Battery cell, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece, a negative pole piece, an isolating membrane and a functional coating, the positive pole piece comprises a positive current collector, the positive current collector comprises a main body part and a tab part, the main body part is provided with a first edge region and a second edge region, the first edge region is connected with the tab part, and the second edge region is arranged far away from the tab part; the negative pole piece comprises a negative current collector; the isolating membrane is located between the positive pole piece and the negative pole piece, the isolating membrane is provided with a third edge area and a fourth edge area, the orthographic projection of the third edge area in the first edge area is overlapped with the first edge area, and the orthographic projection of the fourth edge area in the second edge area is overlapped with the second edge area; the functional coating is located in at least one of the first edge area, the second edge area, the third edge area and the fourth edge area. According to the battery cell provided by the invention, the reliability of the battery cell can be improved.

Description

Technical Field

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

[0002] As a portable energy source and reserve energy, batteries have become an indispensable part of our daily life, such as mobile phones, laptops, electric vehicles, electric cars and so on.

[0003] With the widespread application of batteries in various fields, higher requirements are placed on their performance. Among them, how to improve the reliability of batteries is an urgent issue in battery technology. Summary of the invention

[0004] The present application provides a battery cell, a battery device and an electrical device, which can improve the reliability of the battery cell.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, the battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and a functional coating. The positive electrode sheet includes a positive current collector, the positive current collector includes a main body and a pole ear portion, the main body has a first edge region and a second edge region, the first edge region is connected to the pole ear portion, and the second edge region is arranged away from the pole ear portion; the negative electrode sheet includes a negative current collector; the separator is located between the positive electrode sheet and the negative electrode sheet, the separator has a third edge region and a fourth edge region, the positive projection of the third edge region in the first edge region overlaps with the first edge region, and the positive projection of the fourth edge region in the second edge region overlaps with the second edge region; the functional coating is located in at least one edge region of the first edge region, the second edge region, the third edge region and the fourth edge region, and the functional coating is configured to expand in response to a preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet; wherein the positive projections of the functional coating and the negative current collector on the first edge region at least partially overlap; and / or, the positive projections of the functional coating and the negative current collector on the second edge region at least partially overlap.

[0006] In the above technical solution, when burrs or conductive foreign matter on the edges of the positive electrode sheet and the negative electrode sheet cause the two to be electrically connected and form a short circuit, the temperature of the electrical connection point will cause a sharp rise in temperature to the preset temperature of the functional coating, and the functional coating is located in at least one edge area among the first edge area, the second edge area, the third edge area and the fourth edge area, and the positive projections of the functional coating and the negative electrode collector on the first edge area at least partially overlap, and / or the positive projections of the functional coating and the negative electrode collector on the second edge area at least partially overlap, which can help the functional coating to expand in response to the preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet, and the disconnection of the electrical connection can reduce the heat continuously generated, and the occurrence of thermal runaway is also reduced, and the reliability of the battery cell is also improved.

[0007] In some embodiments of the first aspect of the present application, the functional coating includes a first functional coating, which is located in a first edge region; the negative electrode plate also includes a negative electrode active material layer located on at least one side of the negative electrode current collector; wherein the positive projection of the negative electrode active material layer in the first edge region is located within the first functional coating.

[0008] In the above technical solution, the first functional coating is located in the first edge region, and the positive projection of the negative electrode active material layer in the first edge region is located in the first functional coating, which can help improve the reliability and cycle performance of the battery cell.

[0009] In some embodiments of the first aspect of the present application, along the width direction of the positive electrode plate, the total width b1 of the first functional coating and the width a1 of the first functional coating covered by the negative electrode active material layer satisfy: a1+x≤b1, wherein x represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate of the battery cell during the manufacturing process, and 0.1mm≤x≤2.5mm.

[0010] In the above technical solution, a1 and b1 satisfying the above relationship can further reduce the occurrence of thermal runaway and improve the reliability of the battery cell.

[0011] In some embodiments of the first aspect of the present application, 0.3 mm ≤ b1 ≤ 6 mm.

[0012] In some embodiments of the first aspect of the present application, the thickness of the first functional coating is 0.5 μm to 5 μm.

[0013] In some embodiments of the first aspect of the present application, the thickness of the first functional coating is 2 μm to 4 μm.

[0014] In the above technical solution, the width b1 and thickness of the first functional coating are respectively within the above value ranges, which can not only help the first functional coating to expand to disconnect the electrical connection between the positive electrode plate and the negative electrode plate, but also enable the battery cell to have a higher energy density.

[0015] In some embodiments of the first aspect of the present application, the functional coating further includes a second functional coating, which is located in the second edge region; the negative electrode plate further includes a negative electrode active material layer located on at least one side of the negative electrode current collector; wherein the positive projection of the negative electrode active material layer in the second edge region is located within the second functional coating.

[0016] In some embodiments of the first aspect of the present application, along the width direction of the positive electrode plate, the total width b2 of the second functional coating and the width a2 of the second functional coating covered by the negative electrode active material layer satisfy: a2+y≤b2, wherein y represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate of the battery cell during the manufacturing process, and 0.1mm≤y≤2.5mm.

[0017] In the above technical solution, a2 and b2 satisfying the above relationship can further reduce the occurrence of thermal runaway and improve the reliability of the battery cell.

[0018] In some embodiments of the first aspect of the present application, 0.3 mm ≤ b2 ≤ 6 mm.

[0019] In some embodiments of the first aspect of the present application, the thickness of the second functional coating is 0.5 μm to 5 μm.

[0020] In some embodiments of the first aspect of the present application, the thickness of the second functional coating is 2 μm to 4 μm.

[0021] In the above technical solution, the width b2 and thickness of the second functional coating are respectively within the above value ranges, which can not only help the second functional coating to expand to disconnect the electrical connection between the positive electrode plate and the negative electrode plate, but also enable the battery cell to have a higher energy density.

[0022] In some embodiments of the first aspect of the present application, the functional coating further includes a third functional coating, the third functional coating is located in the third edge region, and the orthographic projection of the third functional coating in the first edge region covers the first edge region.

[0023] In some embodiments of the first aspect of the present application, the negative electrode pole piece also includes a negative electrode active material layer located on at least one side of the negative electrode collector; wherein, along the width direction of the isolation membrane, the total width b3 of the third functional coating and the width a3 of the third functional coating covered by the negative electrode active material layer satisfy: a3+z≤b3, wherein z represents the eccentricity design reserved value between the positive electrode pole piece and the negative electrode pole piece of the battery cell during the manufacturing process, and 0.5mm≤z≤3.0mm.

[0024] In some embodiments of the first aspect of the present application, 1mm≤b3≤10mm.

[0025] In some embodiments of the first aspect of the present application, the thickness of the third functional coating is 0.5 μm to 5 μm.

[0026] In some embodiments of the first aspect of the present application, the thickness of the third functional coating is 2 μm to 4 μm.

[0027] In some embodiments of the first aspect of the present application, the functional coating further includes a fourth functional coating, the fourth functional coating is located in the fourth edge region, and the orthographic projection of the fourth functional coating in the second edge region covers the second edge region.

[0028] In some embodiments of the first aspect of the present application, the negative electrode pole piece also includes a negative electrode active material layer located on at least one side of the negative electrode collector; wherein, along the width direction of the isolation membrane, the total width b4 of the third functional coating and the width a4 of the fourth functional coating covered by the negative electrode active material layer satisfy: a4+f≤b4, wherein x represents the eccentricity design reserved value between the positive electrode pole piece and the negative electrode pole piece of the battery cell during the manufacturing process, and 0.5mm≤f≤3.0mm.

[0029] In some embodiments of the first aspect of the present application, 1mm≤b4≤10mm.

[0030] In some embodiments of the first aspect of the present application, the thickness of the fourth functional coating is 0.5 μm to 5 μm.

[0031] In some embodiments of the first aspect of the present application, the thickness of the fourth functional coating is 2 μm to 4 μm.

[0032] In some embodiments of the first aspect of the present application, the functional coating includes a foaming agent, and the foaming temperature of the foaming agent is 140°C to 500°C.

