Battery cell, battery, and electric device

Abstract

The present application relates to a battery cell, a battery, and an electric device. The battery cell comprises an electrolyte and a positive electrode sheet. The electrolyte contains an electrolyte salt, the electrolyte salt comprises a salt capable of releasing free halogen ions during use of the battery cell, and the concentration A of the electrolyte salt in the electrolyte is 0.5 mol / L to 2 mol / L; the positive electrode sheet comprises a composite current collector and a positive electrode film layer arranged on at least one side of the composite current collector, the composite current collector comprises a supporting layer and a metal layer arranged on at least one side of the supporting layer, and the thickness B of the metal layer is 500 nm to 4000 nm. The battery cell can ensure both high quality energy density and good cycle performance.

Description

Battery cells, batteries and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2024102710278, filed with the Patent Office of China on March 8, 2024, entitled “Battery Cell, Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] In recent years, the application of lithium-ion batteries and other batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. Consequently, higher requirements are being placed on the battery's mass energy density and cycle life. Therefore, how to improve the mass energy density and cycle life of batteries is a pressing technical challenge.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and one of its purposes includes: providing a battery cell, a battery and an electrical device, which have good mass energy density and cycle life.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a battery cell, which includes an electrolyte and a positive electrode plate, the electrolyte containing an electrolyte salt, the electrolyte salt including a salt that can release free halogen ions during the use of the battery cell, and the concentration A of the electrolyte salt in the electrolyte is 0.5 mol / L~2 mol / L; the positive electrode plate includes a composite current collector and a positive electrode film layer provided on at least one side of the composite current collector, the composite current collector includes a support layer and a metal layer provided on at least one side of the support layer, and the thickness B of the metal layer is 500nm~4000nm.

[0009] The above-mentioned battery cell fully considers the corrosion effect of the free halogen ions present in the electrolyte on the metal layer of the composite current collector and the influence on the cycle life of the battery. Therefore, by controlling the above-mentioned electrolyte salt concentration A and the thickness B of the metal layer in the composite current collector within an appropriate range, the two are matched and restricted with each other. The concentration A of the electrolyte salt and the thickness B of the metal layer in the composite current collector should not be too large or too small. The two are within a mutually balanced range. In this way, the electrolyte can play a better role in improving the cycle life of the battery without seriously corroding the metal layer and thus affecting the flow capacity of the composite current collector, thereby improving the cycle life of the battery cell while taking into account good quality energy density.

[0010] In any embodiment of the present application, the battery cell satisfies at least one of the following characteristics:

[0011] (1) A is 1 mol / L to 1.5 mol / L;

[0012] (2) B is 700nm~1500nm.

[0013] In any embodiment of the present application, the battery cell satisfies at least one of the following characteristics: B is 1200 nm to 1400 nm.

[0014] Further controlling the molar concentration of the electrolyte salt in the electrolyte and the thickness of the metal layer within the above ranges can help further improve the cycle life and power performance of the battery cell.

[0015] In any embodiment of the present application, the free halogen ions include F - 、Cl - Br - and I - At least one of .

[0016] In any embodiment of the present application, the electrolyte salt includes a fluorine-containing lithium salt.

[0017] In any embodiment of the present application, the fluorine-containing lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0018] In any embodiment of the present application, the material of the metal layer includes aluminum metal material.

[0019] In any embodiment of the present application, the metal layer includes at least one of an aluminum single substance layer and an aluminum alloy layer.

[0020] In any embodiment of the present application, the material of the support layer includes a polymer material.

[0021] In any embodiment of the present application, the thickness of the support layer is 5 μm to 20 μm.

[0022] In any embodiment of the present application, the positive electrode plate further includes a protective layer provided on at least one side of the metal layer, and the protective layer includes a metal oxide.

[0023] Since the metal oxide in the protective layer is corroded by free halogen ions in the electrolyte at a lower rate than the metal layer, it can protect the metal layer to a certain extent, inhibit the corrosion rate of the metal layer, and thus protect the flow capacity of the composite current collector.

[0024] In any embodiment of the present application, the thickness of the protective layer is 3 nm to 100 nm.

[0025] In any embodiment of the present application, the thickness of the protective layer is 5 nm to 20 nm.

[0026] In any embodiment of the present application, the metal oxide includes at least one of aluminum oxide, tin oxide and silicon oxide.

[0027] In any embodiment of the present application, the protective layer is provided on both side surfaces of the metal layer, the protective layer located on the surface of the metal layer away from the support layer is the first protective layer, the thickness of the first protective layer is D1, and the protective layer located on the surface of the metal layer facing the support layer is the second protective layer, the thickness of the second protective layer is D2, and D1≥D2.

[0028] The first protective layer is closer to the positive electrode film layer, which is more susceptible to corrosion from free halogen ions in the electrolyte, so the required protective layer thickness is the same or greater. Further controlling the thickness of the second protective layer to be smaller can effectively reduce the corrosion rate while reducing the overall thickness of the composite current collector.

[0029] In any embodiment of the present application, the protective layer located on the surface of the metal layer facing away from the support layer is a first protective layer, the positive electrode film layer is disposed on the first protective layer, the volume average particle size Dv50 of the positive electrode active material in the positive electrode film layer is greater than the thickness of the first protective layer, and at least a portion of the positive electrode active material in the positive electrode film layer penetrates the first protective layer. This can improve the bonding strength between the positive electrode film layer and the composite current collector.

