Battery, preparation method thereof and electric device comprising battery

Abstract

The invention provides a battery, a preparation method thereof and an electric device comprising the battery, the battery comprises a positive pole piece and an electrolyte, the positive pole piece comprises a positive current collector, the positive current collector comprises a conductive layer, the electrolyte comprises first anions and second anions, the first anions comprise hexafluorophosphate anions, the second anions comprise hexafluorophosphate anions, and the third anions comprise hexafluorophosphate anions. The first anions comprise one or more anions selected from anions shown in the formula 1 and anions shown in the formula 2, the second anions comprise one or more anions selected from anions shown in the formula 1 and anions shown in the formula 2, the thickness of the conductive layer is H1 [mu] m, the concentration of the first anions in the electrolyte is C1 mol / L, the concentration of the second anions in the electrolyte is C2 mol / L, and the battery meets the condition that H1 is larger than or equal to 0.2 * (C2 / C1) and smaller than or equal to (C2 / C1) + 3. According to the invention, the safety performance of the battery can be improved, and meanwhile, the battery has good electrochemical performance. Formula 1 and Formula 2

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202280015918.6, filed on September 30, 2022, entitled “Battery, Method of Preparation Thereof, and Electrical Device Including Thereof”. Technical Field

[0002] This application belongs to the field of battery technology, specifically relating to a battery, its preparation method, and an electrical device containing the same. Background Technology

[0003] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the increasing application and promotion of batteries, their safety has received growing attention; if battery safety cannot be guaranteed, it cannot be used. Therefore, how to enhance battery safety performance without affecting its electrochemical performance is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a battery, a method for preparing the same, and an electrical device comprising the same, which can reduce the impact of positive electrode current collector corrosion on battery safety and electrochemical performance, thereby improving battery safety while ensuring good electrochemical performance.

[0005] This application provides a battery comprising a positive electrode and an electrolyte, wherein the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive current collector includes a conductive layer, and the electrolyte includes a solvent and a solute, the solute being an ionic salt formed by cations and anions, the cations including one or more selected from alkali metal cations and alkaline earth metal cations, optionally including one or more selected from lithium ions, sodium ions, and potassium ions, and the anions including a first anion and a second anion. The first anion includes a hexafluorophosphate anion, and the second anion includes one or more anions selected from the anions shown in Formula 1 and Formula 2. R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 can also be bonded into a ring. The thickness of the conductive layer is H1 μm. The concentration of the first anion in the electrolyte is C1 mol / L, the concentration of the second anion is C2 mol / L, and the battery satisfies 0.2×(C2 / C1)≤H1≤(C2 / C1)+3.

[0006] Formula 1 Formula 2 The inventors of this application made a surprising discovery through numerous experiments: by adjusting the thickness H1μm of the conductive layer and the relationship between the concentrations of the first anion C1mol / L and the second anion C2mol / L to satisfy 0.2×(C2 / C1)≤H1≤(C2 / C1) + 3, the impact of conductive layer corrosion on battery safety and electrochemical performance can be reduced. This allows the battery to maintain good electrochemical performance while improving its safety, such as a longer battery life.

[0007] In any embodiment of this application, 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2. Therefore, the impact of conductive layer corrosion on battery safety and electrochemical performance can be further reduced.

[0008] In any embodiment of this application, 0.2 ≤ H1 ≤ 8, and optionally, 1 ≤ H1 ≤ 5. This allows for improved battery safety while maintaining good electrochemical performance.

[0009] In any embodiment of this application, 0.1 ≤ C1 ≤ 1. The first anion helps to improve the ionic conductivity of the electrolyte, accelerate ion transport, and improve the battery's capacity utilization.

[0010] In any embodiment of this application, 0.1 ≤ C2 ≤ 1.5, and optionally, 0.5 ≤ C2 ≤ 1.5. The second anion can increase the ion dissociation degree of the electrolyte, reduce the viscosity of the electrolyte, and increase the ionic conductivity of the electrolyte. Furthermore, the second anion also has the characteristics of good high-temperature resistance and resistance to hydrolysis, thereby improving the cycle performance of the battery.

[0011] In any embodiment of this application, 0.6 ≤ C1 + C2 ≤ 2.5, and optionally, 0.6 ≤ C1 + C2 ≤ 2.0.

[0012] In any embodiment of this application, 0.1 ≤ C2 / C1 ≤ 5, and optionally, 0.5 ≤ C2 / C1 ≤ 5.

[0013] When the concentrations of the first anion and the second anion satisfy 0.6≤C1+C2≤2.5 and / or 0.1≤C2 / C1≤5, they can inhibit the corrosion of the conductive layer to a certain extent, improve the safety performance of the battery, and also enable the battery to maintain excellent cycle performance.

[0014] In any embodiment of this application, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer. This further improves the safety performance of the battery and avoids thermal runaway problems caused by short circuits between the positive and negative electrodes.

[0015] In any embodiment of this application, the thickness of the organic support layer is H2μm, and the battery satisfies 0.1≤H1 / H2≤1, optionally, 0.2≤H1 / H2≤0.6. This allows for improved battery safety while maintaining good electrochemical performance.

[0016] In any embodiment of this application, the thickness of the organic support layer is H2μm, 1≤H2≤10, and optionally, 4≤H2≤7. This allows for improved battery safety while maintaining high energy density.

[0017] In any embodiment of this application, the total thickness of the positive current collector is H0 μm, 5 ≤ H0 ≤ 15, and optionally, 9 ≤ H0 ≤ 15.

[0018] In any embodiment of this application, the total thickness of the positive electrode current collector is H0 μm, the elongation at break of the positive electrode current collector is S0, and the battery satisfies 5S0–(H0 / 10)≤C1 / C2≤100S0+(H0 / 9). When the battery also satisfies 5S0–(H0 / 10)≤C1 / C2≤100S0+(H0 / 9), the impact of conductive layer corrosion on battery safety and electrochemical performance can be further reduced, thereby enabling the battery to have better safety and electrochemical cycle performance.

[0019] In any embodiment of this application, 2% ≤ S0 ≤ 3.5%.

[0020] In any embodiment of this application, the organic support layer comprises one or more of polymeric materials and polymer-based composite materials.