[0033] In the above technical solution, the foaming agent with a foaming temperature of 140°C to 500°C can make the functional coating expand in time when the positive electrode plate and the negative electrode plate are electrically connected to help disconnect their electrical connection, thereby reducing the occurrence of thermal runaway and improving the reliability of the battery cell.

[0034] In some embodiments of the first aspect of the present application, the mass fraction of the foaming agent in the functional coating is 80% to 90%.

[0035] In the above technical solution, the mass fraction of the foaming agent in the functional coating is within the above range, which can help the functional coating to disconnect the electrical connection between the positive electrode plate and the negative electrode plate in time, so as to reduce the heat generated by the electrical connection to reduce the occurrence of thermal runaway, thereby further improving the reliability of the battery cell.

[0036] In some embodiments of the first aspect of the present application, the foaming agent includes a first foaming agent and a second foaming agent, the foaming temperature of the first foaming agent is T1, the foaming temperature of the second foaming agent is T2, and T1 and T2 satisfy: 140°C≤T1 <T2≤500℃。

[0037] In the above technical solution, by combining the first foaming agent and the second foaming agent with different foaming temperatures, the occurrence of thermal runaway can be further reduced, thereby further improving the reliability of the battery cell.

[0038] In some embodiments of the first aspect of the present application, 140°C≤T1<300°C; and / or, 300°C≤T2≤500°C.

[0039] In the above technical solution, T1 and T2 are respectively within the above ranges, which can further reduce the occurrence of thermal runaway and improve the reliability of the battery cell.

[0040] In some embodiments of the first aspect of the present application, the mass fraction A of the first foaming agent in the functional coating and the mass fraction B of the second foaming agent in the functional coating satisfy: 0.5≤A / B≤1.

[0041] In the above technical solution, A / B satisfies the above relationship, which can further help reduce the occurrence of thermal runaway.

[0042] In some embodiments of the first aspect of the present application, 30%≤A≤50%; and / or, 45%≤B≤70%.

[0043] In the above technical solution, A and B are respectively set within the above ranges, which can work synergistically to make the functional coating continue to expand, so as to further reduce the occurrence of re-contact between the positive electrode plate and the negative electrode plate, thereby helping to reduce the occurrence of thermal runaway.

[0044] In some embodiments of the first aspect of the present application, the first foaming agent includes at least one of an azo foaming agent, a hydrazide foaming agent, a nitroso foaming agent, an alkane foaming agent, a chlorofluorocarbon foaming agent, a urea foaming agent, and an alkyl sodium sulfate foaming agent; Optionally, the first foaming agent includes at least one of an azo foaming agent, a hydrazide foaming agent and a nitroso foaming agent.

[0045] In some embodiments of the first aspect of the present application, the second foaming agent includes at least one of a phenolic foaming agent, a silica foaming agent, a silicate foaming agent, a polyurethane foaming agent, and a polyolefin foaming agent; Optionally, the second foaming agent includes at least one of a silicate foaming agent, a polyurethane foaming agent and a polyolefin foaming agent.

[0046] In some embodiments of the first aspect of the present application, the thickness of the functional coating is 0.5 μm to 5 μm, and the volume expansion rate of the functional coating is 3000% to 6000%.

[0047] In the above technical solution, the thickness and volume expansion rate of the functional coating are set within the above ranges, which can help improve the reliability of the battery cell while also enabling the battery cell to have higher energy density and reliability.

[0048] In some embodiments of the first aspect of the present application, the gas production of the foaming agent is greater than or equal to 100 mL / g.

[0049] In some embodiments of the first aspect of the present application, the gas production of the foaming agent is in the range of 100 mL / g to 350 mL / g.

[0050] In the above technical solution, the gas production of the foaming agent is within the above range, which can help the functional coating to expand to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet.

[0051] In some embodiments of the first aspect of the present application, the volume distribution particle size Dv50 of the foaming agent is 0.01 μm~1 μm.

[0052] In some embodiments of the first aspect of the present application, the volume distribution particle size Dv99 of the foaming agent is 0.01 μm~5 μm.

[0053] In the above technical solution, the volume distribution particle size of the foaming agent is within the above range, which can help the functional coating to expand in response to a preset temperature and improve the energy density of the battery cell.

[0054] In some embodiments of the first aspect of the present application, the functional coating further includes a foaming aid and a binder, the mass fraction of the foaming aid in the functional coating is 5% to 10%, and the mass fraction of the binder in the functional coating is 5% to 10%.

[0055] In the above technical solution, the mass fractions of the foaming aid and the binder are respectively within the above ranges, which can help reduce the occurrence of thermal runaway and improve the reliability of the battery cell.

[0056] In some embodiments of the first aspect of the present application, the foaming aid includes at least one of urea, urea derivatives, phthalic acid, ethanolamine and organic salts; And / or, the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and acrylonitrile multipolymer.

[0057] In some embodiments of the first aspect of the present application, the peel strength of the functional coating at a temperature below 105° C. is greater than or equal to 10 N / m.

[0058] In a second aspect, an embodiment of the present application provides a battery device, comprising a battery cell as described in the first aspect of the present application.

[0059] In a third aspect, an embodiment of the present application provides an electrical device, including a battery device as described in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 A schematic diagram of the structure of a vehicle provided for some embodiments of the present application.

[0062] Figure 2 A schematic diagram of the structure of a battery device provided in some embodiments of the present application.

[0063] Figure 3 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application.

[0064] Figure 4 A schematic diagram of the internal structure of a battery cell provided in some embodiments of the present application.

[0065] Figure 5 A schematic diagram of the structure of the positive electrode plate provided in some embodiments of the present application.

[0066] Figure 6 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application.

[0067] Figure 7 for Figure 6 A partial enlarged view of middle A.

[0068] Figure 8 for Figure 6 A partial enlarged view of B.

[0069] icon: 1-vehicle; 2-battery device; 3; controller; 4-motor; 5-housing; 5a-first housing portion; 5b-second housing portion; 5c-accommodation space; 6-battery module; 7-battery cell; 71-positive electrode plate; 711-positive current collector; 7111-main body; 7111a-first edge region; 7111b-second edge region; 7111c-first central region; 712-positive electrode active material layer; 7112-ear portion; 72-negative electrode plate; 721-negative current collector; 722-negative electrode active material layer; 73-separation membrane; 731-third edge region; 732-fourth edge region; 733-second central region; 74-functional coating; 741-first functional coating; 742-second functional coating; 743-third functional coating; 744-fourth functional coating. DETAILED DESCRIPTION

[0070] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0071] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0072] The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0073] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0074] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" 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 direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0075] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0076] The term "multiple" as used in the present application refers to more than two (including two). Similarly, the term "multiple groups" refers to more than two groups (including two groups), and the term "multiple sheets" refers to more than two sheets (including two sheets).

[0077] 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.

[0078] 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.

[0079] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed between the positive electrode and the negative electrode. The separator is set 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.

[0080] 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 disposed on at least one surface of the positive electrode current collector.

[0081] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0082] 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, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium with surface silver plating may be used. The composite current collector may include a polymer material base layer 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 a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0083] As an example, 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 conventional materials that can be used as positive electrode active materials for batteries may also be used.

[0084] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0085] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0086] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0087] As an example, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used.

[0088] In some embodiments, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode active material is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0089] As an example, the negative electrode active material may adopt the negative electrode active material for the battery 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 and 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.

[0090] 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.

[0091] 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. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0092] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0093] 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.

[0094] The liquid electrolyte includes an electrolyte salt and a solvent.

[0095] 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.

[0096] 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.

[0097] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of battery cells, such as additives that improve overcharge / fast charge performance of battery cells, additives that improve high temperature performance of battery cells, and additives that improve low temperature performance of battery cells.

[0098] Among them, the gel electrolyte includes a polymer as a skeleton network and can be used in combination with an ionic liquid-lithium salt.

[0099] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0100] As examples, the polymer of the polymer solid electrolyte may include polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, a polyionic liquid, cellulose, and the like.

[0101] As an example, the inorganic solid electrolyte can be an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON 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.

[0102] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0103] In some embodiments, the electrode assembly may be a wound structure, a laminated structure, or a mixed structure of a wound structure and a laminated structure.

