Battery monomer, battery device, electric equipment and energy storage equipment

Abstract

The utility model provides a battery monomer, a battery device, electric equipment and energy storage equipment, and relates to the technical field of batteries. The battery monomer comprises a shell, an electrode assembly and a buffer assembly, the buffer assembly is arranged between the electrode assembly and the inner wall of the shell along a first direction, and the buffer assembly can be compressed after entering the shell, so that the buffer assembly and the electrode assembly can completely fill an inner cavity of the shell in the first direction to realize full-group margin shell entering. Moreover, by limiting the compression ratio of the buffer assembly, a proper expansion space and resilience force can be provided for the electrode assembly, so that the pressure required by lithium deposition can be provided in the charging and discharging process, the compact lithium deposition on the negative electrode side of the single lithium metal battery can be maintained, the density of a byproduct layer can be increased, and the occurrence of side reaction can be reduced.

Description

TECHNICAL FIELD

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

[0002] New energy batteries are increasingly widely used in life and industry. For example, new energy vehicles equipped with batteries have been widely used. In addition, batteries are increasingly used in the field of energy storage and the like.

[0003] In related technologies, the pressure expansion in a lithium metal battery monomer has a strong correlation with the deposition of lithium and the cycle performance of the battery monomer. If the electrode assembly in the lithium metal battery monomer cannot obtain sufficient pressure during the charging and discharging process, the deposition of lithium on the negative electrode side will be affected, and thus the reliability and service life of the battery monomer are affected.

[0004] The above statements are only used to provide background technical information related to the present application, and do not necessarily constitute the prior art. CONTENT OF THE UTILITY MODEL

[0005] In view of the above problems, embodiments of the present application provide a battery monomer, a battery device, a power utilization device and an energy storage device, which can alleviate the problem that the reliability and service life of the battery monomer are affected due to the electrode assembly not obtaining sufficient pressure during use of the battery monomer.

[0006] In a first aspect, embodiments of the present application provide a battery monomer, comprising a shell, an electrode assembly and a buffer assembly; the electrode assembly is arranged in the interior of the shell; the buffer assembly is arranged between the electrode assembly and the inner wall of the shell along a first direction; after the buffer assembly and the electrode assembly are arranged in the interior of the shell, the sum of the sizes of the buffer assembly and the electrode assembly in the first direction is equal to the inner cavity size of the shell, the inner cavity size of the shell is the distance between the two inner walls of the shell in the first direction, and the compression rate of the buffer assembly in the first direction after being arranged in the shell is W, W satisfies: 20%≤W≤30%; the stress of the buffer assembly under pressure is σ MPa, σ satisfies: σ=9.5W-0.0067.

[0007] In the technical solution, the sum of the size of the buffer assembly and the electrode assembly in the first direction after the buffer assembly is accommodated in the shell is equal to the size of the inner cavity of the shell, and the buffer assembly can be compressed in the first direction, so that the buffer assembly and the electrode assembly can completely fill the inner cavity of the shell in the first direction, and the accommodation margin can reach 100%. Moreover, the buffer assembly is arranged between the electrode assembly and the inner wall of the shell, so that stress concentration during deformation of the electrode assembly can be avoided in the compression and rebound process, and the stress uniformity of the electrode assembly is improved. In addition, the compression rate of the buffer assembly after being accommodated in the shell is limited to between 20% and 30%, on the one hand, the buffer assembly can form an appropriate compression amount, so that the buffer assembly can be compressed and deformed with the expansion of the electrode assembly to provide space for the expansion of the electrode assembly during charging and discharging; on the other hand, the buffer assembly can provide appropriate rebound force, so that the buffer assembly can provide part of the pressure required for lithium deposition during charging and discharging. At the same time, by establishing a corresponding relationship between the compression rate of the buffer assembly and the pressure stress of the buffer assembly, the pressure stress range of the buffer assembly can be limited, and the compression rate of the buffer assembly can be gradually changed within the compressible range with the change of the pressure stress, so that the buffer assembly can provide a compression amount and rebound force matched with the current stage at different stages of charging and discharging.

[0008] In some embodiments, the buffer assembly comprises an adhesive layer, an elastic layer and a support plate arranged in the first direction and connected in sequence; the side of the adhesive layer away from the elastic layer is connected to the inner wall of the shell; and the elastic layer is configured to provide an elastic force to enable the support plate to abut against the electrode assembly.

[0009] In the technical solution, the buffer assembly adopts a three-layer structure design, which can improve the connection stability between the buffer assembly and the shell, and facilitate the accommodation operation of the buffer assembly and the electrode assembly in the shell.

[0010] In some embodiments, the surface of the side of the support plate facing the electrode assembly is an abutting surface, the abutting surface is a plane and is in contact with the outer surface of the electrode assembly; and in the same plane perpendicular to the first direction, the range of the orthogonal projection of the abutting surface exceeds the range of the orthogonal projection of the electrode assembly.

[0011] In the technical solution, by setting the range of the orthogonal projection of the abutting surface to exceed the range of the orthogonal projection of the electrode assembly and designing the abutting surface as a plane, the outer surface of the electrode assembly can be completely in contact with the abutting surface during charging and discharging, and the stress uniformity of the electrode assembly can be further improved, which is helpful for denser lithium deposition.

[0012] In some embodiments, the elastic layer has a three-dimensional porous network structure.

[0013] In the technical solution, by designing the elastic layer as a three-dimensional porous network structure, the elastic performance of the elastic layer can be improved, and the compression capacity and rebound force of the buffer assembly can be improved.

[0014] In some embodiments, a sealed cavity is formed in the interior of the elastic layer, and the sealed cavity is filled with gas.

[0015] In the above technical solution, by arranging the sealed cavity filled with gas in the interior of the elastic layer, the elastic performance of the elastic layer can be further improved.

[0016] In some embodiments, the inner wall of the shell includes a first inner wall, the first inner wall is perpendicular to a first direction, the first direction is a thickness direction of the battery monomer, and the buffer assembly includes a first buffer assembly, the first buffer assembly is arranged between the electrode assembly and the first inner wall.

[0017] In the above technical solution, along the thickness direction of the battery monomer, the first buffer assembly is arranged between the electrode assembly and the first inner wall, so that the first buffer assembly can act on the outer surface of the electrode assembly in the thickness direction (i.e. the large surface in the outer surface of the electrode assembly), and can better inhibit the expansion of the electrode assembly during charging and discharging, thereby improving the compactness of lithium deposition.

[0018] In some embodiments, the number of the first inner walls is two, the two first inner walls are oppositely arranged along the first direction, the number of the first buffer assemblies is two, the two first buffer assemblies are respectively and one-to-one connected to the two first inner walls, and the electrode assembly is clamped between the two first buffer assemblies.