[0030] In any embodiment of the present application, the composite current collector has a recessed portion that is recessed from the first protective layer toward the support layer, the volume average particle size Dv50 of the positive electrode active material is less than or equal to the average depth of the recessed portion, and the positive electrode active material is disposed in at least a portion of the recessed portion.

[0031] Through this setting, at least half of the positive electrode active material at the interface between the positive electrode film layer and the composite current collector can be embedded in the recessed portion, and the bonding force between the positive electrode active material and the first protective layer is further enhanced, thereby further improving the bonding force between the positive electrode film layer and the composite current collector, and reducing the risk of peeling between the positive electrode film layer and the composite current collector during the battery cycle, thereby further improving the battery cycle performance.

[0032] In any embodiment of the present application, the battery cell includes a shell, a negative electrode sheet and a separator. The positive electrode sheet, the negative electrode sheet and the separator are formed into an electrode assembly through a winding process or a lamination process. The shell is used to accommodate the electrode assembly.

[0033] In any embodiment of the present application, the shape of the housing is square, and the housing includes a shell and at least one end cover; wherein,

[0034] The housing has an opening at only one end, and the end cover covers the opening; or

[0035] Both ends of the shell have openings, and the two end covers respectively cover the two openings of the shell.

[0036] In any embodiment of the present application, the shell is a soft package structure, and the material of the shell includes aluminum-plastic film.

[0037] In any embodiment of the present application, the outer shell is in the shape of a cylinder, and the outer shell includes a shell and at least one end cover, the end cover covers the opening of the shell, and the outer diameter of the cylinder is greater than or equal to 30 mm.

[0038] The second aspect of the present application further provides a battery, comprising one or more battery cells provided by the first aspect of the present application.

[0039] The third aspect of the present application further provides an electrical device, which includes at least one of the battery cell provided in the first aspect of the present application and the battery provided in the second aspect.

[0040] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0042] FIG1 is a schematic diagram of a battery according to one embodiment of the present application.

[0043] FIG2 is a schematic diagram of the expanded cross-sectional structure of the composite current collector of the positive electrode plate in the battery shown in FIG1 .

[0044] FIG3 is a schematic diagram of an expanded cross-sectional structure of a composite current collector of a positive electrode sheet according to another embodiment.

[0045] FIG. 4 is an exploded view of the battery shown in FIG. 1 according to one embodiment of the present application.

[0046] FIG5 is a schematic diagram of a battery module according to an embodiment of the present application.

[0047] FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0048] FIG. 7 is an exploded view of the battery pack shown in FIG. 6 according to an embodiment of the present application.

[0049] FIG8 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0050] Description of reference numerals:

[0051] 1. Battery pack; 2. Upper case; 3. Lower case; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device; 7. Composite current collector; 71. Support layer; 72. Metal layer; 73. Protective layer. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0053] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0054] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0055] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0056] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0057] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0058] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0059] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0060] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0061] To address the technical challenges of improving battery mass energy density and cycle life, one approach is to replace traditional pure metal layers with composite current collectors. Composite current collectors typically consist of a central support layer and metal layers positioned on one or both sides of the support layer. Using composite current collectors allows for thinner and lighter current collectors. This significantly reduces the thickness of the metal layer, reducing metal usage and lowering costs. Furthermore, while reducing the weight of the current collector, it also facilitates increasing the mass proportion of active materials, thereby improving the battery's mass energy density in many ways. However, as the thickness of the metal layer decreases, the corrosion resistance of the composite current collector also decreases. Exposure to corrosive agents such as hydrofluoric acid (HF) can corrode the composite current collector, severely impacting the battery's current handling capacity. Insufficient current handling capacity significantly impacts the battery's cycle life. Continuing to use a battery cell with insufficient current handling capacity can pose safety risks. For example, if the current exceeds the battery's tolerance, excessive heat can be generated within the battery, potentially leading to fires and other safety hazards.

[0062] For example, when the metal layer in the composite current collector of the positive electrode plate is corroded and damaged, it can also cause the electroactive material to fall off, causing the metal layer in the damaged area to short-circuit with the negative electrode plate, triggering a series of side reactions. In severe cases, the resulting metal layer reaction fragments can cause an internal short circuit or penetrate the composite current collector, leading to battery failure. Therefore, the corrosion of the metal layer is a major cause of the long-term cycle performance degradation of batteries.

[0063] Based on this, in one embodiment of the present application, a battery cell is provided, comprising a positive electrode plate and an electrolyte. The electrolyte contains an electrolyte salt, which includes a salt capable of releasing free halogen ions during use of the battery cell, and the concentration A of the electrolyte salt in the electrolyte is 0.5 mol / L to 2 mol / L. The positive electrode plate comprises a composite current collector and a positive electrode film layer disposed on at least one side of the composite current collector, the composite current collector comprising a support layer and a metal layer disposed on at least one side of the support layer, and the thickness B of the metal layer is 500 nm to 4000 nm.

[0064] It is worth noting that the thickness B of the metal layer refers to the thickness of the metal layer on one side of the support layer.

[0065] If the electrolyte salt concentration A is too low, there will be insufficient lithium ion carriers during the battery cell's charge and discharge process, affecting the battery's charge and discharge performance. If the electrolyte salt concentration A is too high, the viscosity of the electrolyte will increase, hindering the flow of lithium ions. The thinner the metal layer thickness B, the more likely it will corrode after a period of use. If the metal layer thickness B is too thick, it will not adversely affect the battery's charge and discharge performance, but will reduce the battery's mass energy density.

