Battery monomer, battery and electric device

Abstract

The utility model provides a battery monomer, a battery and a power utilization device, the battery monomer comprises a shell and an electrode assembly accommodated in the shell, the electrode assembly comprises a first pole piece and a second pole piece which have opposite polarities and are wound along a winding direction, the electrode assembly is provided with a bending area, an active material layer of the first pole piece is arranged on the surface of a current collector, and the active material layer of the second pole piece is arranged on the surface of the current collector. At least part of the conductive coating is arranged on the side, away from the current collector, of the active material layer, and at least part of the conductive coating is located in the bending area. In the structure, the conductive coating is arranged on the surface of the active material layer in the bending area in the electrode assembly, so that the conductive coating can be used for bonding and covering the active material layer, and the possibility of cracking and powder falling of the active material layer in the recycling process of the battery monomer is reduced; and the covered active material layer is not easily influenced to participate in electrochemical reaction, so that the attenuation of the capacity of the battery monomer in the recycling process is reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery and an electrical device. Background Art

[0002] Batteries have the advantages of high specific energy and high power density. They are widely used in electronic devices and transportation vehicles, such as mobile phones, laptops, electric vehicles, electric airplanes, electric ships, electric tools, etc.

[0003] As the application range of batteries becomes wider and wider, people have higher and higher requirements on the quality of batteries. How to reduce the capacity decay during the cycle use of batteries has attracted more and more attention from technicians in this field. Utility Model Content

[0004] In view of the above problems, the present application provides a battery cell, a battery and an electrical device, wherein the capacity attenuation of the battery cell is small.

[0005] In a first aspect, some embodiments of the present application provide a battery cell, which includes a shell and an electrode assembly housed in the shell; the electrode assembly includes a first pole sheet and a second pole sheet with opposite polarities, and the first pole sheet and the second pole sheet are wound along a winding direction; the electrode assembly has a bending area; the first pole sheet includes a current collector, an active material layer and a conductive coating, the active material layer is arranged on the surface of the current collector, at least part of the conductive coating is arranged on the side of the active material layer away from the current collector, and at least part of the conductive coating is located in the bending area.

[0006] In the above structure, since a conductive coating is provided on the surface of the active material layer in the bending area of ​​the electrode assembly, the conductive coating can not only bond and cover the active material layer, thereby reducing the possibility of cracking and powder loss of the active material layer during the cycle use of the battery cell, but also is not easy to affect the covered active material layer to participate in the electrochemical reaction, thereby reducing the attenuation of the capacity of the battery cell during the cycle use.

[0007] According to the battery cells provided in some embodiments of the present application, the interlayer peeling strength between the conductive coating and the active material layer is greater than the interlayer peeling strength between the active material layer and the current collector.

[0008] By setting the interlayer peeling strength between the conductive coating and the active material layer to be greater than the interlayer peeling strength between the active material layer and the current collector, the bonding strength of the conductive coating on the active material layer is made greater than the bonding strength of the active material layer on the current collector, so that the conductive coating can be bonded to and covered with the active material layer, making it less likely for the conductive coating to crack and shed.

[0009] According to the battery cells provided in some embodiments of the present application, the interlayer peeling strength between the conductive coating and the active material layer is A, 15N / m≤A≤30N / m, which not only enables the conductive coating to adhere well to the active material layer, but also makes the conductive coating have a lower cost, which is beneficial to reducing the cost of the first electrode sheet.

[0010] According to the battery cells provided in some embodiments of the present application, the glass transition temperature of the conductive coating is higher than the glass transition temperature of the active material layer. By setting the glass transition temperature of the conductive coating to be higher than the glass transition temperature of the active material layer, the toughness of the conductive coating is stronger than that of the active material layer. By setting the conductive coating on the surface of the active material layer facing away from the current collector in the bending region, the toughness of the first pole piece in the bending region can be improved, which is beneficial to reducing the possibility of cracking of the active material layer in the first pole piece in the bending region.

[0011] According to the battery cell provided in some embodiments of the present application, a plurality of conductive coatings are provided, and at least two conductive coatings are arranged at intervals along the winding direction. By arranging at least two conductive coatings at intervals along the winding direction, at least two conductive coatings can intermittently cover the active material layer along the winding direction, so that the active material layer can be bonded and covered with the conductive coating to reduce the possibility of cracking and powder loss of the active material layer during the cycle use of the battery cell, and the use of the conductive coating can be reduced, which is beneficial to reducing the cost of the first pole piece, thereby helping to reduce the cost of the battery cell.

[0012] According to the battery cell provided in some embodiments of the present application, a plurality of conductive coatings are provided, and at least two conductive coatings are arranged at intervals along the winding axial direction. By arranging at least two conductive coatings at intervals along the winding axial direction, at least two conductive coatings can cover the active material layer discontinuously along the winding axial direction, so that the active material layer can be bonded and covered with the conductive coating to reduce the possibility of cracking and powdering of the active material layer during the cycle use of the battery cell, and the use of the conductive coating can be reduced, which is beneficial to reducing the cost of the first pole piece, thereby helping to reduce the cost of the battery cell.

[0013] According to the battery cell provided in some embodiments of the present application, the active material layer further includes two second surfaces arranged opposite to each other along the winding axis, and the conductive coating extends along the winding axis and is connected between the two second surfaces. By extending the conductive coating along the winding axis and connecting between the two second surfaces, the conductive coating can be continuously extended between the two second surfaces of the active material layer, so that the conductive coating can traverse the conductive coating along the winding axis, so that the conductive coating can better cover the active material layer.

[0014] According to the battery cells provided in some embodiments of the present application, in the winding direction, the size of the conductive coating is B, 5mm≤B≤25mm, which not only ensures that the conductive coating has sufficient size in the winding direction to bond and cover the active material layer, but also makes it less likely that the conductive coating will increase the cost of the battery cell and reduce the capacity of the battery cell due to excessive size.

