end cap 40, and the insulating member can be used to isolate the electrical connection components in the shell 10 from the end cap 40 to reduce the risk of short circuit. Exemplarily, the insulating member can be plastic, rubber, etc. According to an example of the present application, the battery cell 100 also includes a transition piece 60, which is connected to the tab for current transmission.

[0081] The electrode assembly 20 consists of a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell 100 primarily relies on the movement of metal ions between the positive and negative electrode sheets to operate. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector. The positive current collector not coated with the positive active material layer protrudes from the positive current collector coated with the positive active material layer, and the positive current collector not coated with the positive active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0082] The negative electrode sheet consists of a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative current collector. The negative current collector uncoated with the negative active material layer protrudes from the negative current collector coated with the negative active material layer. The negative current collector uncoated with the negative active material layer serves as the negative electrode tab. The negative current collector can be made of copper, and the negative active material can be carbon, silicon, or other materials. To ensure that high currents can pass without melting, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together.

[0083] The material of the separator can be PP (polypropylene) or PE (polyethylene). The electrode assembly 20 of the embodiment of the present application is a wound structure. In addition, the electrode assembly 20 can be a wound structure or a laminated structure.

[0084] The following describes a buffer pad 30 according to an embodiment of the first aspect of the present application with reference to Figures 4 to 11. Figure 4 is a schematic diagram of a buffer pad 30 according to an embodiment of the present application; Figure 5 is a schematic diagram of a buffer pad 30 according to another embodiment of the present application; Figure 6 is a cross-sectional view of a battery cell 100 according to an embodiment of the present application; Figure 7 is a cross-sectional view of a battery cell 100 from another angle according to an embodiment of the present application; Figure 8 is a cross-sectional view of a battery cell 100 according to another embodiment of the present application; Figure 9 is a cross-sectional view of a battery cell 100 from another angle according to another embodiment of the present application; Figure 10 is a cross-sectional view of a battery cell 100 according to yet another embodiment of the present application; and Figure 11 is a cross-sectional view of a battery cell 100 from yet another angle according to yet another embodiment of the present application.

[0085] As shown in FIG4 , an embodiment of the present application proposes a buffer pad 30 , which includes a plurality of buffer zones arranged sequentially along a first direction within the plane where the buffer pad 30 is located, and at least two of the plurality of buffer zones have different liquid absorption rates.

[0086] Among them, the buffer pad 30 is arranged inside the battery cell 100. The buffer pad 30 has a certain liquid absorption and storage capacity. Therefore, when the battery cell 100 is injected with liquid, the injection amount of the electrolyte can be increased, so that the electrolyte inside the battery cell 100 can meet the usage needs while also storing part of the electrolyte. In this way, in the later stage of the cycle of the battery cell 100, when the electrolyte is reduced, part of the electrolyte stored in the buffer pad 30 can be squeezed out under the action of the expansion force, thereby increasing the wetting effect of the electrode assembly 20, slowing down the occurrence of lithium decomposition, and thus improving the cycle service life of the battery cell 100.

[0087] The liquid absorption rate of the cushion 30 refers to the amount of electrolyte absorbed by the cushion 30 within a given period of time. The absorption rate is measured by immersing the same mass of a substance in a standard electrolyte for the same time period (T). The difference in mass before and after immersion is ΔM. The absorption rate (X = ΔM / T) is calculated by multiplying the difference in mass and time.

[0088] For example, the first direction may be a height direction of the buffer pad 30, or a length direction of the buffer pad 30. The number of the buffer zones may be two, three, or more.

[0089] At least two of the multiple buffer zones have different liquid absorption rates, that is, two of the multiple buffer zones may have different liquid absorption rates, or all of the buffer zones may have different liquid absorption rates. The number of buffer zones and the liquid absorption rates of the buffer zones may be designed according to actual usage requirements. For example, at locations where the electrolyte is concentrated, the liquid absorption rate of the buffer zone may be smaller, and at locations where the electrolyte is less distributed, the liquid absorption rate of the corresponding buffer zone may be relatively higher. This can balance the distribution of the electrolyte inside the battery cell 100, thereby improving the wetting effect of the electrode assembly 20 and reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, thereby improving the cycle life of the battery cell 100.

[0090] According to the buffer pad 30 of the present application, by setting multiple buffer zones, and at least two of the multiple buffer zones having different liquid absorption rates, the distribution of the electrolyte can be balanced, thereby improving the wetting effect of the electrode assembly 20 and reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, thereby improving the cycle life of the battery cell 100.

[0091] According to an example of the present application, as shown in FIG4 , in the first direction, the liquid absorption rate of the buffer pad 30 gradually increases, gradually decreases, or first gradually increases and then gradually decreases.

[0092] For example, the buffer pad 30 is arranged vertically. Under the action of gravity, the electrolyte infiltration direction is from bottom to top. At this time, the liquid absorption rate of the buffer pad 30 gradually increases from bottom to top, and the liquid absorption rate of the buffer pad 30 gradually decreases from top to bottom.

[0093] For example, the buffer pad 30 is arranged vertically, and at the same time, the electrolyte infiltration direction is from the left and right ends of the battery cell 100 to the middle position. At this time, in the direction from left to right, or from right to left, the liquid absorption of the buffer pad 30 first gradually increases and then gradually decreases.

