Electrode sheet and preparation method therefor, and battery and electric apparatus

Abstract

An electrode sheet and a preparation method therefor, and a battery and an electric apparatus. The electrode sheet comprises a current collector, and an active layer and a composite film layer, which are sequentially arranged on at least one side of the current collector, wherein the active layer comprises an active material and a functional additive, and the composite film layer comprises a polymer and a porous material. When the electrode sheet is used for preparing a battery, the cycling stability of the battery can be improved.

Description

Electrode sheet and preparation method thereof, battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese Patent Application No. 202410044463.1 filed on January 11, 2024, entitled “Electrode Sheet and Preparation Method thereof, Battery and Electrical Device”, which is incorporated into this application in its entirety by reference. Technical Field

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

[0004] Secondary batteries are becoming increasingly popular due to their clean and renewable characteristics, and have been widely used in many fields such as consumer electronics, electric vehicles, and energy storage.

[0005] With the expansion of the application fields of secondary batteries, people have higher and higher requirements for the cycle stability of secondary batteries. The cycle stability of traditional secondary batteries can hardly meet people's increasingly stringent requirements for secondary battery performance.

[0006] Therefore, traditional technologies still need to be further improved.

[0007] Summary of the Invention

[0008] Based on this, it is necessary to provide an electrode sheet and a preparation method thereof, a battery and an electrical device, aiming to improve the cycle stability performance of the battery.

[0009] In a first aspect of the present application, an electrode sheet is provided, comprising a current collector and an active layer and a composite membrane layer sequentially disposed on at least one side of the current collector;

[0010] The active layer includes active materials and functional additives, and the composite membrane layer includes polymers and porous materials.

[0011] In the above-mentioned electrode sheet, the surface of the current collector is provided with an active layer and a composite membrane layer in sequence, the active material layer contains functional additives, and the composite membrane layer contains polymers and porous materials. On the one hand, the dense nature of the polymer after film formation is utilized to make the composite membrane layer play a role in binding the functional additives, thereby slowing down the diffusion of the functional additives in the active layer into the electrolyte; on the other hand, the porous material contained in the composite membrane layer can provide an ion transmission channel so that the composite membrane layer maintains good ion transmission capacity, and the pores of the porous material also increase the tortuosity of the outward diffusion path of the functional additives in the active layer, further improving the binding force on the functional additives. The synergistic effect of various aspects, when the above-mentioned electrode sheet is used to prepare a battery, reduces the probability of the functional additives diffusing into the solution during the charge and discharge process, not only making the functional additives stably and continuously play a role on the electrode sheet, but also reducing the probability of adverse reactions of the functional additives due to diffusion into the solution, thereby improving the cycle stability of the battery.

[0012] It should be noted that a polymer is a substance composed of multiple high molecular chains, and the molecular chains are entangled with each other or act on the surface of an object to form a film through electrostatic effects, van der Waals forces, hydrogen bonds or chemical cross-linking.

[0013] In some embodiments, in the composite membrane layer, the porous material accounts for 10% to 80% by mass.

[0014] In some embodiments, in the composite membrane layer, the porous material accounts for 40% to 60% by mass.

[0015] In some embodiments, the thickness of the composite film layer is 0.1 μm to 5 μm.

[0016] In some embodiments, the thickness of the composite film layer is 0.5 μm to 2 μm.

[0017] The thickness of the composite membrane layer is regulated to improve the ability to slow down the diffusion of functional additives in the active layer while maintaining the good ion transmission capability of the composite membrane layer.

[0018] In some embodiments, the polymer comprises a polymer of formula (I):

[0019] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0020] In some embodiments, the polymer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyethylene sulfonate, or polystyrene.

[0021] The above polymer has good oxidation resistance and is better adapted to the chemical environment of the positive electrode. When the charging voltage reaches 4.3V, it is difficult for oxidation reaction to occur.

[0022] In some embodiments, the polymer is supported on at least a portion of the outer surface of the porous material and the inner surface of the pore structure of the porous material.

[0023] It can be understood that the porous material includes an outer surface and an inner surface of the pore structure, and the molecular chains in the polymer will be entangled on the outer surface or the inner surface of the pore structure or pass through the pore structure, thereby loading at least part of the outer surface or inner surface of the porous material, thereby being tightly compounded with the porous material.

[0024] In some embodiments, the functional additive satisfies at least one of the following conditions (1) to (2):

[0025] (1) The functional additive includes at least one of a physical adsorption type battery additive or a chemical reaction type battery additive;

[0026] (2) The functional additive is a solid functional additive.

[0027] In some embodiments, the porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve, or an organometallic framework material.

[0028] In some embodiments, the porous material satisfies at least one of the following conditions (1) to (4):

[0029] (1) The inorganic aerogel includes at least one of silica aerogel, titania aerogel, zirconia aerogel, alumina aerogel, magnesia aerogel, vanadium oxide aerogel, boron nitride aerogel or titanium nitride aerogel;

[0030] (2) The organic aerogel includes at least one of polymethyl methacrylate aerogel, polystyrene aerogel, or polyimide aerogel;

[0031] (3) The molecular sieve includes at least one of a microporous silica-alumina molecular sieve, a mesoporous silica-alumina molecular sieve, or a macroporous silica-alumina molecular sieve;

[0032] (4) The organic metal framework material comprises at least one of a zeolite imidazole framework, a dimethyl imidazole cobalt, an iron-containing organic metal framework material, a zinc-containing organic metal framework material, or a chromium-containing organic metal framework material. In some embodiments, the mass ratio of the functional additive to the active material is (0.1-2):(94-99).

[0033] In some embodiments, the active layer satisfies at least one of the following conditions (1) to (2):

[0034] (1) The active layer further includes a conductive agent; the conductive agent accounts for 0.5% to 2% by mass in the active layer;

[0035] (2) The active layer further includes a binder; the binder accounts for 0.5% to 2% by mass in the active layer.

[0036] In some embodiments, the electrode sheet is a positive electrode sheet.

[0037] In a second aspect of the present application, a method for preparing an electrode sheet is provided, comprising the following steps:

[0038] An active layer is formed on at least one side of a current collector using an active slurry; the active slurry includes an active material and a functional additive;

[0039] A composite film layer is formed on the surface of the active layer away from the current collector by using a composite slurry to prepare an electrode sheet; the composite slurry includes a polymer and a porous material.