[0104] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into the wound structure.

[0105] In some embodiments, the electrode assembly is a laminate structure.

[0106] 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.

[0107] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet is folded to form a plurality of stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0108] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded sections.

[0109] 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.

[0110] As an example, the separator may be disposed continuously, and may be disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0111] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0112] 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.

[0113] 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.

[0114] In some embodiments, the housing may be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing plays a role in protecting the electrode assembly, and a sealed bag is also included between the housing and the electrode assembly, and the sealed bag is used to encapsulate the electrode assembly and the electrolyte. Specifically, the sealed bag may be a bag-shaped insulating member or an aluminum-plastic film. When the housing is a sealed structure, it is used to encapsulate components such as the electrode assembly and the electrolyte.

[0115] In some embodiments, the housing includes an end cap and a shell, the shell is provided with an opening, and the end cap is provided to cover the opening. The shell may be provided with one or more openings. One or more end caps may also be provided.

[0116] In some embodiments, at least one electrode terminal is disposed on the housing, and the electrode terminal is electrically connected to the electrode tab. The electrode terminal may be directly connected to the electrode tab, or may be indirectly connected to the electrode tab through a current collecting member. The electrode terminal may be disposed on an end cap, or may be disposed on the housing.

[0117] In some embodiments, an explosion-proof valve is provided on the housing, and the explosion-proof valve is used to release the internal pressure of the battery cell.

[0118] 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.

[0119] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells and battery devices, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, for example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

[0120] With the widespread application of batteries in various fields, higher requirements are placed on their reliability. However, during the battery manufacturing process, it is necessary to trim the edges of the positive and negative current collectors, die-cut the tabs, and weld the tabs. The above operations may form burrs or conductive foreign matter at the edges. These burrs and conductive foreign matter can cause the positive and negative pole pieces to be electrically connected and short-circuited, causing thermal runaway, thereby reducing the reliability of the battery.

[0121] In view of this, the embodiment of the present application provides a battery cell including a positive electrode sheet, a negative electrode sheet, a separator and a functional coating. The positive electrode sheet includes a positive electrode collector, the positive electrode collector includes a main body and a pole ear part, the main body has a first edge region and a second edge region, the first edge region is connected to the pole ear part, and the second edge region is arranged away from the pole ear part; the negative electrode sheet includes a negative electrode collector; the separator is located between the positive electrode sheet and the negative electrode sheet, the separator has a third edge region and a fourth edge region, the positive projection of the third edge region in the first edge region overlaps with the first edge region, and the positive projection of the fourth edge region in the second edge region overlaps with the second edge region; the functional coating is located in at least one edge region of the first edge region, the second edge region, the third edge region and the fourth edge region, and the functional coating is configured to expand in response to a preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet; wherein the positive projections of the functional coating and the negative electrode collector on the first edge region at least partially overlap; and / or, the positive projections of the functional coating and the negative electrode collector on the second edge region at least partially overlap.

[0122] In the above technical solution, when burrs or conductive foreign matter on the edges of the positive electrode sheet and the negative electrode sheet cause the two to be electrically connected and form a short circuit, the temperature of the electrical connection point will cause a sharp rise in temperature to the preset temperature of the functional coating, and the functional coating is located in at least one edge area among the first edge area, the second edge area, the third edge area and the fourth edge area, and the positive projections of the functional coating and the negative electrode collector on the first edge area at least partially overlap, and / or the positive projections of the functional coating and the negative electrode collector on the second edge area at least partially overlap, which can help the functional coating to expand in response to the preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet, and the disconnection of the electrical connection can reduce the heat continuously generated, and the occurrence of thermal runaway is also reduced, and the reliability of the battery cell is also improved.

[0123] The battery apparatus mentioned in the embodiments of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple battery cells, which are connected in series, in parallel or in mixed connection through a busbar component. In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells.

[0124] As an example, the battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, the battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0125] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

[0126] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0127] As an example, the battery cell assembly may also be housed in the case by directly fixing a plurality of battery cells to the case.

[0128] As an example, the box may include a first sub-box and a second sub-box. The first sub-box and the second sub-box are buckled together to form a closed space inside the box to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first sub-box can be a top cover or a bottom plate.

[0129] As an example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0130] 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.

[0131] In some embodiments, the battery device may be an energy storage device, which includes a box body, at least one side of which is provided with a door. The energy storage device includes an energy storage container, an energy storage cabinet, and the like.

[0132] Please refer to Figure 1 , Figure 1This is a schematic diagram of the structure of a vehicle provided in some embodiments of the present application. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended range vehicle. Please continue to refer to Figure 1 The vehicle 1 is provided with a battery device 2 inside, and the battery device 2 can be provided at the bottom, head or tail of the vehicle 1. The battery device 2 can be used to power the vehicle 1. For example, the battery device 2 can be used as an operating power source for the vehicle 1 and for the circuit system of the vehicle, such as for the working power requirements during the starting, navigation and operation of the vehicle.

[0133] The vehicle 1 may further include a controller 3 and a motor 4 , wherein the controller 3 is used to control the battery device 2 to supply power to the motor 4 , for example, to meet the power requirements of the vehicle 1 during starting, navigation and driving.

[0134] In some embodiments of the present application, the battery device 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.

[0135] Figure 2 A schematic diagram of the structure of a battery device provided in some embodiments of the present application.

[0136] Continue to refer Figure 2 The battery device 2 includes a box body 5 and a battery cell, and the battery cell is accommodated in the box body 5.

[0137] The box 5 is used to accommodate the battery cells, 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 cells. 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.

[0138] In order to improve the sealing performance after the first box body 5a and the second box body 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 5a and the second box body 5b.

[0139] 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.

[0140] In the battery device 2, there can be one or more battery cells. If there are multiple battery cells, the multiple battery cells can be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells are connected in series and in parallel. Multiple battery cells can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells is accommodated in the box 5; of course, multiple battery cells can also be connected in series, in parallel, or in mixed connection to form a battery module 6, and the multiple battery modules 6 are then connected in series, in parallel, or in mixed connection to form a whole, and accommodated in the box 5. The battery device may also include other structures. For example, the battery device may also include a busbar component for realizing electrical connection between multiple battery cells.

[0141] In some embodiments, the battery cell includes a housing, an electrode assembly and other functional components. The housing includes a shell and an end cap, the shell has an opening, and the end cap closes the opening to isolate the internal environment of the battery cell from the external environment.

[0142] The shell is a component used to cooperate with the end cap to form the internal environment of the battery cell, wherein the formed internal environment can be used to accommodate the electrode assembly, electrolyte and other components. The shell and the end cap can be independent components. The shell can be of various shapes and sizes. Specifically, the shape of the shell can be determined according to the specific shape and size of the electrode assembly. The shell can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0143] The end cap refers to a component that covers the opening of the shell to isolate the internal environment of the battery cell from the external environment. Without limitation, the shape of the end cap can be adapted to the shape of the shell to match the shell. Optionally, the end cap can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap is not easily deformed when squeezed and collided, so that the battery cell can have a higher structural strength and reliability can also be improved. Functional components such as electrode terminals can be provided on the end cap. The electrode terminal can be used to electrically connect to the electrode assembly for outputting or inputting electrical energy of the battery cell. The material of the end cap can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this.

[0144] In some embodiments, an insulating structure may be provided inside the end cap, and the insulating structure may be used to isolate the electrical connection components in the housing from the end cap to reduce the risk of short circuit. For example, the insulating structure may be made of plastic, rubber, or the like.

[0145] The electrode assembly is the part where the electrochemical reaction occurs in the battery cell. One or more electrode assemblies may be contained in the shell. The electrode assembly is mainly formed by winding or stacking the positive electrode sheet and the negative electrode sheet, and usually a separator is provided between the positive electrode sheet and the negative electrode sheet, which is used to separate the positive electrode sheet and the negative electrode sheet to avoid short circuit between the positive electrode sheet and the negative electrode sheet. The parts of the positive electrode sheet and the negative electrode sheet with active materials constitute the main body of the electrode assembly, and the parts of the positive electrode sheet and the negative electrode sheet without active materials each constitute a pole ear. The positive pole ear and the negative pole ear may be located together at one end of the main body or respectively at both ends of the main body.