[0094] In this embodiment, by setting the liquid absorption rate of the buffer pad 30 to gradually increase, gradually decrease, or first gradually increase and then gradually decrease in the first direction, the adaptability of the electrolyte storage capacity in the buffer pad 30 and the electrolyte consumption in the electrode assembly 20 can be improved, and the distribution uniformity of the electrolyte in the battery cell 100 can be further improved, thereby improving the wetting effect of the electrode assembly 20, reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, and thereby improving the cycle service life of the battery 1000.

[0095] According to an example of the present application, as shown in FIG4 , in the first direction, the liquid absorption rates of the plurality of buffer zones increase sequentially, decrease sequentially, or increase first and then decrease.

[0096] That is to say, in the first direction, the liquid absorption rates of the plurality of buffer zones vary in a gradient manner, and the liquid absorption rates in the same area are the same.

[0097] In this embodiment, by arranging the liquid absorption rates of the plurality of buffer zones in the first direction to increase sequentially, decrease sequentially, or increase first and then decrease, the difficulty of manufacturing the buffer pad 30 can be reduced, thereby increasing the production rate of the buffer pad 30 and reducing the production cost.

[0098] According to an example of the present application, the ratio of the liquid absorption rates of two adjacent buffer zones is greater than or equal to 1.05 and less than or equal to 1.1.

[0099] Specifically, the buffer pad 30 is disposed within the battery housing 10, with at least one large surface of the buffer pad 30 in contact with a large surface of the electrode assembly 20. The size of the buffer pad 30 is designed and manufactured based on the size of the electrode assembly 20. The multiple buffer zones are sequentially arranged along a first direction within the plane in which the buffer zones are located. That is, the multiple buffer zones are sequentially arranged along the first direction of a large surface of the electrode assembly 20. The multiple buffer zones can divide the electrode assembly 20 into multiple regions along the first direction, and the multiple regions correspond one-to-one to the multiple buffer zones.

[0100] For example, the buffer zone includes multiple buffer zones, and the liquid absorption rates of the multiple buffer zones are A1...An, wherein the liquid absorption rate ratio of two adjacent buffer zones is greater than or equal to 1.05 and less than or equal to 1.1, that is, the ratio of An / An+1 or the ratio of An / An-1 is in the range of [1.05, 1.1].

[0101] Among them, in the later stage of the battery 1000 cycle, the electrode assembly 20 expands and the electrolyte is partially consumed, so that the electrolyte content in the two adjacent areas is different. At this time, the buffer zone with high liquid absorption rate can be arranged corresponding to the area with low electrolyte content, so as to balance the distribution of electrolyte inside the battery cell 100, improve the wetting effect of the electrode assembly 20, and reduce the occurrence of lithium deposition on the surface of the electrode assembly 20, thereby improving the cycle service life of the battery cell 100.

[0102] For example, the ratio of the liquid absorption rates of two adjacent buffer zones may be 1.05, 1.06, 1.07, 1.08, 1.09 or 1.1.

[0103] In this embodiment, by setting the ratio of the liquid absorption rates of two adjacent buffer zones to be greater than or equal to 1.05 and less than or equal to 1.1, the liquid absorption rates of at least two buffer zones among the multiple buffer zones can be different, thereby balancing the distribution of the electrolyte inside the battery cell 100, thereby improving the wetting effect of the electrode assembly 20, reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, and thus improving the cycle life of the battery cell 100.

[0104] According to an example of the present application, as shown in FIG4 , the plurality of buffer zones include a first region and a second region, and the ratio of the liquid absorption rate of the first region to the liquid absorption rate of the second region is greater than or equal to 1.05 and less than or equal to 1.2.

[0105] Specifically, the plurality of buffer zones may include only two areas: a first area and a second area; the plurality of buffer zones may also include other areas, such as a third area, a fourth area, etc. The first area and the second area may be adjacent areas or non-adjacent areas.

[0106] For example, as shown in FIG4 , the cushioning pad 30 is divided into two regions: a first region and a second region. The first region is located above the second region. The ratio of the liquid absorption rate of the first region to the liquid absorption rate of the second region can be 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.15, or 1.2.

[0107] In this embodiment, by setting the first area and the second area, and the ratio of the liquid absorption rate of the first area to the liquid absorption rate of the second area is greater than or equal to 1.05 and less than or equal to 1.2, the extrusion amount of the electrolyte in the first area can be greater than the extrusion amount in the second area, thereby increasing the wetting rate of the electrode at the corresponding position of the first area, and effectively preventing the occurrence of lithium deposition at the electrode interface.

[0108] According to an example of the present application, as shown in Figures 4 and 5, the first direction is along the up and down direction, and the first area is located on the upper side of the second area; or the first direction is along the horizontal direction, and the second area includes two, and the two second areas are symmetrically arranged on the left and right sides of the first area.