[0040] In some embodiments, the porous material satisfies at least one of the following conditions (1) to (3):

[0041] (1) The pore size of the porous material is 0.1 nm to 100 nm;

[0042] (2) The porosity of the porous material is 80% to 99.8%;

[0043] (3) The volume average particle size of the porous material is 0.1 μm to 5 μm.

[0044] By regulating the porosity and pore size of the porous material, the porosity and pore size of the formed composite membrane layer can be further regulated. While maintaining a good barrier effect on the functional additives in the active layer, its ion transmission capacity is improved, thereby further improving the cycle performance of the battery.

[0045] In a third aspect of the present application, a battery is provided, comprising the electrode sheet according to the first aspect or the electrode sheet prepared by the method for preparing the electrode sheet according to the second aspect.

[0046] In a fourth aspect of the present application, an electrical device is provided, comprising at least one of the electrode sheet of the first aspect, the electrode sheet produced by the method for producing the electrode sheet of the second aspect, and the battery of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0048] FIG1 is a schematic diagram of an embodiment of a battery cell;

[0049] Figure 2 is an exploded view of Figure 1;

[0050] FIG3 is a schematic diagram of an embodiment of a battery pack;

[0051] FIG4 is an exploded view of FIG3 ;

[0052] FIG5 is a schematic diagram of an embodiment of an electrical device using a battery as a power source;

[0053] FIG6 is an electron microscope image of a slice of the composite film layer prepared in Example 1.

[0054] Description of reference numerals:

[0055] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover; 5. Electrical device. DETAILED DESCRIPTION

[0056] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0058] In this application, unless otherwise specified, all operating steps are carried out at room temperature, and "room temperature" generally refers to 4°C to 30°C, preferably 20±5°C.

[0059] In this application, the unit "°C" means degrees Celsius.

[0060] In this application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen, such as methane loses a hydrogen to form a methyl group; "alkenyl or alkynyl" refers to a group formed when an alkene or alkyne loses a hydrogen, such as ethylene loses a hydrogen to form vinyl, and acetylene loses a hydrogen to form ethynyl.

[0061] In the present application, the number of carbon atoms in the "alkyl group having 1 to 5 carbon atoms" may be 1 to 5, including 1, 2, 3, 4, and 5. Non-limiting examples include methane, ethyl, and n-propyl.

[0062] In the present application, the term "substituted or unsubstituted" means that the functional group described after the term may or may not have a substituent.

[0063] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0064] In this application, "aryl" refers to a hydrocarbon group containing at least one aromatic ring, including non-fused-ring aromatic groups and fused-ring aromatic groups. A fused-ring aromatic group is a group formed by linking two or more aromatic rings through two common adjacent ring atoms, i.e., a fused ring.

[0065] Aromatic ring refers to a cyclic hydrocarbon compound with aromatic properties: that is, a hydrocarbon compound with a cyclic closed-ring conjugated system.

[0066] In the present application, "heteroaromatic group" refers to a group formed when a hydrocarbon compound containing a heteroatom loses a hydrogen atom and has a cyclic closed-ring conjugated system; further, the type of heteroatom can be N, O, P, S, etc.

[0067] In this application, the term "ring atoms" refers to the number of atoms bonded to form a ring. When a ring is substituted with a substituent, the atoms contained in the substituent are not included in the ring atoms. The term "ring atoms" used below applies unless otherwise specified. For example, a benzene ring has 6 ring atoms, and a naphthalene ring has 10 ring atoms.

[0068] In traditional technology, adding functional additives to the electrode sheet can improve the interface stability of the electrode sheet and thus improve the cycle performance of the battery.

[0069] However, further research found that when functional additives are doped on the electrode sheets, during the charge and discharge process of the battery, especially in battery systems such as electrolyte systems or gel electrolyte systems that use solvents as the main ion transmission channels, the functional additives easily diffuse into the electrolyte, failing to achieve the purpose of stable function, and will also react with the solvent to produce adverse effects, which will in turn have an adverse effect on the battery's cycle performance.

[0070] Based on this, after a lot of experimental research, the technical solution of this application was obtained.

[0071] In one embodiment of the present application, an electrode sheet is provided, which includes a current collector and an active layer and a composite membrane layer sequentially arranged on at least one side of the current collector; the active layer includes active materials and functional additives, and the composite membrane layer includes a polymer and a porous material.

[0072] In the above-mentioned electrode sheet, the surface of the current collector is provided with an active layer and a composite membrane layer in sequence, the active material layer contains functional additives, and the composite membrane layer contains polymers and porous materials. On the one hand, the dense nature of the polymer after film formation is utilized to make the composite membrane layer play a role in binding the functional additives, thereby slowing down the diffusion of the functional additives in the active layer into the electrolyte; on the other hand, the porous material contained in the composite membrane layer can provide an ion transmission channel so that the composite membrane layer maintains good ion transmission capacity, and the pores of the porous material also increase the tortuosity of the outward diffusion path of the functional additives in the active layer, further improving the binding force on the functional additives. The synergistic effect of various aspects, when the above-mentioned electrode sheet is used to prepare a battery, reduces the probability of the functional additives diffusing into the solution during the charge and discharge process, not only making the functional additives stably and continuously play a role on the electrode sheet, but also reducing the probability of adverse reactions of the functional additives due to diffusion into the solution, thereby improving the cycle stability of the battery.

[0073] It should be noted that a polymer is a substance composed of multiple high molecular chains, and the molecular chains are entangled with each other or act on the surface of an object to form a film through electrostatic effects, van der Waals forces, hydrogen bonds or chemical cross-linking.

[0074] In some embodiments, the porous material comprises an open-pore structure.

[0075] Open pore structure refers to the pores in porous materials that are connected to the outside world.

[0076] In some embodiments, the porosity of the composite membrane layer is 20% to 90%.

[0077] In some of the embodiments, the porosity of the composite membrane layer is further regulated to improve its ion transport capability while maintaining a good barrier effect on the functional additives in the active layer, thereby further improving the cycle performance of the battery.

[0078] Specifically, the porosity of the composite membrane layer mainly depends on the ratio of the polymer and the porous material, that is, the porosity of the composite membrane layer can indirectly reflect the ratio of the polymer and the porous material.

[0079] In the above-mentioned "20% to 90%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%; or a range consisting of any two values, for example, it can be 20% to 80%, 20% to 70%, 20% to 60%, 20% to 50%, 20% to 40%, 30% to 80%, 40% to 80%, 50% to 80%, 60% to 80%, 70% to 80%, 20% to 70%, 30% to 60%, 30% to 50%, 50% to 70% or 20% to 70%.