[0015] According to the battery cells provided in some embodiments of the present application, the thickness of the conductive coating in the thickness direction of the current collector is C, 2μm≤C≤10μm. This not only ensures that the conductive coating has sufficient thickness in the thickness direction of the current collector to bond and cover the active material layer, thereby reducing the possibility of the conductive coating falling off from the active material layer, but also makes it less likely that the conductive coating will be wasted due to excessive thickness.

[0016] According to the battery cell provided in some embodiments of the present application, the first pole piece includes a plurality of bends arranged along the winding direction; in the winding direction, the bend closest to the winding start end of the first pole piece is provided with a conductive coating. By providing the conductive coating on the bend closest to the winding start end of the first pole piece, the bend with the largest bending degree is provided with the conductive coating, so that the conductive coating can reduce the possibility of cracking and powdering of the active material layer in the bend with the largest bending degree.

[0017] According to the battery cells provided in some embodiments of the present application, in the winding direction, at least the two bends closest to the winding starting ends of the first pole piece are provided with a conductive coating, so that the conductive coating can reduce the possibility of cracking and powdering of the active material layer in the bends with a larger bending degree.

[0018] According to the battery cells provided by some embodiments of the present application, in the winding direction, the thickness of the conductive coating in the bend near the winding start end is greater than the thickness of the conductive coating in the bend away from the winding start end. By making the thickness of the conductive coating on the bend in the innermost circle thicker, the bonding and covering ability of the conductive coating on the bend in the innermost circle is stronger, which can match the greater bending degree of the bend in the innermost circle, which is conducive to reducing the possibility of cracking and powder loss of the active material layer in the bend.

[0019] According to the battery cells provided in some embodiments of the present application, in the winding direction, the size of the conductive coating in the bend away from the winding start end is larger than the size of the conductive coating in the bend near the winding start end. By setting the size of the conductive coating in the bend away from the winding start end in the winding direction to be larger than the size of the conductive coating in the bend near the winding start end in the winding direction, the conductive coating can adapt to the size of the bend in each coil layer in the winding direction, so that the conductive coating can better bond and cover the bend in each coil layer, which is conducive to reducing the possibility of cracking and powder loss of the active material layer on the bend in each coil layer.

[0020] According to the battery cells provided in some embodiments of the present application, the electrode assembly also includes a straight area connected to the bending area, a portion of the conductive coating is located in the straight area, and the other portion is located in the bending area, so that the conductive coating can be better coated on the surface of the active material layer located in the bending portion and the surface of the active material layer located in the transition portion between the straight portion and the bending portion.

[0021] In a second aspect, some embodiments of the present application further provide a battery, the battery comprising a battery cell provided by any of the above technical solutions. Since the battery comprises the battery cell provided by the above technical solution, the capacity attenuation of the battery is small.

[0022] In a third aspect, some embodiments of the present application further provide an electrical device, which includes a battery provided by the above technical solution, and the battery is used to provide electrical energy.

[0023] The technical solution provided by the embodiments of the present disclosure brings at least the following beneficial effects:

[0024] Some embodiments of the present application provide a battery cell, which includes a shell and an electrode assembly contained in the shell, the electrode assembly includes a first pole piece and a second pole piece of opposite polarity wound along a winding direction, the electrode assembly has a bending area, the active material layer of the first pole piece is arranged on the surface of the current collector, at least part of the conductive coating is arranged on the side of the active material layer away from the current collector, and at least part of the conductive coating is located in the bending area. In the above structure, since the surface of the active material layer in the bending area of ​​the electrode assembly is provided with a conductive coating, the conductive coating can not only bond and cover the active material layer, reducing the possibility of cracking and powdering of the active material layer during the cycle use of the battery cell, but also is not easy to affect the covered active material layer to participate in the electrochemical reaction, reducing the attenuation of the capacity of the battery cell during the cycle use.

[0025] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limitations of the present application. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings.

[0027] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0028] Figure 2 A schematic diagram of disassembling a battery provided in some embodiments of the present application;

[0029] Figure 3 A schematic diagram of disassembling a battery cell provided in some embodiments of the present application;

[0030] Figure 4 A schematic diagram of the internal structure of a battery cell provided in some embodiments of the present application;

[0031] Figure 5 A schematic diagram of a portion of the internal structure of an electrode assembly in a battery cell provided in some embodiments of the present application;

[0032] Figure 6 A schematic diagram of the internal structure of the first pole piece provided in some embodiments of the present application;

[0033] Figure 7 A schematic diagram of the structure of the first electrode sheet in the electrode assembly provided in some embodiments of the present application after unfolding;

[0034] Figure 8 A schematic diagram of the structure of the first electrode sheet in the electrode assembly after unfolding provided in some other embodiments of the present application;

[0035] Fig. 9 This is a schematic diagram of the structure of the unfolded first electrode sheet in the electrode assembly provided in some further embodiments of the present application.

[0036] In the attached picture:

[0037] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodation space; 7. Battery cell;

[0038] 20. Shell; 201. Main body; 202. Cover;

[0039] 30. Electrode assembly; 301. First pole piece; 3011. Current collector; 3012. Active material layer; 30121. Second surface; 3013. Conductive coating; 3014. Bend portion; 3015. Straight portion; 302. Second pole piece; 303. Bend region; 304. Straight region; 305. Isolator;

[0040] X, winding direction; Y, winding axis. DETAILED DESCRIPTION

[0041] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0042] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the embodiments of the present application should have the common meanings understood by technicians in the field to which the embodiments of the present application belong.

[0043] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0044] In addition, the technical terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0045] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0046] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0047] At present, judging from the development of the market situation, the application of batteries is becoming more and more extensive. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields.