[0066] Without wishing to be limited to any theory, the above-mentioned battery cell of the present application fully considers the corrosion effect of the free halogen ions present in the electrolyte on the metal layer of the composite current collector and the influence on the cycle life of the battery. Therefore, by controlling the above-mentioned electrolyte salt concentration A and the thickness B of the metal layer in the composite current collector within a suitable range, the two are matched and restricted with each other. The electrolyte salt concentration A and the thickness B of the metal layer in the composite current collector should not be too large or too small. The two are within a mutually balanced range. In this way, the electrolyte can play a better role in improving the cycle life of the battery without seriously corroding the metal layer and thus affecting the flow capacity of the composite current collector, thereby improving the cycle life of the battery cell while taking into account good quality energy density.

[0067] It is understood that the support layer has two surfaces that are opposite to each other in its thickness direction, and the metal layer can be provided on one or both of the two side surfaces of the support layer. It is understood that the composite current collector in the positive electrode sheet has two surfaces that are opposite to each other in its thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the composite current collector.

[0068] Please refer to Figures 1 and 2. Figure 1 shows a schematic diagram of a battery cell according to an embodiment of the present application. Figure 2 shows a schematic diagram of the expanded cross-sectional structure of the composite current collector of the positive electrode plate in the battery cell shown in Figure 1. The positive electrode plate in the battery cell 5 includes a composite current collector 7 and a positive electrode film layer (not shown) provided on both surfaces of the composite current collector 7. The composite current collector 7 includes a support layer 71 and a metal layer 72 provided on both surfaces of the support layer 71.

[0069] The thickness of each film layer of the composite current collector including the protective layer can be measured by using a scanning electron microscope to test the thickness cross section of the current collector and the thickness of each film layer.

[0070] In other embodiments, any two of the above point values ​​may be used as end values ​​to form a range, and the following is similar.

[0071] In some embodiments, the concentration A of the electrolyte salt in the electrolyte solution is 0.5 to 2 mol / L. For example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, or 2 mol / L. In other embodiments, it can be a range consisting of any two of the above-mentioned values ​​as end points, and the same applies to the following.

[0072] Controlling the molar concentration of the electrolyte salt in the electrolyte can further improve the electrolyte's ion transport properties. It can also prevent excessive concentrations of free halogen ions in the electrolyte, which can produce more hydrohalic acid and increase the risk of corrosion of the composite current collector. This can help improve the corrosion resistance of the composite current collector in the battery cell, further improving the cycle life and power performance of the battery cell. Optionally, the concentration A of the electrolyte salt in the electrolyte is 1 mol / L to 1.5 mol / L, and further 1.2 mol / L to 1.5 mol / L.

[0073] In some embodiments, the thickness B of the metal layer in the composite current collector is 500nm to 4000nm. As an example, it can be 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1800nm, 2000nm, 2200nm, 2500nm, 3000nm, 3500nm, or 4000nm. The thickness of a conventional pure metal current collector is generally around 10 microns. As an example, a conventional positive electrode current collector generally uses a 13-micron thick pure aluminum foil. In the present application, the thickness of the metal layer in the composite current collector is controlled within the above range, which can not only make the composite current collector have good conductivity and reduce the internal resistance of the battery cell, but also improve the mass energy density of the battery cell on the basis of the same weight. Optionally, the thickness B of the metal layer in the composite current collector is 700 nm to 1500 nm, further 1000 nm to 1500 nm, and further 1200 nm to 1400 nm.

[0074] In some embodiments, the free halide ions include F - 、Cl - Br - and I - As mentioned above, these free halogen ions are generally provided by the electrolyte salt in the electrolyte.

[0075] Among the above-mentioned free halogen ions, the most commonly used and most corrosive in electrolyte is F. - The electrolyte salts capable of releasing free halogen ions include but are not limited to hexahalophosphates such as lithium hexahalophosphate. The hydrolysis of lithium hexafluorophosphate releases HF, which contains free F - .

[0076] In some embodiments, the concentration of the free halogen ions in the electrolyte is 0.5 mg / L to 200 mg / L. For example, it can be 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, 160 mg / L, 180 mg / L, or 200 mg / L. Furthermore, the concentration of the free halogen ions in the electrolyte is 0.5 mg / L to 50 mg / L. Controlling the concentration of the free halogen ions in the electrolyte within the above range enables the electrolyte to have a good ability to transport active ions and can reduce the rate at which hydrohalic acid corrodes the metal layer of the composite current collector, which is beneficial to further improve the cycle life and power performance of the battery cell.

[0077] Furthermore, the electrolyte salt includes a fluorine-containing lithium salt. Wherein, the fluorine-containing lithium salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0078] Furthermore, the fluorine-containing lithium salt includes lithium hexafluorophosphate, and optionally includes one or more of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0079] In some embodiments, the molar concentration of the fluorine-containing lithium salt in the electrolyte is 0.5 mol / L to 2 mol / L. As an example, it can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or 2 mol / L.

[0080] In some embodiments, the metal layer comprises a metal material. The metal material includes, but is not limited to, aluminum. Furthermore, the metal layer comprises at least one of an aluminum layer and an aluminum alloy layer. It is understood that the metal layer may comprise a stack of aluminum layers and aluminum alloy layers.

