Battery cell, battery device, power consuming device, and energy storage device

Abstract

Embodiments of the present application provide a battery monomer, a battery device, a power consumption device and an energy storage device. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer arranged on at least one side of the positive electrode current collector, and a functional layer arranged on the side of the positive electrode film layer away from the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a layered transition metal oxide, the layered transition metal oxide comprises a component with a general formula of Li a M b O c , wherein 0.8≤a≤1.3, 0.8 The functional layer comprises a solid-state electrolyte and an oligomer, the mass percentage of the solid-state electrolyte is 40%-80%, and the mass percentage of the oligomer is 9%-33%. The battery monomer has good thermal safety performance, kinetic performance and high energy density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery monomer, a battery device, a power utilization device and an energy storage device. BACKGROUND

[0002] With the increasing demand for the endurance mileage of power utilization devices, higher requirements are put forward for the energy density of battery monomers. In order to meet the application requirements of high endurance and high efficiency, high-energy-density cathode materials are widely used. However, such materials often have the problem of insufficient thermal safety performance under extreme working conditions such as high temperature, which easily leads to battery thermal runaway and further brings safety hazards. Therefore, how to improve the energy density while considering the thermal safety performance has become an important issue to be solved in the current battery material technology. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the background art. To this end, one object of the present application is to provide a battery monomer, a battery device, a power utilization device and an energy storage device to improve the thermal safety performance of high-capacity cathode active materials.

[0004] The first aspect of the present application provides a battery monomer, which comprises a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector, a positive electrode film layer arranged on at least one side of the positive electrode current collector, and a functional layer arranged on the side of the positive electrode film layer away from the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprising a layered transition metal oxide, the layered transition metal oxide comprising a component with a general formula of Li a M b O c , wherein 0.8≤a≤1.3, 0.8

[0005] To meet the application requirements of high endurance and high efficiency, high-energy-density cathode materials such as layered transition metal oxides are widely used, however, such materials often have the problem of insufficient thermal safety performance under extreme working conditions such as high temperature, which easily leads to battery thermal runaway. Specifically, studies have shown that at high temperature (160℃-250℃), the stability of the chemical bond (M-O bond) between M element and O element is reduced due to the lithium ion release, and thus the layered transition metal oxide under the lithium ion release state is easy to release oxygen (such as oxygen, oxygen free radicals, etc.), and the released oxygen reacts with the electrolyte and the lithium of the negative electrode and the negative electrode active material to generate a large amount of heat, leading to battery thermal runaway.

[0006] The applicant has found that by arranging a functional layer including a solid-state electrolyte and an oligomer on the surface of the positive electrode film layer away from the positive electrode current collector, the battery monomer can have high energy density, good kinetic performance, and thermal safety performance. Although the mechanism is not clear, experiments show that this may be related to the low porosity of the functional film layer. The solid-state electrolyte has high ionic conductivity and can balance the kinetic performance of the battery. However, the porosity of the film layer formed by the solid-state electrolyte and the high molecular polymer (or only the solid-state electrolyte) is often more than 20%, which is difficult to efficiently block the oxygen released from the positive active material. The present application creatively finds that the use of an oligomer combined with a solid-state electrolyte can further reduce the porosity of the functional layer. The oligomer fills the gap between the solid-state electrolyte particles, reduces the oxygen release path, and enhances the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode, so that the functional layer can achieve good thermal safety performance with a lower thickness, thereby achieving the balance of the thermal safety performance, high energy density, and kinetic performance of the battery monomer.

[0007] In the embodiments of the present application, when the mass ratio of the solid-state electrolyte and the oligomer is within the above range, the thermal safety performance, kinetic performance, and energy density of the battery monomer are further improved. Although the mechanism is not completely clear, experiments show that this may be because the oligomer fills the gap between the solid-state electrolyte particles, effectively reduces the porosity of the functional coating, and enhances the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode. Although the oligomer does not have or only has low ionic conductivity, the solid-state electrolyte particles in the functional layer can be in sufficient contact to form a continuous ionic conduction network, so that the functional layer as a whole has good ionic conduction ability, thereby improving the thermal safety performance of the battery monomer while balancing the kinetic performance of the battery.

[0008] In some embodiments, the oligomer includes one or more of a polyethylene glycol diacrylate (PEGDA) oligomer, a vinyl carbonate (VC) oligomer, a cyclic ether (DOL) oligomer, an ethyl 2-cyanoacrylate (ECA) oligomer, and an isocyanate oligomer.