[0021] In any embodiment of this application, the polymeric material comprises one or more selected from polyolefins, polyacetylenes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyols, polysulfones, polysulfides, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubber, derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials. Optionally, it comprises one or more selected from polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyacetylenes, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polymethyl methacrylate, polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalate), polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polyvinyl alcohol, and poly(4-hydroxymethyl methacrylate). Hydroxybenzoic acid, Poly2 hydroxyl 6 Naphthoic acid, polyaniline, polypyrrole, polythiophene, polystyrene, sodium polystyrene sulfonate, cellulose, starch, silicone rubber, acrylonitrile butadiene One or more of the following: styrene copolymers, derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials. In any embodiment of this application, the polymer-based composite material includes the polymer material and additives, wherein the additives include one or more selected from metallic materials and inorganic non-metallic materials.

[0022] In any embodiment of this application, the conductive layer comprises one or more selected from metallic materials, and optionally includes one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloy, silver alloy, nickel alloy and titanium alloy.

[0023] In any embodiment of this application, R1, R2, and R3 independently represent a fluorine atom, trifluoromethyl, pentafluoroethyl, or heptafluoropropyl.

[0024] In any embodiment of this application, R1 and R2 are the same.

[0025] In any embodiment of this application, the electrolyte further includes a third anion, which includes one or more selected from tetrafluoroborate anion, difluorooxalate-borate anion, dias(oxalate-borate) anion, difluorophosphate anion, difluorodias(oxalate-phosphate) anion, and tetrafluorooxalate-phosphate anion. These anions help to form a high-performance protective film on the surface of the positive and / or negative electrodes, thereby further improving at least one of the battery's cycle performance, rate performance, and storage performance.

[0026] In any embodiment of this application, the battery further includes a negative electrode and a separator, the separator being located between the positive electrode and the negative electrode.

[0027] The second aspect of this application provides a method for preparing a battery, comprising the following steps 1 and 2.

[0028] Step 1: Assemble the positive electrode, separator, negative electrode and electrolyte into a battery.

[0029] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive current collector includes a conductive layer.

[0030] The electrolyte includes a solvent and a solute, wherein the solute is an ionic salt formed by cations and anions. The cations include one or more selected from alkali metal cations and alkaline earth metal cations, and optionally include one or more selected from lithium ions, sodium ions and potassium ions. The anions include a first anion and a second anion. The first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from the anions shown in Formula 1 and Formula 2. R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 can also be bonded to form a ring.

[0031] Formula 1 Formula 2 The thickness of the conductive layer is H1μm, and the concentration of the first anion in the electrolyte is C1mol / L and the concentration of the second anion is C2mol / L.

[0032] Step 2: Select batteries from the batteries obtained in Step 1 that satisfy 0.2×(C2 / C1)≤H1≤(C2 / C1) + 3, and optionally satisfy 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2.

[0033] In any embodiment of this application, the method further includes: step 3, selecting batteries from the batteries obtained in step 2 that satisfy at least one of the following conditions (1) to (9), (1) 0.2≤H1≤8, (2) 1≤H1≤5, (3) 0.1≤C1≤1, (4) 0.1≤C2≤1.5, (5) 0.5 ≤ C2 ≤ 1.5, (6) 0.6 ≤ C1 + C2 ≤ 2.5, (7) 0.6≤C1+C2≤2.0, (8) 0.1≤C2 / C1≤5, (9) 0.5≤C2 / C1≤5.

[0034] In any embodiment of this application, in step 1, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer, the thickness of the organic support layer is H2μm, the total thickness of the positive electrode current collector is H0μm, and the elongation at break of the positive electrode current collector is S0.

[0035] In any embodiment of this application, the method further includes: step 4, selecting batteries from the batteries obtained in step 2 or step 3 that satisfy at least one of the following conditions (1) to (8), (1)5S0– (H0 / 10)≤C1 / C2≤100S0+ (H0 / 9), (2) 0.1 ≤ H1 / H2 ≤ 1, (3) 0.2 ≤ H1 / H2 ≤ 0.6, (4) 1≤H2≤10, (5) 4≤H2≤7, (6) 5≤H0≤15, (7) 9≤H0≤15, (8) 2%≤S0≤3.5%.

[0036] The batteries obtained by the preparation method of this application have both high safety performance and good electrochemical performance.

[0037] A third aspect of this application provides an electrical device, including the battery of the first aspect of this application or a battery prepared by the method of the second aspect of this application.

[0038] The inventors of this application surprisingly discovered through numerous experiments that by adjusting the relationship between the thickness H1 μm of the conductive layer, the concentration C1 mol / L of the first anion, and the concentration C2 mol / L of the second anion to satisfy 0.2 × (C2 / C1) ≤ H1 ≤ (C2 / C1) + 3, the impact of conductive layer corrosion on battery safety and electrochemical performance can be reduced. This allows for improved battery safety while maintaining good electrochemical performance. The electrical device of this application includes the battery provided in this application and therefore possesses at least the same advantages as the battery described above. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of one embodiment of the battery cell of this application.

[0041] Figure 2 This is an exploded view of one embodiment of the battery cell of this application.

[0042] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0043] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0044] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0045] Figure 6 This is a schematic diagram of one embodiment of the positive electrode sheet of this application.

[0046] Figure 7 This is a schematic diagram of another embodiment of the positive electrode sheet of this application.

[0047] Figure 8 This is a schematic diagram of one embodiment of an electrical device that uses the battery of this application as a power source.

[0048] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 101 Positive current collector, 102 Positive active material layer, 1011 Conductive layer, 1012 Organic support layer, 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0049] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery, its manufacturing method, and an electrical device incorporating the same. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0053] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the method may also 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0055] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0056] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0057] To improve battery safety, in addition to enhancing the thermal safety of the materials themselves, optimizations are being made to the electrode assembly design, such as the use of composite current collectors. Composite current collectors typically consist of an organic support layer (or insulating layer) between two conductive layers (e.g., a metal layer). This improves battery safety and prevents thermal runaway caused by short circuits between the positive and negative electrodes. However, to avoid sacrificing battery energy density and to reduce production costs, current technologies typically reduce the thickness of the conductive layer.