[0048] The battery mentioned in the embodiments of the present application includes one or more battery modules. The battery module refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0049] In the embodiment of the present application, the battery cell may be a secondary battery cell, which refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0050] The battery cells can be lithium-ion battery cells, sodium-ion battery cells, sodium-lithium-ion battery cells, lithium metal battery cells, sodium metal battery cells, lithium-sulfur battery cells, magnesium-ion battery cells, nickel-hydrogen battery cells, nickel-cadmium battery cells, lead-acid battery cells, etc., which are not limited in the embodiments of the present application.

[0051] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode and a negative electrode. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are inserted and removed back and forth between the positive electrode and the negative electrode.

[0052] In some embodiments, the electrode assembly further includes a separator, which is disposed between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting while allowing active ions to pass through.

[0053] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0054] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0055] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, stainless steel, copper, aluminum, nickel, silver-surface-treated aluminum, silver-surface-treated stainless steel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base and a metal layer. The composite current collector may 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 substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0056] As an example, the positive electrode active material layer includes a positive electrode active material. The positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as Li FePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and at least one of a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, Li Mn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、L iNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、Li Ni 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Ni 0.80 Co 0.15Al 0.05 O2) and its modified compounds, etc.

[0057] In some embodiments, the positive electrode may be carbon foam or metal foam. The metal foam may be nickel foam, copper foam, aluminum foam or alloy foam. When the metal foam is used as the positive electrode, the positive electrode active material may not be provided on the surface of the metal foam, but the positive electrode active material may also be provided. As an example, lithium source material, potassium metal or sodium metal may be filled or / and deposited in the metal foam, and the lithium source material is lithium metal and / or lithium-rich material.

[0058] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0059] As an example, the negative electrode current collector may be a metal foil, a foamed metal, a foamed carbon or a composite current collector. For example, as a metal foil, stainless steel, copper, aluminum, nickel, silver-surface-treated aluminum, silver-surface-treated stainless steel, a carbon electrode, carbon, nickel or titanium, etc. may be used. The foamed metal may be a foamed nickel, a foamed copper, a foamed aluminum or a foamed alloy, etc. The composite current collector may include a polymer material base and a metal layer. The composite current collector may 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 substrate (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0060] As an example, the negative electrode active material may adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0061] In some embodiments, the negative electrode may be foamed carbon or foamed metal. The foamed metal may be foamed nickel, foamed copper, foamed aluminum or foamed alloy, etc. When the foamed metal is used as the negative electrode sheet, the surface of the foamed metal may not be provided with a negative electrode active material, but of course, a negative electrode active material may also be provided.

[0062] As an example, a lithium source material, potassium metal or sodium metal may be filled or / and deposited in the negative electrode current collector, and the lithium source material is lithium metal and / or lithium-rich material.

[0063] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0064] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet.

[0065] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical stability and mechanical stability can be selected.

[0066] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without special restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surface of the positive and negative electrodes.

[0067] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode sheet and the negative electrode sheet and plays the role of transmitting ions and isolating the positive and negative electrodes.

[0068] In some embodiments, the battery cell further includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. The electrolyte can be liquid, gel or solid.

[0069] In some embodiments, the liquid electrolyte includes an electrolyte salt and a solvent.

[0070] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0071] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent can also be selected from ether solvents. Ether solvents can include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0072] The gel electrolyte includes a polymer-based electrolyte skeleton network combined with an ionic liquid-lithium salt.

[0073] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0074] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, and the like.

[0075] As an example, the inorganic solid electrolyte can be an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous Li PON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0076] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0077] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0078] In some embodiments, the electrode assembly is a laminate structure.

[0079] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0080] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet may be folded to form a plurality of stacked folded segments, with a positive electrode sheet being sandwiched between adjacent folded segments.

[0081] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of folded sections that are stacked.

[0082] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0083] As an example, the separator may be disposed continuously, and disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0084] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0085] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0086] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film.

[0087] As an example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square-shell battery cell, a blade-shaped battery cell, a polygonal battery, such as a hexagonal battery.

[0088] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0089] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0090] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0091] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0092] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0093] In a battery cell having an electrode assembly of a winding structure, the active material layer on the electrode sheet in the bending area formed by the winding of the electrode assembly is prone to cracking or even powdering, especially after the battery cell has undergone cyclic charge and discharge, the cracking or powdering problem of the active material layer will be more serious, which seriously affects the capacity of the battery cell.

[0094] In order to reduce the attenuation of the capacity of a battery cell, some embodiments of the present application provide a battery cell, which includes a shell and an electrode assembly contained in the shell, the electrode assembly includes a first pole piece and a second pole piece of opposite polarity wound along a winding direction, the electrode assembly has a bending area, the active material layer of the first pole piece is arranged on the surface of the current collector, at least part of the conductive coating is arranged on the side of the active material layer away from the current collector, and at least part of the conductive coating is located in the bending area. In the above structure, since the surface of the active material layer in the bending area of ​​the electrode assembly is provided with a conductive coating, the conductive coating can not only bond and cover the active material layer, reducing the possibility of cracking and powdering of the active material layer during the cycle use of the battery cell, but also will not affect the covered active material layer to participate in the electrochemical reaction, reducing the attenuation of the capacity of the battery cell during the cycle use.

[0095] The battery cells described in the embodiments of the present application are suitable for use in batteries and electrical devices using the batteries.

[0096] Electrical devices may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, electric tools, etc. Vehicles may be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles or extended-range vehicles, etc. Spacecraft include aircraft, rockets, space shuttles and spacecrafts, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc.

[0097] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device in an embodiment of the present application.

[0098] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application.

[0099] like Figure 1 As shown, a battery 2 is disposed inside the vehicle 1, and the battery 2 may be disposed at the bottom, head, or tail of the vehicle 1. The battery 2 may be used to power the vehicle 1, for example, the battery 2 may be used as an operating power source for the vehicle 1.

[0100] The vehicle 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery 2 to supply power to the motor 4 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1 .