[0080] In some embodiments, the polymer is supported on at least a portion of the outer surface of the porous material and the inner surface of the pore structure of the porous material.

[0081] It can be understood that the porous material includes an outer surface and an inner surface of the pore structure, and the molecular chains in the polymer will be entangled on the outer surface or the inner surface of the pore structure or pass through the pore structure, thereby loading at least part of the outer surface or inner surface of the porous material, thereby being tightly compounded with the porous material.

[0082] Based on the total area of ​​the inner and outer surfaces of the porous material, the area of ​​the surface loaded with the polymer accounts for 50% to 100%.

[0083] Alternatively, the area fraction of the surface loaded with polymer may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%.

[0084] In some embodiments, in the composite membrane layer, the porous material accounts for 10% to 80% by mass.

[0085] In some embodiments, in the composite membrane layer, the porous material accounts for 40% to 60% by mass.

[0086] In the above-mentioned "10% to 80%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%; or a range consisting of any two values, for example, it can be 10% to 80%, 10% to 70%, 10% to 60%, 10% to 50%, 10% to 40%, 20% to 80%, 30% to 80%, 40% to 80%, 50% to 80%, 60% to 80%, 30% to 70%, 30% to 60%, 30% to 50%, 40% to 70%, 50% to 70%.

[0087] In some embodiments, in the composite film layer, the polymer accounts for 20% to 90% by weight.

[0088] In some embodiments, in the composite film layer, the polymer accounts for 40% to 60% by weight.

[0089] In the above-mentioned "20% to 90%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%; or a range consisting of any two values, for example, it can be 10% to 80%, 10% to 70%, 10% to 60%, 10% to 50%, 10% to 40%, 20% to 80%, 30% to 80%, 40% to 80%, 50% to 80%, 60% to 80%, 30% to 70%, 30% to 60%, 30% to 50%, 40% to 70%, 50% to 70%.

[0090] In some embodiments, the thickness of the composite film layer is 0.1 μm to 5 μm.

[0091] In this application, the unit "μm" means micrometer.

[0092] In some embodiments, the thickness of the composite film layer is 0.5 μm to 2 μm.

[0093] The thickness of the composite membrane layer is regulated to improve the ability to slow down the diffusion of functional additives in the active layer while maintaining the good ion transmission capability of the composite membrane layer.

[0094] In the above “0.1μm~5μm”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm; or any two values The range of the composition can be, for example, 0.1μm to 0.5μm, 0.1μm to 1μm, 0.1μm to 2μm, 0.1μm to 3μm, 0.2μm to 4μm, 0.3μm to 5μm, 1μm to 2μm, 1μm to 3μm, 1μm to 4μm, 1μm to 5μm, 2μm to 3μm, 2μm to 4μm, 2μm to 5μm, 3μm to 4μm, 3μm to 5μm, 4μm to 5μm.

[0095] In some embodiments, the thickness of the active layer is 30 μm to 60 μm.

[0096] In the above-mentioned "30μm~60μm", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm; or a range consisting of any two values.

[0097] In some embodiments, the electrode sheet is a positive electrode sheet.

[0098] In some embodiments, the polymer comprises a polymer represented by formula (I):

[0099] wherein R1 and R2 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a cyano group, a halogen group, a substituted or unsubstituted aromatic group having 6 to 10 ring atoms, a substituted or unsubstituted heteroaromatic group having 5 to 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group or a carbonate group, and n is the degree of polymerization.

[0100] The above polymer has good oxidation resistance and is better adapted to the chemical environment of the positive electrode. When the charging voltage reaches 4.3 volts (V), it is difficult for oxidation reaction to occur.

[0101] Furthermore, the electrochemical oxidation potential test method of the above polymer can adopt the following steps:

[0102] The above polymer is dissolved in an organic solvent to form a transparent solution, and then the transparent solution is poured on a template. After the solvent evaporates, a polymer film can be obtained.

[0103] The polymer film is cut into a suitable size, and then the polymer film and the stainless steel positive and negative electrodes are assembled into a symmetrical simulated battery according to the structure of SS (stainless steel sheet) / polymer film / SS (stainless steel sheet). Subsequently, a cyclic voltammetry test is performed on it using an electrochemical workstation: the voltage range is 0-4.3V. If there is no sharp increase in current during the test, it is determined that the electrochemical oxidation potential of the polymer is greater than or equal to 4.3V.

[0104] In some embodiments, R1 and R2 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, an aromatic group having 6 to 10 ring atoms, an aromatic group having 6 to 10 ring atoms substituted by a halogen, a heteroaromatic group having 5 to 10 ring atoms, a heteroaromatic group having 5 to 10 ring atoms substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0105] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0106] In some embodiments, the cation in the sulfonate group may be NH4 + , at least one of alkali metal ions; further, the alkali metal ions include at least one of potassium ions, lithium ions or sodium ions.

[0107] In some embodiments, R1 and R2 are independently selected from any one of H, a chain alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, a cyano group, a halogen, a phenyl group, a phenyl group substituted by a halogen, a pyrrolyl group, a pyrrolone group, a pyrrolyl group substituted by a halogen, a pyrrolone group substituted by a halogen, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a carbonic acid group, or a carbonate group.

[0108] In some embodiments, R1 and R2 are independently selected from any one of H, methyl, ethyl, propyl, methyl substituted by chlorine, ethyl substituted by chlorine, propyl substituted by chlorine, cyano, halogen, phenyl, phenyl substituted by halogen, pyrrol, pyrrolone, pyrrol substituted by halogen, pyrrolone substituted by halogen, sulfonic acid, sulfonate, carboxylic acid, carboxylate, carbonic acid or carbonate.

[0109] In some embodiments, the polymer film layer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyethylene sulfonate, or polystyrene.

[0110] In some embodiments, the functional additive includes at least one of a physical adsorption type battery additive or a chemical reaction type battery additive.

[0111] It is understandable that the above functional additives may be electrode additives commonly used in the art, including but not limited to at least one of electrolyte additives and electrode additives.

[0112] In some embodiments, the functional additive includes at least one of a film-forming additive, an acid-binding agent, a flame retardant additive, an overcharge protection additive, an additive for improving low-temperature performance, or an additive for improving high-temperature performance.

[0113] As an example: the above-mentioned additives include lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluoroborate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, methyl trifluoroethyl carbonate, trifluoropropylene carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, vinyl acetate, propane sultone, butane sultone, propene sultone, fluoropropane sultone, vinyl sulfate, dimethylsiloxane, trimethylsilyl trifluoromethanesulfonate, vinyltrimethoxysilane, dimethyl phenylphosphonate, dimethyl benzylphosphonate, and at least one of succinonitrile.