[0109] Specifically, according to an example of the present application, the first direction is along the up-down direction, and the first area is located on the upper side of the second area. Among them, such an arrangement is mainly adapted to the electrode assembly 20 structure in which the electrolyte infiltration direction is from bottom to top, for example, the electrode assembly 20 of the M6U structure. After the battery 1000 has been circulated for a period of time, the electrolyte inside the battery cell 100 will decrease accordingly and the expansion force of the electrode assembly 20 will increase. At this time, most of the electrolyte will gather at the lower part of the electrode assembly 20 and the reflux speed will be slow, which will cause the upper part of the electrode assembly 20 to not be wetted in time. Then, setting the first area above the second area can make the electrolyte above the buffer pad 30 squeeze out more under the action of the same expansion force, so that the upper part of the electrode assembly 20 can replenish the electrolyte in time, effectively reducing the probability of lithium plating at the interface of the upper electrode piece of the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0110] In some other embodiments, the first direction is along the horizontal direction, and the second area includes two, and the two second areas are symmetrically arranged on the left and right sides of the first area. Among them, such an arrangement is mainly adapted to the structure of the electrode assembly 20 in which the electrolyte infiltrates from the left and right ends to the center position, for example, the electrode assembly 20 of the M6T structure. After the battery 1000 has been circulated for a period of time, the electrolyte inside the battery cell 100 will be reduced accordingly and the expansion force of the electrode assembly 20 will increase. As the expansion force becomes larger, the electrolyte inside the electrode assembly 20 will be squeezed to the left and right ends, which will cause the infiltration effect of the central area to be relatively poor. Therefore, setting the first area between the two second areas can increase the amount of electrolyte infiltration in the central area, and then enable the central area to replenish the electrolyte in time, effectively reducing the probability of lithium plating at the electrode interface in the central area of ​​the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0111] In this embodiment, by arranging the buffer pad 30 in the first direction along the vertical direction, the first region is located above the second region. This allows the electrolyte above the buffer pad 30 to be squeezed out more under the action of the same expansion force, thereby allowing the upper portion of the electrode assembly 20 to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the interface of the upper electrode piece of the electrode assembly 20, thereby increasing the cycle life of the battery cell 100. In addition, by arranging the first direction along the horizontal direction, the second region includes two, and the two second regions are symmetrically arranged on the left and right sides of the first region, the electrolyte infiltration amount in the central region can be increased, thereby allowing the central region to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the interface of the electrode piece in the central region of the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0112] According to an example of the present application, as shown in FIG. 4 and FIG. 5 , the ratio of the total area of ​​the first region to the total area of ​​the buffer pad 30 is greater than or equal to 0.3 and less than or equal to 0.7.

[0113] The total area of ​​the first region may refer to the total area of ​​the first region of the contact surface between the buffer pad 30 and the electrode assembly 20 ; the total area of ​​the buffer pad 30 may refer to the total area of ​​the contact surface between the buffer pad 30 and the electrode assembly 20 .

[0114] For example, the ratio of the total area of ​​the first region to the total area of ​​the cushioning pad 30 may be 0.3, 0.4, 0.5, 0.6, or 0.7.

[0115] This embodiment can be used to limit the first area by setting the ratio of the total area of ​​the first area to the total area of ​​the buffer pad 30 to be greater than or equal to 0.3 and less than or equal to 0.7, and thus can limit the total liquid storage capacity of the buffer pad 30, so that the electrolyte stored in the buffer pad 30 can timely infiltrate the electrode without causing excessive electrolyte.

[0116] According to an example of the present application, as shown in FIG. 4 and FIG. 5 , the porosity of the first region is 40%-95%, and the porosity of the second region is 5%-60%.

[0117] Specifically, the porosity refers to the percentage of the pore volume in the cushion pad 30 to the total volume of the cushion pad 30 in a natural state. The greater the porosity, the higher the liquid absorption rate.

[0118] For example, the porosity of the first region may be 40%, 50%, 60%, 70%, 80% or 95%; and the porosity of the second region may be 5%, 10%, 20%, 30%, 40%, 50% or 60%.

[0119] In this embodiment, by setting the porosity of the first region to 40%-95% and the porosity of the second region to 5%-60%, the electrolyte storage capacity in the first region and the second region can meet the electrolyte replenishment required inside the battery cell 100, thereby solving the problem that some electrodes cannot be wetted in time.

[0120] According to an example of the present application, as shown in FIG. 4 and FIG. 5 , the porosity of the first region is 75%-90%, and the porosity of the second region is 10%-40%.

[0121] Among them, the porosity is proportional to the liquid absorption rate. The larger the porosity, the higher the liquid absorption rate.

[0122] For example, the porosity of the first region may be 75%, 80%, 85% or 90% and the porosity of the second region may be 10%, 20%, 30% or 40%.

[0123] In this embodiment, by setting the porosity of the first area to 75%-90% and the porosity of the second area to 10%-40%, the liquid absorption rate of the first area can always be greater than the liquid absorption rate of the second area, thereby ensuring that the amount of electrolyte extruded in the first area is greater than the amount extruded in the second area, thereby solving the problem of uneven electrolyte distribution and some electrodes not being able to be wetted in time.

[0124] According to an example of the present application, the buffer pad 30 is configured to have a compressibility of 5%-20% under a first preset pressure condition; and / or, the buffer pad 30 is configured to have a compressibility of 40%-60% under a second preset pressure condition; and / or, the buffer pad 30 is configured to have a compressibility of 60%-80% under a third preset pressure condition; and / or, the buffer pad 30 is configured to have a compressibility greater than or equal to 80% under a fourth preset pressure condition, and the first preset pressure < the second preset pressure < the third preset pressure < the fourth preset pressure.