[0058] When the electrolyte contains fluorosulfonyl imide salts or fluorosulfonates, it corrodes the conductive layer (e.g., aluminum foil). When the conductive layer is thick, the corrosion is insufficient to significantly affect battery performance. However, the inventors of this application discovered during their research that when the thickness of the conductive layer decreases, even slight corrosion by the electrolyte can significantly impact battery performance. In this case, fluorosulfonyl imide salts and fluorosulfonates in the electrolyte undergo oxidation at the positive electrode. The oxidation products combine with metals (e.g., aluminum) in the conductive layer, and these products further dissolve into the electrolyte, leaving corrosion pits on the conductive layer surface. This can lead to breakage of the positive electrode and even seriously threaten the battery's safety and lifespan.

[0059] Battery In view of the above problems, this application provides a battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte. This application does not impose any particular limitation on the type of battery; for example, the battery may be a lithium-ion battery, a sodium-ion battery, etc., and in particular, the battery may be a lithium-ion rechargeable battery.

[0060] The battery mentioned in the embodiments or implementations of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include battery cells, battery modules, or battery packs. A battery cell is the smallest unit constituting a battery, capable of charging and discharging independently. This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1The example shown is a square-structured battery cell 5.

[0061] In some embodiments, a single battery cell includes an electrode assembly, and the single battery cell may also include an outer packaging. The electrode assembly is made from a positive electrode, a negative electrode, and a separator, etc., through a winding process and / or a stacking process. The outer packaging is used to encapsulate the electrode assembly and the electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0062] In some embodiments, such as Figure 2 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and can be adjusted as needed.

[0063] In some embodiments of this application, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0064] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0065] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack. Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0066] Electrolyte The electrolyte includes a solvent and a solute, wherein the solute is an ionic salt formed by cations and anions. The cations include one or more selected from alkali metal cations and alkaline earth metal cations. The anions include a first anion and a second anion. The first anion includes a hexafluorophosphate anion. The second anion includes one or more selected from the anion shown in Formula 1 (fluorosulfonylimide anion) and the anion shown in Formula 2 (fluorosulfonate anion). R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 can also be bonded to form a ring.

[0067] Formula 1 Formula 2 Currently, the most widely used commercial non-aqueous electrolyte system is a mixed carbonate solution containing hexafluorophosphate. However, hexafluorophosphate has poor thermal stability at high temperatures, decomposing to form PF5 at higher temperatures. PF5 has strong Lewis acidity and interacts with the lone pair electrons on the oxygen atoms in solvent molecules, causing solvent decomposition. Furthermore, PF5 is highly sensitive to trace amounts of water in non-aqueous electrolytes, generating HF upon contact with water. Fluorosulfonyl imide salts and fluorosulfonates have the advantages of high thermal stability and insensitivity to water. Combining them with hexafluorophosphate can significantly improve the thermal stability and cycle performance of batteries.

[0068] In this application, "fluorinated alkyl" refers to a group in which at least one hydrogen atom in an alkyl group is replaced by a fluorine atom. It can be a partially fluorinated alkyl group or a perfluoroalkyl group.

[0069] In some embodiments, R1, R2, and R3 may optionally represent fluorine atoms, trifluoromethyl, pentafluoroethyl, heptafluoropropyl, or nonafluorobutyl, respectively.

[0070] In some embodiments, the second anion may optionally include one or more selected from bis(trifluoromethylsulfonyl)imide anion, bis(pentafluoroethylsulfonyl)imide anion, bis(nonafluorobutylsulfonyl)imide anion, (trifluoromethylsulfonyl)(nonafluorobutylsulfonyl)imide anion, (fluorosulfonyl)(trifluoromethylsulfonyl)imide anion, perfluoropropane disulfonylimide anion, fluorosulfonate anion, and trifluoromethylsulfonate anion.

[0071] In some embodiments, R1 and R2 may be the same.

[0072] In this application, the cation includes one or more selected from alkali metal cations and alkaline earth metal cations. Optionally, the alkali metal cation includes one or more selected from lithium ions, sodium ions, and potassium ions. Optionally, the alkaline earth metal cation includes magnesium ions, calcium ions, or combinations thereof.

[0073] In some embodiments, the cation may optionally include one or more selected from lithium ions, sodium ions, and potassium ions, and more preferably include lithium ions, sodium ions, or combinations thereof.

[0074] In some embodiments, the electrolyte further includes a third anion, the third anion comprising anion selected from tetrafluoroborate anion (BF4). - ), difluorooxalate borate anion (DFOB) - ), dioxaborate anion (BOB) - ), difluorophosphate anion (PO2F2) - ), difluorodioxanol phosphate anion (DFOP) - ) and tetrafluorooxalate phosphate anion (TFOP) - One or more of the following. These anions help to form a high-performance protective film on the surface of the positive and / or negative electrodes, thereby further improving at least one of the battery's cycle performance, rate performance, storage performance, etc.

[0075] This application does not impose specific limitations on the type of solvent, which can be selected according to actual needs. In some embodiments, the solvent may include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonic acid lactone (PS).

[0076] 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 performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0077] In this application, the components and their specific contents in the electrolyte can be determined according to methods known in the art. For example, they can be determined by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), or inductively coupled plasma optical emission spectrometry (ICP-OES).

[0078] [Positive electrode plate] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0079] In some embodiments, the positive current collector includes a conductive layer.

[0080] In some embodiments, the positive electrode current collector may consist only of a conductive layer; alternatively, in some embodiments, the positive electrode current collector may include an organic support layer in addition to the conductive layer. The conductive layer is disposed on at least one surface of the organic support layer and also between the organic support layer and the positive electrode active material layer. For example, the organic support layer has two surfaces opposite each other in its thickness direction, and the conductive layer is disposed on either or both of these opposing surfaces to form a composite current collector. This further improves battery safety performance and prevents thermal runaway caused by short circuits between the positive and negative electrodes.

[0081] When the positive electrode current collector consists only of a conductive layer, the thickness of the conductive layer decreases, the cross-sectional area becomes smaller, and the resistance increases, which can improve the battery's safety performance and increase its energy density. Furthermore, the reduced thickness of the conductive layer improves flexibility, thereby reducing the risk of positive electrode breakage (e.g., winding breakage) during battery manufacturing. However, in this case, the electronic conductivity of the positive electrode current collector deteriorates, and battery polarization is more likely to increase, which is detrimental to the battery's cycle performance and rate performance, while its effect on improving battery safety performance is weaker.