[0081] In some embodiments, the material of the support layer includes a polymer material.

[0082] Furthermore, polymer materials include, but are not limited to, polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their cross-linked products and their copolymers, one or more thereof.

[0083] In some embodiments, the material of the support layer is a polymer material; accordingly, the support layer is a polymer material layer.

[0084] In some embodiments, the support layer comprises, in addition to a polymer material, additives, thereby forming a polymer-based composite material. Accordingly, the support layer is a polymer-based composite material layer. The additives may include one or more of a metal material and an inorganic non-metallic material. Optionally, the metal material includes one or more of aluminum, nickel, iron, silver, titanium, and alloys thereof. Optionally, the inorganic non-metallic material includes one or more of graphite, conductive carbon, aluminum oxide, silicon oxide, silicon carbide, and silicon dioxide.

[0085] Furthermore, the thickness of the support layer is 5 μm to 20 μm, and as examples may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 15 μm, 16 μm, 18 μm, 20 μm; further may be 5 to 12 μm.

[0086] In some embodiments, the composite current collector further includes a bonding layer disposed between the support layer and the metal layer to bond the two. In some embodiments, the bonding layer has a thickness of 200 nm to 1500 nm. It is understood that the thickness of the bonding layer includes, but is not limited to, 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, and 1500 nm.

[0087] In some embodiments, the adhesive layer comprises an adhesive, and the adhesive includes one or more of polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide.

[0088] In some embodiments, the composite current collector further includes a protective layer disposed on at least one side of the metal layer, the protective layer comprising a metal oxide. Because the metal oxide in the protective layer is corroded more slowly by free halogen ions in the electrolyte than the metal layer, it can protect the metal layer to a certain extent, inhibiting the corrosion rate of the metal layer and thereby maintaining the flow capacity of the composite current collector.

[0089] Furthermore, the protective layer includes a metal oxide, and the metal oxide includes at least one of aluminum oxide, tin oxide, and silicon oxide. Furthermore, the protective layer is a metal oxide layer. The metal oxide in the protective layer of the composite current collector can react with a hydrohalic acid such as hydrofluoric acid (HF) to form a metal halide such as metal fluoride (AlF3). The metal halide further reduces the corrosion rate of the metal layer within the protective layer by the hydrohalic acid.

[0090] It is understood that the protective layer can be provided on the surface of one or both sides of the metal layer. It is understood that the protective layer can also be provided at other locations besides this. For example, in some examples, the protective layer is provided on the entire surface of the metal layer (equivalent to the protective layer covering the metal layer). These protective layers can reduce the corrosion rate of the metal layer by halogen ions such as hydrofluoric acid (HF).

[0091] It is worth noting that, for example, when the protective layer is arranged on both sides of the metal layer in the thickness direction, the thickness of the single-sided protective layer refers to the thickness of a single protective layer on one side of the metal layer, rather than the sum of the thicknesses of the two protective layers on both sides of the metal layer.

[0092] Furthermore, the protective layer is provided on both sides of the metal layer. The protective layer located on the surface of the metal layer facing away from the support layer is the first protective layer. Because the surface of the metal layer facing away from the support layer is closer to the positive electrode film layer, it is more susceptible to corrosion from free halogen ions in the electrolyte. The first protective layer provided on this surface can effectively inhibit corrosion of the metal layer.

[0093] Furthermore, the protective layer located on the surface of the metal layer facing the support layer is a second protective layer. Since the positive electrode sheet of the battery cell is soaked in electrolyte during use, the surface of the metal layer opposite the support layer may also be soaked in electrolyte and subsequently corroded by free halogen ions in the electrolyte. The second protective layer disposed on this surface can also inhibit corrosion of the metal layer on this surface. Furthermore, this second protective layer can also enhance the adhesion between the metal layer and the support layer.

[0094] Furthermore, the thickness of the first protective layer is D1, and the thickness of the second protective layer is D2, where D1 ≥ D2. This is because the first protective layer is closer to the positive electrode film layer, which is more susceptible to corrosion from free halogen ions in the electrolyte, and therefore requires the same or greater thickness for the protective layer. Further reducing the thickness of the second protective layer can effectively reduce the corrosion rate while reducing the overall thickness of the composite current collector.

[0095] Furthermore, D1 is 3 nm to 100 nm, and can be optionally 5 nm to 20 nm.

[0096] Furthermore, D2 is 3 nm to 100 nm, and can be optionally 5 nm to 20 nm, and more preferably 5 nm to 10 nm.

[0097] It can be understood that the composite current collector in the positive electrode sheet has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the composite current collector.

[0098] Furthermore, the volume average particle size Dv50 of the positive electrode active material is greater than the thickness of the first protective layer D1. Furthermore, at least a portion of the positive electrode active material in the positive electrode film penetrates the first protective layer, thereby improving the bonding strength between the positive electrode film and the composite current collector.

[0099] Furthermore, the composite current collector has a recessed portion extending from the first protective layer toward the support layer. The volume average particle size Dv50 of the positive electrode active material is less than or equal to the average depth of the recessed portion, and the positive electrode active material is disposed in at least a portion of the recessed portion. This configuration allows at least half of the positive electrode active material at the interface between the positive electrode film and the composite current collector to be embedded within the recessed portion. This improves the adhesion between the positive electrode active material and the first protective layer, further enhancing the adhesion between the positive electrode film and the composite current collector, and reducing the risk of delamination between the positive electrode film and the composite current collector during battery cycling, thereby further improving the battery's cycling performance.