[0101] In some embodiments of the present application, the battery 2 can not only serve as an operating power source for the vehicle 1, but also serve 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.

[0102] Figure 2 This is a schematic diagram of the disassembled structure of a battery provided in some embodiments of the present application. Figure 2 As shown, the battery 2 includes a housing 5 and a battery cell 7, and the battery cell 7 is accommodated in the housing 5. The battery cell 7 may be the smallest unit constituting the battery.

[0103] The box 5 is used to accommodate the battery cell 7, and the box 5 can be of various structures. In some embodiments, the box 5 can include a first box portion 5a and a second box portion 5b, the first box portion 5a and the second box portion 5b cover each other, and the first box portion 5a and the second box portion 5b jointly define a storage space 5c for accommodating the battery cell 7. The second box portion 5b can be a hollow structure with one end open, the first box portion 5a is a plate-like structure, and the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c; the first box portion 5a and the second box portion 5b can also be hollow structures with one side open, and the open side of the first box portion 5a covers the open side of the second box portion 5b to form a box 5 with a storage space 5c. Of course, the first box portion 5a and the second box portion 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0104] In order to improve the sealing performance after the first box body part 5a and the second box body part 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body part 5a and the second box body part 5b.

[0105] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box.

[0106] In the battery 2, the battery cell 7 can be one or more. If there are more than one battery cell 7, the battery cells 7 can be connected in series, in parallel or in mixed connection. Mixed connection means that the battery cells 7 are both connected in series and in parallel. The battery cells 7 can be directly connected in series, in parallel or in mixed connection, and then the whole formed by the battery cells 7 can be accommodated in the box 5; of course, the battery modules 6 can also be formed by connecting the battery cells 7 in series, in parallel or in mixed connection, and then the battery modules 6 can be formed into a whole by connecting the battery cells 7 in series, in parallel or in mixed connection, and then accommodated in the box 5.

[0107] The battery cell 7 may be a cylindrical battery cell, a square battery cell, or a battery cell of other shapes.

[0108] like Figure 3As shown, in some embodiments, the battery cell 7 includes a housing 20 and an electrode assembly 30. The electrode assembly 30 is accommodated in the housing 20.

[0109] The shell 20 can be in various shapes and sizes, such as a rectangular parallelepiped, a hexagonal prism, etc. Specifically, the shape of the shell 20 can be determined according to the specific shape and size of the electrode assembly 30. The shell 20 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0110] The electrode assembly 30 is a component where electrochemical reactions occur in the battery cell 7. One or more electrode assemblies 30 may be contained in the housing 20.

[0111] Some embodiments of the present application provide a battery cell 7, continue to refer to Figure 3 The battery cell 7 includes a housing 20 and an electrode assembly 30 contained in the housing 20. Figure 4 The electrode assembly 30 includes a first electrode sheet 301 and a second electrode sheet 302 with opposite polarities, and the first electrode sheet 301 and the second electrode sheet 302 are wound along a winding direction X. Figure 5 The electrode assembly 30 has a bending region 303, and further reference is made to Figure 6 The first electrode sheet 301 includes a current collector 3011, an active material layer 3012 and a conductive coating 3013. The active material layer 3012 is arranged on the surface of the current collector 3011, at least part of the conductive coating 3013 is arranged on the side of the active material layer 3012 away from the current collector 3011, and at least part of the conductive coating 3013 is located in the bending area 303.

[0112] The shell 20 is a component used to enclose a sealed space in the battery cell 7, which may include a main body 201 and a cover 202. The main body 201 is a hollow structure with an opening, and the cover 202 covers an opening of the main body 201 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 30 and the electrolyte.

[0113] The electrode assembly 30 is contained in the hollow structure surrounded by the shell 20. Figure 4 and Figure 5 , which may include a pole piece and a separator 305, and the pole piece may include a first pole piece 301 and a second pole piece 302 with opposite polarities. For example, the first pole piece 301 may be a positive pole piece, and the second pole piece 302 may be a negative pole piece; or the first pole piece 301 may be a negative pole piece, and the second pole piece 302 may be a positive pole piece.

[0114] The positive electrode sheet and the negative electrode sheet can be used as the positive electrode and the negative electrode respectively. During the charge and discharge process of the battery cell 7, active ions (such as lithium ions) are inserted and removed back and forth between the positive electrode and the negative electrode. The separator 305 is stacked between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet and the negative electrode sheet, and can prevent the positive and negative electrodes from short-circuiting while allowing active ions to pass through.

[0115] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The electrolyte can be liquid, gel or solid. Those skilled in the art can select the type of electrolyte according to actual conditions.

[0116] The first pole piece 301 and the second pole piece 302 are wound along the winding direction X, so that the electrode assembly 30 is a winding structure. The electrode assembly 30 in a winding structure has a bending area 303. After the first pole piece 301 and the second pole piece 302 are wound, they are bent in the bending area 303 to form a bending portion 3014. Since the bending portion 3014 of the first pole piece 301 and the second pole piece 302 is bent, the active material layer 3012 thereon will be subjected to the effect of extrusion force or tension force, and the structure of the active material layer 3012 will be affected, and it is easy to crack, or the active material will fall off, which is called powdering. In particular, during the hot pressing process and the charge-discharge cycle use of the electrode assembly 30, the cracking and powdering of the active material layer 3012 in the bending area 303 are more obvious.

[0117] In addition, since the innermost bending portion 3014 of the first pole piece 301 and the innermost bending portion 3014 of the second pole piece 302 are bent to the greatest extent, it is more likely to cause the active material to fall off. The falling off of active material, especially the falling off of active material on the negative pole piece, not only causes the number of lithium ions that can be provided by the active material of the negative pole piece to be less than that of the active material of the adjacent positive pole piece, but also makes the lithium ion deposition phenomenon of the lithium-ion battery 2 more likely to occur during charging, and also makes the capacity decay of the battery cell 7 more obvious.