[0146] Figure 3 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application is shown in FIG. Figure 4 A schematic diagram of the internal structure of a battery cell provided in some embodiments of the present application, Figure 5 A schematic diagram of the structure of the positive electrode plate provided in some embodiments of the present application.

[0147] Please refer to Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the embodiment of the present application provides a battery cell 7, including a positive electrode sheet 71, a negative electrode sheet 72, a separator 73 and a functional coating 74. The positive electrode sheet 71 includes a positive electrode collector 711, and the positive electrode collector 711 includes a main body 7111 and a pole ear 7112. The main body 7111 has a first edge region 7111a and a second edge region 7111b. The first edge region 7111a is connected to the pole ear 7112, and the second edge region 7111b is arranged away from the pole ear 7112; the negative electrode sheet 72 includes a negative electrode collector 721; the separator 73 is located between the positive electrode sheet 71 and the negative electrode sheet 72, and the separator 73 has a third edge region 731 and a fourth edge region 732. The orthographic projection of the third edge region 731 overlaps with the first edge region 7111a, and the fourth edge region 732 overlaps with the first edge region 7111a. The edge region 732 overlaps with the second edge region 7111b in its orthographic projection on the second edge region 7111b; the functional coating 74 is located in at least one edge region among the first edge region 7111a, the second edge region 7111b, the third edge region 731 and the fourth edge region 732, and the functional coating 74 is configured to expand in response to a preset temperature to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72; wherein the orthographic projections of the functional coating 74 and the negative electrode current collector 721 on the first edge region 7111a at least partially overlap; and / or the orthographic projections of the functional coating 74 and the negative electrode current collector 721 on the second edge region 7111b at least partially overlap.

[0148] Herein, the first edge region 7111a refers to a region extending from one end of the pole ear portion 7112 close to the main body portion 7111 to the edge of the first central region 7111c of the main body portion 7111 close to the pole ear portion 7112 along the width direction of the positive electrode current collector 711; the second edge region 7111b refers to a region extending from the edge of the main body portion 7111 away from the pole ear portion 7112 to the edge of the first central region 7111c away from the pole ear portion 7112 along the width direction of the positive electrode current collector 711; it can be understood that the first central region 7111c of the positive electrode current collector 711 is located between the first edge region 7111a and the second edge region 7111b, and the first edge region 7111a is located between the central region of the positive electrode current collector 711 and the pole ear portion 7112, wherein the first edge region 7111a and the second edge region 7111b are regions not coated with positive active materials, and the central region of the positive electrode current collector 711 is a region coated with positive active materials; The third edge region 731 refers to a region extending from the edge of the isolation membrane 73 located on the same side as the pole ear portion 7112 to the edge of the second center region 733 along the width direction of the isolation membrane 73; the fourth edge region 732 refers to a region extending from the edge of the isolation membrane 73 located on the opposite side of the pole ear portion 7112 to the edge of the second center region 733 along the width direction of the isolation membrane 73; wherein the second center region 733 of the isolation membrane 73 is located between the third edge region 731 and the fourth edge region 732.

[0149] Herein, the orthographic projection refers to an orthographic projection projected onto the surface of the first edge region 7111 a or the surface of the second edge region 7111 b along the thickness direction of the main body 7111 .

[0150] Herein, the functional coating 74 is located in at least one edge region among the first edge region 7111a, the second edge region 7111b, the third edge region 731 and the fourth edge region 732. It is understandable that the functional coating 74 can be formed by coating the above-mentioned edge regions by spot coating, full coating or other methods, even if it expands in the above-mentioned edge regions, it can disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet. Exemplarily, the functional coating 74 covers at least one edge region among the first edge region 7111a, the second edge region 7111b, the third edge region 731 and the fourth edge region 732, that is, the functional coating 74 is formed by full coating, which can not only help it to expand in time to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet, but also can bury some burrs or conductive foreign matter to reduce the occurrence of the above-mentioned electrical connection.

[0151] In the above technical solution, when burrs or conductive foreign matter on the edges of the positive electrode sheet 71 and the negative electrode sheet 72 cause the two to be electrically connected and form a short circuit, the temperature of the electrical connection point will cause a sharp rise in temperature to the preset temperature of the functional coating 74, and the functional coating 74 is located in at least one edge area of ​​the first edge area 7111a, the second edge area 7111b, the third edge area 731 and the fourth edge area 732, and the positive projections of the functional coating 74 and the negative electrode collector 721 on the first edge area 7111a at least partially overlap, and / or the positive projections of the functional coating 74 and the negative electrode collector 721 on the second edge area 7111b at least partially overlap, which can help the functional coating 74 to expand in response to the preset temperature to disconnect the electrical connection between the positive electrode sheet 71 and the negative electrode sheet 72, and the disconnection of the electrical connection can reduce the heat continuously generated, and the occurrence of thermal runaway is also reduced, and the reliability of the battery cell 7 is also improved.

[0152] In an embodiment of the present application, the functional coating 74 , the positive electrode plate 71 , the negative electrode plate 72 and the isolation membrane 73 may also be optimized to further reduce the occurrence of thermal runaway and improve the electrochemical properties of the battery cell 7 , such as cycle performance.

[0153] See also Figure 5 As shown, in some embodiments of the present application, the main body 7111 of the positive electrode current collector 711 also includes a first central area 7111c, the first central area 7111c is located between the first edge area 7111a and the second edge area 7111b, and the first edge area 7111a is located between the central area and the ear portion 7112, wherein the first edge area 7111a and the second edge area 7111b are areas not coated with positive electrode active materials, and the central area is an area for coating with positive electrode active materials.

[0154] In some embodiments of the present application, the functional coating 74 includes a first functional coating 741, which is located in the first edge area 7111a; the negative electrode plate 72 also includes a negative electrode active material layer 722 located on at least one side of the negative electrode current collector 721; wherein the positive projection of the negative electrode active material layer 722 in the first edge area 7111a is located within the first functional coating 741.

[0155] Herein, the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a can be understood as that the width of the negative electrode active material layer 722 is greater than the width of the positive electrode active material layer 712. The orthographic projection of the first functional coating 741 in the first edge region 7111a covers the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a, that is, the edges of the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a in the length direction and the width direction do not exceed the edges of the orthographic projection of the first functional coating 741 in the first edge region.

[0156] In the above technical solution, the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a can help reduce the occurrence of lithium plating, thereby helping to improve the cyclability of the battery cell 7. The first functional coating 741 is located in the first edge region 7111a, and the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a covers the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a, which can not only reduce the occurrence of burrs on the first edge region 7111a contacting the negative electrode sheet 72, but also can timely disconnect the electrical connection between the positive electrode sheet 71 and the negative electrode sheet 72, thereby further improving the reliability of the battery cell 7.

[0157] Please continue reading Figure 5 As shown, in some embodiments of the present application, along the width direction of the positive electrode plate 71, the total width b1 of the first functional coating 741 and the width a1 of the first functional coating 741 covered by the negative electrode active material layer 722 satisfy: a1+x≤b1, wherein x represents the eccentricity design reserved value between the positive electrode plate 71 and the negative electrode plate 72 during the manufacturing process of the battery cell 7, and 0.1mm≤x≤2.5mm.

[0158] In the above technical solution, a1 and b1 satisfying the above relationship can help the orthographic projection of the first functional coating 741 in the first edge region 7111a cover the orthographic projection of the negative electrode active material layer 722 in the first edge region 7111a, thereby further improving the reliability of the battery cell 7.

[0159] In some embodiments of the present application, 0.3 mm ≤ b1 ≤ 6 mm.

[0160] In the above technical solution, the width b1 of the first functional coating 741 is within the above value range, which can help the first functional coating 741 to expand to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, so as to improve the reliability of the battery cell 7 and enable the battery cell 7 to have a higher energy density.

[0161] Exemplarily, b1 can be, but is not limited to, 0.3mm, 0.5mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, 5.2mm, 5.4mm, 5.6mm, 5.8mm, 6mm, or a range consisting of any two of the above values.