[0125] Specifically, the compressibility of the buffer pad 30 refers to the percentage of the reduced volume of the buffer pad 30 to the volume of the buffer pad 30 in its natural state. The preset pressure can be a preset value set according to the expansion force of the electrode assembly 20 and the gas pressure inside the battery housing 10. During the cycle of the battery cell 100, the electrode sheet will continue to expand, causing the space inside the battery cell 100 to become smaller and the internal pressure to increase. As the cycle time increases, the internal pressure will gradually increase. The compressibility of the buffer pad 30 increases with the increase in pressure, so that the buffer pad 30 can match the expansion force of the electrode assembly 20 throughout its life cycle, and can effectively absorb the expansion force of the electrode assembly 20, improve the wrinkling phenomenon of the electrode sheet, and thus improve the cycle capacity of the electrode assembly 20.

[0126] For example, under the first preset pressure condition, the compressibility of the buffer pad 30 can be 6%, 10%, 15% or 19%; under the second preset pressure condition, the compressibility of the buffer pad 30 can be 41%, 45%, 50%, 55% or 59%; under the third preset pressure condition, the compressibility of the buffer pad 30 can be 61%, 65%, 70% or 75%; under the fourth preset pressure condition, the compressibility of the buffer pad 30 can be 80%, 85% or above.

[0127] In this embodiment, the compressibility of the buffer pad 30 is increased as the preset pressure increases, so that the buffer pad 30 can match the expansion force of the electrode assembly 20 throughout its life cycle, and can effectively absorb the expansion force of the electrode assembly 20, improve the wrinkling phenomenon of the electrode sheet, and thus improve the cycle capacity of the electrode assembly 20.

[0128] According to an example of the present application, the first preset pressure is 0-0.2 MPa, the second preset pressure is 0.2 MPa-0.5 MPa, the third preset pressure is 0.5 MPa-0.8 MPa, and the fourth preset pressure is 0.8 MPa-1 MPa.

[0129] The preset pressure may be a preset value set according to the expansion force of the electrode assembly 20 and the gas pressure inside the battery case 10 .

[0130] For example, the first preset pressure can be 0.1MPa, 0.15MPa or 0.2MPa; the second preset pressure can be 0.25MPa, 0.3MPa, 0.4MPa or 0.5MPa; the third preset pressure can be 0.55MPa, 0.6MPa, 0.7MPa or 0.8MPa; the fourth preset pressure can be 0.85MPa, 0.9MPa, 0.95MPa or 1.0MPa.

[0131] In this embodiment, the first preset pressure is set to 0-0.2MPa, the second preset pressure is set to 0.2MPa-0.5MPa, the third preset pressure is set to 0.5MPa-0.8MPa, and the fourth preset pressure is set to 0.8MPa-1MPa. The compressibility of the buffer pad 30 at the first preset pressure is 5%-20%; the compressibility at the second preset pressure is 40%-60%; the compressibility under the third preset pressure is 60%-80%; and the compressibility at the fourth preset pressure is greater than or equal to 80%. In this way, the buffer pad 30 can match the expansion force of the electrode assembly 20 throughout its life cycle, thereby effectively absorbing the expansion force of the electrode assembly 20, improving the wrinkling phenomenon of the electrode piece, and thus improving the cycle capacity of the electrode assembly 20.

[0132] According to an example of the present application, the buffer pad 30 is a polyethylene piece, a polypropylene piece, a polyethylene terephthalate piece, an aerogel piece, a foam material piece and / or a silicone rubber piece.

[0133] Specifically, the buffer pad 30 can be made of one of the above materials, which all have high resistance to electrolyte corrosion, compressibility, and resilience, and are low in price and simple in manufacturing process.

[0134] In this embodiment, by setting the buffer pad 30 to a polyethylene part, a polypropylene part, a polyethylene terephthalate part, an aerogel part, a foam material part and / or a silicone rubber part, the possibility of the buffer pad 30 being corroded or crushed by the electrolyte can be reduced, the reliability of the buffer pad 30 throughout the life cycle of the battery cell 100 can be improved, and the service life of the buffer pad 30 can be increased; at the same time, the production cost of the buffer pad 30 can also be reduced, and the production cost of the battery 1000 can be reduced.

[0135] According to the battery cell 100 of the second aspect embodiment of the present application, it includes: a shell 10, an electrode assembly 20 and a buffer pad 30 according to the first aspect embodiment of the present application, the shell 10 has a accommodating cavity 101, and the accommodating cavity 101 is filled with electrolyte; the electrode assembly 20 is arranged in the accommodating cavity 101; the buffer pad 30 is arranged between the electrode assembly 20 and the inner wall surface of the accommodating cavity 101, and / or the buffer pad 30 is arranged between two adjacent electrode assemblies 20.

[0136] That is to say, the buffer pad 30 can be arranged only between the electrode assembly 20 and the inner wall of the accommodating cavity 101, or only between two adjacent electrode assemblies 20, or both between the electrode assembly 20 and the inner wall of the accommodating cavity 101 and between two connected electrode assemblies 20.