[0019] In the above technical solution, the first buffer assembly is arranged on both sides of the electrode assembly along the thickness direction of the battery monomer, which can improve the compactness of lithium deposition on both sides of the electrode assembly in the thickness direction.

[0020] In some embodiments, the inner wall of the shell includes a second inner wall, the second inner wall is perpendicular to the first direction, the first direction is a length direction of the battery monomer, and the buffer assembly includes a second buffer assembly, the second buffer assembly is arranged between the electrode assembly and the second inner wall.

[0021] In the above technical solution, along the length direction of the battery monomer, the second buffer assembly is arranged between the electrode assembly and the second inner wall, so that the second buffer assembly can act on the outer surface of the electrode assembly in the length direction, and can better inhibit the expansion of the electrode assembly in the length direction during charging and discharging, thereby improving the compactness of lithium deposition.

[0022] In some embodiments, the number of the second inner walls is two, the two second inner walls are oppositely arranged along the first direction, the number of the second buffer assemblies is two, the two second buffer assemblies are respectively and one-to-one connected to the two second inner walls, and the electrode assembly is clamped between the two second buffer assemblies.

[0023] In the technical solution, the second buffer assembly is arranged on both sides of the electrode assembly along the length direction of the battery cell, so that the compactness of lithium deposition on both sides of the electrode assembly in the length direction can be improved.

[0024] In some embodiments, the number of electrode assemblies is at least two; the battery cell further comprises an elastic pad arranged between two adjacent electrode assemblies.

[0025] In the technical solution, the elastic pad is arranged between two adjacent electrode assemblies, so that the electrode assembly can be more easily compressed, thereby facilitating the shell entering operation of the electrode assembly.

[0026] In some embodiments, the side surface of the elastic pad facing the electrode assembly is a contact surface, the contact surface is a plane and is in contact with the outer surface of the electrode assembly; the arrangement direction of the two adjacent electrode assemblies is a second direction, and in the same plane perpendicular to the second direction, the range of the normal projection of the contact surface exceeds the range of the normal projection of the electrode assembly.

[0027] In the technical solution, the range of the normal projection of the contact surface exceeds the range of the normal projection of the electrode assembly, and the contact surface is designed as a plane, so that the outer surface of the electrode assembly facing the elastic pad can be completely in contact with the contact surface during charging and discharging, and the stress uniformity of the electrode assembly can be further improved, which helps to make the lithium deposition more compact.

[0028] In a second aspect, the embodiments of the present application further provide a battery device comprising the battery cell provided in any one of the embodiments of the first aspect.

[0029] In a third aspect, the embodiments of the present application further provide a use electric equipment comprising the battery device provided in any one of the embodiments of the second aspect, and the battery device is used for providing electric energy.

[0030] In a fourth aspect, the embodiments of the present application further provide an energy storage equipment comprising the battery device provided in any one of the embodiments of the second aspect, and the battery device is used for storing electric energy. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The structural schematic diagram of a vehicle according to some embodiments of the present application is shown;

[0033] Figure 2Exploded structural schematic diagram of a battery device according to some embodiments of the present application;

[0034] Figure 3 Exploded structural schematic diagram of a battery cell according to some embodiments of the present application;

[0035] Figure 4 Longitudinal cross-sectional structural schematic diagram of a battery cell according to some embodiments of the present application;

[0036] Figure 5 Longitudinal cross-sectional structural schematic diagram of a buffer assembly according to some embodiments of the present application;

[0037] Figure 6 Structural schematic diagram of an electrode assembly entering a shell using an extrusion tool according to some embodiments of the present application;

[0038] Figure 7 Cross-sectional structural schematic diagram of a first battery cell according to some embodiments of the present application;

[0039] Figure 8 Cross-sectional structural schematic diagram of a second battery cell according to some embodiments of the present application;

[0040] Figure 9 Cross-sectional structural schematic diagram of a third battery cell according to some embodiments of the present application;

[0041] Figure 10 Cross-sectional structural schematic diagram of a fourth battery cell according to some embodiments of the present application;

[0042] Figure 11 Cross-sectional structural schematic diagram of a fifth battery cell according to some embodiments of the present application.

[0043] Reference signs are as follows:

[0044] 1000 - vehicle;

[0045] 100 - battery device, 110 - battery cell assembly, 120 - box, 1201 - first box, 1202 - second box;

[0046] 200 - controller;

[0047] 300 - motor;

[0048] 10 - battery cell, 11 - shell, 111 - shell body, 112 - end cap, 12 - electrode assembly, 121 - tab, 13 - electrode terminal;

[0049] 20-buffering assembly, 21-adhesive layer, 22-elastic layer, 23-support plate, 201-first buffering assembly, 202-second buffering assembly;

[0050] 30-elastic pad;

[0051] 40-extrusion tool. DETAILED DESCRIPTION

[0052] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0053] Unless otherwise defined, all technical and scientific terms used in the embodiments of the present application have the same meanings as those commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application; the terms “comprising” and “having” and any variations thereof in the specification and the above description of drawings are intended to cover non-exclusive inclusion.

[0054] The “embodiment” mentioned in the present application means that the specific features, structures or characteristics described in combination with the embodiments can be included in at least one embodiment of the present application. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment independent of or to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present application can be combined with other embodiments.

[0055] The special term “exemplary” mentioned in the embodiments of the present application means “as an example, embodiment or illustration”. Any embodiment described as “exemplary” is not necessarily interpreted as superior or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0056] In the description of the embodiments of the present application, the technical terms “first”, “second”, “third” and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0057] In the description of the embodiments of the present application, the technical term "and / or" is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents the "or" relationship between the front and rear associated objects.

[0058] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0059] In the description of the embodiments of the present application, the technical terms "up", "down", "in", "out", "front", "back", "left", "right", "top", "bottom" and the like indicate the orientation or positional relationship based on the working state of the embodiments of the present application, and 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 devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application.

[0060] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "on", "above" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0061] In the description of the embodiments of the present application, "parallel" not only includes the case of absolute parallel, but also includes the case of approximate parallel which is generally recognized in engineering; at the same time, "vertical" not only includes the case of absolute vertical, but also includes the case of approximate vertical which is generally recognized in engineering.

[0062] In the description of the embodiments of the present application, the meaning of "multiple" is more than two (including two), unless otherwise explicitly specified and limited.

[0063] In the description of the embodiments of the present application, the same reference signs represent the same components, and for the sake of brevity, detailed description of the same components is omitted in different embodiments. It should be understood that the thickness, length and other dimensions of various components in the embodiments of the present application shown in the drawings, and the overall thickness, length and other dimensions of the integrated device are only exemplary and should not constitute any limitation on the present application.