[0162] In some embodiments of the present application, the thickness of the first functional coating 741 is 0.5 μm to 5 μm.

[0163] In the above technical solution, the thickness of the first functional coating 741 is within the above value range, which can not only help the first functional coating 741 to expand to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, but also enable the battery cell 7 to have a higher energy density.

[0164] In some optional embodiments of the present application, the thickness of the first functional coating 741 is 2 μm to 4 μm.

[0165] For example, the thickness of the first functional coating 741 may be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 4.1 μm, 4. .7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm or a range consisting of any two of the above values.

[0166] In the above embodiment, the width and thickness of the first functional coating 741 can be measured by using instruments well known in the art, for example, by using an optical microscope and a scanning electron microscope.

[0167] Please continue reading Figure 5As shown, in some embodiments of the present application, the functional coating 74 also includes a second functional coating 742, and the second functional coating 742 is located in the second edge area 7111b; the negative electrode plate 72 also includes a negative electrode active material layer 722 located on at least one side of the negative electrode current collector 721; wherein, the positive projection of the negative electrode active material layer 722 in the second edge area 7111b is located within the second functional coating 742.

[0168] Herein, the orthographic projection of the negative electrode active material layer 722 in the second edge region 7111b can be understood as the width of the negative electrode active material layer 722 being greater than the width of the positive electrode active material layer 712. The orthographic projection of the second functional coating 742 in the second edge region 7111b covers the orthographic projection of the negative electrode active material layer 722 in the second edge region 7111b, that is, the edges of the orthographic projection of the negative electrode active material layer 722 in the second edge region 7111b in the length direction and the width direction do not exceed the edges of the orthographic projection of the second functional coating 742 in the second edge region.

[0169] Please continue reading Figure 5 As shown, in some embodiments of the present application, along the width direction of the positive electrode plate 71, the total width b2 of the second functional coating 742 and the width a2 of the second functional coating 742 covered by the negative electrode active material layer 722 satisfy: a2+y≤b2, wherein y represents the eccentricity design reserved value between the positive electrode plate 71 and the negative electrode plate 72 during the manufacturing process of the battery cell 7, and 0.1mm≤y≤2.5mm.

[0170] In the above technical solution, a2 and b2 satisfying the above relationship can further reduce the occurrence of thermal runaway and improve the reliability of the battery cell 7.

[0171] In some embodiments of the present application, 0.3 mm ≤ b2 ≤ 6 mm.

[0172] In the above technical solution, the width b2 of the second functional coating 742 is within the above value range, which can help the second functional coating 742 to expand to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, so as to improve the reliability of the battery cell 7 and enable the battery cell 7 to have a higher energy density.

[0173] Exemplarily, b2 can be, but is not limited to, 0.3mm, 0.5mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, 5.2mm, 5.4mm, 5.6mm, 5.8mm, 6mm, or a range consisting of any two of the above values.

[0174] In some embodiments of the present application, the thickness of the second functional coating 742 is 0.5 μm to 5 μm.

[0175] In the above technical solution, the thickness of the second functional coating 742 is within the above value range, which can not only help the second functional coating 742 to expand to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, but also enable the battery cell 7 to have a higher energy density.

[0176] In some embodiments of the present application, the thickness of the second functional coating 742 is 2 μm to 4 μm.

[0177] For example, the thickness of the second functional coating 742 may be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 4.1 μm, 4. .7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm or a range consisting of any two of the above values.

[0178] In some embodiments of the present application, the functional coating 74 may include the first functional coating 741 and the second functional coating 742, and the first functional coating 741 is located in the first edge region 7111a, and the second functional coating 742 is located in the second edge region 7111b. This can further reduce the occurrence of thermal runaway and further improve the reliability of the battery cell 7.

[0179] See also Figure 6 As shown, in some embodiments of the present application, the functional coating 74 further includes a third functional coating 743, the third functional coating 743 is located in the third edge region 731, and the orthographic projection of the third functional coating 743 in the first edge region 7111a covers the first edge region 7111a.

[0180] See also Figure 6 and Figure 7As shown, in some embodiments of the present application, the negative electrode plate 72 also includes a negative electrode active material layer 722 located on at least one side of the negative electrode collector 721; wherein, along the width direction of the isolation membrane 73, the total width b3 of the third functional coating 743 and the width a3 of the third functional coating 743 covered by the negative electrode active material layer 722 satisfy: a3+z≤b3, wherein z represents the eccentricity design reserved value between the positive electrode plate 71 and the negative electrode plate 72 of the battery cell 7 during the manufacturing process, and 0.5mm≤z≤3.0mm.

[0181] In some embodiments of the present application, 1mm≤b3≤10mm.

[0182] In some embodiments of the present application, the thickness of the third functional coating 743 is 0.5 μm to 5 μm.

[0183] In some embodiments of the present application, the thickness of the third functional coating 743 is 2 μm to 4 μm.

[0184] Please continue reading Figure 6 As shown, in some embodiments of the present application, the functional coating 74 further includes a fourth functional coating 744, which is located in the fourth edge region 732, and the orthographic projection of the fourth functional coating 744 in the second edge region 7111b covers the second edge region 7111b.

[0185] See also Figure 6 and Figure 8 As shown, in some embodiments of the present application, the negative electrode plate 72 also includes a negative electrode active material layer 722 located on at least one side of the negative electrode collector 721; wherein, along the width direction of the isolation membrane 73, the total width b4 of the fourth functional coating 744 and the width a4 of the fourth functional coating 744 covered by the negative electrode active material layer 722 satisfy: a4+f≤b4, wherein x represents the eccentricity design reserved value between the positive electrode plate 71 and the negative electrode plate 72 of the battery cell 7 during the manufacturing process, and 0.5mm≤f≤3.0mm.

[0186] In some embodiments of the present application, 1mm≤b4≤10mm.

[0187] In some embodiments of the present application, the thickness of the fourth functional coating 744 is 0.5 μm to 5 μm.

[0188] In some embodiments of the present application, the thickness of the fourth functional coating 744 is 2 μm to 4 μm.

[0189] In some embodiments of the present application, the functional coating 74 may further include at least two of the first functional coating 741, the second functional coating 742, the third functional coating 743, and the fourth functional coating 744. For example, the functional coating 74 includes the first functional coating 741, the second functional coating 742, the third functional coating 743, and the fourth functional coating 744, the first functional coating 741 is located in the first edge region 7111a, the second functional coating 742 is located in the second edge region 7111b, the third functional coating 743 is located in the third edge region 731, and the fourth functional coating 744 is located in the fourth edge region 732.

[0190] In the embodiment of the present application, the functional coating 74 contains a suitable material that can help it to expand to reduce the occurrence of thermal runaway, thereby further improving the reliability of the battery cell 7 .

[0191] In some embodiments of the present application, the functional coating 74 includes a foaming agent, and the foaming temperature of the foaming agent is 140° C. to 500° C.

[0192] In the above technical solution, the foaming agent with a foaming temperature of 140°C~500°C can make the functional coating 74 expand in time when the positive electrode plate 71 and the negative electrode plate 72 are electrically connected, so as to help disconnect their electrical connection, thereby reducing the occurrence of thermal runaway and improving the reliability of the battery cell 7.

[0193] In some embodiments of the present application, the thickness of the functional coating is 0.5 μm to 5 μm, and the volume expansion rate of the functional coating is 3000% to 6000%.

[0194] In the above technical solution, the thickness of the functional coating is set within the above range, which can improve the reliability of the battery cell and also enable the battery cell to have a higher energy density. The volume expansion rate of the functional coating is set within the above range, which can help to disconnect the electrical connection between the positive electrode plate and the negative electrode plate after expansion, reduce the occurrence of electrical connection again, and further reduce the occurrence of thermal runaway, so that the reliability of the battery cell is further improved.

[0195] In addition, a suitable mass fraction of the foaming agent in the functional coating 74 can also help it expand, disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72 in time, reduce the occurrence of thermal runaway, and thus further improve the reliability of the battery cell 7.

[0196] In some embodiments of the present application, the mass fraction of the foaming agent in the functional coating 74 is 80% to 90%.