[0009] In the embodiments of the present application, the oligomer within the above range has the characteristics of high temperature resistance and high pressure resistance, and can stably exist in the positive electrode, thereby further improving the thermal safety performance of the battery monomer.

[0010] In some embodiments, the monomer is easy to form an oligomer by in-situ polymerization, which is conducive to improving the effect of the oligomer on filling the pores between the solid-state electrolyte particles.

[0011] In some embodiments, the mass ratio of the solid-state electrolyte is 50%-70% based on the mass of the functional layer.

[0012] In the embodiments of the present application, when the mass ratio of the solid-state electrolyte is within the above range, the thermal safety performance, the kinetics performance and the energy density of the battery cell are further improved.

[0013] In some embodiments, the porosity of the functional layer is greater than 0% and less than or equal to 10%.

[0014] In the embodiments of the present application, when the porosity is within the above range, the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode is enhanced, so that the kinetics performance of the battery is taken into account while the thermal safety performance of the battery cell is improved.

[0015] In some embodiments, the ionic conductivity of the solid-state electrolyte is greater than 10 -4 S / m.

[0016] In the embodiments of the present application, when the solid-state electrolyte is within the above range, the kinetics performance of the battery cell is further improved.

[0017] In some embodiments, the Young's modulus of the solid-state electrolyte is 0.1 GPa-25 GPa under a pressure of 200 MPa.

[0018] In the embodiments of the present application, when the Young's modulus of the solid-state electrolyte is within the above range, the thermal safety performance, the kinetics performance and the energy density of the battery cell are further improved. Although the mechanism is not completely clear, it may be because the solid-state electrolyte within the above Young's modulus range has a large degree of deformation after being cold-pressed into a film, and the aspect ratio of the solid-state electrolyte particles is high, which is beneficial to the formation of a continuous ion conduction network in the functional layer, so that the functional layer as a whole has good ion conduction capability.

[0019] In some embodiments, the average aspect ratio of the particles of the solid-state electrolyte is 30 nm-1 μm, and the aspect ratio of the particles of the solid-state electrolyte is greater than 1 and less than 50.

[0020] In the embodiments of the present application, when the morphology of the solid-state electrolyte is within the above range, the solid-state electrolyte is easy to form a close particle lap, and the thermal safety performance, the kinetics performance and the energy density of the battery cell are further improved.

[0021] In some embodiments, the solid-state electrolyte includes at least one of pyrochlore-type solid-state electrolyte, NASICON-type solid-state electrolyte, garnet-type solid-state electrolyte, halide-based solid-state electrolyte, Li3La(PO4)2.

[0022] In some embodiments, the pyrochlore-type solid-state electrolyte includes Li x1 La x2Q2O6F, wherein 0 < x1 < 3, 0 < x2 < 4, and Q comprises Nb or Ta; the NASICON-type solid-state electrolyte comprises one or more of lithium titanium aluminum phosphate oxide, lithium silicon zirconium phosphate oxide; the garnet-type solid-state electrolyte comprises one or more of lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide; the halide-based solid-state electrolyte comprises one or more of oxygen-doped lithium aluminum chloride, lithium hexachloroindate.

[0023] In some embodiments, the solid-state electrolyte is Li3La(PO4)2(LLPO).

[0024] In some embodiments, the solid-state electrolyte is Li3La(PO4)2(LLPO).

[0025] In some embodiments, the oligomer is formed in situ from a solidified monomer, the solidified monomer comprises one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl 2-cyanoacrylate, isocyanate, and the initiator comprises one or more of azobisisobutyronitrile (AIBN), polypropylene (elastic modulus greater than or equal to 1500 MPa), hexafluorophosphate, aluminum triflate, 2-hydroxy-2-methylpropionphenone (HMPP).

[0026] In some embodiments, the mass ratio of the initiator is 0.05%-5% based on the mass of the functional layer.

[0027] In some embodiments, the oligomer is formed in situ from a solidified monomer, the solidified monomer comprises one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl 2-cyanoacrylate, isocyanate, and the initiator comprises one or more of azobisisobutyronitrile (AIBN), polypropylene (elastic modulus greater than or equal to 1500 MPa), hexafluorophosphate, aluminum triflate, 2-hydroxy-2-methylpropionphenone (HMPP).

[0028] In some embodiments, the functional layer further comprises a flame retardant.