[0064] At present, from the development of market situation, the application of battery is more and more widely. The battery is not only applied to the energy storage power supply system of hydropower, thermal power, wind power and solar power station, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, and aerospace and other fields. But with the continuous popularization of battery application, people's requirements for battery are also getting higher and higher.

[0065] Taking lithium metal battery monomer as an example, lithium metal battery monomer is a kind of battery with pure lithium metal as negative active material, whose core feature is to realize the storage and release of electric energy by relying on the redox reaction of lithium metal. The positive electrode is usually matched with sulfide, oxide and other materials, and the electrolyte is mostly organic electrolyte or solid electrolyte. The key advantage of this kind of battery monomer is that the energy density is extremely high, but the lithium metal negative electrode is easy to form lithium dendrite. The pressure expansion in lithium metal battery monomer has a strong correlation with the deposition of lithium and the cycle performance of the battery monomer. A certain pressure is needed in the charging and discharging process of lithium metal battery monomer to keep the lithium on the negative side dense deposition, increase the density of by-product layer and reduce the occurrence of side reactions. The volume expansion caused by lithium deposition-stripping in the cycle process depends on the external buffer materials such as elastic gasket, spring and the like to provide expansion space and expansion pressure. Among them, the additional device required by lithium metal battery monomer increases the complexity of its system application, limits the application range, and at the same time reduces the energy density of the system, which weakens the advantage of high energy density of lithium metal battery monomer itself. At the same time, the hard expansion extrusion between the internal pole pieces increases the local unevenness, which leads to the increase of polarization and accelerates the capacity attenuation of the battery monomer. In addition, the conventional lithium metal battery monomer cannot be put into the shell with full group margin, and there is a gap between the electrode assembly and the shell. The cycle under no stress will also cause the deterioration of the performance of the battery monomer. Therefore, special structure design is needed to improve the uniform expansion pressure problem of lithium metal battery monomer in the cycle process.

[0066] Based on the above problems, the embodiments of the present application provide a battery monomer, which comprises a shell, an electrode assembly and a buffer assembly, the buffer assembly is arranged between the electrode assembly and the inner wall of the shell along a first direction, and the buffer assembly can be compressed after entering the shell, so that the buffer assembly and the electrode assembly can completely fill the inner cavity of the shell in the first direction to achieve full group margin entering the shell. Moreover, by limiting the compression rate of the buffer assembly, appropriate expansion space and rebound force can be provided for the electrode assembly to provide the required pressure for lithium deposition in the charging and discharging process, so as to maintain the dense deposition of lithium metal battery monomer negative side lithium, increase the density of byproduct layer, and reduce the occurrence of side reactions.

[0067] The technical scheme provided by the embodiments of the present application is suitable for a lithium metal battery monomer, a battery device containing the lithium metal battery monomer, and a power consumption equipment using the battery device as a power supply and an energy storage equipment using the battery device as an energy storage element. The power consumption equipment can be a vehicle, a ship, a spacecraft, etc. The energy storage equipment can be an energy storage container, an energy storage cabinet, etc.

[0068] For the convenience of description, the embodiments of the present application take the application of the battery device in a vehicle as an example for illustration.

[0069] Reference Figure 1 , Figure 1 A structural schematic diagram of a vehicle according to some embodiments of the present application is shown. The vehicle 1000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid automobile or a range extended automobile, etc. The vehicle 1000 is internally provided with a battery device 100, which can be arranged at the bottom, the head or the tail of the vehicle 1000. The battery device 100 can be used for power supply of the vehicle 1000, for example, the battery device 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0070] In some embodiments, the battery device 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle.

[0071] Reference Figure 2 , Figure 2 A disassembled structural schematic diagram of the battery device according to some embodiments of the present application is shown. The battery device includes a box body 120 and a battery monomer assembly 110, and the box body 120 has a containing cavity, and the battery monomer assembly 110 is contained in the containing cavity of the box body 120.

[0072] In some embodiments, a battery apparatus may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or in a mixed configuration via a busbar.

[0073] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0074] As an example, a battery cell assembly can be a battery module, which consists of multiple battery cells arranged and fixed together to form an independent module.

[0075] As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0076] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0077] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0078] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0079] As an example, such as Figure 2 As shown, the housing 120 may include a first housing 1201 and a second housing 1202. The first housing 1201 and the second housing 1202 are fastened together to form a closed space inside the housing 120 to house the battery cell assembly 110. Here, "closed" refers to covering or closing, which can be sealed or unsealed. The first housing 1201 may be a top cover or a bottom plate.

[0080] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The frame may be formed by multiple side walls, and the top cover and bottom plate are connected to the frame respectively, so that the interior of the enclosure forms a closed space to house the individual battery cells.

[0081] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0082] refer to Figure 3 , Figure 3A schematic diagram of a battery cell according to some embodiments of the present application is shown. The battery cell 10 includes an electrode assembly 12, an electrolyte, and a housing 11, wherein the electrode assembly 12 and the electrolyte are disposed within the housing 11, and the housing 11 is configured to encapsulate the electrode assembly 12 and the electrolyte.

[0083] In some embodiments, the electrode assembly 12 can include a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. During charging and discharging of the battery cell, active ions (e.g., lithium ions) are intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The separator disposed between the positive electrode sheet and the negative electrode sheet can prevent short circuiting of the positive electrode sheet and the negative electrode sheet, while allowing the active ions to pass through.

[0084] In some embodiments, the electrode assembly 12 can have a jelly-roll structure, a stacked structure, or a hybrid structure of the jelly-roll and the stacked structure.

[0085] As an example, the positive electrode sheet and the negative electrode sheet are stacked and can be wound into a jelly-roll structure.

[0086] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked. As an example, a plurality of positive electrode sheets are provided, and the negative electrode sheet is folded to form a plurality of folded segments that are stacked, with one positive electrode sheet sandwiched between adjacent folded segments.

[0087] As an example, the positive electrode sheet and the negative electrode sheet are each folded to form a plurality of folded segments that are stacked.

[0088] As an example, a plurality of separators are provided, each disposed between any adjacent positive electrode sheet or negative electrode sheet.

[0089] As an example, the separators are provided continuously and are disposed between any adjacent positive electrode sheet and negative electrode sheet by folding or winding.