[0137] Among them, when the buffer pad 30 is arranged between the electrode assembly 20 and the inner wall of the accommodating cavity 101, it can not only support and cushion the electrode assembly 20, but also separate the battery shell 10 from the electrode assembly 20, effectively preventing the electrode assembly 20 from squeezing the battery shell 10 after expansion. When the buffer pad 30 is arranged between two adjacent electrode assemblies 20, the buffer pad 30 can not only support and cushion the two adjacent electrode assemblies 20, but also separate the adjacent electrode assemblies 20, effectively preventing the adjacent electrode assemblies 20 from squeezing each other after expansion. At the same time, whether the buffer pad 30 is arranged between the electrode assembly 20 and the inner wall of the accommodating cavity 101 or between two adjacent electrode assemblies 20, it can replenish the electrolyte for the electrode assembly 20, thereby improving the wetting effect of the electrode assembly 20 and improving the cycle life of the battery cell 100.

[0138] In addition, the shell 10 is a component for accommodating the electrode assembly 20, the electrolyte and the buffer pad 30. It is mainly used to isolate the inside of the battery cell 100 from the outside, effectively preventing the inside of the battery cell 100 from communicating with the outside, thereby improving the reliability of the battery cell 100. The electrolyte is filled in the battery shell 10, and the electrode assembly 20 is immersed in the electrolyte. Among them, on the one hand, the electrolyte provides some active lithium ions, which are used as conductive ions during the charging and discharging process; on the other hand, the electrolyte provides ion channels, allowing lithium ions to move freely therein, thereby enabling the battery cell 100 to complete the charging and discharging process. The electrode assembly 20 is the core component of the battery cell 100, and is mainly composed of a negative electrode sheet, a positive electrode sheet and a diaphragm.

[0139] Among them, the positive electrode plate is a positive electrode active material coated on the surface of the positive electrode current collector. In some specific embodiments, the positive electrode active material layer includes a ternary material, lithium manganese oxide or lithium iron phosphate, and the positive electrode current collector is aluminum foil. For example, the positive electrode active material uses the ternary positive electrode material LiNi0.8Co0.1Mn0.1O2. The negative electrode plate is a negative electrode active material coated on the surface of the negative electrode current collector. In some specific embodiments, the negative electrode current collector is copper foil, and the negative electrode active material layer includes graphite or silicon. For example, graphite can be used as the negative electrode active material. The diaphragm is provided between the positive electrode plate and the negative electrode plate to play a role of isolation.

[0140] According to the battery cell 100 of the embodiment of the present application, by setting the buffer pad 30 of the above-mentioned first aspect embodiment, using the different liquid absorption rates of at least two buffer zones in the buffer pad 30, when the electrode assembly 20 expands, the expansion force of the electrode assembly 20 can squeeze the buffer member provided inside the shell 10, and part of the electrolyte stored in the buffer pad 30 can be squeezed out under the action of the expansion force. At the same time, the amount of electrolyte squeezed out of different buffer zones is different. Therefore, the buffer pad 30 of the present application can increase the distribution of the electrolyte inside the battery cell 100, thereby improving the wetting effect of the electrode assembly 20, reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, and thus improving the cycle life of the battery cell 100.

[0141] The following describes the preparation process of the battery cell 100 according to the above embodiment based on some specific embodiments.

[0142] First, prepare the negative electrode sheet, positive electrode sheet, separator, and electrolyte. The positive electrode active material uses the ternary positive electrode material LiNi0.8Co0.1Mn0.1O2, and the positive electrode current collector uses aluminum foil. The negative electrode active material uses graphite, and the negative electrode current collector uses copper foil. The separator uses a polyethylene (PE) porous polymer membrane (7 μm thick).

[0143] Specifically, the negative electrode sheet is prepared by mixing graphite, conductive carbon black (SP), styrene-butadiene rubber emulsion (SBR), and sodium carboxymethyl cellulose in a mass ratio of 96.2:0.8:1.8:1.2, dissolving the mixture in deionized water, and applying the resulting slurry to both surfaces of a copper foil (6 μm thick) to form a first active material layer. Subsequently, a second active material, conductive carbon black (SP), styrene-butadiene rubber emulsion (SBR), and sodium carboxymethyl cellulose are mixed in a mass ratio of 96.2:0.8:1.8:1.2, and applying the resulting slurry to both surfaces of the first active material layer. The mixture is then dried, cold-pressed, and cut into the negative electrode sheets.

[0144] The preparation method of the positive electrode sheet is to mix the active material LiNi0.8Co0.1Mn0.1O2 with conductive carbon black (SP) and polyvinylidene fluoride (PVDF) in a mass ratio of 96.8:2.2:1, and then dissolve the mixed material in N-methylpyrrolidone (NMP), and prepare the positive electrode slurry after slurrying, and then coat the positive electrode slurry on aluminum foil (thickness 12um), and then dry the coated aluminum foil, cold press, and cut to obtain the positive electrode sheet.

[0145] The preparation method of the electrolyte is to mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:6:1, and then dissolve fully dried lithium salt (LiPF6) in a mixed organic solvent at a ratio of 1 mol / L to obtain the required electrolyte.

[0146] The prepared positive electrode sheet, separator, and negative electrode sheet are then stacked in order, with the separator positioned between the positive and negative electrode sheets. The stacked sheets are then wound to form the desired electrode assembly 20. The two electrode assemblies 20 are welded to the end caps 40, and the cushioning pad 30 is inserted between the two electrode assemblies 20. The entire structure is then placed in the housing 10 to form a dry cell. The prepared electrolyte is then injected into the high-temperature dried dry cell. After vacuum packaging, standing, formation, and shaping, a lithium-ion secondary battery is obtained.