[0100] Furthermore, the volume average particle size Dv50 of the positive electrode active material is 5 μm to 12 μm. As an example, the volume average particle size Dv50 of the positive electrode active material may be: 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm.

[0101] It is understood that the first protective layer in the recessed portion can be discontinuous or continuous. Furthermore, the first protective layer in the recessed portion is discontinuous, and the positive electrode active material is provided in the recessed portion, i.e., the positive electrode active material penetrates the first protective layer. Furthermore, the positive electrode active material is embedded in at least a portion of the recessed portion.

[0102] Dv50 is well known in the art and can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000). Dv50 represents the particle size at which the cumulative volume percentage of particles, starting from the smallest particle size, reaches 50%, based on the particle size volume distribution.

[0103] Particle size and volume distribution can be determined by the following method: Add an appropriate amount of the sample to be tested to a clean beaker and thoroughly sonicate to ensure complete dispersion. The test instrument is a Malvern 2000 (USA). The sample is poured into the injection tower and then circulated with the solution into the test optical system. The particles are illuminated by a laser beam, and the energy distribution of the scattered light is measured to determine the particle size distribution (shading degree: 8-12%). A particle size and volume distribution graph is then plotted based on the test data.

[0104] In this application, the average depth of the recessed portion is tested using the following method:

[0105] 1) Sample Preparation: a. Randomly select an electrode sheet, cut it into strips approximately 5 mm wide, and soak it in liquid nitrogen for 10 min. b. Remove the strip with tweezers and quickly break it with a knife, forming a cross section perpendicular to its length. With the non-contact blade facing upward, attach the cut section to an A4 paper for later use. c. Use conductive adhesive to attach the cut section to a long sample stage, with the cross section slightly protruding (<1 mm) from the edge of the stage. Finally, place the strip upright on a scanning electron microscope (SEM) specimen holder.

[0106] 2) Parameter settings: The scanning electron microscope mode was In-lens, the voltage was 10 kV, the aperture was 30 μm, and the working distance was 4.5 mm;

[0107] 3) Test process: Use a magnification of about 3K to find the concave parts in the electrode plate, take several pictures at magnifications of 30K, 10K, and 5K (1K=1000), randomly select 12 locations of the concave parts, measure the depth of each concave part, and then take the average value to get the average depth of the concave parts.

[0108] In some embodiments, the step of forming the composite current collector including the recessed portion includes: pressing the composite current collector using a textured work roller, for example, using a convex-concave roller to form the recessed portion.

[0109] In another embodiment of the present application, the method for preparing the positive electrode sheet of the battery cell mentioned above comprises the following steps:

[0110] Disposing an electrode slurry containing an electrode active material on at least one side of the composite current collector and drying the slurry to form a positive electrode film layer;

[0111] Pressure is applied to the positive electrode film layer to form recessed portions, and at least a portion of the recessed portions is embedded with electrode active material.

[0112] In some embodiments, the step of applying pressure to the positive electrode film layer includes: performing a pressing process on the positive electrode film layer, such as a cold pressing process after drying the coating slurry.

[0113] FIG3 shows a schematic diagram of the expanded cross-sectional structure of a composite current collector for a positive electrode sheet according to another embodiment. The composite current collector 7 includes a support layer 71, a metal layer 72 disposed on both surfaces of the support layer 71, and a protective layer 73 disposed on both surfaces of the two metal layers 72 facing and away from the support layer 71 (i.e., both side surfaces of the metal layer 71 in the thickness direction). In other words, the composite current collector 7 includes a support layer 71, a protective layer 73 disposed on both surfaces of the support layer 71, a metal layer 72, and a protective layer 73, respectively.

[0114] Furthermore, the thickness of a single protective layer is 3nm to 100nm; as an example, the thickness can be 3nm, 4nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, and 100nm. Controlling the thickness of the protective layer to be above 3nm can improve the coverage and density of the protective layer and enhance the protective performance of the protective layer; while controlling it to be below 100nm is based on the consideration that increasing the thickness of the protective layer will increase the resistivity of the composite current collector, increase the resistance of the battery, and thus affect the performance of the battery. If the thickness of the protective layer is controlled within this range, the composite current collector can have both a low corrosion risk and a suitable resistivity, so that the composite current collector has good conductivity. Furthermore, the thickness of the protective layer is 5nm to 20nm, which can further achieve a lower corrosion risk and a more suitable resistivity for the composite current collector.

[0115] It is worth noting that, for example, when the protective layer is arranged on both side surfaces of the metal layer in the thickness direction, the thickness of a single protective layer refers to the thickness of a single protective layer on one side of the metal layer, rather than the sum of the thicknesses of the two protective layers on both side surfaces of the metal layer.

[0116] It can be understood that the protective layer can be formed on the metal layer by coating, evaporation, chemical vapor deposition, etc., and can also be formed on the metal layer by bonding with an adhesive layer. Optionally, it is formed on the metal layer by evaporation, chemical vapor deposition, etc.

[0117] Furthermore, the positive electrode film layer in the positive electrode sheet includes a positive electrode active material.