[0029] In some embodiments, the functional layer further comprises a flame retardant.

[0030] In some embodiments, the flame retardant comprises one or more of tributyl phosphate, cresyl-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, dibromomethane, trichloromethyl bromide, dichloromethyl bromide, octabromodiphenyl ether, pentabromoethyl benzene, tetrabromobisphenol A, aluminum hydroxyl oxide, magnesium hydroxide, antimony trioxide, aluminum hydroxide.

[0031] In some embodiments, the flame retardant comprises one or more of tributyl phosphate, cresyl-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, dibromomethane, trichloromethyl bromide, dichloromethyl bromide, octabromodiphenyl ether, pentabromoethyl benzene, tetrabromobisphenol A, aluminum hydroxyl oxide, magnesium hydroxide, antimony trioxide, aluminum hydroxide.

[0032] In some embodiments, the mass ratio of the flame retardant is 5%-20% based on the mass of the functional layer.

[0033] In the embodiments of the present application, when the mass ratio of the flame retardant is within the above range, the thermal safety performance of the battery monomer can be improved while the kinetic performance of the battery monomer is taken into account.

[0034] In some embodiments, the functional layer further comprises a lithium salt.

[0035] In the embodiments of the present application, when the functional layer further comprises a lithium salt, lithium ions in the lithium salt are dispersed in the oligomer, thereby improving the ionic conductivity of the functional layer and further improving the kinetic performance of the battery monomer.

[0036] In some embodiments, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide, and lithium carbonate.

[0037] In the embodiments of the present application, when the lithium salt is selected from the above categories, the kinetic performance of the battery monomer is further improved.

[0038] In some embodiments, the mass ratio of the lithium salt is 2%-20% based on the mass of the functional layer.

[0039] In the embodiments of the present application, when the mass ratio of the lithium salt is within the above range, the thermal safety performance, kinetic performance, and energy density of the battery monomer are further improved.

[0040] In some embodiments, the functional layer further comprises a high polymer.

[0041] In some embodiments, the high polymer comprises one or more of polyvinylidene fluoride, sodium carboxymethylcellulose, styrene butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene acrylic acid copolymer, ethylene vinyl acetate copolymer, and acrylonitrile multivariate copolymer.

[0042] In some embodiments, the mass ratio of the high polymer is 0.5%-5% based on the mass of the functional layer.

[0043] In the embodiments of the present application, when the mass ratio of the high polymer is within the above range, the compactness and interface adhesion of the functional layer can be maintained on the premise of taking into account the mechanical strength and ion transmission efficiency.

[0044] In some embodiments, the thickness of the functional layer is 2-10 microns.

[0045] In the embodiments of the present application, when the thickness of the functional layer is within the above range, the thermal safety and high energy density of the battery monomer can be taken into account.

[0046] Embodiments of the second aspect of the application provide a method for preparing a battery cell, comprising the following steps: coating a positive electrode slurry on at least one side of a positive electrode current collector surface to form a positive electrode film layer; coating a functional layer slurry on a side of the positive electrode film layer surface away from the positive electrode current collector, wherein the functional layer slurry comprises a solid-state electrolyte and a solidified monomer and an initiator; curing the solidified monomer in situ to obtain a functional layer, thereby obtaining a positive electrode sheet; assembling a bare cell by combining the positive electrode sheet with a separator and a negative electrode sheet; and performing the steps of electrolyte injection, packaging and formation on the bare cell to obtain the battery cell.

[0047] In embodiments of the application, the battery cell prepared by the above method has good thermal safety performance, kinetic performance and high energy density. Although the mechanism is not clear, experiments show that this may be because the oligomers formed by in-situ curing of the solidified monomer fill the gaps between the solid-state electrolyte particles, reducing the path for oxygen release, more efficiently separating the oxygen released from the positive electrode from the electrolyte and the negative electrode, so that the functional layer can achieve good thermal safety performance with a lower thickness, thereby achieving a balance between the thermal safety performance of the battery cell and the high energy density and kinetic performance.

[0048] In some embodiments, the in-situ curing of the solidified monomer comprises in-situ curing of the solidified monomer by heating or ultraviolet irradiation.

[0049] In some embodiments, the mass percentage of the solid-state electrolyte is 40%-80% and the mass percentage of the solidified monomer is 9%-33%, based on the mass of the functional layer.