[0147] According to an example of the present application, the electrode assembly 20 is a vertically arranged wound electrode assembly 20, the first direction is along the up and down direction, a pole ear is formed on the top of the electrode assembly 20, and the liquid absorption rate of the buffer pad 30 increases in the direction from bottom to top.

[0148] Among them, the wound electrode assembly refers to the electrode assembly 20 formed by winding. The electrode assembly 20 is arranged vertically, and the tab is formed at the top of the electrode assembly 20, and thus, the electrolyte flows in an up-and-down direction. After the battery 1000 circulates for a period of time, the electrolyte inside the electrode assembly 20 will decrease accordingly and the expansion force of the electrode assembly 20 will increase. At this time, most of the electrolyte will gather at the lower part of the electrode assembly 20 and the reflux speed will be slow. Therefore, the buffer pad 30 is arranged in the direction from bottom to top, and the liquid absorption rate is increased, so that the upper part of the electrode assembly 20 can be replenished with electrolyte in time, thereby effectively reducing the probability of lithium plating at the interface of the upper electrode sheet of the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0149] In this embodiment, the electrode assembly 20 is arranged as a vertically wound electrode assembly 20, and the liquid absorption rate of the buffer pad 30 is increased in the direction from bottom to top, so that the upper part of the electrode assembly 20 can be replenished with electrolyte in time, thereby effectively reducing the probability of lithium deposition at the interface of the upper electrode plate of the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0150] According to an example of the present application, the electrode assembly 20 is a horizontally arranged wound electrode assembly 20, the first direction is along the horizontal direction, the electrode assembly 20 has pole ears formed at both ends in the horizontal direction, and the liquid absorption rate of the buffer pad 30 increases in the direction from the two ends of the electrode assembly 20 toward the middle.

[0151] The wound electrode assembly refers to an electrode assembly 20 formed by winding. The electrode assembly 20 is arranged horizontally, with tabs located at both ends of the electrode assembly 20 in the horizontal direction. This allows electrolyte to flow inward from the ends of the electrode assembly 20. Furthermore, the liquid absorption rate of the buffer pad 30 increases from the ends toward the center of the electrode assembly 20. That is, in the first direction, the liquid absorption rate of the buffer pad 30 first increases and then decreases. After the battery cell 100 has been circulated for a period of time, the electrolyte inside the battery cell 100 will decrease accordingly and the expansion force of the electrode assembly 20 will increase. As the expansion force increases, the electrolyte inside the electrode assembly 20 will be squeezed to the left and right ends, which will cause the wetting effect in the central area to be relatively poor. Therefore, from the two ends of the electrode assembly 20 toward the middle, the liquid absorption rate of the buffer pad 30 increases, which can increase the electrolyte infiltration amount in the central area, and thus enable the central area to replenish the electrolyte in time, effectively reducing the probability of lithium plating at the electrode interface in the central area of ​​the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0152] In this embodiment, the electrode assembly 20 is arranged as a horizontally wound electrode assembly, and the liquid absorption rate of the buffer pad 30 is increased in the direction from the two ends toward the middle of the electrode assembly 20. This can increase the electrolyte infiltration amount in the central area of ​​the electrode assembly 20, and thus enable the central area to be replenished with electrolyte in a timely manner, effectively reducing the probability of lithium deposition at the electrode plate interface in the central area of ​​the electrode assembly 20, thereby increasing the cycle service life of the battery cell 100.

[0153] The battery 1000 according to the embodiment of the third aspect of the present application includes the battery cell 100 according to the embodiment of the second aspect of the present application.

[0154] According to the battery 1000 of the embodiment of the present application, the overall performance of the battery 1000 is improved by providing the battery cell 100 of the embodiment of the second aspect described above.

[0155] The electrical device according to the fourth embodiment of the present application includes the battery 1000 according to the third embodiment of the present application, and the battery 1000 is used to provide electrical energy.

[0156] According to the electric device of the embodiment of the present application, the overall performance of the electric device is improved by providing the battery 1000 of the embodiment of the third aspect mentioned above.

[0157] The battery cell 100 according to four specific embodiments of the present application will be described below with reference to FIG. 3 to FIG. 11 .

[0158] Example 1:

[0159] 3 , the battery cell 100 includes a shell 10 , an electrode assembly 20 and a buffer pad 30 , wherein the shell 10 specifically includes a housing 101 filled with electrolyte; the electrode assembly 20 and the buffer pad 30 each include two, and the buffer pad 30 is arranged between the electrode assembly 20 and the inner wall of the housing cavity 101 .

[0160] Specifically, the electrode assembly 20 is a vertically arranged wound electrode assembly, and a pole ear is formed on the top of the electrode assembly 20. The buffer pad 30 includes a plurality of buffer zones, and the plurality of buffer zones are arranged in sequence along the first direction within the plane where the buffer pad 30 is located. The plurality of buffer zones include a first area and a second area, and the ratio of the liquid absorption rate of the first area to the liquid absorption rate of the second area is greater than or equal to 1.05 and less than or equal to 1.2. The first direction is the up and down direction, and the first area is located on the upper side of the second area. The ratio between the total area of ​​the first area and the total area of ​​the buffer pad 30 is greater than or equal to 0.3 and less than or equal to 0.7; the porosity of the first area is 75%-90%, and the porosity of the second area is 10%-40%.