[0197] In the above technical solution, the mass fraction of the foaming agent in the functional coating 74 is within the above range, which can help the functional coating 74 to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72 in time, so as to reduce the heat generated by the electrical connection to reduce the occurrence of thermal runaway, thereby further improving the reliability of the battery cell 7.

[0198] Exemplarily, the mass fraction of the foaming agent in the functional coating 74 may be, but is not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90% or a range consisting of any two of the above values.

[0199] In an embodiment of the present application, the functional coating 74 may further include a plurality of foaming agents with different foaming temperatures, which may help the functional coating 74 to continue to expand after the electrical connection between the positive electrode plate 71 and the negative electrode plate 72 is disconnected. This may not only reduce the occurrence of thermal runaway, but also reduce the occurrence of re-contact between the positive electrode plate 71 and the negative electrode plate 72, thereby further improving the reliability of the battery cell 7.

[0200] In some embodiments of the present application, the foaming agent includes a first foaming agent and a second foaming agent, the foaming temperature of the first foaming agent is T1, the foaming temperature of the second foaming agent is T2, and T1 and T2 satisfy: 140°C ≤ T1 <T2≤500℃。

[0201] In the above technical solution, by combining the first foaming agent and the second foaming agent with different foaming temperatures, the functional coating 74 can be helped to continue to expand, so as to increase the probability of disconnecting the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, thereby further reducing the occurrence of thermal runaway, thereby further improving the reliability of the battery cell 7.

[0202] In some embodiments of the present application, 140°C≤T1<300°C; and / or, 300°C≤T2≤500°C.

[0203] In the above technical solution, T1 and T2 are respectively within the above ranges, which can help the functional coating 74 to continue to expand at different temperatures, so as to further reduce the occurrence of thermal runaway and improve the reliability of the battery cell 7.

[0204] In the above embodiment, the foaming temperature of the foaming agent can be tested by placing it in a temperature control box.

[0205] Furthermore, the first foaming agent and the second foaming agent each having a suitable mass fraction in the functional coating 74 can also help the functional coating 74 to expand appropriately, so as to further increase the probability of disconnecting the electrical connection between the positive and negative electrode sheets 72 .

[0206] In some embodiments of the present application, the mass fraction A of the first foaming agent in the functional coating 74 and the mass fraction B of the second foaming agent in the functional coating 74 satisfy: 0.5≤A / B≤1. A / B satisfying the above relationship enables the functional coating to expand sustainably in different temperature ranges, thereby helping to reduce the occurrence of electrical connection between the positive electrode sheet and the negative electrode sheet again, thereby further reducing the probability of thermal runaway.

[0207] In some embodiments of the present application, 33%≤A≤50%; and / or, 45%≤B≤67%. A and B are respectively set within the above ranges, which can synergistically cause the functional coating to continue to foam, further reducing the occurrence of re-contact between the positive electrode sheet and the negative electrode sheet, thereby helping to reduce the occurrence of thermal runaway.

[0208] For example, A may be, but is not limited to, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or a range consisting of any two of the above values. B may be, but is not limited to, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, or a range consisting of any two of the above values.

[0209] In the embodiment of the present application, a suitable type of foaming agent may be selected to reduce the temperature after the positive and negative electrode sheets 72 are electrically connected, so as to further reduce the occurrence of thermal runaway, thereby improving the reliability of the battery cell 7 .

[0210] In some embodiments of the present application, the first foaming agent may include at least one of an azo foaming agent, a hydrazide foaming agent, a nitroso foaming agent, an alkane foaming agent, a fluorochlorocarbon foaming agent, a urea foaming agent and a sodium alkyl sulfate foaming agent.

[0211] In some optional embodiments of the present application, the first foaming agent may include at least one of an azo foaming agent, a hydrazide foaming agent and a nitroso foaming agent.

[0212] Exemplarily, the azo foaming agent may include at least one of azodicarbonamide, azobisisobutyronitrile, diisopropyl azodicarboxylate, diethyl azodicarboxylate, barium azodicarboxylate, and barium azodicarboxylate. The hydrazide foaming agent may include at least one of 4,4-disulfonylhydrazide diphenyl ether, benzenesulfonylhydrazide, p-benzenesulfonylhydrazide, p-toluenesulfonylhydrazide, 3,3'-disulfonylhydrazide diphenyl sulfone, 2,4-toluene disulfonylhydrazide, 4,4'-oxybisbenzenesulfonylhydrazide, 1,3-benzene disulfonylhydrazide, and 1,4-benzene disulfonylhydrazide. The nitroso foaming agent may include at least one of N,N-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide. The alkane foaming agent may include at least one of n-pentane, n-hexane, and n-heptane. The fluorochlorocarbon foaming agent may include trichlorofluoromethane. The urea-based foaming agent may include at least one of urea, p-toluenesulfonyl urea, p-toluenesulfonyl semicarbazide, and 4,4'-oxybis(benzenesulfonyl semicarbazide). The sodium alkyl sulfate foaming agent may include sodium dodecyl sulfate.

[0213] In some embodiments of the present application, the second foaming agent includes at least one of a phenolic foaming agent, a silica foaming agent, a silicate foaming agent, a polyurethane foaming agent and a polyolefin foaming agent.

[0214] In some optional embodiments of the present application, the second foaming agent includes at least one of a silicate foaming agent, a polyurethane foaming agent and a polyolefin foaming agent.

[0215] Exemplarily, the phenolic foaming agent may include at least one of phenol formaldehyde resin, cresol formaldehyde resin, xylenol formaldehyde resin and phenol furfural resin. The silica foaming agent may include at least one of silicone foaming agent and alumina silica foaming agent. The silicate foaming agent may include at least one of magnesium silicate, aluminum silicate and calcium silicate. The polyurethane foaming agent may include at least one of dimethylformamide (DMF) and dimethyl ether (DME). The polyolefin foaming agent may include at least one of polystyrene and polystyrene propylene.

[0216] In some embodiments of the present application, the gas production of the foaming agent is greater than or equal to 100 mL / g.

[0217] In the above technical solution, the gas production of the foaming agent is within the above range, which can help the functional coating 74 to expand to disconnect the electrical connection between the positive electrode plate 71 and the negative electrode plate 72, so as to further reduce the occurrence of thermal runaway and improve the reliability of the battery cell 7.

[0218] In some optional embodiments of the present application, the gas production of the foaming agent is in the range of 100 mL / g to 350 mL / g.

[0219] In the above embodiment, the gas production and gas composition of the foaming agent can be obtained by thermogravimetry-mass spectrometry (TG-MS).

[0220] In the embodiment of the present application, the particle size of the foaming agent may also be optimized to help the functional coating 74 expand in response to a preset temperature and to increase the energy density of the battery cell 7 .

[0221] In some embodiments of the present application, the volume distribution particle size Dv50 of the foaming agent is 0.01 μm~1 μm.

[0222] In this article, Dv50 refers to the value of Dv50, which is the particle size of the negative foaming agent particles when the foaming agent particles are accumulated from small to large and account for 50% of the total volume.

[0223] In some embodiments of the present application, the volume distribution particle size Dv99 of the foaming agent is 0.01 μm~5 μm.

[0224] In this article, Dv99 refers to the value of Dv99, the particle size of the blowing agent particles when the blowing agent particles are accumulated from small to large and the accumulated volume accounts for 99% of the total volume.

[0225] In the above technical solution, the volume distribution particle size of the foaming agent is within the above range, which can help the foaming agent to be evenly dispersed in the functional coating 74 and make the functional coating 74 have a suitable thickness, which can help the functional coating 74 to expand in response to a preset temperature and improve the energy density of the battery cell 7.

[0226] In the above embodiment, Dv50 and Dv99 of the foaming agent can be obtained by testing with a laser particle size analyzer.

[0227] In some embodiments of the first aspect of the present application, the functional coating 74 further includes a foaming aid and a binder, the mass fraction of the foaming aid in the functional coating 74 is 5% to 10%, and the mass fraction of the binder in the functional coating 74 is 5% to 10%.