[0118] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0119] As an example, the positive electrode active material may include at least one of the following lithium ion active materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0120] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0121] As an example, the positive electrode active material may include at least one of the following sodium ion active materials: one or more of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0122] As an optional technical solution of the present application, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides may be Na x MO2, wherein M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0123] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4) n- The polyanionic compound can also be a compound with sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4) n- The halogen can be one or more of F, Cl and Br. The polyanionic compound can also be a compound with sodium ions, tetrahedral (YO4) n-Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ The halogen can be one or more of F, Cl and Br. The polyanionic compounds can include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) wherein M′ in NaM′PO4F may include one or more of V, Fe, Mn and Ni.

[0124] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may include Na a Me b Me' c (CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0125] In some embodiments, the positive electrode film layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin.

[0126] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 to 25000 mPa·s. When coating the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm 2 ~35mg / cm 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0128] It is understood that the battery cell also includes a negative electrode sheet, which is arranged opposite the positive electrode sheet. Furthermore, the battery cell also includes a separator. The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly.

[0129] The negative electrode plate includes a negative electrode current collector. Further, the negative electrode plate may also include a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0130] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0131] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0132] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, 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.

[0133] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0134] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0135] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0136] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or on both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 to 10000 mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 ~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0137] The electrolyte is used to soak the positive and negative electrodes and conduct ions between them. In addition to the electrolyte salts mentioned above, the electrolyte also includes a solvent for dissolving the electrolyte salts.

[0138] In some embodiments, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate, fluoroethylene carbonate (FEC), 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.

[0139] In some embodiments, the electrolyte may 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 battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0140] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0141] In some embodiments, the battery further includes a separator.

[0142] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0143] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0144] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0145] In some embodiments, the isolation film has a thickness of 6 μm-40 μm, and optionally 12 μm-20 μm.

[0146] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process; the battery cell also includes a shell, which is used to accommodate the above-mentioned electrode assembly.

[0147] A battery includes at least one battery cell. A battery may include one or more battery cells.

[0148] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0149] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0150] In some embodiments, the housing is square in shape and includes a shell and at least one end cap. Furthermore, the shell has an opening at only one end, with the end cap covering the opening. Alternatively, the shell has openings at both ends, with the two end caps covering the two openings of the shell, respectively.

[0151] In some embodiments, the housing is cylindrical in shape and includes a shell and at least one end cap, the end cap being secured to an opening in the shell. Furthermore, the outer diameter of the cylinder is greater than or equal to 30 mm. Furthermore, the shell has an opening at only one end, with the end cap securing the opening; or, the shell has openings at both ends, with the two end caps securing the two openings in the shell, respectively.

[0152] In some embodiments, the housing is a soft-pack structure. Further, the housing is made of an aluminum-plastic film.

[0153] For example, FIG1 shows an example of a battery cell having a square structure.

[0154] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery may also be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic. Further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0155] In some embodiments, referring to FIG4 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0156] In some embodiments, the battery may be a battery module or a battery pack. A battery module includes at least one battery cell. A battery module may contain one or more battery cells, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0157] FIG5 shows an example battery module 4. Referring to FIG5 , in the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0158] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0159] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0160] Figures 6 and 7 illustrate an example battery pack 1. Referring to Figures 6 and 7 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0161] In addition, one embodiment of the present application further provides an electrical device, comprising the battery provided herein. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, and the like. Examples of mobile devices include, but are not limited to, mobile phones and laptop computers; examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0162] As an electrical device, a battery can be selected according to its usage requirements.

[0163] FIG8 shows an example of an electric device 6. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density, a battery pack or battery module may be used.

[0164] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0165] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0166] Example 1

[0167] (1) Preparation of positive electrode sheet

[0168] Preparation of composite current collector: Aluminum metal layers were evaporated on both surfaces of the PET support layer to form a composite current collector, wherein the thickness of the support layer was 8 μm and the thickness of the single-side aluminum metal layer was shown in Table 1.

[0169] The positive electrode active material (Dv50 is 5 μm, NCM with a mass ratio of 4:1) 811 and NCM 523 ), conductive carbon black SP and binder PVDF are dispersed in solvent NMP in a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the composite current collector, and after drying and cold pressing, a positive electrode sheet is obtained, wherein the coating amount per unit area on both sides is 0.27g / 1540.25mm 2 .

[0170] (2) Preparation of negative electrode sheet

[0171] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.17g / 1540.25mm 2 .

[0172] (3) Isolation film

[0173] A 12μm thick polypropylene isolation film was selected.

[0174] (4) Preparation of electrolyte

[0175] An organic solvent was prepared: a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with the volume ratio of EC, EMC, and DEC being 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte. The concentration of the lithium salt LiPF6 in the electrolyte is shown in Table 1.

[0176] (5) Preparation of the battery: The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound into a square bare cell; the bare cell is placed in an aluminum-plastic film, and then baked at 80°C to remove water, and 10g of the above-mentioned electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, and capacity separation, a finished battery is obtained.

[0177] Other Examples and Comparative Examples

[0178] The batteries of other embodiments and comparative examples are prepared in a similar manner to the battery of Example 1, except that at least one of the thickness parameter of the metal layer in the composite current collector and the concentration parameter of the lithium salt LiPF6 in the electrolyte is different, as shown in Table 1.

[0179] The following is the performance parameter test.

[0180] (1) Free F in the electrolyte of the battery - The test method for the content is as follows: the finished battery obtained by formation is disassembled and the electrolyte therein is taken out as a sample, and the concentration of free halogen ions in the electrolyte is determined by ion chromatography. The results are shown in Table 2.