[0114] In some embodiments, the functional additive is a solid functional additive.

[0115] Additives in solid form are easier to stably dope into the active layer.

[0116] It can be understood that solid functional additives are in solid state at 25°C and normal pressure.

[0117] In some embodiments, the functional additives include but are not limited to at least one of lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, lithium tetrafluorooxalatophosphate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, and succinonitrile.

[0118] In some embodiments, the porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve, or an organometallic framework material.

[0119] In some embodiments, the inorganic aerogel may include at least one of silica aerogel, titania aerogel, zirconia aerogel, alumina aerogel, magnesia aerogel, vanadium oxide aerogel, boron nitride aerogel, or titanium nitride aerogel.

[0120] In some embodiments, the organic aerogel includes a polymer aerogel; as an example, the organic gel may include at least one of polymethyl methacrylate aerogel, polystyrene aerogel, or polyimide aerogel.

[0121] In some embodiments, the molecular sieve may include at least one of a microporous silica-alumina (SiO 2 / Al 2 O 3 ) molecular sieve, a mesoporous silica-alumina molecular sieve, or a macroporous silica-alumina molecular sieve.

[0122] In some embodiments, the organic metal framework material includes at least one of a zeolite imidazole framework, cobalt dimethyl imidazole, an organic metal framework material containing iron, an organic metal framework material containing zinc, or an organic metal framework material containing chromium.

[0123] In some embodiments, the organometallic framework may include ZIF-8 (C8H 12 N4.Zn, zeolite imidazole framework-8), ZIF-67 (C8H 12 N4.Co, dimethyl imidazole cobalt), MIL-100 (C9H6O6Fe, 1,3,5-pyromellitic acid iron), MIL-101 (C 24 H 16 Cr3FO 15 , tris[M-[1,4-benzenedicarboxylic acid (2-)]-chloro-M3-oxotriCr), or MOF-5(Zn4O(C8H6O4)3×(HCON(CH3)2)8(C6H5Cl), zinc, tris[[-[1,4-benzenedicarboxylic acid (2-)-KO1).

[0124] In some embodiments, the mass ratio of the functional additive to the active material is (0.1-2):(94-99).

[0125] In some embodiments, the electrode sheet is a positive electrode, and the active material is a positive electrode active material. The positive electrode active material can be selected from common positive electrode active materials in the art, including but not limited to: positive electrode active materials for lithium ion batteries, positive electrode active materials for sodium ion batteries, and positive electrode active materials for potassium ion batteries.

[0126] The positive electrode active material of a lithium ion battery, the positive electrode active material of a sodium ion battery and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material or potassium ion active material, respectively.

[0127] Further, as an example, the lithium ion active material may include at least one of the following 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 NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or its modified compounds. Examples of lithium phosphates containing olivine structures may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4, referred to as LFP), lithium manganese phosphate (such as LiMnPO4) or lithium manganese iron phosphate. In any embodiment of the present application, the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO4, x is any number from 0 to 1.

[0128] It can be understood that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4 lithium manganese phosphate. When x is 1, LiFe x Mn (1-x)PO4 is LiFePO4 lithium iron phosphate (LFP).

[0129] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charge and discharge process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0130] For example, LiFe x Mn (1-x) PO4 can be further expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0131] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x , y is 0.2~1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn or Al, and A is one or more of S, N, F, Cl, Br or I.

[0132] The battery is accompanied by Li intercalation and deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery. Furthermore, the battery voltage is usually between 2V and 5V.

[0133] In some embodiments, the above-mentioned active material includes a high-voltage positive electrode active material; further, the above-mentioned active material includes a nickel-containing active material; for example, it can be at least one of a nickel-containing ternary material, lithium nickel cobalt oxide, lithium nickel manganese oxide or lithium nickel cobalt manganese oxide; more specifically, it can be at least one of lithium nickel manganese cobalt oxide, nickel manganese spinel or nickel-rich lithium manganese oxide.

[0134] As an example, the sodium ion active material may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, or a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0135] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr or Cu, and 0<x≤1.

[0136] 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. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce; Y includes at least one of P, S or Si; n represents (YO4) n- valence.

[0137] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y includes at least one of P, S, or Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl or Br.

[0138] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and a class of compounds containing an optional halogen anion. Y includes at least one of P, S or Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce, m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl or Br.

[0139] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7)(NFPP), NaM1PO4F or Na3(VO y )2(PO4)2F (3-2y) At least one of .

[0140] M1 is at least one of V, Fe, Mn or Ni, and 0≤y≤1.

[0141] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce. Prussian blue compounds are, for example, Na a M2 b M3 c (CN)6, wherein M2 and M3 are each independently selected from at least one of Ni, Cu, Fe, Mn, Co or Zn, 0<a≤2, 0<b<1, 0<c<1.

[0142] In some embodiments, the active layer further includes a conductive agent.

[0143] In some embodiments, the conductive agent accounts for 0.5% to 2% by mass in the active layer.

[0144] In any embodiment of the present application, the conductive agent may be any commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene, or composite conductive agents thereof.

[0145] In some embodiments, the active layer further includes a binder.

[0146] In some embodiments, the binder accounts for 0.5% to 2% by weight in the active layer.

[0147] In any embodiment of the present application, the binder of the above-mentioned binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, 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) or at least one of fluorine-containing acrylate resin and polyvinyl butyral (PVB).

[0148] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector, for example, a metal foil such as aluminum foil.

[0149] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0150] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.

[0151] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0152] It can be understood that the current collector has two surfaces arranged opposite to each other in its own thickness direction, and an active layer and a composite membrane layer are sequentially provided on at least one surface. It can be one of the surfaces or both surfaces at the same time.

[0153] It should be noted that "the active layer and the composite film layer are sequentially arranged on at least one side of the current collector" means that at least part of the area of ​​the two corresponding projection surfaces formed by the orthographic projection of the active layer and the composite film layer on the same plane overlap; optionally, based on the total area of ​​the projection surface of the active layer, the area of ​​the overlapping part of its projection surface and the projection surface of the composite film layer may be 20% to 100%, which can be optionally 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0154] In one embodiment of the present application, a method for preparing the electrode sheet is provided, comprising the following steps S10 to S20.

[0155] Step S10: forming an active layer on at least one side of the current collector using an active slurry; the active slurry includes an active material and a functional additive.