[0082] In some embodiments, the positive electrode current collector optionally includes an organic support layer and a conductive layer disposed on at least one surface of the organic support layer, wherein the conductive layer is disposed between the organic support layer and the positive electrode active material layer. This can significantly improve battery safety performance.

[0083] In this application, the conductive layer can be directly disposed on at least one surface of the organic support layer, or indirectly disposed on at least one surface of the organic support layer. For example, other layers can also be disposed between the conductive layer and the organic support layer.

[0084] In some embodiments, the thickness of the conductive layer is H1 μm, the concentration of the first anion in the electrolyte is C1 mol / L, the concentration of the second anion is C2 mol / L, and the battery satisfies 0.2×(C2 / C1)≤H1≤(C2 / C1) + 3.

[0085] Compared to the first anion, the second anion in the electrolyte (fluorosulfonamide-containing anion and / or fluorosulfonate-containing anion) has the advantages of high thermal stability and insensitivity to water, which can improve the ion dissociation degree and ionic conductivity of the electrolyte, thereby improving the cycle performance of the battery. However, during charging, the second anion undergoes an oxidation reaction at the positive electrode, and its oxidation products combine with the metal (e.g., aluminum) in the conductive layer. Furthermore, the combined products dissolve into the electrolyte, leading to corrosion of the conductive layer.

[0086] In particular, when the positive electrode current collector uses only a thin conductive layer, or when it is a composite current collector formed by a thin conductive layer and an organic support layer, the conductive layer is thinner in the thickness direction than that of a traditional positive electrode current collector (e.g., with a thickness of approximately 12 μm-20 μm). This results in a weaker ability to withstand electrolyte corrosion, leading to a more significant impact of positive electrode current collector corrosion on battery safety and electrochemical performance. For example, corrosion pits may form on the surface of the conductive layer of the positive electrode current collector, leading to problems such as shortened battery life and significantly reduced safety performance. The decomposition products of the first anion (or hexafluorophosphate) (e.g., fluorinated lithium salts) can deposit on the surface of the conductive layer of the positive electrode current collector, thereby inhibiting the corrosion of the conductive layer by the second anion and protecting the conductive layer. However, its protective effect on the conductive layer is limited and insufficient to compensate for the corrosion caused by the second anion.

[0087] Therefore, in existing battery designs, when the electrolyte does not contain a second anion, its thermal stability is poor, resulting in suboptimal battery cycle performance. When the electrolyte contains a second anion, it corrodes the conductive layer, particularly thinner conductive layers, potentially forming corrosion pits on their surface. This can lead to shortened battery life and significantly reduced safety performance. Current batteries, however, require either thin conductive layers used as standalone positive electrode current collectors or composite current collectors formed by combining thin conductive layers with organic support layers to enhance battery safety.

[0088] The inventors of this application made a surprising discovery through numerous experiments: by adjusting the thickness H1μm of the conductive layer and the relationship between the concentrations of the first anion C1mol / L and the second anion C2mol / L to satisfy 0.2×(C2 / C1)≤H1≤(C2 / C1) + 3, the impact of conductive layer corrosion on battery safety and electrochemical performance can be reduced. This allows the battery to maintain good electrochemical performance while improving its safety, such as a longer battery life.

[0089] In some embodiments, optionally, 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2. This can further reduce the impact of conductive layer corrosion on battery safety and electrochemical performance.

[0090] The first anion helps to improve the ionic conductivity of the electrolyte, accelerate ion transport, and enhance battery capacity. In some embodiments, the concentration of the first anion in the electrolyte is C1 mol / L, optionally 0.1 ≤ C1 ≤ 1. For example, C1 can be a range consisting of any value from 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or higher.

[0091] The second anion can increase the ion dissociation degree of the electrolyte, reduce the viscosity of the electrolyte, and increase the ionic conductivity of the electrolyte. Furthermore, the second anion also has good high-temperature resistance and is not easily hydrolyzed, thereby improving the cycle performance of the battery. In some embodiments, the concentration of the second anion in the electrolyte is C2 mol / L, optionally 0.1 ≤ C2 ≤ 1.5. For example, C2 can be any range consisting of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or any of the above values. More preferably, 0.5 ≤ C2 ≤ 1.5.

[0092] In some embodiments, optionally, 0.6 ≤ C1 + C2 ≤ 2.5. For example, C1 + C2 can be a range consisting of 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or any of the above values. More optionally, 0.6 ≤ C1 + C2 ≤ 2.0.

[0093] In some embodiments, optionally, 0.1 ≤ C2 / C1 ≤ 5. For example, C2 / C1 can be a range consisting of any of the values ​​0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, or above. More optionally, 0.5 ≤ C2 / C1 ≤ 5, and 1 ≤ C2 / C1 ≤ 5.

[0094] In some embodiments, optionally, the electrolyte simultaneously satisfies 0.6≤C1+C2≤2.5 and 0.1≤C2 / C1≤5; more preferably, the electrolyte simultaneously satisfies 0.6≤C1+C2≤2.0 and 0.5≤C2 / C1≤5.

[0095] The inventors of this application discovered through numerous experiments that when the concentrations of the first anion and the second anion satisfy 0.6≤C1+C2≤2.5 and / or 0.1≤C2 / C1≤5, it can inhibit the corrosion of the conductive layer to a certain extent, improve the safety performance of the battery, and at the same time enable the battery to maintain excellent cycle performance.

[0096] In some embodiments, the conductive layer may include one or more metallic materials, optionally including one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloys, silver alloys, nickel alloys, and titanium alloys, and more preferably aluminum or aluminum alloys. Aluminum has good electrical conductivity and flexibility, facilitating electron conduction and processing. Furthermore, fresh aluminum foil is easily oxidized in air, thereby forming a protective film on the surface that blocks external moisture and air corrosion, resulting in more stable thermodynamic properties for the aluminum foil or aluminum alloy foil.

[0097] In some embodiments, the organic support layer may include one or more of polymeric materials and polymer-based composite materials.