[0118] The current collector 3011 may be a current collector 3011 structure for carrying other functional layers such as an active material layer 3012 in the first pole piece 301. The active material layer 3012 may be a functional layer disposed on the surface of the current collector 3011, which may be coated on the surface of the current collector 3011 by an active material through a coating process. For example, both surfaces of the current collector 3011 disposed opposite to each other in the thickness direction may be provided with the active material layer 3012, or one of the two surfaces of the current collector 3011 disposed opposite to each other in the thickness direction may be provided with the active material layer 3012. Those skilled in the art may provide the active material layer 3012 on the surface of the current collector 3011 according to actual conditions.

[0119] The conductive coating 3013 may be a coating structure with conductive capability. At least part of the conductive coating 3013 is disposed on the side of the active material layer 3012 away from the current collector 3011. It may be that the entire conductive coating 3013 is completely disposed on the side of the active material layer 3012 away from the current collector 3011 and is not connected to other structures in the first pole piece 301. It may also be that part of the conductive coating 3013 is located in the area of ​​the first pole piece 301 with the active material layer 3012, and another part of the conductive coating 3013 is located in the area without the active material layer 3012, that is, part of the conductive coating 3013 is disposed on the side of the active material layer 3012 away from the current collector 3011, and another part of the conductive coating 3013 is disposed on the surface of the current collector 3011. Since the conductive coating 3013 has conductive capability, it is not easy to affect the active material in the covered active material layer 3012 to participate in the electrochemical reaction, so that the arrangement of the conductive coating 3013 is not easy to affect the capacity of the battery cell 7.

[0120] By providing a conductive coating 3013 on the side of the active material layer 3012 facing away from the current collector 3011, and making at least a portion of the conductive coating 3013 located in the bending area 303, the conductive coating 3013 can be bonded to and covered with the active material layer 3012 in the bending area 303, thereby reducing the possibility of cracking and powdering of the active material layer 3012 during the recycling and hot pressing of the battery cell 7, reducing the attenuation of the capacity of the battery cell 7 during the recycling process, and helping to maintain the capacity of the battery cell 7.

[0121] For example, the conductive coating 3013 may include polyvinylidene fluoride adhesive and conductive graphite, so that the conductive coating 3013 has good bonding strength and good conductivity.

[0122] In some embodiments, the mass fraction of the polyvinylidene fluoride binder in the conductive coating 3013 is D, and D≥3%. By setting the range of the mass fraction D of the polyvinylidene fluoride binder in the conductive coating 3013 to D≥3%, the conductive coating 3013 has good bonding strength, which is conducive to bonding the active material to the active material layer 3012 as a whole when the conductive coating 3013 is adhered to the active material layer 3012, and is conducive to reducing the possibility of cracking and powdering of the active material layer 3012.

[0123] In some embodiments, the mass fraction of the conductive graphite in the conductive coating 3013 is E, and E≥3%. By setting the range of the mass fraction of the conductive graphite E to D≥3%, the conductive coating 3013 has good conductivity, so that the conductive coating 3013 coated on the surface of the active material layer 3012 is not likely to affect the active material to participate in the electrochemical reaction, which is conducive to reducing the possibility of capacity reduction of the battery cell 7.

[0124] In some embodiments, the conductive coating 3013 may be formed of a conductive slurry containing a polyvinylidene fluoride adhesive and conductive graphite. For example, the active material slurry may be applied to the surface of the current collector 3011 through a coating process and dried to form the active material layer 3012, and then the conductive slurry may be applied to the active material layer 3012, and after a cold pressing process, the active material layer 3012 and the conductive coating 3013 may be formed on the first pole piece 301. After the cold pressing process, the active material layer 3012 can become tighter and can be better bonded to the current collector 3011, and part of the conductive slurry will penetrate into the active material layer 3012, so that the conductive coating 3013 can be better bonded to the surface of the active material layer 3012, which is conducive to improving the bonding and covering ability of the conductive coating 3013 to the active material layer 3012.

[0125] In some embodiments, the interlayer peeling strength between the conductive coating 3013 and the active material layer 3012 is greater than the interlayer peeling strength between the active material layer 3012 and the current collector 3011 .

[0126] The interlayer peeling strength between the conductive coating 3013 and the active material layer 3012 can be used to measure the bonding strength of the conductive coating 3013 on the active material layer 3012. The interlayer peeling strength between the active material layer 3012 and the current collector 3011 can be used to measure the bonding strength of the active material layer 3012 on the current collector 3011.

[0127] By setting the interlayer peeling strength between the conductive coating 3013 and the active material layer 3012 to be greater than the interlayer peeling strength between the active material layer 3012 and the current collector 3011, the bonding strength of the conductive coating 3013 on the active material layer 3012 is greater than the bonding strength of the active material layer 3012 on the current collector 3011, so that the conductive coating 3013 can be bonded and covered with the active material layer 3012, making it less likely for the conductive coating 3013 to crack and shed.

[0128] In some embodiments, the interlayer peeling strength between the conductive coating layer 3013 and the active material layer 3012 is A, 15 N / m≤A≤30 N / m.

[0129] By setting the range of the interlayer peel strength A between the conductive coating 3013 and the active material layer 3012 to 15N / m≤A≤30N / m, the adhesion strength between the conductive coating 3013 and the active material layer 3012 can be improved, which not only enables the conductive coating 3013 to be well adhered to the active material layer 3012, but also makes the conductive coating 3013 have a lower cost, which is beneficial to reducing the cost of the first electrode 301.

[0130] In some embodiments, 18N / m≤A≤25N / m. For example, the interlayer peel strength A between the conductive coating 3013 and the active material layer 3012 can be set to 20N / m, 22N / m or 25N / m, so that the conductive coating 3013 can be well bonded to the active material layer 3012 and the conductive coating 3013 has a lower cost, which is conducive to reducing the cost of the first electrode 301.