[0228] In the above technical solution, the mass fraction of the foaming aid is within the above range, which can make the functional coating 74 have a lower preset temperature to help reduce the occurrence of thermal runaway; the mass fraction of the binder in the functional coating 74 is within the above range, which can make the functional coating 74 have suitable adhesion and reduce the occurrence of its falling off, thereby helping the functional coating 74 to reduce the occurrence of thermal runaway.

[0229] In some embodiments of the present application, the foaming aid includes at least one of urea, urea derivatives, phthalic acid, ethanolamine and organic salts.

[0230] In some embodiments of the present application, the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and acrylonitrile multipolymer.

[0231] In some embodiments of the present application, the peel strength of the functional coating 74 at a temperature below 105° C. is greater than or equal to 10 N / m.

[0232] In some embodiments of the present application, the functional coating 74 is prepared by a micro-gravure process. The specific preparation method is as follows: The components constituting the functional coating are dissolved in a solvent to prepare a slurry with a solid content of 30% to 40%, and a gravure roller with a certain width and roller depth is used to coat the edge area of ​​the positive electrode collector or the isolation membrane, and the functional coating is formed after drying. The solvent can be an oily solvent, such as N-methylpyrrolidone, N-dimethylacetamide and N-dimethylformamide.

[0233] 1. Implementation Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0234] Example 1 (1) Preparation of functional coatings The foaming material, the foaming aid, the adhesive and the solvent are stirred and mixed in a mass ratio of 85:8:7:150 to obtain a coating slurry. The coating slurry is applied to the first edge area and the second edge area of ​​the aluminum foil using a gravure roller with an edge having a certain width and roller depth. After drying, the aluminum foil with a functional coating is obtained.

[0235] (2) Preparation of positive electrode sheet The positive electrode active material LFP, the binder polyvinylidene fluoride (PVDF), the conductive agent carbon nanotube (CNT) and the N-methylpyrrolidone (NMP) solvent were stirred and mixed in a mass ratio of 97:1.6:1.4:50 to prepare a positive electrode slurry. The positive electrode slurry was evenly coated on the surface of the central area of ​​the aluminum foil (the central area was located between the first edge area and the second edge area), and the positive electrode sheet was obtained after drying, cold pressing and cutting, wherein the width of the positive electrode active material layer was 110mm and the thickness was 166um.

[0236] (3) Preparation of negative electrode sheet Graphite, conductive carbon black, binder sodium methyl cellulose (CMC) and deionized water were stirred and mixed in a mass ratio of 95:2:3:100 to prepare negative electrode slurry. The negative electrode slurry was evenly coated on the surface of the copper foil, and then dried, pressed, trimmed, cut and stripped to prepare negative electrode sheets, wherein the width of the negative electrode active material was 116 mm and the thickness was 272 um.

[0237] (4) Preparation of electrolyte In a nitrogen atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solution, and lithium hexafluorophosphate (LiPF6) was dissolved in the mixed solution to obtain an electrolyte, wherein the volume molar concentration of LiPF6 in the electrolyte was 1 mol / L (5) Isolation film A polyethylene film with a thickness of 13 μm was used as the separator.

[0238] (6) Preparation of batteries The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly, wherein the separator is between the positive and negative electrode sheets, the tabs are welded to the electrode assembly, and the electrode assembly with the tabs welded is placed in an aluminum shell, and baked at 90°C to remove water, and then the above-mentioned electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery then undergoes the processes of static, hot and cold pressing, formation, shaping, capacity testing, etc. in sequence to obtain a secondary battery.

[0239] Embodiments 2 to 22 Compared with Example 1, the differences between Examples 2 to 22 are shown in Table 1, wherein the functional coating in Example 21 faces the positive electrode sheet, and the functional coating in Example 22 faces away from the positive electrode sheet, that is, faces the negative electrode sheet.

[0240] Comparative Examples 1 to 3 Compared with Example 1, the differences of Comparative Example 1 are shown in Table 1.

[0241] 2. Test part (1) Short circuit point temperature test The temperature of the internal short point is measured by placing an external sensor at the internal short position to monitor the temperature of the battery cell surface at the internal short position in real time.

[0242] (2) Thickness and quality change test of functional coating First, the positive electrode sheet coated with the functional coating in the above embodiment is placed in a temperature control box, the temperature change in the temperature control box is controlled (140°C~500°C), and the change in the edge thickness H of the positive electrode sheet at different temperatures is tested and recorded. If the thickness H shows a significant increase in the thickness of the primary sheet at 140°C~300°C and 300°C~500°C, it indicates that one of the first foaming agent and the second foaming agent is contained. If the thickness of the primary sheet increases significantly at 140°C~300°C, and the thickness of the primary sheet increases significantly again when the temperature is raised from 140°C~300°C to 300°C~500°C, it indicates that both the first foaming agent and the second foaming agent are contained.

[0243] Secondly, if the electrode does not show a significant increase in thickness when the temperature is raised from 140℃~300℃ to 300℃~500℃, the electrode needs to be weighed: 1) If the weight does not decrease significantly (no weight loss), the first foaming agent has not decomposed, and the functional coating does not contain the second foaming agent; 2) If the weight decreases significantly (weight loss), the first foaming agent has decomposed, and the coating contains the second foaming agent (the reason why the thickness has not increased significantly is that the increase in foaming thickness of the second foaming agent offsets the decrease in thickness caused by the decomposition of the first foaming agent).

[0244] Thickness increase standard: H1 / H0≥1.5 before and after the change (H1---pole thickness after the change, H0---pole thickness before the change) Significant weight reduction (weight loss) standard: M1 / M0≤90% before and after the change (M1---pole weight after the change, M0---pole weight before the change) Heating and thickness measurement process: 140℃~500℃, each 10℃ is a step, and stand at this temperature for 5 minutes, and test the thickness of the electrode before and after standing. (140℃*5min, 150℃*5min, 160℃*5min, 170℃*5min, 500℃*5min) (3) Width and thickness test of functional coating Width of functional coating: measured by optical microscopy and scale.

[0245] Thickness test of functional coating: measured by micrometer.

[0246] III. Analysis of test results of various embodiments and comparative examples The secondary batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 1 below.

[0247] Table 1

[0248]

[0249] Note: A foaming agent - azodicarbonamide, B foaming agent - xylenol formaldehyde resin, C foaming agent - N,N'-dinitrosopentamethylenetetramine, D foaming agent - alumina silica gel.

[0250] H1 / H0-One value in the table represents the thickness change after one foaming; two values ​​represent the thickness change after two foamings.

[0251] The width column in the table has only one value, which means that the width of the functional coating in the edge area is the value. For example, in Example 1, the width of the functional coating located in the first edge area is 3 mm, and the width of the functional coating located in the second edge area is also 3 mm.

[0252] From the comparison of the test results of Examples 1 to 6, Examples 9 to 22 and Comparative Example 3, it can be seen that when the burrs or conductive foreign matter on the edges of the positive electrode sheet and the negative electrode sheet cause the two to be electrically connected and form a short circuit, the temperature of the electrical connection point will cause a sharp rise in temperature to the preset temperature of the functional coating. The functional coating is located on the first edge region, the second edge region, the third edge region and the fourth edge region, which can help the functional coating to expand in response to the preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet. The disconnection of the electrical connection can reduce the heat continuously generated therefrom, thereby reducing the occurrence of thermal runaway and improving the reliability of the battery cell.

[0253] From the comparison of the test results of Example 1, Example 4 and Example 10, it can be seen that when the functional coating contains the first foaming agent and the second foaming agent, the short-circuit point temperature can be further reduced, which helps to further reduce the occurrence of thermal runaway. Similarly, from the comparison of the test results of Example 2, Example 5 and Example 9, and the comparison of the test results of Example 3, Example 6 and Example 11, the above technical effects can also be obtained.

[0254] It can be seen from the test results of Examples 9, 10 and 11 that when the sizes of the conductive foreign matter are the same, the functional coating includes the first foaming agent and the second foaming agent, and as the content of the second foaming agent increases, the short-circuit point temperature gradually decreases.

[0255] From the comparison of the test results of Examples 11 to 13, it can be seen that when the mass ratio of the first foaming agent to the second foaming agent is in the range of 0.5 to 1, and the mass content of the first foaming agent in the functional coating is in the range of 33% to 50%, and the mass content of the second foaming agent in the functional coating is in the range of 45% to 67%, the short-circuit point temperature can be further reduced.