[0090] In some embodiments, the positive electrode sheet can include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0091] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active material is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0092] As an example, the positive current collector can employ a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, a pure metal, an alloy, a surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, nickel, titanium, or silver, etc. can be employed. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0093] As an example, the positive active material can use, but is not limited to, a lithium transition metal oxide and / or an olivine-structured lithium-containing phosphate positive active material. In some embodiments, the positive active material is selected from a lithium transition metal oxide. In some embodiments, the lithium transition metal oxide is selected from a lithium cobalt oxide, a lithium nickel oxide, a lithium manganese oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide, or a combination thereof. Examples of the lithium transition metal oxide can include, but are not limited to, at least one of a lithium cobalt oxide, a lithium nickel oxide, a lithium manganese oxide, a lithium nickel cobalt oxide, a lithium manganese cobalt oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide, and modified compounds thereof, etc. Examples of the olivine-structured lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0094] In some embodiments, the negative tab can include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0095] As an example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active material is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0096] As an example, the negative current collector can employ a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, a pure metal, an alloy, a surface-treated metal, including but not limited to stainless steel, copper, aluminum, nickel, nickel, titanium, or silver, etc. can be employed. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0097] As an example, the negative active material is elemental lithium. The negative active material can also be an alloy of lithium with other various metal or non-metal elements, and an inert current collector. The metal elements include tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), platinum (Pt), and the like. The quasi-metal elements include boron (B), carbon (C), silicon (Si), and the like. The inert current collector includes a copper foil current collector or a modified copper foil current collector.

[0098] In some embodiments, the separator is a separator film. The type of the separator film is not particularly limited in the present application, and any known porous structure separator film having good chemical stability and mechanical stability can be used. As an example, the base film of the separator film can use, but is not limited to, a polyethylene porous film, a polypropylene porous film, a polyimide porous film, and a porous film formed by a plurality of polymers.

[0099] In some embodiments, the separator is a solid-state electrolyte. The solid-state electrolyte is disposed between the positive electrode sheet and the negative electrode sheet, and simultaneously functions as an ion transmission and a separator of the positive and negative electrode sheets.

[0100] In some embodiments, the shape of the electrode assembly 12 can be cylindrical, flat, or multi-prismatic, and the like.

[0101] In some embodiments, the electrode assembly 12 is provided with a tab 121, which can guide the current from the electrode assembly, and the tab includes a positive tab and a negative tab.

[0102] In some embodiments, the electrolyte functions as an ion conductor between the positive and negative electrode sheets. The type of the electrolyte is not particularly limited in the present application, and can be selected according to the needs. The electrolyte can be liquid, gel, or solid. As an example, the electrolyte can use, but is not limited to, a lithium ion electrolyte, an ester electrolyte, an ether electrolyte, and the like.

[0103] In some embodiments, the housing 11 is a hollow structure, and the inside of the housing 11 forms a containing space for containing the electrode assembly 12 and the electrolyte.

[0104] The shape of the housing 11 can be determined according to the specific shape of the electrode assembly 12. For example, if the electrode assembly 12 is a cuboid structure, a cuboid housing can be selected.

[0105] The material of the housing 11 can be various, such as metal or plastic. Alternatively, the material of the housing 11 can be copper, iron, aluminum, steel, aluminum alloy, and the like. As an example, the housing 11 can be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell), or an aluminum-plastic film, and the like.

[0106] In some embodiments, at least one electrode terminal 13 is arranged on the shell 11, and the electrode terminal 13 is electrically connected with the tab 121. The electrode terminal 13 can be directly connected with the tab 121, or indirectly connected with the tab 121 through a current collecting member. The electrode terminal 13 can be arranged on the end cover 112, or arranged on the shell 111.

[0107] In some embodiments, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging.

[0108] As an example, the battery cell can be a prismatic battery cell or a battery cell of other shapes having a bottom surface and side surfaces, such as a square battery cell, a blade battery cell, a multi-prismatic battery cell, for example, a hexagonal battery cell, and the like. The embodiments of the present application are not limited thereto.

[0109] The technical solutions of the embodiments of the present application are described in detail below with reference to the accompanying drawings. The technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0110] Reference Figure 3 , Figure 4 and Figure 6 , Figure 4 is a longitudinal sectional structure schematic diagram of a battery cell provided according to some embodiments of the present application; Figure 6 is a structure schematic diagram of realizing the entry of an electrode assembly into a shell by using an extrusion tool according to some embodiments of the present application.

[0111] In a first aspect, as shown in Figure 4 , the embodiments of the present application provide a battery cell 10, comprising a shell 11, an electrode assembly 12 and a buffer assembly 20; the electrode assembly 12 is arranged inside the shell 11; the buffer assembly 20 is arranged between the electrode assembly 12 and the inner wall of the shell 11 along a first direction; when the buffer assembly 20 and the electrode assembly 12 are placed inside the shell 11, the sum of the sizes of the buffer assembly 20 and the electrode assembly 12 in the first direction is equal to the inner cavity size of the shell 11, the inner cavity size of the shell 11 is the distance between the two inner walls of the shell 11 in the first direction, and the compression rate of the buffer assembly 20 after entering the shell in the first direction is W, W satisfies: 20%≤W≤30%; the stress of the buffer assembly 20 under pressure is σ MPa, σ satisfies: σ=9.5W-0.0067.

[0112] Specifically, the battery cell 10 can be a square battery cell 10, which has a length direction of the battery cell 10, a thickness direction of the battery cell 10 and a height direction of the battery cell 10 perpendicular to each other.

[0113] Optionally, the first direction can be a length direction of the battery monomer 10 or a thickness direction of the battery monomer 10.

[0114] Specifically, the buffer assembly 20 is a layer structure with a certain elasticity, which can be compressed to absorb the expansion force of the electrode assembly 12 and can also provide a rebound force to provide the required partial pressure when lithium is deposited on the electrode assembly 12.

[0115] Specifically, the buffer assembly 20 after entering the shell refers to the buffer assembly 20 after the buffer assembly 20 and the electrode assembly 12 are completely placed in the inside of the shell 11.

[0116] Specifically, the compression rate of the buffer assembly 20 after entering the shell in the first direction refers to the ratio between the maximum size d1 of the buffer assembly 20 after entering the shell that can still be compressed in the first direction and the size D of the buffer assembly 20 in the free state in the first direction.

[0117] Wherein, the size of the buffer assembly 20 after entering the shell that has been compressed in the first direction is d2, and the ratio between the sum of d1 and d2 and D is the maximum compression rate of the buffer assembly 20. It should be understood that d2 can be greater than or equal to 0, when d2 is equal to 0, it means that the buffer assembly 20 is in a free state after entering the shell and is not compressed, but at this time the buffer assembly 20 is in close contact with the inner wall of the shell 11 and the electrode assembly 12 in the first direction, which meets the 100% entering shell margin condition; when d2 is greater than 0, it means that the buffer assembly 20 is in a compressed state after entering the shell, and the buffer assembly 20 can provide a rebound force in the first direction, so that the buffer assembly 20 is in close contact with the inner wall of the shell 11 and the electrode assembly 12, which meets the 100% entering shell margin condition.