[0131] For example, the interlayer peel strength A between the conductive coating 3013 and the active material layer 3012 can be measured according to the national standard GB / T 2792-2014. The specific measurement method can refer to the national standard GB / T 2792-2014 and will not be described in detail here.

[0132] In some embodiments, the glass transition temperature of the conductive coating 3013 is higher than the glass transition temperature of the active material layer 3012 .

[0133] The glass transition temperature refers to the temperature at which an amorphous polymer (including the non-crystalline part of a crystalline polymer) changes from a glassy state to a highly elastic state or from a highly elastic state to a glassy state. It can be used to measure the toughness of the conductive coating 3013 and the active material layer 3012 at the same temperature. The toughness of a structure with a higher glass transition temperature is greater than that of a structure with a lower glass transition temperature.

[0134] By setting the glass transition temperature of the conductive coating 3013 to be higher than the glass transition temperature of the active material layer 3012, the toughness of the conductive coating 3013 is made stronger than that of the active material layer 3012. Setting the conductive coating 3013 on the surface of the active material layer 3012 facing away from the current collector 3011 in the bending area 303 can improve the toughness of the first pole piece 301 in the bending area 303, which is beneficial to reduce the possibility of cracking of the active material layer 3012 in the first pole piece 301 in the bending area 303.

[0135] In some embodiments, continue to refer to Figure 7 The conductive coating 3013 is provided with a plurality of conductive coatings 3013, and at least two conductive coatings 3013 are arranged at intervals along the winding direction X.

[0136] By setting multiple conductive coatings 3013 on the surface of the active material layer 3012 away from the current collector, the multiple conductive coatings 3013 can better adhere to and cover the active material layer 3012 in the bending area 303, which is beneficial to further reduce the possibility of cracking and powdering of the active material layer 3012 of the battery cell 7 during the cycle use.

[0137] At least two conductive coatings 3013 are arranged at intervals along the winding direction X. It can be that among the multiple conductive coatings 3013, there are at least two conductive coatings 3013 arranged at intervals along the winding direction X, so that the multiple conductive coatings 3013 can be arranged in multiple sections along the winding direction X.

[0138] By arranging at least two conductive coatings 3013 at intervals along the winding direction X, the at least two conductive coatings 3013 can intermittently cover the active material layer 3012 along the winding direction X, so that the active material layer 3012 can be bonded and covered with the conductive coating 3013 to reduce the possibility of cracking and powder loss of the active material layer 3012 during the recycling of the battery cell 7, and the use of the conductive coating 3013 can be reduced, which is beneficial to reducing the cost of the first pole piece 301, thereby helping to reduce the cost of the battery cell 7.

[0139] In some embodiments, continue to refer to Figure 8 There are multiple conductive coatings 3013, and at least two conductive coatings 3013 are arranged at intervals along the winding axis Y.

[0140] At least two conductive coatings 3013 are spaced apart along the winding axis Y. It may be that among the multiple conductive coatings 3013, there are at least two conductive coatings 3013 spaced apart along the winding axis Y, so that the multiple conductive coatings 3013 can be arranged in multiple sections along the winding axis Y.

[0141] By arranging at least two conductive coatings 3013 at intervals along the winding axis Y, at least two conductive coatings 3013 can intermittently cover the active material layer 3012 along the winding axis Y, so that the active material layer 3012 can be bonded and covered with the conductive coating 3013 to reduce the possibility of cracking and powder loss of the active material layer 3012 during the recycling of the battery cell 7, and the use of the conductive coating 3013 can be reduced, which is beneficial to reducing the cost of the first pole piece 301, thereby helping to reduce the cost of the battery cell 7.

[0142] In some embodiments, the active material layer 3012 further includes two second surfaces 30121 oppositely disposed along the winding axis Y, and the conductive coating 3013 extends along the winding axis Y and is connected between the two second surfaces 30121 .

[0143] The second surface 30121 may be a surface on the active material layer 3012, and the two second surfaces 30121 are arranged opposite to each other along the winding axial direction Y, and the two second surfaces 30121 are two end surfaces of the active material layer 3012 in the winding axial direction Y. By extending the conductive coating 3013 along the winding axial direction Y and connecting between the two second surfaces 30121, the conductive coating 3013 can be continuously extended and arranged between the two second surfaces 30121 of the active material layer 3012, so that the conductive coating 3013 can traverse the conductive coating 3013 along the winding axial direction Y, so that the conductive coating 3013 can better cover the active material layer 3012.

[0144] In some embodiments, continue to refer to Fig. 9 In the winding direction X, the size of the conductive coating 3013 is B, 5mm≤B≤25mm.

[0145] By setting the size B of the conductive coating 3013 in the winding direction X to a range of 5mm≤B≤25mm, not only does the conductive coating 3013 have sufficient size in the winding direction X to bond and cover the active material layer 3012, but it also makes it less likely that the conductive coating 3013 will be too large to increase the cost of the battery cell 7 or reduce the capacity of the battery cell 7.

[0146] In some embodiments, 8 mm ≤ B ≤ 20 mm. Exemplarily, the dimension B of the conductive coating 3013 in the winding direction X can be set to 10 mm, 15 mm, or 18 mm, so that the conductive coating 3013 has a sufficient dimension in the winding direction X to bond and cover the active material layer 3012 while not easily increasing the cost of the battery cell 7 and reducing the capacity of the battery cell 7 due to excessive dimension.

[0147] In some embodiments, in the thickness direction of the current collector 3011 , the thickness of the conductive coating 3013 is C, and 2 μm≤C≤10 μm.

[0148] By setting the size C of the conductive coating 3013 in the thickness direction of the current collector 3011 to a range of 2μm≤C≤10μm, not only does the conductive coating 3013 have sufficient thickness in the thickness direction of the current collector 3011 to bond and cover the active material layer 3012, thereby reducing the possibility of the conductive coating 3013 falling off the active material layer 3012, but the conductive coating 3013 is also less likely to be wasted due to excessive thickness.