[0181] (2) The test method for high temperature storage life is as follows:

[0182] (1.1) At 25°C ± 2°C, discharge a fresh battery at a constant current rate of 0.33C to 2.8V, charge it at a constant current rate of 0.33C to 4.2V, charge it at a constant voltage to a current of less than or equal to 0.05C, and then discharge it at a constant current rate of 0.33C to 2.8V. The initial discharge capacity C0 of the battery is measured.

[0183] (1.2) Charge the battery at a constant current rate of 0.33C to 4.2V, then charge it at a constant voltage rate until the current is less than or equal to 0.05C. Store the fully charged battery in an oven at 60℃±2℃.

[0184] (1.3) Remove the batteries from the oven at intervals of 7 days, 10 days, 15 days, 20 days, or 30 days, and allow the batteries to cool naturally to 25°C ± 2°C. At this temperature, discharge the batteries at a constant current rate of 0.33C to 2.8V, and test the discharge capacity of the batteries.

[0185] If the discharge capacity of the battery obtained in step (1.3) is higher than 80% of the initial discharge capacity (C0) of the battery, repeat steps (1.1) and (1.2) to extend the storage time; until the discharge capacity of the battery decays to equal to or less than 80% of the initial discharge capacity (C0) of the battery for the first time, record the storage time, which is the storage life of the battery, in days, rounded to an integer multiple of 10;

[0186] The high temperature storage life is used to characterize the cycling performance of the battery.

[0187] (3) The test method for the growth rate of DC resistance (DCR) after storage for a corresponding period of time is as follows:

[0188] Pre-storage DCR test: At 25°C±2°C, charge fresh batteries at a constant current rate of 0.33C to 4.2V. Then charge at a constant voltage rate until the current is less than or equal to 0.05C. Discharge at a constant current rate of 0.33C to 50% C0, adjusting the battery to 50% SOC (state of charge), at which point the voltage is V1. Then discharge at a rate of 4C for 30s, with the end-of-discharge voltage at V2. The DCR1 is measured after 10s. DCR1 = (V1-V2) / I, where I is 4C.

[0189] Post-storage DCR test: At 25°C ± 2°C, charge the battery at the end of its storage life at a constant current rate of 0.33C to 4.2V. Then charge it at a constant voltage rate until the current is less than or equal to 0.05C. Discharge it at a constant current rate of 0.33C to 50% C0. The battery is adjusted to 50% SOC, at which point the voltage is V3. Then discharge it at a rate of 4C for 30s. The voltage at the end of discharge is V4. The data is collected after 10s. DCR2 = (V3 - V4) / I, where I is 4C.

[0190] The DC resistance growth rate (%) is (DCR2-DCR1) / DCR1*100%.

[0191] The power performance of the battery is characterized by the DC resistance growth rate.

[0192] Table 1

[0193] As can be seen from Table 1 above, the thickness of the metal layer in Comparative Example 1 is relatively small, and the metal layer will be corroded after the battery has been used for a period of time, which will lead to a shorter storage life. Although the thickness of the metal layer in Comparative Example 2 is 1200nm, the lithium salt concentration of the electrolyte is relatively low, resulting in insufficient lithium salt in the later stage of battery use, and the storage life of the battery is reduced. Although the thickness of the metal layer in Comparative Example 3 is 1200nm, the lithium salt concentration in the electrolyte is relatively high, resulting in excessive viscosity of the lithium salt in the later stage of battery use, making battery ion transmission difficult, and thus reducing the storage life of the battery. Compared with Comparative Examples 1-3, the storage life of the batteries of Examples 1-8 is significantly higher, indicating that each embodiment effectively improves the life of the battery by regulating the thickness of the metal layer and matching the lithium salt concentration of the electrolyte. Moreover, each embodiment improves the mass energy density of the battery compared to the pure metal current collector.

[0194] In Example 6, the electrolyte solution has a high lithium salt concentration, which poses a risk of corrosion short-circuiting in the relatively thin metal layer in the later stages of battery use, reducing the battery cycle life. In Example 7, the electrolyte salt concentration is relatively low, resulting in insufficient lithium ion carriers during battery cell use, affecting the battery cycle life. Comparing Examples 6 and 7 with other examples shows that, based on the examples of this application, further controlling the lithium salt concentration of the electrolyte solution to 1 to 1.5 mol / L can further extend the battery's storage life.

[0195] By comparing Example 3 with other examples, it can be seen that, based on the examples of the present application, the thickness of the metal layer is controlled to be between 700nm and 4000nm, and further to 1200nm and 4000nm, which can further improve the storage life of the battery; at the same time, considering that the thickness of the metal layer is too large, the energy density of the battery will be reduced (for example, Example 5), therefore, in order to take into account both the storage life and energy density of the battery, the thickness of the metal layer is further controlled to be between 700nm and 1500nm, and further to 1200nm and 1500nm.

[0196] Examples 8 to 12

[0197] The same as Example 1, the only difference is the thickness of the metal layer of the composite current collector in the positive electrode and the preparation steps of the electrolyte. Specifically, the thickness of the metal layer and the free F in the electrolyte are different. - The concentrations are different, as shown in Table 2.

[0198] The preparation steps of the electrolyte are as follows: the organic solvent is a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content of <10ppm, the fully dried lithium salt LiPF6 (lithium hexafluorophosphate) is dissolved in the organic solvent and mixed evenly to obtain an electrolyte. Among them, the concentration of the lithium salt LiPF6 in each embodiment is controlled to vary within 0.5mol / L~2mol / L, and the water content in the electrolyte is slightly different, thereby making the free F in the electrolyte of each embodiment - concentration changes.