[0256] From the comparison of the test results of Examples 9, 14 and 15, it can be seen that as the width of the functional coating increases, the short-circuit point temperature can be further reduced.

[0257] From the comparison of the test results of Examples 9, 16 and 17, it can be seen that as the thickness of the functional coating increases, the short-circuit point temperature can be further reduced.

[0258] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: A positive electrode sheet, comprising a positive electrode current collector, wherein the positive electrode current collector comprises a main body and a pole ear portion, wherein the main body has a first edge region and a second edge region, wherein the first edge region is connected to the pole ear portion, and the second edge region is arranged away from the pole ear portion; A negative electrode sheet, including a negative electrode current collector; a separator, located between the positive electrode sheet and the negative electrode sheet, the separator having a third edge region and a fourth edge region, the orthographic projection of the third edge region on the first edge region overlaps with the first edge region, and the orthographic projection of the fourth edge region on the second edge region overlaps with the second edge region; a functional coating located in at least one edge region of the first edge region, the second edge region, the third edge region, and the fourth edge region, the functional coating being configured to expand in response to a preset temperature to disconnect the electrical connection between the positive electrode sheet and the negative electrode sheet; The orthographic projections of the functional coating and the negative electrode current collector on the first edge region at least partially overlap; and / or the orthographic projections of the functional coating and the negative electrode current collector on the second edge region at least partially overlap; The functional coating includes a third functional coating and / or a fourth functional coating, wherein the third functional coating is located in the third edge region, and the orthographic projection of the third functional coating in the first edge region covers the first edge region; the fourth functional coating is located in the fourth edge region, and the orthographic projection of the fourth functional coating in the second edge region covers the second edge region.

2. The battery cell according to claim 1, characterized in that: The functional coating comprises a first functional coating and / or a second functional coating, wherein the first functional coating is located in the first edge region, and the second functional coating is located in the second edge region; The negative electrode sheet further includes a negative electrode active material layer located on at least one side of the negative electrode current collector; The orthographic projection of the negative electrode active material layer in the first edge region is located in the first functional coating layer, and the orthographic projection of the negative electrode active material layer in the second edge region is located in the second functional coating layer.

3. The battery cell according to claim 2, characterized in that: Along the width direction of the positive electrode plate, the total width b1 of the first functional coating and the width a1 of the first functional coating covered by the negative electrode active material layer satisfy: a1+x≤b1, wherein x represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate during the manufacturing process of the battery cell, and 0.1mm≤x≤2.5mm.

4. The battery cell according to claim 3, characterized in that: 0.3mm≤b1≤6mm.

5. The battery cell according to claim 2, characterized in that: The thickness of the first functional coating is 0.5 μm to 5 μm.

6. The battery cell according to claim 5, characterized in that: The thickness of the first functional coating is 2 μm to 4 μm.

7. The battery cell according to claim 2, characterized in that: Along the width direction of the positive electrode plate, the total width b2 of the second functional coating and the width a2 of the second functional coating covered by the negative electrode active material layer satisfy: a2+y≤b2, wherein y represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate of the battery cell during the manufacturing process, and 0.1mm≤y≤2.5mm.

8. The battery cell according to claim 7, characterized in that: 0.3mm≤b2≤6mm.

9. The battery cell according to claim 7, characterized in that: The thickness of the second functional coating is 0.5 μm to 5 μm.

10. The battery cell according to claim 9, characterized in that: The thickness of the second functional coating is 2 μm-4 μm.

11. The battery cell according to claim 1, characterized in that: The negative electrode sheet further includes a negative electrode active material layer located on at least one side of the negative electrode current collector; Among them, along the width direction of the isolation membrane, the total width b3 of the third functional coating and the width a3 of the third functional coating covered by the negative electrode active material layer satisfy: a3+z≤b3, wherein z represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate of the battery cell during the manufacturing process, and 0.5mm≤z≤3.0mm.

12. The battery cell according to claim 11, characterized in that: 1mm≤b3≤10mm.

13. The battery cell according to claim 1, characterized in that: The thickness of the third functional coating is 0.5 μm to 5 μm.

14. The battery cell according to claim 13, characterized in that: The thickness of the third functional coating is 2 μm to 4 μm.

15. The battery cell according to claim 10, characterized in that: The negative electrode sheet further includes a negative electrode active material layer located on at least one side of the negative electrode current collector; Among them, along the width direction of the isolation membrane, the total width b3 of the fourth functional coating and the a4 of the fourth functional coating covered by the negative electrode active material layer satisfy: a4+f≤b4, wherein f represents the eccentricity design reserved value between the positive electrode plate and the negative electrode plate of the battery cell during the manufacturing process, and 0.5mm≤f≤3.0mm.

16. The battery cell according to claim 15, characterized in that: 1mm≤b4≤10mm.

17. The battery cell according to claim 1, characterized in that: The thickness of the fourth functional coating is 0.5 μm to 5 μm.

18. The battery cell according to claim 17, characterized in that: The thickness of the fourth functional coating is 2 μm to 4 μm.

19. The battery cell according to claim 1, characterized in that: The functional coating includes a foaming agent, and the foaming temperature of the foaming agent is 140° C. to 500° C.

20. The battery cell according to claim 19, characterized in that: The mass fraction of the foaming agent in the functional coating is 80% to 90%.

21. The battery cell according to claim 20, characterized in that: The foaming agent includes a first foaming agent and a second foaming agent, the foaming temperature of the first foaming agent is T1, the foaming temperature of the second foaming agent is T2, and T1 and T2 satisfy: 140°C≤T1 <T2≤500℃。 22. The battery cell according to claim 21, characterized in that: 140℃≤T1<300℃； And / or, 300℃≤T2≤500℃.

23. The battery cell according to claim 21, characterized in that: The mass fraction A of the first foaming agent in the functional coating and the mass fraction B of the second foaming agent in the functional coating satisfy: 0.5≤A / B≤1.

24. The battery cell according to claim 23, characterized in that: 33%≤A≤50%； And / or, 45%≤B≤67%.

25. The battery cell according to claim 21, characterized in that: The first foaming agent includes at least one of an azo foaming agent, a hydrazide foaming agent, a nitroso foaming agent, an alkane foaming agent, a chlorofluorocarbon foaming agent, a urea foaming agent and an alkyl sodium sulfate foaming agent; Optionally, the first foaming agent includes at least one of an azo foaming agent, a hydrazide foaming agent and a nitroso foaming agent.

26. The battery cell according to claim 25, characterized in that: The second foaming agent includes at least one of a phenolic foaming agent, a silica foaming agent, a silicate foaming agent, a polyurethane foaming agent and a polyolefin foaming agent; Optionally, the second foaming agent includes at least one of a silicate foaming agent, a polyurethane foaming agent and a polyolefin foaming agent.

27. The battery cell according to claim 19, characterized in that: The thickness of the functional coating is 0.5 μm to 5 μm, and the volume expansion rate of the functional coating is 3000% to 6000%.

28. The battery cell according to claim 19, characterized in that: The gas production of the foaming agent is greater than or equal to 100 mL / g; Optionally, the gas production of the foaming agent is 100 mL / g to 350 mL / g.

29. The battery cell according to claim 19, characterized in that: The volume distribution particle size Dv50 of the foaming agent is 0.01 μm~1 μm; And / or, the volume distribution particle size Dv99 of the foaming agent is 0.01 μm~5 μm.

30. The battery cell according to claim 19, characterized in that The functional coating further comprises a foaming aid and a binder, wherein the mass fraction of the foaming aid in the functional coating is 5% to 10%, and the mass fraction of the binder in the functional coating is 5% to 10%.

31. The battery cell according to claim 30, characterized in that: The foaming aid comprises at least one of urea, urea derivatives, phthalic acid, ethanolamine and organic salts; And / or, the binder includes at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and acrylonitrile multipolymer.

32. A battery device, characterized in that: Comprising the battery cell as described in any one of claims 1 to 31.

33. An electrical device, characterized in that: Comprising a battery device as claimed in claim 32.

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