[0149] In some embodiments, 3 μm ≤ C ≤ 7 μm. For example, the dimension C of the conductive coating 3013 in the thickness direction of the current collector 3011 can be set to 3 μm, 5 μm or 6 μm, which not only makes the conductive coating 3013 have sufficient thickness in the thickness direction of the current collector 3011 to bond and cover the active material layer 3012, but also reduces the possibility of the conductive coating 3013 falling off from the active material layer 3012, and makes the conductive coating 3013 less likely to be wasted due to excessive thickness.

[0150] In some embodiments, the first pole piece 301 includes a plurality of bends 3014 arranged along the winding direction X; in the winding direction X, the bend 3014 closest to the winding start end of the first pole piece 301 is provided with a conductive coating 3013 .

[0151] The bending portion 3014 may be a portion of the first pole piece 301 that is bent in the bending region 303, and a plurality of the bending portions 3014 are provided along the winding direction X. After the first pole piece 301 is wound along the winding direction X, a plurality of coils are formed, and the bending portion 3014 refers to a portion of the first pole piece 301 that is bent in the bending region 303 in the coil. Exemplarily, in the square shell battery 2, the bending region 303 is located at the side portion of the electrode assembly 30, and the bending portion 3014 is a portion of a coil of the first pole piece 301 that is bent into a semicircular shape in the bending region 303. Exemplarily, in the cylindrical battery 2, the bending region 303 is the entire electrode assembly 30 that is wound in a cylindrical shape, and the bending portion 3014 is the entire coil portion of the first pole piece 301 that is circular.

[0152] In the winding direction X, the bend 3014 closest to the winding start end of the first pole piece 301 may be the bend 3014 located in the innermost coil layer, which has the smallest radius of curvature and the largest bending degree among the multiple bends 3014, and the active material layer 3012 thereon is more prone to cracking and powdering. By providing the conductive coating 3013 on the bend 3014 closest to the winding start end of the first pole piece 301, the conductive coating 3013 is provided on the bend 3014 with the largest bending degree, so that the conductive coating 3013 can reduce the possibility of cracking and powdering of the active material layer 3012 in the bend 3014 with the largest bending degree.

[0153] In some embodiments, in the winding direction X, at least two bent portions 3014 closest to the winding start end of the first pole piece 301 are provided with a conductive coating 3013 .

[0154] Since the bending portion 3014 closer to the winding start end of the first pole piece 301 has a smaller radius of curvature and a greater bending degree, the active material layer 3012 thereon is more likely to crack and shed. By providing the conductive coating 3013 on at least the two bending portions 3014 closest to the winding start end of the first pole piece 301, the conductive coating 3013 can reduce the possibility of cracking and shed active material layer 3012 in the bending portion 3014 with a greater bending degree.

[0155] Those skilled in the art can set the number of the bending portions 3014 provided with the conductive coating 3013 according to actual conditions, so that the conductive coating 3013 can be provided on the surface of the active material layer 3012 in the bending portion 3014 with a larger bending degree.

[0156] In some embodiments, in the winding direction X, the thickness of the conductive coating 3013 in the bending portion 3014 close to the winding starting end is greater than the thickness of the conductive coating 3013 in the bending portion 3014 far from the winding starting end.

[0157] By setting the thickness of the conductive coating 3013 in the bending portion 3014 close to the starting end of the winding along the winding direction X to be greater than the thickness of the conductive coating 3013 in the bending portion 3014 away from the starting end of the winding, the thickness of the conductive coating 3013 on the bending portion 3014 in the innermost circle layer is thicker, and the bonding and covering capabilities of the conductive coating 3013 on the bending portion 3014 in the innermost circle layer are stronger, which can match the greater bending degree of the bending portion 3014 in the innermost circle layer, which is beneficial to reduce the possibility of cracking and powdering of the active material layer 3012 in the bending portion 3014.

[0158] In some embodiments, in the winding direction X, the size of the conductive coating 3013 in the bending portion 3014 away from the winding starting end is larger than the size of the conductive coating 3013 in the bending portion 3014 close to the winding starting end.

[0159] Since in the winding direction X, the size of the bending portion 3014 far from the starting end of the winding is larger than the size of the bending portion 3014 close to the starting end of the winding, by setting the size of the conductive coating 3013 in the bending portion 3014 far from the starting end of the winding in the winding direction X to be larger than the size of the conductive coating 3013 in the bending portion 3014 close to the starting end of the winding in the winding direction X, the conductive coating 3013 can adapt to the size of the bending portion 3014 in each circle layer in the winding direction X, so that the conductive coating 3013 can better bond and cover the bending portion 3014 in each circle layer, which is beneficial to reduce the possibility of cracking and powdering of the active material layer 3012 on the bending portion 3014 in each circle layer.

[0160] In some embodiments, the electrode assembly 30 further includes a straight region 304 connected to the bending region 303 , and a portion of the conductive coating 3013 is located in the straight region 304 , and another portion is located in the bending region 303 .

[0161] The straight region 304 may be a region having a straight structure in the winding structure formed after the first pole piece 301 and the second pole piece 302 are wound along the winding direction X, and is connected to the bent region 303 to form the winding structure of the electrode assembly 30. The first pole piece 301 includes a straight portion 3015 located in the straight region 304, and the straight portion 3015 of the first pole piece 301 is bent.

[0162] The portion of the first pole piece 301 located in the straight region 304 and the portion of the second pole piece 302 located in the straight region 304 are both arranged substantially straight.

[0163] The bending region 303 is a region where the winding structure has a bending structure, and the portion of the first pole piece 301 located in the bending region 303 (bending portion 3014) and the portion of the second pole piece 302 located in the bending region 303 (bending portion 3014) are both bent. Exemplarily, the bending portion 3014 of the first pole piece 301 and the bending portion 3014 of the second pole piece 302 are both arc-shaped.