[0050] In embodiments of the application, when the mass percentages of the solid-state electrolyte and the solidified monomer are within the above ranges, the thermal safety performance, kinetic performance and energy density of the battery cell are further improved. Although the mechanism is not completely clear, experiments show that this may be because the oligomers formed by in-situ curing of the solidified monomer fill the gaps between the solid-state electrolyte particles, effectively reducing the porosity of the functional coating and enhancing the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode. Although the solidified monomer does not have or only has a low ionic conductivity, the solid-state electrolyte particles in the functional layer can be in sufficient contact to form a continuous ionic conduction network, so that the functional layer as a whole has good ionic conduction ability, thereby improving the thermal safety performance of the battery cell while balancing the kinetic performance of the battery.

[0051] In some embodiments, the mass percentage of the solid-state electrolyte is 50%-70%, based on the mass of the functional layer.

[0052] In the embodiments of the present application, when the mass ratio of the solid-state electrolyte and the solidified monomer is within the above range, the thermal safety performance, the kinetics performance and the energy density of the battery monomer are further improved.

[0053] In some embodiments, the solidified monomer includes one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl 2-cyanoacrylate, isocyanate, and the initiator includes one or more of azobisisobutyronitrile, polypropylene (elastic modulus greater than or equal to 1500 MPa), hexafluorophosphate, aluminum triflate, 2-hydroxy-2-methylpropionphenone (HMPP).

[0054] In some embodiments, the mass ratio of the initiator is 0.05%-5% based on the mass of the functional layer.

[0055] In the embodiments of the present application, when the solidified monomer and the initiator are selected from the above range, the thermal safety performance, the kinetics performance and the energy density of the battery monomer are further improved.

[0056] In some embodiments, the solid-state electrolyte includes at least one of pyrochlore-type solid-state electrolyte, NASICON-type solid-state electrolyte, garnet-type solid-state electrolyte, halide-based solid-state electrolyte, Li3La(PO4)2.

[0057] In the embodiments of the present application, when the solid-state electrolyte is selected from the above range, the thermal safety performance, the kinetics performance and the energy density of the battery monomer are further improved.

[0058] In some embodiments, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a layered transition metal oxide including a component with a general formula of Li a M b O c wherein 0.8≤a≤1.3, 0.8

[0059] In some embodiments, the Dv50 of the particles of the solid-state electrolyte is 30nm-500nm.

[0060] In the embodiments of the present application, when the Dv50 of the particles of the solid-state electrolyte is within the above range, the solid-state electrolyte has good dispersibility in the first slurry, and due to the lower particle size, the particles are more closely packed, further reducing the porosity of the functional layer, thereby further improving the thermal safety performance, the kinetics performance and the energy density of the battery monomer.

[0061] In some embodiments, the coating the functional layer slurry on the surface of the positive electrode membrane layer away from the positive electrode current collector includes: coating a first slurry on the surface of the positive electrode membrane layer away from the positive electrode current collector to prepare a first layer, wherein the first slurry includes a solid electrolyte; coating a second slurry on the surface of the first layer away from the positive electrode current collector, so that the second slurry penetrates into the first layer and solidifies in situ in the first layer to form a functional layer, to obtain a positive electrode sheet.

[0062] In the embodiments of the present application, the battery monomer prepared by the above method has good thermal safety performance, kinetic performance and high energy density.

[0063] In some embodiments, the first slurry further includes a solvent and a high polymer, wherein the solvent includes one or more of N-methylpyrrolidone, N-dimethylacetamide, and N-dimethylformamide.

[0064] In the embodiments of the present application, when the first slurry includes the above-mentioned solvent, the processability of the first slurry is improved.

[0065] In some embodiments, the mass percentage of the solid components of the first slurry is 30%-60% based on the mass of the first slurry.

[0066] In the embodiments of the present application, when the mass percentage of the solid components of the first slurry is within the above-mentioned range, the processability of the first slurry is further improved.

[0067] The embodiments of the third aspect of the present application provide a battery device, including the battery monomer of any one of the embodiments of the first aspect or the battery monomer prepared by the preparation method of any one of the embodiments of the second aspect, and the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0068] The embodiments of the fourth aspect of the present application provide a power utilization device, including the battery device of any one of the embodiments of the third aspect, and the battery device is used to provide electric energy.

[0069] The embodiments of the fifth aspect of the present application provide an energy storage device, including the battery device of any one of the embodiments of the third aspect, and the battery device is used to store electric energy.