[0156] The types of active materials and functional additives are selected as above and will not be described in detail here.

[0157] Step S20: using a composite slurry to form a composite film layer on the surface of the active layer away from the current collector to prepare an electrode sheet; the composite slurry includes a polymer and a porous material.

[0158] The types of polymer and porous material are selected as above and will not be described in detail here.

[0159] In some embodiments, the active slurry includes a solvent; further, the solid content of the active slurry is 40 wt % to 80 wt %, and the viscosity at 25° C. is adjusted to 5000 mPa·s to 25000 mPa·s.

[0160] In this application, the unit "mPa·s" refers to millipascal·second.

[0161] In some embodiments, the solvent includes, but is not limited to, at least one of water, N-methylpyrrolidone, and dimethylformamide.

[0162] In some embodiments, the steps of forming the active layer in step S10 are specifically as follows:

[0163] The active slurry is coated on the current collector and dried to form an active layer.

[0164] In some embodiments, the composite slurry includes a solvent; optionally, the solvent includes but is not limited to at least one of N-methylpyrrolidone and dimethylformamide.

[0165] In some embodiments, the solid content of the composite slurry is 0.1 wt% to 50 wt%.

[0166] In some embodiments, the pore size of the porous material is 0.1 nm to 100 nm.

[0167] In this application, the unit "nm" refers to nanometers.

[0168] Optionally, the pore size of the porous material is 0.5 nm to 100 nm.

[0169] In the above-mentioned "0.1nm~100nm", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.1nm, 0.5nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm; or a range consisting of any two numerical values, for example, it can be 0.3nm~1nm, 1nm~10nm, 10nm~50nm, 10nm~40nm, 10nm~30nm, 10nm~20nm, 20nm~50nm, 20nm~40nm, 20nm~30nm, 30nm~50nm.

[0170] It can be understood that the pore size of a porous material refers to the diameter of the pores of the porous material.

[0171] In some embodiments, the porosity of the porous material is 80% to 99.8%.

[0172] In the above-mentioned "80% to 99.8%", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 90%, 91%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.8%; or a range consisting of any two values.

[0173] In some embodiments, the volume average particle size of the porous material is 0.1 μm to 5 μm.

[0174] In the above "0.1μm~5μm", the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm; or a range consisting of any two values.

[0175] By regulating the porosity and pore size of the porous material, the porosity and pore size of the formed composite membrane layer can be further regulated. While maintaining a good barrier effect on the functional additives in the active layer, its ion transmission capacity is improved, thereby further improving the cycle performance of the battery.

[0176] In some embodiments, the method for forming the composite film layer in step S20 may adopt a coating preparation method commonly used in the art, including but not limited to: an immersion method, a coating method, and the like.

[0177] In some embodiments, the method for forming the composite film layer in step S20 is an immersion method; further, the method specifically includes the following steps:

[0178] The product obtained in step S10 is immersed in the composite slurry and then dried.

[0179] Specifically, the thickness of the formed composite membrane layer can be regulated by controlling the solid content of the composite slurry or the immersion time.

[0180] One embodiment of the present application further provides a battery, which includes the above-mentioned electrode sheet.

[0181] In some embodiments, the battery is a secondary battery.

[0182] In some embodiments, the electrode sheet is a positive electrode sheet, and the negative electrode sheet in the battery can adopt various negative electrode sheet systems in the art, which are illustrated here by way of example but are not limited to the following.

[0183] In some embodiments, the battery may be a lithium metal secondary battery or a lithium ion secondary battery.

[0184] In some embodiments, the battery is a lithium metal secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for lithium metal batteries as is known in the art.

[0185] In some embodiments, the negative electrode sheet directly adopts a lithium-containing metal sheet.

[0186] In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer stacked together.

[0187] Furthermore, the lithium-containing metal in the lithium-containing metal sheet and the lithium-containing metal layer can be lithium metal, or an alloy formed by lithium metal and other metal or non-metal elements.

[0188] Further, the other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In) or platinum (Pt); the non-metallic elements include at least one of boron (B), carbon (C) or silicon (Si).

[0189] In some embodiments, the conductive layer may be copper foil.

[0190] In any embodiment of the present application, the negative electrode sheet can be prepared by directly pressing a lithium-containing metal sheet to obtain the negative electrode sheet, or by stacking and pressing the lithium-containing metal layer and the conductive layer to obtain the negative electrode sheet.

[0191] In some embodiments, the battery is a lithium-ion secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used in lithium-ion batteries and is well known in the art.

[0192] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active layer supported on a surface of the current collector.

[0193] The components of the negative electrode active layer include a negative electrode active material.

[0194] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0195] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials or iron-based materials.

[0196] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal or lithium metal alloys.

[0197] In any embodiment of the present application, the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0198] In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0199] In any embodiment of the present application, the negative electrode conductive agent may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, or graphene. Specifically, the negative electrode conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene, or composite conductive agents thereof.

[0200] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0201] The negative electrode binder may be a binder commonly used in the art, and may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) or carboxymethyl chitosan (CMCS).

[0202] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

[0203] In any embodiment of the present application, the negative electrode active layer may further optionally include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of the other additives in the negative electrode active layer is 0 to 15 wt%.

[0204] In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil.

[0205] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0206] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver or silver alloy.

[0207] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0208] In any embodiment of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned 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 to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0209] In some embodiments, the solvent includes but is not limited to water.

[0210] In some embodiments, the solid content of the negative electrode slurry is 30 wt % to 70 wt %, and the viscosity at 25° C. is adjusted to 2000 mPa·s to 10000 mPa·s.

[0211] In some embodiments, the surface density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm 2 ~0.03g / cm 2 .

[0212] In this application, the unit "g / cm 2 ” refers to grams per square centimeter.

[0213] The area density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0214] In some embodiments, the battery further includes a separator and an electrolyte. Examples of the separator and the electrolyte are described below, including but not limited to the following.

[0215] Depending on its form, the electrolyte can be either an electrolyte solution or a gel electrolyte, both of which contain a solvent as a charge transfer medium. Generally, the electrolyte solution includes an electrolyte salt and a solvent; the gel electrolyte mainly includes an electrolyte salt, a solvent and a polymer matrix.

[0216] The presence of the polymer matrix makes the gel electrolyte exhibit semi-solid characteristics.

[0217] In some embodiments, the electrolyte salt may be selected from electrolyte salts commonly used in the art, such as lithium ion electrolyte salts.