[0164] A portion of the conductive coating 3013 is located in the straight area 304, and the other portion is located in the bent area 303, which means that a portion of the conductive coating 3013 is arranged on the surface of the active material layer 3012 of the first pole piece 301 located in the straight portion 3015, and the other portion is arranged on the surface of the active material layer 3012 of the first pole piece 301 located in the bent portion 3014, so that the conductive coating 3013 can be better coated on the surface of the active material layer 3012 located in the bent portion 3014 and the surface of the active material layer 3012 located at the transition portion between the straight portion 3015 and the bent portion 3014.

[0165] Exemplarily, the second pole piece 302 has the same structure as the first pole piece 301 , and the conductive coating 3013 in the second pole piece 302 is also at least partially located on the surface of the active material layer 3012 in the bending region 303 .

[0166] For example, continue to refer to Figure 4 In the bending area 303, the multiple bending portions 3014 in the first pole piece 301 and the multiple bending portions 3014 in the second pole piece 302 are arranged alternately, that is, in the bending area 303, they are arranged in the order of a bending portion 3014 of the first pole piece 301, a bending portion 3014 of the second pole piece 302, a bending portion 3014 of the first pole piece 301...

[0167] Some embodiments of the present application further provide a battery 2, which includes a battery cell 7 provided by the above technical solution.

[0168] Since the battery 2 includes the battery cell 7 provided by the above technical solution, the capacity attenuation of the battery 2 is relatively small.

[0169] Some embodiments of the present application further provide an electric device, the electric device comprising the battery 2 provided by the above technical solution, the battery 2 is used to provide electric energy. The electric device can be any electric device provided by the above technical solution.

[0170] Some embodiments of the present application provide a battery cell 7, which includes a housing 20 and an electrode assembly 30, wherein a first pole piece 301 and a second pole piece 302 in the electrode assembly 30 are wound along a winding direction X, and the electrode assembly 30 has a connected bending region 303 and a straight region 304. The first pole piece 301 includes a plurality of bending portions 3014 arranged in the winding direction X and located in the bending region 303, and in the winding direction X, at least one bending portion 3014 closest to the winding start end of the first pole piece 301 is provided with a plurality of conductive coatings 3013, and the plurality of conductive coatings 3013 are arranged at intervals along the winding direction X. In the above structure, since the surface of the active material layer 3012 in the bending area 303 of the electrode assembly 30 is provided with a conductive coating 3013, the conductive coating 3013 can not only bond and cover the active material layer 3012, thereby reducing the possibility of cracking and powder loss of the active material layer 3012 during the recycling of the battery cell 7, but also is not easy to affect the covered active material layer 3012 to participate in the electrochemical reaction, thereby reducing the attenuation of the capacity of the battery cell 7 during the recycling process.

[0171] 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 replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: comprising a shell and an electrode assembly accommodated in the shell; The electrode assembly comprises a first pole piece and a second pole piece with opposite polarities, wherein the first pole piece and the second pole piece are wound along a winding direction; The electrode assembly has a bending area; The first pole piece includes a current collector, an active material layer and a conductive coating, wherein the active material layer is arranged on the surface of the current collector, at least part of the conductive coating is arranged on the side of the active material layer away from the current collector, and at least part of the conductive coating is located in the bending area.

2. The battery cell according to claim 1, characterized in that: The interlayer peeling strength between the conductive coating and the active material layer is greater than the interlayer peeling strength between the active material layer and the current collector.

3. The battery cell according to claim 1, characterized in that: The interlayer peeling strength between the conductive coating layer and the active material layer is A, 15N / m≤A≤30N / m.

4. The battery cell according to claim 1, characterized in that: The glass transition temperature of the conductive coating layer is higher than the glass transition temperature of the active material layer.

5. The battery cell according to claim 1, characterized in that: The conductive coatings are provided in plurality, and at least two of the conductive coatings are arranged at intervals along the winding direction.

6. The battery cell according to claim 1, characterized in that: There are a plurality of conductive coatings, and at least two of the conductive coatings are spaced apart along the winding axial direction.

7. The battery cell according to claim 1, characterized in that: The active material layer further includes two second surfaces disposed opposite to each other along the winding axis, and the conductive coating extends along the winding axis and is connected between the two second surfaces.

8. The battery cell according to claim 1, characterized in that: In the winding direction, the size of the conductive coating is B, 5mm≤B≤25mm.

9. The battery cell according to claim 1, characterized in that: In the thickness direction of the current collector, the thickness of the conductive coating is C, 2 μm≤C≤10 μm.

10. The battery cell according to claim 1, characterized in that: The first pole piece includes a plurality of bending portions arranged along a winding direction; In the winding direction, the bent portion closest to the winding start end of the first pole piece is provided with the conductive coating.

11. The battery cell according to claim 10, characterized in that: In the winding direction, at least two of the bent portions closest to the winding starting end of the first pole piece are provided with the conductive coating.

12. The battery cell according to claim 11, characterized in that: In the winding direction, the thickness of the conductive coating in the bent portion close to the winding start end is greater than the thickness of the conductive coating in the bent portion far from the winding start end.

13. The battery cell according to claim 11, characterized in that: In the winding direction, a size of the conductive coating in the bent portion away from the winding start end is larger than a size of the conductive coating in the bent portion close to the winding start end.

14. The battery cell according to claim 1, characterized in that: The electrode assembly further includes a straight region connected to the bending region, a portion of the conductive coating is located in the straight region, and another portion is located in the bending region.

15. A battery, characterized in that: Comprising the battery cell according to any one of claims 1 to 14.

16. An electrical device, characterized in that: Comprising the battery of claim 15, the battery being used to provide electrical energy.

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