[0070] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0071] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0072] Figure 1 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0073] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0074] Figure 3 This is an exploded structural diagram of a battery cell according to some embodiments of this application;

[0075] Explanation of reference numerals in the attached figures:

[0076] 1000 vehicles;

[0077] Battery unit 100, controller 200, motor 300;

[0078] Box 10, Part 11, Part 2 12;

[0079] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, electrode assembly 23, tab 23a. Detailed Implementation

[0080] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0081] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0082] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0083] In this document, the terms“example” and“exemplary” are used as adjectives only to indicate a certain implementation or a certain aspect of an implementation. In no way, are these terms to be interpreted to limit the scope of the application or the patentable concept. In this document, the terms“coupled” and“connected,” along with their derivatives, can be used. It should be understood that these terms are not intended as synonyms for each other. Rather, these terms are used to describe a certain relationship or connection, and are used in different contexts. For example, a connection can be a connection without any intervening medium, or a connection with an intervening medium. The term“and / or” includes combinations thereof, i.e., items A or B, or both A and B. The term“and / or” also includes variants such as“A, B, and / or C,” where C is a third item (which can be the same as A or B). Likewise, the term“and / or” includes variants such as“at least one of A and / or B” and“A and / or B.” In addition, the characters“ / ” and“,” are generally used to represent an“or” relationship between the associated objects.

[0084] In the description of the embodiments of the present application, the term“plurality” refers to two or more (including two), and similarly, the term“multiple groups” refers to two or more groups (including two groups), and the term“multiple pieces” refers to two or more pieces (including two pieces).

[0085] In the description of the embodiments of the present application, the technical terms“center”,“longitudinal”,“transverse”,“length”,“width”,“thickness”,“upper”,“lower”,“front”,“rear”,“left”,“right”,“vertical”,“horizontal”,“top”,“bottom”,“inner”,“outer”,“clockwise”,“counterclockwise”,“axial”,“radial”,“circumferential” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0086] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms“mounting”,“connection”,“connection”,“fixing” and the like should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, or can be a communication or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0087] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all combinations of any two of the range limits, unless otherwise indicated. For example, a range of "1 to 10" is intended to include any number from 1 to 10, including the end values in the range. Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed

[0088] Unless otherwise indicated, all steps of the application can be performed in any order, preferably in the order as described. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in the order as described, or the method can comprise steps (b) and (a) in the order as described. For example, the method can further comprise step (c) means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or the method can comprise steps (a), (c) and (b), or the method can comprise steps (c), (a) and (b), etc.

[0089] Unless otherwise indicated, the terms "comprising" and "including" as used herein are meant to be open terms, i.e., to include both open and closed terms. For example, the terms "comprising" and "including" can mean that other components can also be included in addition to the recited components, or that only the recited components can be included.

[0090] Unless otherwise indicated, all technical features of the application, as well as optional technical features, can be combined to form new technical solutions.

[0091] With the market demand for the endurance mileage of electrical devices increasing, higher requirements are put forward for the energy density of battery monomers. In order to meet the application requirements of high endurance and high efficiency, high-energy-density positive electrode materials are widely used. However, such materials often have insufficient thermal safety performance under extreme working conditions such as high temperature, which can easily cause battery thermal runaway and thus bring safety hazards. Therefore, how to improve the energy density while considering the thermal safety performance has become an important issue that needs to be solved in the current battery material technology.

[0092] The first aspect of the present application provides a battery monomer, which comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer arranged on at least one side of the positive electrode current collector, and a functional layer arranged on the side of the positive electrode film layer away from the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a layered transition metal oxide, the layered transition metal oxide comprises a component with a general formula of Li a M b O c , wherein 0.8≤a≤1.3, 0.8 a M b O c , wherein the functional layer comprises a solid-state electrolyte and an oligomer, the mass fraction of the solid-state electrolyte is 40%-80%, and the mass fraction of the oligomer is 9%-33%.

[0093] In this paper, the layered transition metal oxide Li a M b O c is a kind of inorganic compound with layered crystal structure, which is usually composed of alkali metal ions (such as lithium) embedded between transition metal oxide layers. Its basic structural unit is formed by two-dimensional layered framework of oxygen octahedral coordinated transition metal, and alkali metal ions can be reversibly inserted and removed between layers. Such materials are widely used in lithium ion battery cathode materials due to their excellent ion conductivity and high specific capacity.

[0094] In some embodiments, a is 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, or any numerical range between any two of them, b is 0.85, 0.90, 0.95, 1.0, or any numerical range between any two of them, and c is 1.6, 1.7, 1.8, 1.9, 2.0, or any numerical range between any two of them.