[0098] In some embodiments, the polymeric material includes one or more selected from polyolefins, polyacetylenes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyols, polysulfones, polysulfides, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubber, derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials.

[0099] Optionally, the polymer material includes materials selected from polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacetylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycarbonate (PC), polymethyl methacrylate (PMMA), polycaprolactam (PA6), polyhexamethylene adipamide (PA66), poly(p-phenylene terephthalamide) (PPTA), polyoxymethylene (POM), polyphenylene ether (PPO), polyphenylene sulfide (PPS), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and poly(4-hydroxymethyl ether). Hydroxybenzoic acid, Poly2 hydroxyl 6 Naphthoic acid, polyaniline (PAN), polypyrrole (PPy), polythiophene (PT), polystyrene, sodium polystyrene sulfonate (PSS), cellulose, starch, silicone rubber, acrylonitrile butadiene One or more of the following: styrene copolymer (ABS), derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials.

[0100] In some embodiments, the polymer-based composite material comprises the polymer material and additives, wherein the additives include one or more selected from metallic materials and inorganic non-metallic materials. This application does not impose specific limitations on the types of metallic and inorganic non-metallic materials, which can be selected according to actual needs.

[0101] In some embodiments, optionally, the thickness H1 μm of the conductive layer satisfies 0.2 ≤ H1 ≤ 8. For example, H1 can be a range consisting of any of the values ​​above 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8. More preferably, 1 ≤ H1 ≤ 5. This can improve battery safety performance while also ensuring good electrochemical performance, such as a longer battery life. It also effectively avoids the following situations: when the conductive layer is too thin, it is not conducive to production and preparation, and there is a risk of it being crushed during cold pressing; when the conductive layer is too thick, it may not effectively improve battery safety performance.

[0102] The positive electrode current collector may consist solely of a conductive layer, or it may include an organic support layer in addition to the conductive layer, with the conductive layer disposed on at least one surface of the organic support layer. In some embodiments, the conductive layer is disposed on one surface of the organic support layer. In some embodiments, the conductive layer is disposed on both surfaces of the organic support layer. It should be noted that the thickness parameter of the conductive layer mentioned above refers to the thickness parameter of the conductive layer located on one side of the organic support layer, or, when the positive electrode current collector consists solely of a conductive layer, the thickness parameter of the conductive layer is the same as the thickness parameter of the positive electrode current collector. When the conductive layer is disposed on both sides of the organic support layer, the thickness of the conductive layer on both sides may be the same or different; the materials of the conductive layers on both sides may be the same or different. Furthermore, when the conductive layer is disposed on both sides of the organic support layer, if the conductive layer parameters (e.g., thickness, material, etc.) on either side satisfy the requirements of this application, it is considered to fall within the protection scope of this application.

[0103] In some embodiments, optionally, the thickness H1 μm of the conductive layer and the thickness H2 μm of the organic support layer satisfy 0.1 ≤ H1 / H2 ≤ 1. For example, H1 / H2 can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or any range of the above values. More preferably, 0.1 ≤ H1 / H2 ≤ 0.8, 0.2 ≤ H1 / H2 ≤ 0.6. This can improve battery safety performance while maintaining good electrochemical performance, such as a longer battery life. It also effectively avoids the following situations: when H1 / H2 is too small, there is a risk of the composite current collector being crushed during cold pressing; when H1 / H2 is too large, it may not effectively improve battery safety performance.

[0104] In some embodiments, optionally, the thickness H2 μm of the organic support layer satisfies 1 ≤ H2 ≤ 10. For example, H2 can be a range consisting of any of the following values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or more. Optionally, 4 ≤ H2 ≤ 7. This allows for both improved battery safety and high energy density.

[0105] Optionally, in some embodiments, the total thickness of the positive current collector, H0 μm, satisfies 5 ≤ ​​H0 ≤ 15. For example, H0 can be a range consisting of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, or any of the above values. More preferably, 9 ≤ H0 ≤ 15. In this application, the total thickness of the positive current collector refers to the sum of the thicknesses of the organic support layer and the conductive layers located on both sides of the organic support layer.

[0106] The inventors of this application also discovered during the research process that the elongation at break of the positive electrode current collector S0 is related to the total thickness of the positive electrode current collector H0μm, the concentration of the first anion C1mol / L and the concentration of the second anion C2mol / L. When C1 / C2 is larger, H0 is larger, and the elongation at break of the positive electrode current collector S0 is larger.

[0107] The elongation at break of the positive electrode current collector refers to the rate of change of its stretched length upon fracture. Comparing a normal positive electrode current collector with a corroded one, it can be seen that when the tensile force is equal, the corroded current collector, due to its inherent defects, fractures at a shorter stretched length, resulting in a lower elongation at break. Besides being related to corrosion, the elongation at break of the positive electrode current collector is also related to its thickness; the thicker the current collector, the greater its elongation at break. A low elongation at break of the positive electrode current collector indicates that the positive electrode is more prone to fracture under the same force. After fracture, the positive electrode active material on the electrode cannot be used, leading to a significant reduction in battery capacity and a marked decline in cycle performance. Furthermore, the fractured positive electrode is conductive; when it comes into contact with the negative electrode, it can directly cause a short circuit within the battery, creating a safety hazard and affecting battery safety performance.

[0108] During the research process, the inventors of this application also unexpectedly discovered that when the battery also satisfies 5S0– (H0 / 10)≤C1 / C2≤100S0+ (H0 / 9), the impact of conductive layer corrosion on battery safety and electrochemical performance can be further reduced, thereby enabling the battery to have better safety and electrochemical cycle performance.

[0109] In some embodiments, optionally, the elongation at break S0 of the positive current collector satisfies 2% ≤ S0 ≤ 3.5%. For example, S0 can be a range consisting of any value of 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, or higher.

[0110] In some embodiments, the positive electrode active material layer comprises a positive electrode active material.