[0118] Optionally, the compression rate W of the buffer assembly 20 after entering the shell in the first direction can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., or can be a range composed of any of the above values.

[0119] Specifically, the compression stress of the buffer assembly 20 refers to the stress of the buffer assembly 20 when the electrode assembly 12 inside the battery monomer 10 expands and extrudes the buffer assembly 20 during charging and discharging.

[0120] Optionally, as shown in Figure 3 and Figure 4 The shell 11 includes a shell body 111 and an end cover 112, the shell body 111 has an opening, and the end cover 112 is used to cover the opening.

[0121] Optionally, the housing 111 is a component used to fit the end cap 112 to form an internal cavity of the battery cell 10, which can be used to accommodate the electrode assembly 12, electrolyte, and other components.

[0122] Alternatively, the housing 111 and the end cap 112 can be separate components. For example, an opening can be provided on the housing 111, and the end cap 112 can be used to close the opening to form an internal cavity for the battery cell 10.

[0123] Optionally, the shape of the end cap 112 can be adapted to the shape of the housing 111 to fit the housing 111. The material of the end cap 112 can be the same as or different from the material of the housing 111.

[0124] Alternatively, the end cap 112 may be attached to the housing 111 by welding, bonding, snap-fitting or other means.

[0125] Optionally, the housing 111 may have an opening on one side or on both sides. Exemplarily, the housing 111 has an opening on one side, and the end cap 112 is one that covers the opening of the housing 111. As another example, the housing 111 may also have an opening on both sides, and two end caps 112 are provided, each covering one of the two openings of the housing 111. For ease of description, the embodiments of this application are illustrated using a structure where the housing 111 has an opening on one side and the end cap 112 covers the opening.

[0126] Optionally, the number of electrode assemblies 12 can be one or more. When the number of electrode assemblies 12 is multiple, the multiple electrode assemblies 12 can be arranged along the thickness direction of the battery cell 10.

[0127] Optionally, such as Figure 6 As shown, the electrode assembly 12 and the buffer assembly 20 can be inserted into the housing 11 using a compression tool 40. For example, before the electrode assembly 12 is inserted into the housing, the buffer assembly 20 can be fixed to the inner wall of the housing 11 along a first direction. Then, the compression tool 40 is used to compress the buffer assembly 20 along the first direction to provide an installation space for the electrode assembly 12 larger than its own volume inside the housing 11. The compression tool 40 is provided with clearance space, through which the electrode assembly 12 can be inserted into the installation space inside the housing 11. Then, the compression tool 40 is removed, and the buffer assembly 20 springs back, allowing the buffer assembly 20, the inner wall of the housing 11, and the electrode assembly 12 to all be in close contact, achieving 100% insertion margin.

[0128] In the technical solution, the sum of the size of the buffer assembly 20 and the electrode assembly 12 in the first direction after the buffer assembly 20 is inserted into the shell 11 is equal to the size of the inner cavity of the shell 11, and the buffer assembly 20 can be compressed in the first direction, so that the buffer assembly 20 and the electrode assembly 12 can completely fill the inner cavity of the shell 11 in the first direction, and the insertion margin can reach 100%.

[0129] In addition, the buffer assembly 20 is arranged between the electrode assembly 12 and the inner wall of the shell 11, so that stress concentration of the electrode assembly 12 during deformation can be avoided in the compression and rebound process, and the stress uniformity of the electrode assembly 12 is improved.

[0130] In addition, the compression rate of the buffer assembly 20 after being inserted into the shell is limited to between 20% and 30%. On the one hand, the buffer assembly 20 can form an appropriate compression amount, so that the buffer assembly 20 can be compressed and deformed with the expansion of the electrode assembly 12 to provide space for the expansion of the electrode assembly 12 during charging and discharging. On the other hand, the buffer assembly 20 can provide appropriate rebound force, so that the buffer assembly 20 can provide part of the pressure required for lithium deposition during charging and discharging.

[0131] Meanwhile, by constructing the corresponding relationship between the compression rate of the buffer assembly 20 and the stress of the buffer assembly 20 under pressure, the stress range of the buffer assembly 20 under pressure can be limited, and the buffer assembly 20 can gradually change the compression rate within the compressible range with the change of the stress under pressure, so as to provide a compression amount and rebound force matched with the current stage at different stages of charging and discharging.

[0132] Reference Figure 4 and Figure 5 , Figure 5 is a schematic view of a longitudinal cross-section structure of the buffer assembly provided according to some embodiments of the present application.

[0133] In some embodiments, as shown in Figure 4 and Figure 5 , the buffer assembly 20 includes an adhesive layer 21, an elastic layer 22 and a support plate 23 arranged in the first direction and connected in sequence; the side of the adhesive layer 21 away from the elastic layer 22 is connected to the inner wall of the shell 11; the elastic layer 22 is configured to provide an elastic force, so that the support plate 23 can abut against the electrode assembly 12.

[0134] Optionally, the adhesive layer 21 can be a glue layer, which can be a polyurethane sealant, a polypropylene glue, a polyethylene glue or the like.

[0135] The adhesive layer 21 is mainly used to fix the buffer assembly 20 on the inner wall of the shell 11, so that the buffer assembly 20 is fixedly connected with the inner wall of the shell 11 when the shell is entered, and then the buffer assembly 20 is compressed by the elasticity of the buffer assembly 20, so as to provide sufficient space for the electrode assembly 12 to enter the shell; and due to the adhesion of the adhesive layer 21, the compressed buffer assembly 20 will not be dislocated between the inner wall of the shell 11 when rebounding.

[0136] Therefore, by arranging the adhesive layer 21, the connection stability between the buffer assembly 20 and the inner wall of the shell 11 can be improved, on the one hand, the operation of placing the buffer assembly 20 and the electrode assembly 12 into the shell 11 can be facilitated, and on the other hand, the dislocation of the electrode assembly 12 in the shell 11 caused by the dislocation between the buffer assembly 20 and the shell 11 during the charging and discharging process can be reduced.

[0137] Optionally, the elastic layer 22 has a three-dimensional porous network structure.

[0138] The three-dimensional porous network structure can be a 3D air fiber layer, which can be made of polyethylene or polyolefin, and a three-dimensional network structure is formed by high-temperature melting and spinning to form the elastic layer 22. The elastic layer 22 can be formed by 3D printing based on the support plate 23.