[0095] In some embodiments, Li a M b O c is LiCoO2, i.e. a is 1, b is 1, and c is 2.

[0096] In some embodiments, Li a Mb O c LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.85 Co 0.1 Mn 0.05 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.91 Co 0.05 Mn 0.04 O2, LiNi 0.95 Co 0.03 Mn 0.02 O2, etc.

[0097] In the present disclosure, “solid-state electrolyte” refers to a material that can efficiently conduct metal ions (e.g., lithium ions) but hardly conduct electrons in a solid state. Compared with liquid electrolytes, solid-state electrolytes have higher thermal stability and safety, which can effectively reduce the risk of short circuit, fire, etc.

[0098] In the present disclosure, “solid-state electrolyte” can be tested by known methods in the art, for example, using X-ray diffraction (XRD) test. As an example, the battery cell is disassembled at 25°C, the functional layer powder is scraped, and the sample is measured according to “GB / T 30415-2013 Inorganic materials - General procedures for X-ray diffraction analysis”.

[0099] In the present disclosure, “oligomer” refers to a relatively low molecular weight molecular chain connected by a small number of monomer units (usually 2-100). As an example, it can be tested by known methods in the art, for example, by testing the molecular weight of the polymer, and the molecular weight is usually between several hundred and several thousand Daltons (Da).

[0100] To meet the application requirements of high endurance and high efficiency, high-energy-density cathode materials such as layered transition metal oxides are widely used, however, such materials often have insufficient thermal safety performance under extreme working conditions such as high temperature, which can easily cause battery thermal runaway. Specifically, studies have shown that at high temperature (160°C-250°C), the stability of the chemical bond (M-O bond) between M element and O element is reduced due to the lithium ion extraction, and thus the layered transition metal oxide under the lithium ion extraction state is easy to release oxygen (such as oxygen, oxygen radicals, etc.), and the released oxygen reacts with the electrolyte and lithium of the anode and the anode active material to generate a large amount of heat, causing battery thermal runaway.

[0101] The applicant found that by arranging a functional layer including a solid-state electrolyte and an oligomer on the surface of the positive electrode film layer away from the positive electrode current collector, the battery monomer can have high energy density, good kinetic performance, and thermal safety performance. Although the mechanism is not clear, experiments show that this may be related to the low porosity of the functional film layer. The solid-state electrolyte has high ionic conductivity and can balance the kinetic performance of the battery. However, the porosity of the film layer formed by the solid-state electrolyte and the high molecular polymer (or only the solid-state electrolyte) is often more than 20%, which is difficult to efficiently block the oxygen released from the positive active material. The present application creatively found that the use of a combination of an oligomer and a solid-state electrolyte can further reduce the porosity of the functional layer. The oligomer fills the gap between the solid-state electrolyte particles, reducing the oxygen release path and enhancing the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode, so that the functional layer can achieve good thermal safety performance with a lower thickness, thereby achieving the balance of battery monomer thermal safety performance, high energy density, and kinetic performance.

[0102] In some embodiments, the mass percentage of the solid-state electrolyte is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any numerical range between any two of the above values, and the mass percentage of the oligomer is 9%, 12%, 15%, 18%, 21%, 24%, 27%, 31%, 32%, 33%, or any numerical range between any two of the above values, based on the mass of the functional layer.

[0103] In the present application, when the mass percentage of the solid-state electrolyte and the oligomer is within the above range, the thermal safety performance, kinetic performance, and energy density of the battery monomer are further improved. Although the mechanism is not completely clear, experiments show that this may be because the oligomer fills the gap between the solid-state electrolyte particles, effectively reducing the porosity of the functional coating and enhancing the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode. Although the oligomer does not have or only has low ionic conductivity, the solid-state electrolyte particles in the functional layer can be in sufficient contact to form a continuous ionic conduction network, so that the functional layer as a whole has good ionic conduction ability, thereby improving the thermal safety performance of the battery monomer while balancing the kinetic performance of the battery.

[0104] In some embodiments, the oligomer includes one or more of a polyethylene glycol diacrylate (PEGDA) oligomer, a vinyl carbonate (VC) oligomer, a cyclic ether (DOL) oligomer, an ethyl 2-cyanoacrylate (ECA) oligomer, and an isocyanate oligomer.