[0111] When the battery of this application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0112] In some embodiments, to further improve the energy density of the battery, the positive electrode active material for lithium-ion batteries may include materials with the general formula LiNi. x Co y M z O 2-p A p One or more of the following lithium transition metal oxides: LiMn2O4, aLi2MnO3·(1-a)LiQO2, and their respective modified compounds. In the general formula LiNi x Co y M z O 2-p A p In the formula aLi₂MnO₃·(1-a)LiQO₂, M includes one or more selected from Mn, Al, Mg, Cu, Zn, Zr, Fe, Sn, B, Ga, Cr, Sr, V, and Ti; A includes one or more selected from N, F, S, and Cl; 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1, and 0≤p≤1. In the general formula aLi₂MnO₃·(1-a)LiQO₂, Q includes one or more selected from Ni, Co, Mn, Fe, Ti, Cr, and Zr; 0<a<1.

[0113] As an example, positive electrode active materials for lithium-ion batteries may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiMn2O4, aLi2MnO3·(1-a)LiMnO2, LiFePO4 and LiMnPO4.

[0114] When the battery of this application is a sodium-ion battery, the positive electrode active material may include, but is not limited to, one or more of sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.) and Prussian blue materials.

[0115] As an example, positive electrode active materials for sodium-ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes elements selected from H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, optionally including one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, optionally including one or more selected from F, Cl and Br.

[0116] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0117] In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some embodiments, the positive electrode active material layer may further include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0119] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone, but is not limited to this.

[0120] The positive electrode of this application is described below with reference to the accompanying drawings.

[0121] Figure 6 This is a schematic diagram of one embodiment of the positive electrode 10 of this application. (See diagram below.) Figure 6 As shown, the positive electrode 10 includes a positive current collector 101 and a positive active material layer 102 disposed on two surfaces of the positive current collector 101. The positive current collector 101 includes an organic support layer 1012 and a conductive layer 1011 disposed on two surfaces of the organic support layer. The conductive layer 1011 is disposed between the organic support layer 1012 and the positive active material layer 102.

[0122] Figure 7 This is a schematic diagram of another embodiment of the positive electrode 10 of this application. (See diagram below.) Figure 7 As shown, the positive electrode 10 includes a positive current collector 101 and a positive active material layer 102 disposed on one surface of the positive current collector 101. The positive current collector 101 includes an organic support layer 1012 and a conductive layer 1011 disposed on one surface of the organic support layer. The conductive layer 1011 is disposed between the organic support layer 1012 and the positive active material layer 102.

[0123] [Negative electrode plate] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative active material layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0124] In some embodiments, the negative electrode active material layer comprises a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, mesophase microcarbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium aluminum alloys. The silicon-based material may include one or more selected from elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more selected from elemental tin, tin oxides (e.g., SnO, SnO2), and tin alloys (e.g., Li-Sn alloys, Li-Sn-O alloys).

[0125] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more selected from styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0127] In some embodiments, the negative electrode active material layer may further include other additives. For example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0128] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0129] The negative electrode active material layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone or deionized water, but is not limited to these.

[0130] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode active material layer.

[0131] [Isolation membrane] The separator is located between the positive and negative electrode plates, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0132] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0133] Preparation method This application also provides a method for preparing a battery, including the following steps 1 and 2.

[0134] Step 1: Assemble the positive electrode, separator, negative electrode and electrolyte into a battery.

[0135] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive current collector includes a conductive layer.

[0136] The electrolyte includes a solvent and a solute, wherein the solute is an ionic salt formed by cations and anions. The cations include one or more selected from alkali metal cations and alkaline earth metal cations, and optionally include one or more selected from lithium ions, sodium ions and potassium ions. The anions include a first anion and a second anion. The first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from the anions shown in Formula 1 and Formula 2. R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 can also be bonded to form a ring.

[0137] The thickness of the conductive layer is H1μm, and the concentration of the first anion in the electrolyte is C1mol / L and the concentration of the second anion is C2mol / L.

[0138] Formula 1 Formula 2 Step 2: Select batteries from the batteries obtained in Step 1 that satisfy 0.2×(C2 / C1)≤H1≤(C2 / C1) + 3, and optionally satisfy 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2.

[0139] In some embodiments, in step 1, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer, the thickness of the organic support layer is H2μm, the total thickness of the positive electrode current collector is H0μm, and the elongation at break of the positive electrode current collector is S0.

[0140] In some embodiments, the method further includes: step 3, selecting from the batteries obtained in step 2 batteries that satisfy at least one of the following conditions (1) to (9), (1) 0.2≤H1≤8, (2) 1≤H1≤5, (3) 0.1≤C1≤1, (4) 0.1≤C2≤1.5, (5) 0.5 ≤ C2 ≤ 1.5, (6) 0.6 ≤ C1 + C2 ≤ 2.5, (7) 0.6≤C1+C2≤2.0, (8) 0.1≤C2 / C1≤5, (9) 0.5≤C2 / C1≤5.

[0141] In some embodiments, the method further includes: step 4, selecting batteries from the batteries obtained in step 2 or step 3 that satisfy at least one of the following conditions (1) to (8), (1)5S0– (H0 / 10)≤C1 / C2≤100S0+ (H0 / 9), (2) 0.1 ≤ H1 / H2 ≤ 1, (3) 0.2 ≤ H1 / H2 ≤ 0.6, (4) 1≤H2≤10, (5) 4≤H2≤7, (6) 5≤H0≤15, (7) 9≤H0≤15, (8) 2%≤S0≤3.5%.

[0142] The batteries obtained by the preparation method of this application have both high safety performance and good electrochemical performance.

[0143] In some embodiments, the battery fabrication method in step 1 is well-known. For example, a positive electrode, a separator, and a negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained. Multiple battery cells can further be connected in series, parallel, or a hybrid configuration to form a battery module. Multiple battery modules can also be connected in series, parallel, or a hybrid configuration to form a battery pack. In some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0144] Electrical appliances This application also provides an electrical device, which includes the battery described in this application. The battery can be used as a power source for the electrical device or as an energy storage unit. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0145] The electrical device can select the specific type of battery according to its usage requirements, such as a battery cell, battery module, or battery pack.

[0146] Figure 8This is a schematic diagram illustrating an example of an electrical device. This device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used as the power source.

[0147] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0148] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0149] The batteries in Examples 1-17 and Comparative Examples 1-3 were prepared according to the following method.