[0139] Therefore, by designing the elastic layer 22 as a three-dimensional porous network structure, the elasticity of the elastic layer 22 can be improved; in addition, the three-dimensional porous network structure does not absorb electrolyte, does not need to be plastic sealed, and there is no risk of affecting the electrolyte due to the plastic sealing breakage.

[0140] Further optionally, a sealed cavity can be formed in the elastic layer 22, and the sealed cavity is filled with gas.

[0141] By arranging the sealed cavity filled with gas in the elastic layer 22, the elasticity of the elastic layer 22 can be further improved; and the gas is enclosed in the sealed cavity and does not affect the electrolyte. It should be noted that the sealed cavity in the elastic layer 22 can be formed by high-temperature melting and spinning during the process of making the three-dimensional porous network structure.

[0142] Optionally, the support plate 23 can be a plate structure made of polypropylene material.

[0143] The support plate 23 has a certain supporting strength and can resist the extrusion force when the electrode assembly 12 expands during charging and discharging, so that the support plate 23 will not be deformed, which is beneficial to further improve the stress uniformity of the electrode assembly 12.

[0144] Further, as Figure 4As shown, the surface of the support plate 23 facing the electrode assembly 12 is the contact surface, which is a plane and contacts the outer surface of the electrode assembly 12; wherein, in the same plane perpendicular to the first direction, the orthographic projection range of the contact surface exceeds the orthographic projection range of the electrode assembly 12.

[0145] In the above technical solution, by setting the orthographic projection range of the contact surface to exceed the orthographic projection range of the electrode assembly 12, and designing the contact surface as a plane, the electrode assembly 12 can completely contact the outer surface of the support plate 23 during the charging and discharging process, which can further improve the uniformity of the force on the electrode assembly 12 and help to make the lithium deposition more dense.

[0146] refer to Figure 7 and Figure 8 , Figure 7 This is a schematic cross-sectional view of a first type of battery cell provided according to some embodiments of this application; Figure 8 This is a schematic cross-sectional view of a second type of battery cell provided according to some embodiments of this application.

[0147] In some embodiments, such as Figure 7 As shown, the inner wall of the outer casing 11 includes a first inner wall, which is perpendicular to a first direction, the first direction being the thickness direction of the battery cell 10; the buffer assembly 20 includes a first buffer assembly 201, which is disposed between the electrode assembly 12 and the first inner wall.

[0148] It should be understood that the first inner wall is part of the inner wall of the outer casing 11. The first buffer assembly 201 is a type of buffer assembly 20 and has the features defined in the buffer assembly 20 in the above embodiments, that is, the first buffer assembly 201 includes an adhesive layer 21, an elastic layer 22 and a support plate 23 arranged and connected in sequence along the thickness direction of the battery cell 10.

[0149] It should be noted that the thickness direction of the battery cell 10 is also the thickness direction of the electrode assembly 12 and the thickness direction of the first buffer assembly 201.

[0150] Among them, the outer surface of electrode assembly 12 has the largest area in its thickness direction, which is the large surface area of ​​the outer surface of electrode assembly 12. During the charging and discharging process, the expansion of electrode assembly 12 in its thickness direction is the most prominent.

[0151] In the above technical solution, along the thickness direction of the battery cell 10, the first buffer component 201 is disposed between the electrode component 12 and the first inner wall, so that the first buffer component 201 can act on the large surface of the outer surface of the electrode component 12, which can better suppress the expansion of the electrode component 12 during charging and discharging, and is conducive to improving the density of lithium deposition.

[0152] Further, as shown in Figure 8 the first direction; the first buffer assembly 201 is arranged on the first inner wall of the shell 11, and the electrode assembly 12 is arranged on the second inner wall of the shell 11.

[0153] It should be noted that, in the process of charging and discharging, the expansion of the electrode assembly 12 is towards both sides in the thickness direction of the electrode assembly 12. If the first buffer assembly 201 is arranged only on one side of the electrode assembly 12 in the thickness direction of the electrode assembly 12, then the two sides of the electrode assembly 12 in the thickness direction of the electrode assembly 12 will be unbalanced after expansion, and the two sides will have differences in lithium deposition and stress.

[0154] In the above technical solution, the first buffer assembly 201 is arranged on both sides of the electrode assembly 12 in the thickness direction of the battery monomer 10, which can improve the compactness of lithium deposition on both sides of the electrode assembly 12 in the thickness direction of the electrode assembly 12, especially for the case where two electrode assemblies 12 are arranged in the shell 11 along the thickness direction of the battery monomer 10. At the same time, the structure of the two oppositely arranged first buffer assemblies 201 in the shell 11 can improve the stress difference problem of the electrode assembly 12 on both sides in the thickness direction of the electrode assembly 12, so as to improve the consistency of lithium deposition on both sides in the thickness direction of the electrode assembly 12.

[0155] Reference Figure 9 and Figure 10 , Figure 9 is a third cross-sectional structure schematic diagram of a battery monomer provided according to some embodiments of the application; Figure 10 is a fourth cross-sectional structure schematic diagram of a battery monomer provided according to some embodiments of the application.

[0156] In some embodiments, as shown in Figure 9 the inner wall of the shell 11 includes a second inner wall, the second inner wall is perpendicular to the first direction, and the first direction is the length direction of the battery monomer 10; the buffer assembly 20 includes a second buffer assembly 202, and the second buffer assembly 202 is arranged between the electrode assembly 12 and the second inner wall.

[0157] It should be understood that the second inner wall belongs to a part of the inner wall of the shell 11, and the second inner wall is different from the first inner wall, and the two belong to different parts of the inner wall of the shell 11. The second buffer assembly 202 belongs to one of the buffer assemblies 20, which has the characteristics defined in the buffer assemblies 20 in the above embodiments, that is, the second buffer assembly 202 includes the adhesive layer 21, the elastic layer 22 and the support plate 23 arranged and connected in turn along the length direction of the battery monomer 10; the second buffer assembly 202 is similar in structure to the first buffer assembly 201, but the two are completely different in layout position.

[0158] It should be noted that the length direction of the battery monomer 10 is also the length direction of the electrode assembly 12.

[0159] In the technical solution, along the length direction of the battery monomer 10, the second buffer assembly 202 is arranged between the electrode assembly 12 and the second inner wall, so that the second buffer assembly 202 can act on the outer surface of the electrode assembly 12 in the length direction thereof, and can better inhibit the expansion of the electrode assembly 12 in the length direction thereof during charging and discharging, and can improve the compactness of lithium deposition.