[0105] In this context, “polyethylene glycol diacrylate (PEGDA) oligomer” is a low molecular weight polymer formed by polymerization of PEGDA monomer, “vinylene carbonate (VC) oligomer” is an oligomer formed by polymerization of VC monomer, “cyclic ether (DOL) oligomer” is an oligomer formed by polymerization of 1,3-dioxolane, “ethyl 2-cyanoacrylate (ECA) oligomer” is an oligomer formed by polymerization of ECA monomer, and “isocyanate oligomer” is an oligomer formed by polymerization of isocyanate monomer.

[0106] In the embodiments of the present application, the oligomers within the above range have the characteristics of high temperature resistance and high pressure resistance, and can stably exist in the positive electrode, further improving the thermal safety performance of the battery cell.

[0107] In some embodiments, the monomers are easily polymerized in situ to form oligomers, which is conducive to improving the effect of the oligomers on filling the pores between the solid electrolyte particles.

[0108] In some embodiments, the mass fraction of the solid electrolyte is 50%-70% based on the mass of the functional layer.

[0109] In the embodiments of the present application, when the mass fraction of the solid electrolyte is within the above range, the thermal safety performance, kinetic performance, and energy density of the battery cell are further improved.

[0110] In some embodiments, the porosity of the functional layer is greater than 0% and less than or equal to 10%.

[0111] In this context, the term “porosity of the functional layer” refers to the percentage of pore volume in the functional layer to the total volume of the functional layer. The porosity can be tested by a method known in the art. As an example, at 25°C, the positive electrode sheet is obtained by disassembling the battery cell, the sheet is cut using an ion beam, and then the cross section of the functional coating is observed and analyzed using a scanning electron microscope (SEM). Since the pores appear black under SEM, while the solid components such as solid electrolyte and oligomer appear gray and white under SEM, the area percentage of the black part (i.e., the pores) in the cross section of the solid electrolyte coating can be calculated and analyzed using image processing software (imageProplus) according to the contrast difference of each component under SEM, as the porosity of the solid electrolyte coating.

[0112] In some embodiments, the porosity of the functional layer is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any numerical range between any two of them.

[0113] In the embodiments of the present application, when the porosity is within the above range, the effect of isolating the oxygen released from the positive electrode film layer from the electrolyte and the negative electrode is enhanced, thereby improving the thermal safety performance of the battery monomer while taking into account the kinetic performance of the battery.

[0114] In some embodiments, the solid-state electrolyte has an ionic conductivity greater than 1.2 x 10 -4 S / m.

[0115] In this paper, the term "ionic conductivity" refers to the migration ability of ions (such as lithium ions) in a solid-state electrolyte under the action of a unit electric field, usually expressed in units of Siemens per meter (S / m). This parameter reflects the conduction performance of the material to ions, and is one of the key indicators for evaluating the performance of solid-state electrolytes.

[0116] In this paper, the ionic conductivity of the solid-state electrolyte can be tested by methods known in the art, for example, by Electrochemical Impedance Spectroscopy (EIS). As an example, the electrolyte material to be tested is pressed into a sheet and sandwiched between two inert electrodes (such as stainless steel or metallic lithium) to form a symmetric battery structure, which is tested at 25°C using an impedance analyzer (frequency range 1 MHz to 0.1 Hz), and according to the relevant provisions in GB / T 36565-2018, the equivalent circuit is fitted and the ionic conductivity of the material is calculated.

[0117] In some embodiments, the solid-state electrolyte has an ionic conductivity greater than 1.2 x 10 -4 S / m, 1.5 x 10 -4 S / m, 2 x 10 -4 S / m, 2.5 x 10 -4 S / m, 3 x 10 -4 S / m, 4 x 10 -4 S / m, 5 x 10 -4 S / m, 6 x 10 -4 S / m, 7 x 10 -4 S / m, 8 x 10 -4 S / m, 9 x 10 -4 S / m, or greater than 1 x 10 -3 S / m.

[0118] In the embodiments of the present application, when the solid-state electrolyte is within the above range, the kinetic performance of the battery monomer is further improved.

[0119] In some embodiments, the solid-state electrolyte has a Young's modulus of 0.1 GPa-25 GPa under a pressure of 200 MPa.

[0120] In the present document, the term "Young's modulus" is a physical quantity characterizing the ability of a material to resist elastic deformation when subjected to tension or compression, with the unit of gigapascal (GPa), the larger the value, the more difficult the material is to be compressed or stretched to deform; the smaller the value, the more easily the material deforms.