[0218] As an example, the lithium ion electrolyte 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 difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) or lithium tetrafluorooxalatophosphate (LiTFOP).

[0219] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), 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), butylene 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) or diethyl sulfone (ESE).

[0220] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is generally 0.5 mol / L to 15 mol / L.

[0221] In some embodiments, the polymer matrix includes, but is not limited to, at least one of polyethylene oxide, polyacrylates, polyvinylidene fluoride, polyacrylonitrile, and polyvinyl chloride.

[0222] Diaphragm: The diaphragm is placed between the positive electrode and the negative electrode.

[0223] The type of the diaphragm of the present application can be any known porous structure diaphragm with good chemical stability and mechanical stability.

[0224] In some embodiments, the separator can be made of at least one of fiberglass, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can 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 can be the same or different.

[0225] The thickness of the diaphragm is controlled to be 2 μm to 15 μm; optionally, the thickness of the diaphragm is controlled to be 2 μm to 13 μm.

[0226] The present application has no particular limitation on the shape of the battery, and the shape of the battery of the present application can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 4 of a square structure as an example.

[0227] In some embodiments, referring to FIG2 , the housing may include a shell 41 and a cover 43. Shell 41 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. Shell 41 may have an opening communicating with the receiving cavity, and cover 43 may be positioned over the opening to seal the receiving cavity.

[0228] The positive electrode sheet, separator and negative electrode sheet can be wound or laminated to form an electrode assembly 42, which is encapsulated in the receiving cavity. The number of electrode assemblies 42 included in the battery cell 4 can be one or more, which can be adjusted according to needs.

[0229] The battery includes one or more battery cells 4 .

[0230] The battery may be a battery module or a battery pack; the battery module or battery pack includes at least one battery cell 4. The number of battery cells contained in the battery module may be one or more, and those skilled in the art may select an appropriate number based on the application and capacity of the battery module.

[0231] Figures 3 and 4 illustrate an exemplary battery pack 1. Battery pack 1 includes a battery case and one or more battery cells 4 disposed within the battery case. The battery case comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for the battery cells 4.

[0232] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0233] The present application also provides an electrical device, which includes the above-mentioned battery.

[0234] Furthermore, in the above-mentioned electrical device, the battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0235] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.

[0236] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0237] In some embodiments, the mobile device may be a mobile phone or a laptop computer, etc.

[0238] In some embodiments, 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, electric trucks, and the like.

[0239] Figure 5 shows an example of an electric device 5. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 5, a battery pack can be used.

[0240] As another example, the power-consuming 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.

[0241] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0242] The following are specific examples.

[0243] The raw materials used in the following examples and comparative examples were all purchased from the market unless otherwise specified.

[0244] Example 1

[0245] (1) Preparation of positive electrode

[0246] S1: A polymer (polyacrylonitrile, number average molecular weight of 50,000) and a porous material (alumina aerogel) were added to an organic solvent DMF in a mass ratio of 60:40 to prepare a composite slurry. The solid content of the composite slurry was 1 wt%.

[0247] Among them, the pore size and porosity of the porous material used in the above steps can be tested by gas adsorption test method. The instrument used is a specific surface area and porosity analyzer. The specific steps are: place the sample to be tested in the sample tube of the instrument, evacuate, immerse the sample tube in liquid nitrogen, fill it with a known amount of gas, and measure the equilibrium pressure of the gas after reaching adsorption equilibrium. Gradually increase the amount of gas to the system to change the pressure. Repeat the operation to obtain the adsorption and desorption isotherm, and the pore size and porosity of the porous material sample to be tested are calculated to be 30nm and 95%, respectively.

[0248] The volume average particle size of the porous material was measured using a Malvern laser particle size analyzer, and the volume average particle size was found to be 2.5 μm.

[0249] In the composite slurry, the mass proportion of the porous material is recorded as Y1 based on the total mass of the porous material and the polymer.

[0250] S2: The positive electrode active material (lithium nickel cobalt manganese oxide, NCM811), conductive agent (SuperP), binder (PVDF), and functional additive (lithium difluorooxalatoborate) are mixed in a mass ratio of 97wt%:1.5wt%:1wt%:0.5wt%, NMP is added and stirred evenly to obtain a positive electrode active slurry with a solid content of 70%.

[0251] S3: The positive electrode active slurry was coated on the surface of the current collector (carbon-coated aluminum foil, thickness of 17 μm), dried to remove NMP, and a positive electrode active layer with a thickness of 50 μm was obtained, with a surface capacity of 3.5 mAh / cm2. 2 ); then immersed in the composite slurry for 100s (seconds), taken out and dried in a vacuum oven to remove DMF, forming a composite film layer to obtain a positive electrode sheet.

[0252] It should be noted that, in the process of preparing the composite membrane layer using the composite slurry, the solvent in the composite slurry is evaporated, and Y1 is the mass proportion of the porous material in the composite membrane layer.

[0253] Furthermore, the ratio of the main components of the composite film layer can be tested by inductively coupled plasma optical emission spectrometry (ICP-OES): Y1 can be reversely deduced based on the ratio of characteristic elements of the porous material and the polymer, such as aluminum and nitrogen.

[0254] The slice of the positive electrode was placed under a scanning electron microscope for imaging. The electron microscope image is shown in Figure 6. Obvious stratification can be observed (as shown by the dotted line in the figure), and the composite film layer is far away from the current collector. Further analysis of the element distribution information marked by the scanning electron microscope shows that the characteristic element aluminum of the porous material of the composite film layer (alumina aerogel) can be captured. A pore structure can be observed at the location of the characteristic element aluminum, and the outer surface and the inner surface of the pore structure are loaded with polymers.

[0255] Furthermore, the thickness of the positive electrode active layer and the composite film layer can be characterized by scanning electron microscopy. The average value of the thickness of the composite film layer is recorded as Y2. The specific parameters are shown in Table 1.

[0256] (2) A 50 μm thick lithium foil was selected and rolled and composited with a 12 μm thick copper foil to obtain a negative electrode sheet.

[0257] (3) Preparation of electrolyte

[0258] Lithium hexafluorophosphate (LiPF6) is dissolved in an organic solvent and stirred to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0259] The organic solvent is a mixed solution of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 50:50.

[0260] (4) A polyethylene film with a thickness of 12 μm was selected as the separator.

[0261] (5) Battery assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked and combined, and wrapped with aluminum-plastic film bags to form a stacked dry cell. The configured electrolyte is injected, vacuum-sealed, and allowed to stand at room temperature for 6 hours to obtain a battery for subsequent testing.