[0199] Table 2

[0200] As can be seen from Table 2, compared with Comparative Examples 1 to 3, the storage life of the batteries of Examples 8 to 12 is significantly higher.

[0201] It can be seen from Examples 8 to 11 that Examples 9 to 11 control the free F in the electrolyte. - When the concentration is within the range of 0.5mg / L to 50mg / L, the storage life of the battery is significantly improved and the DC resistance growth rate is significantly reduced, which further improves the cycle life and power performance of the battery.

[0202] It can be seen from Examples 10 and 12 that free F in the electrolyte -On the basis of the above concentration range, the thickness of the metal layer is controlled within 1200nm~4000nm, and further within 1200nm~1500nm, which further improves the cycle life and power performance of the battery; further controlling the thickness of the metal layer within 1200nm~1500nm, further improves the cycle life, power performance and energy density of the battery.

[0203] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0204] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A battery cell, comprising: An electrolyte solution containing an electrolyte salt, wherein the electrolyte salt includes a salt capable of releasing free halogen ions during use of the battery cell, and the concentration A of the electrolyte salt in the electrolyte solution is 0.5 mol / L to 2 mol / L; and A positive electrode plate, the positive electrode plate includes a composite current collector and a positive electrode film layer arranged on at least one side of the composite current collector, the composite current collector includes a support layer and a metal layer arranged on at least one side of the support layer, and the thickness B of the metal layer is 500nm to 4000nm.

2. The battery cell according to claim 1, wherein: The battery cell meets at least one of the following characteristics: (1) A is 1 mol / L to 1.5 mol / L; (2) B is 700nm~1500nm.

3. The battery cell according to any one of claims 1 to 2, wherein: B is 1200nm~1400nm.

4. The battery cell according to any one of claims 1 to 3, wherein: The free halogen ions include F - 、Cl - Br - and I - At least one of .

5. The battery cell according to any one of claims 1 to 4, wherein: The electrolyte salt includes a fluorine-containing lithium salt. The battery cell according to claim 5 , wherein: The fluorine-containing lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

7. The battery cell according to any one of claims 1 to 6, wherein: The material of the metal layer includes aluminum metal material.

8. The battery cell according to claim 7, wherein: The metal layer includes at least one of an aluminum single substance layer and an aluminum alloy layer.

9. The battery cell according to any one of claims 1 to 8, wherein: The material of the support layer includes polymer material.

10. The battery cell according to any one of claims 1 to 9, wherein: The thickness of the support layer is 5 μm to 20 μm.

11. The battery cell according to any one of claims 1 to 10, wherein: The positive electrode plate further includes a protective layer provided on at least one side of the metal layer, and the protective layer includes a metal oxide.

12. The battery cell according to claim 11, wherein: The thickness of the protective layer is 3nm to 100nm.

13. The battery cell according to claim 12, wherein: The thickness of the protective layer is 5nm to 20nm.

14. The battery cell according to any one of claims 11 to 13, wherein: The metal oxide includes at least one of aluminum oxide, tin oxide and silicon oxide.

15. The battery cell according to any one of claims 11 to 14, wherein: The protective layer is provided on both side surfaces of the metal layer. The protective layer located on the surface of the metal layer facing away from the support layer is the first protective layer, and the thickness of the first protective layer is D1. The protective layer located on the surface of the metal layer facing the support layer is the second protective layer, and the thickness of the second protective layer is D2, and D1≥D2.

16. The battery cell according to any one of claims 11 to 15, wherein: The protective layer located on the surface of the metal layer facing away from the support layer is the first protective layer, the positive electrode film layer is arranged on the first protective layer, the volume average particle size Dv50 of the positive electrode active material in the positive electrode film layer is greater than the thickness of the first protective layer, and at least part of the positive electrode active material in the positive electrode film layer passes through the first protective layer.

17. The battery cell according to claim 16, wherein: The composite current collector has a recessed portion extending from the first protective layer toward the support layer. The volume average particle size Dv50 of the positive electrode active material is less than or equal to the average depth of the recessed portion. The positive electrode active material is disposed in at least a portion of the recessed portion.

18. The battery cell according to any one of claims 1 to 17, wherein: The battery cell includes a housing, a negative electrode sheet and a separator. The positive electrode sheet, the negative electrode sheet and the separator are wound or laminated to form an electrode assembly. The housing is used to accommodate the electrode assembly.

19. The battery cell according to claim 18, wherein: The outer shell is in a square shape and comprises a shell and at least one end cover; wherein, The housing has an opening at only one end, and the end cover covers the opening; or Both ends of the shell have openings, and the two end covers respectively cover the two openings of the shell.

20. The battery cell according to claim 18, wherein The shell is a soft package structure, and the material of the shell includes aluminum-plastic film.

21. The battery cell according to claim 18, wherein The outer shell is in the shape of a cylinder and comprises a shell and at least one end cover, wherein the end cover covers an opening of the shell, and an outer diameter of the cylinder is greater than or equal to 30 mm.

22. A battery comprising one or more battery cells according to any one of claims 1 to 21.

23. An electrical device, wherein: Comprising at least one of the battery cell according to any one of claims 1 to 21 and the battery according to claim 22.

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