[0160] Further, as shown in Figure 10 , the number of second inner walls is two, and the two second inner walls are oppositely arranged along the first direction; the number of second buffer assemblies 202 is two, and the two second buffer assemblies 202 are respectively and one-to-one connected to the two second inner walls, and the electrode assembly 12 is clamped between the two second buffer assemblies 202.

[0161] It should be noted that during charging and discharging, the expansion of the electrode assembly 12 is towards both sides in the length direction thereof. If the second buffer assembly 202 is arranged only on one side of the electrode assembly 12 in the length direction thereof, then after expansion, the electrode assembly 12 will be unbalanced on both sides in the length direction thereof, and the two sides will have differences in lithium deposition and stress.

[0162] In the technical solution, the second buffer assembly 202 is arranged on both sides of the electrode assembly 12 along the length direction of the battery monomer 10, which can improve the compactness of lithium deposition on both sides of the electrode assembly 12 in the length direction thereof; at the same time, the structure of two oppositely arranged second buffer assemblies 202 in the outer shell 11 can improve the stress difference problem on both sides of the electrode assembly 12 in the length direction thereof, so as to improve the consistency of lithium deposition on both sides of the electrode assembly 12 in the length direction thereof.

[0163] Referring to Figure 11 , Figure 11 is a fifth cross-sectional structure of a battery monomer provided according to some embodiments of the present application.

[0164] In some embodiments, as shown in Figure 11 , the number of electrode assemblies 12 is at least two; the battery monomer 10 further comprises an elastic pad 30, and the elastic pad 30 is arranged between two adjacent electrode assemblies 12.

[0165] Specifically, the elastic pad 30 is a layer structure with a certain elasticity, which can be compressed to absorb the expansion force of the electrode assembly 12, and can also provide a rebound force to provide part of the pressure required for lithium deposition of the electrode assembly 12.

[0166] Exemplarily, the elastic pad 30 can be a single-layer structure, and the material thereof can include, but is not limited to, at least one of foamed polyethylene, polypropylene, polyurethane, silicone rubber, etc.

[0167] Specifically, the number of the electrode assemblies 12 can be two or more, and when the number of the electrode assemblies 12 is more than two, the elastic pad 30 can be arranged between each two adjacent electrode assemblies 12, or only between part of the two adjacent electrode assemblies 12.

[0168] In the above technical solution, by arranging the elastic pad 30 between the two adjacent electrode assemblies 12, on the one hand, when entering the shell, the electrode assembly 12 can be more easily compressed to facilitate the electrode assembly 12 to be placed into the shell 11; on the other hand, the elastic pad 30 can also cooperate with the buffer assembly 20 to absorb the expansion volume of the electrode assembly 12 during charging and discharging and provide the required resilience to the electrode assembly 12; at the same time, the elastic pad 30 can also improve the problem of uneven stress between the two adjacent electrode assemblies 12.

[0169] Further, the side of the elastic pad 30 facing the electrode assembly 12 is a contact surface, and the contact surface is a plane and is in contact with the outer surface of the electrode assembly 12; wherein the arrangement direction of the two adjacent electrode assemblies 12 is the second direction, and in the same plane perpendicular to the second direction, the range of the orthogonal projection of the contact surface exceeds the range of the orthogonal projection of the electrode assembly 12.

[0170] In the above technical solution, by arranging the range of the orthogonal projection of the contact surface to exceed the range of the orthogonal projection of the electrode assembly 12, and designing the contact surface as a plane, the outer surface of the electrode assembly 12 can be completely in contact with the contact surface during the charging and discharging process, which can further improve the uniformity of the stress of the electrode assembly 12 and help the lithium deposition to be more dense.

[0171] Reference Figures 4 to 6 and Figure 8The battery monomer 10 provided by the embodiments of the present application comprises a shell 11, an electrode assembly 12, and a buffer assembly 20; the electrode assembly 12 is arranged inside the shell 11; the buffer assembly 20 is arranged between the electrode assembly 12 and the inner wall of the shell 11 along a first direction, the first direction being the thickness direction of the battery monomer 10; after the buffer assembly 20 and the electrode assembly 12 are placed inside the shell 11, the sum of the sizes of the buffer assembly 20 and the electrode assembly 12 in the first direction is equal to the inner cavity size of the shell 11, the inner cavity size of the shell 11 being the distance between the two inner walls of the shell 11 in the first direction, and the compression rate of the buffer assembly 20 after being placed in the shell in the first direction is W, W satisfying 20%≤W≤30%; the stress of the buffer assembly 20 under pressure is σ MPa, σ satisfying σ=9.5W-0.0067. The buffer assembly 20 comprises an adhesive layer 21, an elastic layer 22, and a support plate 23 arranged in the first direction and connected in sequence; the side of the adhesive layer 21 away from the elastic layer 22 is connected to the inner wall of the shell 11; the elastic layer 22 is configured to provide an elastic force, so that the support plate 23 can abut against the electrode assembly 12; the elastic layer 22 is a three-dimensional porous network structure with elasticity. The surface of the side of the support plate 23 facing the electrode assembly 12 is an abutting surface, the abutting surface is a plane and is in contact with the outer surface of the electrode assembly 12; wherein, in the same plane perpendicular to the first direction, the range of the orthogonal projection of the abutting surface exceeds the range of the orthogonal projection of the electrode assembly 12. The number of the buffer assemblies 20 is two and they are oppositely arranged along the thickness direction of the battery monomer 10.

[0172] In a second aspect, the embodiments of the present application further provide a battery device comprising the battery monomer 10 provided by any one of the embodiments of the first aspect.

[0173] In a third aspect, the embodiments of the present application further provide a power consumption device comprising the battery device provided by any one of the embodiments of the second aspect, the battery device being used to provide electric energy.

[0174] In a fourth aspect, the embodiments of the present application further provide an energy storage device comprising the battery device provided by any one of the embodiments of the second aspect, the battery device being used to store electric energy.

[0175] The preparation method and test results of the embodiments of the present application are as follows:

[0176] (I) Preparation of lithium metal battery monomer

[0177] Preparation of electrode assembly 12 (bare cell) with length 104 mm and width 97 mm: negative electrode sheet is slitted into a size of 101 mm in length and 91 mm in width, and positive electrode sheet is slitted into a size of 100 mm in length and 50 mm in width. The width of the separator is 97 mm, and the size of the negative electrode sheet in the up-down direction exceeds the length, with each reserved 3 mm. The positive electrode sheet and the negative electrode sheet are stacked layer by layer, with 39 layers of negative electrode sheets and 38 layers of positive electrode sheets, and the outermost layer of the stack is wound with an additional turn of the separator to finish. The bare cell is hot-pressed at 70° for 3 s to obtain the electrode assembly 12.