[0150] Preparation of electrolyte In an argon-filled glove box (water content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30:70 to obtain an organic solvent. Then, 2 wt% of vinylene carbonate (VC) was added to the organic solvent, followed by the addition of thoroughly dried lithium salts to prepare the electrolyte. The types and concentrations of lithium salts are shown in Table 1.

[0151] Preparation of positive electrode sheet Aluminum foil is placed in a mechanical roller and rolled into a conductive layer of predetermined thickness by applying a pressure of 20-40 tons. Then, a mixed solution of polyvinylidene fluoride (PVDF) and NMP is coated onto the surface of the surface-cleaned organic support layer, polyethylene terephthalate (PET). Finally, the conductive layer of predetermined thickness is bonded to both surfaces of the organic support layer and dried to ensure a tight bond, thus obtaining the positive electrode current collector. The specific thickness parameters of the conductive layer and the organic support layer are shown in Table 2.

[0152] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3O2 (NCM523), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of solvent NMP at a mass ratio of 80:10:10 to form a positive electrode slurry with a solid content of 50wt%. The positive electrode slurry is uniformly coated on the surface of the positive electrode current collector prepared above, and after drying and cold pressing, a positive electrode sheet is obtained.

[0153] Preparation of negative electrode sheet The negative electrode active material graphite, conductive agent carbon black (Super P), thickener sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber (SBR) are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 80:15:3:2 to form a negative electrode slurry with a solid content of 30 wt%. The negative electrode slurry is uniformly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0154] Preparation of the separating membrane A porous polyethylene membrane with a thickness of 16 μm was used as the separator.

[0155] Battery manufacturing The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain the electrode assembly. The electrode assembly is placed in the outer packaging, dried, and then injected with electrolyte. After vacuum sealing, standing, formation, and shaping, a soft-pack battery is obtained.

[0156] Table 1

[0157] Table 2

[0158] Test section (1) Needle prick test At 25°C, the battery was charged at a constant current of 1C to 4.2V, and then charged at a constant voltage of 4.2V until the current was less than or equal to 0.05C. A high-temperature resistant steel needle with a diameter of 3mm was used to puncture the center of the battery surface at a speed of 0.1mm / s until the battery ran out of control. The state of the battery during thermal runaway was recorded.

[0159] (2) Cyclic performance test At 25℃, the battery was charged at a constant current of 1C to 4.2V, and then charged at a constant voltage of 4.2V until the current was less than or equal to 0.05C. At this point, the battery was fully charged, and the charging capacity was recorded as the first charge capacity. After the battery was left to rest for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This constituted one charge-discharge cycle, and the discharge capacity was recorded as the first discharge capacity. The battery was subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle was recorded. The battery capacity retention rate (%) after 500 cycles at 25℃ = discharge capacity after 500 cycles / discharge capacity of the first cycle × 100%. For accuracy, the average value of 5 parallel samples was used as the test result.

[0160] Table 3

[0161] The test results in Table 3 show that by adjusting the relationship between the thickness of the conductive layer (H1μm), the concentration of the first anion (C1mol / L), and the concentration of the second anion (C2mol / L) to satisfy 0.2×(C2 / C1)≤H1≤(C2 / C1) +3, and optionally 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2, the safety and cycle performance of the battery can be significantly improved. At this point, the probability of the battery catching fire is significantly reduced, and the adverse effects of increased corrosion caused by the reduction in the thickness of the conductive layer on the battery cycle performance can also be significantly reduced.

[0162] Based on the test results of Examples 1, 11 and Comparative Example 1, it can be seen that when the electrolyte composition is the same, the conductive layer of Comparative Example 1 is thinner. Therefore, even if the conductive layer is slightly corroded by the electrolyte, it will significantly affect the safety performance and cycle performance of the battery.

[0163] Based on the test results of Examples 3, 6-9 and Comparative Example 2, it can be seen that when the electrolyte composition is the same, the conductive layer of Comparative Example 2 is thicker, which causes the condition 0.2×(C2 / C1) + 0.2≤H1≤(C2 / C1) + 2 to not be met. In this case, the conductivity of the positive current collector is stronger, and even with the use of an organic support layer, it cannot effectively prevent short circuits between the positive and negative electrodes, resulting in poor battery safety performance. In addition, because the conductive layer of Comparative Example 2 is thicker, it is not conducive to heat dissipation during cycling. In this case, there are more side reactions inside the battery, which in turn leads to poor battery cycle performance.

[0164] Comparative Example 3 uses ordinary 12μm thick aluminum foil as the positive electrode current collector. It has low resistance and good conductivity. As a result, the positive and negative electrodes are prone to short circuit during the nail penetration test, which leads to poor battery safety performance. At the same time, compared with the composite current collector formed by the conductive layer and the organic support layer, the positive electrode current collector using pure aluminum foil has poor heat preservation performance, which in turn leads to poor dynamic performance on the positive electrode side of the battery. The lithium insertion and extraction resistance of the positive electrode is large during charging and discharging, which easily triggers more side reactions. Therefore, the cycle performance of the battery is also poor.

[0165] Based on the test results of Examples 1-17, it can also be seen that when the battery further satisfies 5S0– (H0 / 10)≤C1 / C2≤100S0+ (H0 / 9), it is beneficial to further improve the battery's safety performance and cycle performance.

[0166] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery comprising a positive electrode and an electrolyte, wherein, The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive current collector includes a conductive layer. The electrolyte comprises a solvent and a solute, wherein the solute is an ionic salt formed by cations and anions. The cations include one or more selected from alkali metal cations and alkaline earth metal cations, and optionally include one or more selected from lithium ions, sodium ions, and potassium ions. The anions include a first anion and a second anion. The first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from the anions shown in Formula 1 and Formula 2. R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 may also be bonded together to form a ring. Formula 1 Formula 2 The thickness of the conductive layer is H1 μm, 0.2≤H1≤8; the concentration of the first anion in the electrolyte is C1 mol / L and the concentration of the second anion is C2 mol / L, 0.1≤C1≤1 and 0.1≤C2≤1.

5.

2. The battery according to claim 1, wherein, 3≤H1≤4, 0.1≤C1≤0.5, 0.5≤C2≤1.5; or, 2.5≤H1≤4, 0.1≤C1≤0.5, 0.5≤C2≤1.

2.