[0161] In addition, the buffer pad 30 has a certain compressibility, wherein, under the pressure condition of 0-0.2MPa, the compressibility of the buffer pad 30 is 5%-20%; under the pressure condition of 0.2MPa-0.5MPa, the compressibility of the buffer pad 30 is 40%-60%; under the pressure condition of 0.5MPa-0.8MPa, the compressibility of the buffer pad 30 is 60%-80%; under the pressure condition of 0.8MPa-1.0MPa, the compressibility of the buffer pad 30 is greater than or equal to 80%.

[0162] The buffer pad 30 is made of polyethylene, polypropylene, polyethylene terephthalate, aerogel, foam material or silicone rubber.

[0163] According to the battery cell 100 of the embodiment of the present application, after the buffer part of the present application is applied to the battery cell 100, since the liquid absorption rates of at least two buffer zones in the buffer pad 30 are different, when the electrode assembly 20 expands, the expansion force of the electrode assembly 20 can squeeze the buffer part provided inside the shell 10, and part of the electrolyte stored in the buffer pad 30 can be squeezed out under the action of the expansion force. At the same time, the amount of electrolyte squeezed out of different buffer zones is different. Therefore, the buffer pad 30 of the present application can increase the distribution of the electrolyte inside the battery cell 100, thereby improving the wetting effect of the electrode assembly 20, reducing the occurrence of lithium deposition on the surface of the electrode assembly 20, and thus improving the cycle life of the battery cell 100.

[0164] Example 2:

[0165] 8 , the structure of this embodiment is substantially the same as that of the first embodiment, wherein the same components are designated by the same reference numerals, and the only difference is that the buffer pad 30 described in the first embodiment is disposed between the electrode assembly 20 and the inner wall of the accommodating cavity 101 , while the buffer pad 30 described in the second embodiment is disposed between the two electrode assemblies 20 .

[0166] When the buffer pad 30 is arranged between two adjacent electrode assemblies 20, the buffer pad 30 can not only support and cushion the two adjacent electrode assemblies 20, but also separate the adjacent electrode assemblies 20, effectively preventing the adjacent electrode assemblies 20 from squeezing each other after expansion; at the same time, it can also replenish the electrolyte for the electrode assembly 20, thereby improving the wetting effect of the electrode assembly 20 and improving the cycle life of the battery cell 100.

[0167] Example 3,

[0168] 10 , the structure of this embodiment is substantially the same as that of the first embodiment, wherein the same components are designated by the same reference numerals, and the only difference is that the buffer pad 30 described in the first embodiment is disposed between the electrode assembly 20 and the inner wall of the accommodating cavity 101 , while the buffer pad 30 described in the third embodiment is disposed between the electrode assembly 20 and the inner wall of the accommodating cavity 101 and between the two electrode assemblies 20 .

[0169] Specifically, there are three buffer pads 30, which are respectively arranged between the electrode assembly 20 and the inner wall of the accommodating cavity 101 and between the two electrode assemblies 20. In this way, the buffer pads 30 can support both large surfaces of the electrode assembly 20, and at the same time separate the two adjacent electrode assemblies 20 and the electrode assembly 20 from the battery shell 10, effectively preventing expansion and extrusion between the electrode assemblies 20 and the electrode assembly 20 on the shell 10.

[0170] Example 4:

[0171] The structure of this embodiment is roughly the same as that of the first embodiment, wherein the same components are designated by the same reference numerals, and the only difference is that the electrode assembly 20 described in the first embodiment is a vertically arranged wound electrode assembly, while the electrode assembly 20 described in the third embodiment is a horizontally arranged wound electrode assembly.

[0172] Specifically, the first direction is the horizontal direction, the buffer zone includes a first area and a second area, and the second area includes two, and the two second areas are symmetrically arranged on the left and right sides of the first area. In this way, the electrolyte infiltration amount in the central area of ​​the electrode assembly 20 can be increased, and the central area can be replenished with electrolyte in time, effectively reducing the probability of lithium deposition at the electrode interface in the central area of ​​the electrode assembly 20, thereby increasing the cycle life of the battery cell 100.

[0173] A comparative example 1 is briefly described below, and this comparative example 1 is used as a comparative example for the above-mentioned embodiment 1 and embodiment 2 of the present application.

[0174] In the comparative example 1, no buffer pad 30 is provided in the battery cell 100 .

[0175] The following test experiments are carried out on Examples 1 to 2 and Comparative Example 1.

[0176] The testing process is as follows:

[0177] The battery cell 100 is tested with a fixture having two steel or aluminum plates, the fixture force is 3000N, and the battery housing 10 is not provided with a buffer pad 30; and a sensor is used to monitor the expansion force value of the buffer large surface of the electrode assembly 20.

[0178] In a constant temperature environment of 25°C, the battery cell 100 is charged and discharged for the first time. Constant current and constant voltage charging (charging to a current of 0.05C) is performed at a charging current of 1.0C (i.e., the current value that completely discharges the theoretical capacity within 1 hour) until the upper limit voltage reaches 4.25V. After standing for 5 minutes, constant current discharge is performed at a discharge current of 1.0C until the final voltage reaches 2.8V. The discharge capacity of the first cycle is recorded; then continuous charge and discharge cycles are performed.

[0179] Here, the capacity retention rate at the nth cycle=(discharge capacity at the nth cycle / discharge capacity at the first cycle)×100.