[0262] (6) Cyclic performance test

[0263] The above-mentioned battery was electrochemically cycled at room temperature (25°C) using a 0.5C constant current and constant voltage charge, followed by a 0.5C constant current and constant voltage discharge test condition. The charge and discharge cutoff voltages were set at 4.3V and 2.8V, respectively. The specific constant current and constant voltage charging conditions were as follows: when charging at a 0.5C constant current to a cutoff voltage of 4.3V, charging at a 4.3V constant voltage was continued until the current dropped to 0.05C, followed by discharging at a 0.5C constant current to 2.8V. One charge-discharge cycle was defined as one cycle. When the capacity decay rate of the battery after discharge reached 80%, the battery life was considered to have ended. The number of cycles at this point was recorded and recorded as Cy80%.

[0264] Please see Table 1 for specific test results.

[0265] Examples 2 to 5

[0266] Examples 2 to 5 are basically the same as Example 1, with the only difference being that the immersion time in the composite slurry in step S3 is different from that in Example 1. The immersion times of Examples 2 to 5 are 10s, 50s, 200s, and 500s, respectively, so that the thickness of the formed composite film layer is different from that in Example 1.

[0267] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0268] Examples 6 to 10

[0269] Examples 6 to 10 are basically the same as Example 1, with the only difference being that in step S1, while keeping the solid content of the composite slurry the same as that in Example 1, the mass ratio of the polymer and the porous material is adjusted differently from that in Example 1. In Example 6, the mass ratio of the polymer and the porous material is 90:10, in Example 7, the mass ratio of the polymer and the porous material is 80:20, in Example 8, the mass ratio of the polymer and the porous material is 50:50, in Example 9, the mass ratio of the polymer and the porous material is 40:60, and in Example 10, the mass ratio of the polymer and the porous material is 20:80.

[0270] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0271] Examples 11 to 15

[0272] Examples 11 to 15 are substantially the same as Example 1, with the only difference being that in step S1 , the type of porous material is different from that in Example 1.

[0273] Specifically, the porous material used in Example 11 is silicon oxide, and the pore size, porosity and volume average particle size are 50nm, 98% and 3μm respectively; the porous material used in Example 12 is polyimide aerogel (number average molecular weight is 50,000), and the pore size, porosity and volume average particle size are 40nm, 80% and 3μm respectively; the porous material used in Example 13 is microporous silica alumina (Si / Al molar ratio is 25), and the pore size, porosity and volume average particle size are 0.5nm, 60% and 150nm respectively; the porous material used in Example 14 is ZIF-8, and the pore size, porosity and volume average particle size are 0.5nm, 80% and 300nm respectively; the porous material used in Example 15 is MOF-5, and the pore size, porosity and volume average particle size are 1nm, 80% and 20μm respectively.

[0274] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0275] Examples 16 to 18

[0276] Examples 16 to 18 are substantially the same as Example 1, except that in step S1, the type of polymer used is different from that in Example 1. Specifically, the polymer used in Example 16 is polypropylene (number average molecular weight of 50,000), the polymer used in Example 17 is polyethylene (number average molecular weight of 50,000), and the polymer used in Example 18 is polystyrene (number average molecular weight of 50,000).

[0277] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0278] Examples 19 to 21

[0279] Examples 19 to 21 are substantially the same as Example 1, except that in step S2, the mass ratios of the positive electrode active material, the conductive agent, the binder, and the functional additive are different from those in Example 1. See Table 1 for details.

[0280] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0281] Examples 22 to 25

[0282] Examples 22 to 25 are basically the same as Example 1, with the only difference being that in step S2, the type of functional additive is different from that in Example 1, while the quality remains the same as that in Example 1.

[0283] Specifically, the functional additive used in Example 22 is lithium dioxalatoborate, the functional additive used in Example 23 is lithium difluorophosphate, and the functional additive used in Example 24 is tetrafluorooxalic acid.

[0284] Lithium phosphate, the functional additive used in Example 25 is succinonitrile.

[0285] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0286] Comparative Example 1

[0287] Comparative Example 1 is basically the same as Example 1, except that the positive electrode sheet is different from that in Example 1, and is specifically prepared as follows:

[0288] The positive electrode active material (lithium nickel cobalt manganese oxide, NCM811), conductive agent (SuperP), and binder (PVDF) were mixed in a mass ratio of 97.5wt%:1.5wt%:1wt%, and NMP was added and stirred evenly to obtain a positive electrode active slurry with a solid content of 70%. The positive electrode active slurry was coated on the surface of the positive electrode current collector carbon-coated aluminum foil and dried to obtain a positive electrode sheet with a surface capacity of 3.5mAh / cm 2 .

[0289] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0290] Comparative Example 2

[0291] Comparative Example 2 is basically the same as Comparative Example 1, except that the positive electrode sheet is different from that in Example 1. The specific preparation is as follows:

[0292] The positive electrode active material (lithium nickel cobalt manganese oxide, NCM811), conductive agent (SuperP), binder (PVDF), and additive (lithium difluorooxalatoborate) were mixed in a mass ratio of 97 wt%: 1.5 wt%: 1 wt%: 0.5 wt%, and NMP was added and stirred evenly to obtain a positive electrode active slurry with a solid content of 70%. The positive electrode active slurry was coated on the surface of the positive electrode current collector carbon-coated aluminum foil, and dried to remove the NMP to obtain a positive electrode sheet with an areal capacity of 3.5 mAh / cm 2 .

[0293] The other steps are the same as those in Comparative Example 1. Please see Table 1 for specific parameters.

[0294] Comparative Example 3

[0295] Comparative Example 3 is basically the same as Example 1, except that the positive electrode sheet is different from that in Example 1, and is specifically prepared as follows:

[0296] The polymer (polyacrylonitrile), porous material (alumina aerogel) and functional additive (lithium difluorooxalatoborate) are added to the organic solvent DMF in a mass ratio of 59:40:1 to prepare a composite slurry. When the solid content of the composite slurry is 1wt%, Y1 represents the mass proportion of the porous material based on the total mass of the porous material, polymer and functional additive.

[0297] The positive electrode active material (lithium nickel cobalt manganese oxide, NCM811), the conductive agent (SuperP), and the binder (PVDF) were mixed at a mass ratio of 97 wt%:1.5 wt%:1.5 wt%, and NMP was added and stirred evenly to obtain a positive electrode active slurry with a solid content of 70%.