3. The battery according to claim 1 or 2, wherein, 1≤H1≤5; and / or, 0.5≤C2≤1.5。 4. The battery according to any one of claims 1-3, wherein, 0.6 ≤ C1 + C2 ≤ 2.5, optionally, 0.6 ≤ C1 + C2 ≤ 2.0; and / or, 0.1≤C2 / C1≤5, optionally, 0.5≤C2 / C1≤5.

5. The battery according to any one of claims 1-4, wherein, The positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer.

6. The battery according to claim 5, wherein, The thickness of the organic support layer is H2 μm, and the battery satisfies 0.1≤H1 / H2≤1, optionally, 0.2≤H1 / H2≤0.

6.

7. The battery according to claim 5 or 6, wherein, The thickness of the organic support layer is H2 μm, 1≤H2≤10, and optionally, 4≤H2≤7.

8. The battery according to any one of claims 5-7, wherein, The total thickness of the positive electrode current collector is H0 μm, 5≤H0≤15, and optionally, 9≤H0≤15.

9. The battery according to any one of claims 5-8, wherein, The total thickness of the positive electrode current collector is H0 μm, the elongation at break of the positive electrode current collector is S0, and the battery satisfies 5S0 – (H0 / 10)≤C1 / C2≤100S0 + (H0 / 9).

10. The battery according to claim 9, wherein, 2%≤S0≤3.5%。 11. The battery according to any one of claims 5-10, wherein, The organic support layer comprises one or more of polymeric materials and polymer-based composite materials. The polymeric material includes one or more selected from polyolefins, polyacetylenes, polyesters, polycarbonates, polyacrylates, polyamides, polyimides, polyethers, polyols, polysulfones, polysulfide polymers, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, polyurethanes, thermoplastic elastomers, rubber, derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials. Optionally, it includes materials selected from polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyacetylenes, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polymethyl methacrylate, polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalate), polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polyvinyl alcohol, and poly(4-hydroxymethyl methacrylate). Hydroxybenzoic acid, Poly2 hydroxyl 6 Naphthoic acid, polyaniline, polypyrrole, polythiophene, polystyrene, sodium polystyrene sulfonate, cellulose, starch, silicone rubber, acrylonitrile butadiene One or more of the following: styrene copolymers, derivatives of the above materials, crosslinks of the above materials, and copolymers of the above materials. The polymer-based composite material includes the polymer material and additives, wherein the additives include one or more selected from metallic materials and inorganic non-metallic materials.

12. The battery according to any one of claims 1-11, wherein, The conductive layer comprises one or more selected from metallic materials, and optionally includes one or more selected from aluminum, silver, nickel, titanium, stainless steel, aluminum alloy, silver alloy, nickel alloy and titanium alloy.

13. The battery according to any one of claims 1-12, wherein, R1, R2, and R3 independently represent a fluorine atom, a trifluoromethyl atom, a pentafluoroethyl atom, or a heptafluoropropyl atom; and / or, R1 and R2 are the same.

14. The battery according to any one of claims 1-13, wherein, The electrolyte further includes a third anion, which includes one or more selected from tetrafluoroborate anion, difluorooxalate-borate anion, dioxalate-borate anion, difluorophosphate anion, difluorodioxalate-phosphate anion, and tetrafluorooxalate-phosphate anion.

15. The battery according to any one of claims 1-14, wherein, The battery also includes a negative electrode and a separator, the separator being located between the positive electrode and the negative electrode.

16. A method for preparing a battery, comprising the following steps: Step 1: Assemble the positive electrode, separator, negative electrode, and electrolyte into a battery. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive current collector includes a conductive layer. The electrolyte comprises a solvent and a solute, wherein the solute is an ionic salt formed by cations and anions. The cations include one or more selected from alkali metal cations and alkaline earth metal cations, and optionally include one or more selected from lithium ions, sodium ions, and potassium ions. The anions include a first anion and a second anion. The first anion includes a hexafluorophosphate anion, and the second anion includes one or more selected from the anions shown in Formula 1 and Formula 2. R1, R2, and R3 each independently represent a fluorine atom or a C1-C5 fluorinated alkyl group. R1 and R2 may also be bonded together to form a ring. Formula 1 Formula 2 The thickness of the conductive layer is H1 μm, and the concentration of the first anion in the electrolyte is C1 mol / L and the concentration of the second anion is C2 mol / L; Step 2: Select batteries from the batteries obtained in Step 1 that satisfy 0.2≤H1≤8, 0.1≤C1≤1, 0.1≤C2≤1.5, optionally satisfy 3≤H1≤4, 0.1≤C1≤0.5, 0.5≤C2≤1.5, or optionally satisfy 2.5≤H1≤4, 0.1≤C1≤0.5, 0.5≤C2≤1.

2.

17. The method according to claim 16, wherein, The method further includes: step 3, selecting batteries from the batteries obtained in step 2 that satisfy at least one of the following conditions. （2）1≤H1≤5， （5）0.5≤C2≤1.5， (6) 0.6 ≤ C1 + C2 ≤ 2.5, (7) 0.6≤C1+C2≤2.0, (8) 0.1≤C2 / C1≤5, (9) 0.5≤C2 / C1≤5.

18. The method according to claim 16 or 17, wherein, In step 1, the positive electrode current collector further includes an organic support layer, the conductive layer is disposed on at least one surface of the organic support layer, and the conductive layer is also disposed between the organic support layer and the positive electrode active material layer. The thickness of the organic support layer is H2 μm, the total thickness of the positive electrode current collector is H0 μm, and the elongation at break of the positive electrode current collector is S0.

19. The method according to claim 18, wherein, The method further includes: step 4, selecting batteries from the batteries obtained in step 2 or step 3 that satisfy at least one of the following conditions (1) to (8), (1)5S0 – (H0 / 10)≤C1 / C2≤100S0 + (H0 / 9), (2) 0.1 ≤ H1 / H2 ≤ 1, (3) 0.2 ≤ H1 / H2 ≤ 0.6, （4）1≤H2≤10， （5）4≤H2≤7， （6）5≤H0≤15， （7）9≤H0≤15， （8）2%≤S0≤3.5%。 20. An electrical device comprising a battery according to any one of claims 1-15 or a battery prepared by the method according to any one of claims 16-19.

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