[0180] After assembly, injection, and high-temperature stabilization, the battery cell 100 undergoes a formation process at a constant temperature of 45°C. Constant-current charging is performed at a charging current of 0.1cc (the current required to completely discharge the theoretical capacity within one hour) until the voltage reaches 3.4V. This is followed by constant-current charging at 0.33C to 3.75V. Ideally, constant-current charging at 0.33C is continued to 4.2V. Constant-voltage charging is then continued until the current reaches 0.05C, at which point the battery 1000 is fully charged. After the fully charged battery 1000 rests for 5 minutes, it is disassembled and the wrinkles at the anode interface are observed.

[0181] The test results of the battery cell 100 cycle capacity retention rate and the electrode assembly 20 interface wrinkling are shown in Table 1:

[0182] Table 1

[0183] The above test results show that compared with comparative example 1, the use of the buffer pad 30 provided in Examples 1 to 2 of the present application can reduce wrinkling on the interface, reduce the expansion force of the electrode assembly 20, and improve the cycle retention rate of the electrode assembly 20. As the number of buffer components increases, the expansion force decreases relatively and the cycle retention rate increases relatively.

[0184] 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 cushion, characterized in that: The buffer pad includes a plurality of buffer zones, which are arranged in sequence along a first direction within a plane where the buffer pad is located, and at least two of the plurality of buffer zones have different liquid absorption rates.

2. The cushion according to claim 1, characterized in that: In the first direction, the liquid absorption rate of the buffer pad gradually increases, gradually decreases, or first gradually increases and then gradually decreases.

3. The cushion according to any one of claims 1 to 2, characterized in that: In the first direction, the liquid absorption rates of the plurality of buffer zones increase sequentially, decrease sequentially, or increase first and then decrease.

4. The cushion according to any one of claims 1 to 3, characterized in that: The ratio of the liquid absorption rates of two adjacent buffer zones is greater than or equal to 1.05 and less than or equal to 1.

1.

5. The cushion according to any one of claims 1 to 4, characterized in that: The plurality of buffer zones include a first region and a second region, and a ratio of a liquid absorption rate of the first region to a liquid absorption rate of the second region is greater than or equal to 1.05 and less than or equal to 1.

2.

6. The cushion according to claim 5, characterized in that: The first direction is along the up-down direction, and the first area is located above the second area; or The first direction is along the horizontal direction, the second area includes two, and the two second areas are symmetrically arranged on the left and right sides of the first area.

7. The cushion according to any one of claims 5 to 6, characterized in that: A ratio of a total area of ​​the first region to a total area of ​​the buffer pad is greater than or equal to 0.3 and less than or equal to 0.

7.

8. The cushion according to any one of claims 5 to 7, characterized in that: The porosity of the first region is 40%-95%, and the porosity of the second region is 5%-60%.

9. The cushion according to any one of claims 5 to 8, characterized in that: The porosity of the first region is 75%-90%, and the porosity of the second region is 10%-40%.

10. The cushion according to any one of claims 1 to 9, characterized in that: The cushion is configured to have a compressibility of 5%-20% under a first preset pressure condition; and / or, The cushion is configured to have a compressibility of 40%-60% under a second preset pressure condition; and / or, The cushion is configured to have a compressibility of 60%-80% under a third preset pressure condition; and / or, The cushion is configured to have a compressibility greater than or equal to 80% under a fourth preset pressure condition, The first preset pressure is less than the second preset pressure, less than the third preset pressure, and less than the fourth preset pressure.

11. The cushioning pad according to claim 10, characterized in that: The first preset pressure is 0-0.2MPa, the second preset pressure is 0.2MPa-0.5MPa, the third preset pressure is 0.5MPa-0.8MPa, and the fourth preset pressure is 0.8MPa-1MPa.

12. The cushioning pad according to any one of claims 1 to 9, characterized in that: The buffer pad is a polyethylene piece, a polypropylene piece, a polyethylene terephthalate piece, an aerogel piece, a foam material piece and / or a silicone rubber piece.

13. A battery cell, characterized in that: include: A housing (10), the housing (10) having a receiving cavity (101), the receiving cavity (101) being filled with an electrolyte; An electrode assembly (20), the electrode assembly (20) being arranged in the accommodating cavity (101); According to any one of claims 1 to 12, the buffer pad is arranged between the electrode assembly (20) and the inner wall surface of the accommodating cavity (101), and / or the buffer pad is arranged between two adjacent electrode assemblies (20).

14. The battery cell according to claim 13, characterized in that: The electrode assembly (20) is a vertically arranged wound electrode assembly (20), the first direction is along the up-down direction, a pole ear is formed on the top of the electrode assembly (20), and the liquid absorption rate of the buffer pad increases in the direction from bottom to top.

15. The battery cell according to any one of claims 13 to 14, characterized in that: The electrode assembly (20) is a horizontally arranged wound electrode assembly (20), the first direction is along the horizontal direction, pole ears are formed at both ends of the electrode assembly (20) in the horizontal direction, and the liquid absorption rate of the buffer pad increases in the direction from the two ends of the electrode assembly (20) toward the middle.

16. A battery, characterized in that: The invention comprises a battery cell according to any one of claims 13 to 15.

17. An electrical equipment, characterized in that: The battery according to claim 16 is used to provide electrical energy.

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