[0298] The positive electrode active slurry was coated on the surface of the current collector (carbon-coated aluminum foil) and dried to remove NMP to obtain a positive electrode active layer with a surface capacity of 3.5 mAh / cm 2 ; Then soak it in the composite slurry for 30 seconds, take it out and dry it in a vacuum oven to remove DMF, forming a composite film layer to obtain a positive electrode sheet.

[0299] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0300] Comparative Example 4

[0301] Comparative Example 4 is basically the same as Example 1, except that no porous material is added in step S1. The specific steps are as follows:

[0302] A polymer (polyacrylonitrile, number average molecular weight of 50,000) was added to an organic solvent DMF to obtain a composite slurry with a solid content of 1 wt%.

[0303] The other steps are the same as those in Example 1. Please see Table 1 for specific parameters.

[0304] The relevant parameters and performance test results of each embodiment and comparative example are shown in Table 1. Among them, the mass ratio of the porous material in the composite film layer is recorded as Y1, the thickness of the composite film layer is recorded as Y2, and the mass ratio of the positive electrode active material, conductive agent, binder, and functional additive in the positive electrode active layer is recorded as W.

[0305] Table 1

[0306] Where, “\” represents the absence of the substance or parameter. “ZIF-8” represents zeolitic imidazole framework-8, and “MOF-5” represents zinc tris[[-[1,4-benzenedicarboxylic acid (2-)-KO1].

[0307] By analyzing the data in Table 1 and comparing the data of Examples 1 to 25 with those of Comparative Examples 1 to 4, it can be seen that the electrode sheet of the present application can improve the cycle stability of the battery.

[0308] 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.

[0309] 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. It should be noted that a person skilled in the art could make several modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the appended claims, and the specification and drawings may be used to interpret the claims.

Claims

1. An electrode sheet, the electrode sheet comprising a current collector and an active layer and a composite film layer sequentially provided on at least one side of the current collector; The active layer includes an active material and a functional additive, and the composite film layer includes a polymer and a porous material.

2. The electrode sheet according to claim 1, wherein, In the composite film layer, the mass ratio of the porous material is 10% - 80%.

3. The electrode sheet according to claim 1 or 2, wherein, In the composite film layer, the mass ratio of the porous material is 40% - 60%.

4. The electrode sheet according to any one of claims 1 to 3, wherein, The thickness of the composite film layer is 0.1 μm - 5 μm.

5. The electrode sheet according to any one of claims 1 to 4, wherein, The thickness of the composite film layer is 0.5 μm - 2 μm.

6. The electrode sheet according to any one of claims 1 to 5, wherein, The polymer includes a polymer of formula (I): Wherein, R1 and R2 are each independently selected from any one of H, a substituted or unsubstituted alkyl group with 1 - 5 carbon atoms, a cyano group, a halogen, a substituted or unsubstituted aromatic group with 6 - 10 ring atoms, a substituted or unsubstituted heteroaromatic group with 5 - 10 ring atoms, a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylic acid ester group, a carbonate group or a carbonate ester group, and n is the degree of polymerization.

7. The electrode sheet according to any one of claims 1 to 6, wherein, The polymer includes at least one of polyethylene, polyvinyl chloride, polypropylene, polyacrylonitrile, sodium polyvinyl sulfonate or polystyrene.

8. The electrode sheet according to any one of claims 1 to 7, wherein, The polymer is loaded on at least part of the outer surface of the porous material and the inner surface of the pore structure of the porous material.

9. The electrode sheet according to any one of claims 1 to 8, wherein, The functional additive satisfies at least one of the following conditions (1) - (2): (1) The functional additive includes at least one of a physically adsorbed battery additive or a chemically reactive battery additive; (2) The functional additive is a solid functional additive.

10. The electrode sheet according to any one of claims 1 to 9, wherein, The porous material includes at least one of an inorganic aerogel, an organic aerogel, a molecular sieve or a metal-organic framework material.

11. The electrode sheet according to claim 10, wherein, The porous material satisfies at least one of the following conditions (1) - (4): (1) The inorganic aerogel includes at least one of silica aerogel, titanium dioxide aerogel, zirconium dioxide aerogel, aluminum oxide aerogel, magnesium oxide aerogel, vanadium oxide aerogel, boron nitride aerogel or titanium nitride aerogel; (2) The organic aerogel includes at least one of poly(methyl methacrylate) aerogel, polystyrene aerogel or polyimide aerogel; (3) The molecular sieve includes at least one of a microporous silica-aluminum molecular sieve, a mesoporous silica-aluminum molecular sieve or a macroporous silica-aluminum molecular sieve; (4) The metal-organic framework material includes at least one of a zeolitic imidazolate framework, cobalt dimethylimidazole, an iron-containing metal-organic framework material, a zinc-containing metal-organic framework material or a chromium-containing metal-organic framework material.

12. The electrode sheet according to any one of claims 1 to 11, wherein, The mass ratio of the functional additive to the active material is (0.1 - 2):(94 - 99).

13. The electrode sheet according to any one of claims 1 to 12, wherein, The active layer satisfies at least one of the following conditions (1) - (2): (1) The active layer further includes a conductive agent; the mass ratio of the conductive agent in the active layer is 0.5% - 2%; (2) The active layer further includes a binder; the mass ratio of the binder in the active layer is 0.5% - 2%.

14. The electrode sheet according to any one of claims 1 to 13, wherein, The electrode sheet is a positive electrode sheet.

15. A method for preparing an electrode sheet, comprising the following steps: Forming an active layer on at least one side of a current collector using an active slurry; the active slurry includes an active material and a functional additive; A composite film layer is formed on the surface of the active layer away from the current collector by using a composite slurry to prepare an electrode sheet; the composite slurry includes a polymer and a porous material.

16. The method for preparing the electrode sheet according to claim 15, wherein, The porous material satisfies at least one of the following conditions (1) to (3): (1) The pore diameter of the porous material is 0.1 nm to 100 nm; (2) The porosity of the porous material is 80% to 99.8%; (3) The volume average particle size of the porous material is 0.1 μm to 5 μm.

17. A battery, the battery includes the electrode sheet according to any one of claims 1 to 14 or the electrode sheet prepared by the preparation method of the electrode sheet according to any one of claims 15 to 16.

18. An electrical device, the electrical device includes at least one of the electrode sheet according to any one of claims 1 to 14, the electrode sheet prepared by the preparation method of the electrode sheet according to any one of claims 15 to 16, and the battery according to claim 17.

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