[0178] Shell entry: the electrode assembly 12 and the buffer assembly 20 (if any) are placed into the inside of the shell 11.

[0179] Top cover welding-helium detection-liquid injection-seal nail welding-insulation film wrapping-lower bin for testing to obtain a lithium metal battery cell.

[0180] The differences between Comparative Example 1 and Examples 1-9 are shown in Table 1. In Comparative Example 1, no buffer assembly 20 is provided, and in Examples 1-9, a buffer assembly 20 with different thicknesses or different layout modes of the buffer assembly 20 on one side or both sides of the electrode assembly 12 in the thickness direction is provided. It should be noted that when the number of buffer assemblies 20 is 1, it means that the buffer assembly 20 is provided on one side of the electrode assembly 12 in the thickness direction thereof; and when the number of buffer assemblies 20 is 2, it means that two buffer assemblies 20 are provided on both sides of the electrode assembly 12 in the thickness direction thereof, and the thicknesses of the two buffer assemblies 20 are consistent.

[0181] (B) Performance test method of battery cell 10

[0182] 1) After the battery cell 10 is left standing for 24 h and after the first full charge of the battery cell 10 is completed, the battery cell 10 is disassembled, and the lithium deposition thickness and deposition morphology on the negative electrode sheet are detected and photographed using a CP device (Contour Profiler).

[0183] 2) Battery cell 10 cycle: the ambient temperature is set to 25°C, and the charge-discharge cycle is performed at a rate of 0.2C-1C (i.e., 13A-65A). The cut-off voltages for charging and discharging are set to 4.3V and 2.8V, respectively. When the discharge capacity decays to 80% of the first cycle discharge capacity, the battery cell 10 is considered to have reached the end of life. After the cycle is completed, the cycle performance of the battery cell 10 is observed and recorded.

[0184] Table 1 Differences between Comparative Example 1 and Examples 1-9 and related test results

[0185]

[0186] Conclusion: Based on Comparative Example 1 and Examples 1-9, it is evident that the solutions described in the above embodiments of this application are beneficial for improving the volume stability and stress uniformity of the battery cell 10 and electrode assembly 12 during charging and discharging, reducing the risk of expansion, deformation, or performance degradation. Specifically, adding a buffer assembly 20 to the battery cell 10 achieves 100% casing margin. Furthermore, the higher the remaining compressibility of the buffer assembly 20 after casing, the better it is for improving the cycle performance (more cycle times) of the battery cell 10. This improvement is particularly pronounced when the remaining compressibility of the buffer assembly 20 after casing is between 20% and 30%. Additionally, by providing buffer assemblies 20 on both sides of the electrode assembly 12 in the thickness direction, the density (smaller lithium deposition thickness) of lithium deposition on the negative electrode sheet of the electrode assembly 12 and the consistency of lithium deposition on both sides of the electrode assembly 12's thickness can be further improved, as well as enhancing the cycle performance of the battery cell 10.

[0187] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. This application is not limited to the specific embodiments applied herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The battery cell comprises: a shell; an electrode assembly arranged in the interior of the shell; a buffer assembly arranged between the electrode assembly and the inner wall of the shell in a first direction; when the buffer assembly and the electrode assembly are arranged in the interior of the shell, the sum of the sizes of the buffer assembly and the electrode assembly in the first direction is equal to the size of the inner cavity of the shell, the size of the inner cavity of the shell is the distance between the two inner walls of the shell in the first direction, and the compression rate of the buffer assembly after being arranged in the shell in the first direction is W, and the W satisfies: 20%≤W≤30%; the stress of the buffer assembly under pressure is σ MPa, and the σ satisfies: σ=9.5W-0.0067.

2. The battery cell according to claim 1, wherein the buffer assembly comprises an adhesive layer, an elastic layer and a support plate arranged in the first direction and connected in sequence; the side of the adhesive layer away from the elastic layer is connected to the inner wall of the shell; the elastic layer is configured to provide an elastic force to enable the support plate to abut against the electrode assembly.

3. The battery cell according to claim 2, wherein the surface of the side of the support plate facing the electrode assembly is an abutting surface, and the abutting surface is a plane and is in contact with the outer surface of the electrode assembly; wherein, in the same plane perpendicular to the first direction, the range of the orthogonal projection of the abutting surface exceeds the range of the orthogonal projection of the electrode assembly.

4. The battery cell according to claim 2, wherein the elastic layer is a three-dimensional porous network structure with elasticity.

5. The battery cell according to claim 2, wherein an inner part of the elastic layer is formed with a sealed cavity, and the sealed cavity is filled with gas.

6. The battery cell according to any one of claims 1-5, wherein the inner wall of the shell comprises a first inner wall, the first inner wall is perpendicular to the first direction, and the first direction is the thickness direction of the battery cell; the buffer assembly comprises a first buffer assembly, and the first buffer assembly is arranged between the electrode assembly and the first inner wall.

7. The battery cell according to claim 6, wherein the number of the first inner walls is two, and the two first inner walls are oppositely arranged along the first direction; the number of the first buffer assemblies is two, and the two first buffer assemblies are respectively and correspondingly connected to the two first inner walls, and the electrode assembly is clamped between the two first buffer assemblies.

8. The battery cell according to any one of claims 1-5, wherein the inner wall of the shell comprises a second inner wall, the second inner wall is perpendicular to the first direction, and the first direction is the length direction of the battery cell; the buffer assembly comprises a second buffer assembly, and the second buffer assembly is arranged between the electrode assembly and the second inner wall.

9. The battery cell according to claim 8, wherein the number of the second inner walls is two, and the two second inner walls are oppositely arranged along the first direction. The second buffer assembly is two in number, and each of the two second buffer assemblies is connected to a second inner wall in one-to-one correspondence, and the electrode assembly is arranged between the two second buffer assemblies. 10.The battery cell of any one of claims 1-5, wherein, The number of the electrode assembly is at least two. The battery cell further comprises an elastic pad arranged between two adjacent electrode assemblies. 11.The battery cell of claim 10, wherein, The side of the elastic pad facing the electrode assembly is a contact surface, the contact surface is a plane and is in contact with the outer surface of the electrode assembly. The arrangement direction of the two adjacent electrode assemblies is a second direction, and in the same plane perpendicular to the second direction, the range of the normal projection of the contact surface exceeds the range of the normal projection of the electrode assembly.

12. A battery device characterized by comprising: A battery cell as claimed in any one of claims 1-11.

13. An electrical device, characterized by A battery device as claimed in claim 12, wherein the battery device is configured to provide electrical energy.

14. An energy storage device, comprising: A battery device as claimed in claim 12, wherein the battery device is configured to store electrical energy.

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