[0121] In the present document, the Young's modulus of the solid-state electrolyte can be tested by methods known in the art. As an example, the solid-state electrolyte to be tested is cold-pressed into a film under a pressure of 200 MPa to reach a density of about 90% (i.e. a porosity of about 10%), and then according to the nanoindentation method, an indenter is pressed into the surface of the solid-state electrolyte film at a constant rate, the load-displacement (indentation depth) curve is measured, and based on the Oliver-Pharr model, the unloading curve is fitted to calculate the Young's modulus of the solid-state electrolyte.

[0122] In some embodiments, the Young's modulus of the solid-state electrolyte is 0.1 GPa, 0.5 GPa, 1 GPa, 2 GPa, 5 GPa, 8 GPa, 10 GPa, 12 GPa, 15 GPa, 18 GPa, 20 GPa, 22 GPa, 25 GPa, or any numerical range between any two of them.

[0123] In the present application, when the Young's modulus of the solid-state electrolyte is within the above range, the thermal safety performance, kinetic performance and energy density of the battery cell are further improved. Although the mechanism is not completely clear, it may be because the solid-state electrolyte within the above Young's modulus range has a large degree of deformation after being cold-pressed into a film, and the aspect ratio of the solid-state electrolyte particles is high, which is beneficial to the formation of a continuous ion conduction network in the functional layer, so that the functional layer as a whole has good ion conduction ability.

[0124] In some embodiments, the average aspect ratio of the particles of the solid-state electrolyte is greater than 1 and less than 50.

[0125] In the present document, the term "average aspect ratio" refers to the average value of the longest diameter of the solid-state electrolyte particles, and the term "aspect ratio" refers to the ratio of the longest diameter to the shortest diameter of the solid-state electrolyte particles, which is used to characterize the roundness of the solid-state electrolyte, the closer the value is to 1, the more round the solid-state electrolyte is.

[0126] In this context, the average length-diameter and length-diameter ratio of the solid-state electrolyte can be tested by methods well known in the art. As an example, at 25°C, the positive electrode sheet is taken out from the disassembled battery, the sheet is cut using an ion beam, and then the cross section of the functional coating is observed and analyzed using a scanning electron microscope (SEM). A number of points are randomly taken for shooting, and the number of points ≥ 10, which can be 10, 20, 50, 100, etc. The particles in the pictures obtained by shooting are identified by AVIZO software, and the shortest diameter and longest diameter of each particle are measured, and the ratio of the longest diameter to the shortest diameter is calculated, and then the average length-diameter and length-diameter ratio are calculated respectively.

[0127] In some embodiments, the average length-diameter of the particles of the solid-state electrolyte is 30 nm, 50 nm, 70 nm, 100 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or any numerical range between any two of them; and the length-diameter ratio of the particles is 1.5, 2, 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 48, or any numerical range between any two of them.

[0128] In the embodiments of the present application, when the morphology of the solid-state electrolyte is within the above range, the solid-state electrolyte is easy to form a close particle overlap, which further improves the thermal safety performance, kinetic performance and energy density of the battery monomer.

[0129] In some embodiments, the solid-state electrolyte includes at least one of pyrochlore-type solid-state electrolyte, NASICON-type solid-state electrolyte, garnet-type solid-state electrolyte, halide-based solid-state electrolyte, Li3La(PO4)2.

[0130] In some embodiments, the pyrochlore-type solid-state electrolyte includes Li x1 La x2 Q2O6F, wherein 0 < x1≤ 3, 0 < x2≤ 4, and Q includes Nb or Ta; the NASICON-type solid-state electrolyte includes one or more of lithium titanium aluminum phosphate oxide, lithium silicon zirconium phosphate oxide; the garnet-type solid-state electrolyte includes one or more of lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide; and the halide-based solid-state electrolyte includes one or more of oxygen-doped lithium aluminum chloride, lithium hexachloroindate.

[0131] An example of the lithium titanium aluminum phosphate oxide is Li 1.2 Al 0.2 Ti 1.8 (PO4)3, abbreviated as LATP; an example of the tantalum-doped lithium lanthanum zirconium oxide is Li 6.4 La3Zr1Ta1O12 , abbreviated as LLZTO; an example of lithium lanthanum zirconium oxide is Li7La3Zr2O 12 , abbreviated as LLZO; an example of lithium zirconium silicate phosphate oxide is Li 10 Zr2Si 1.5 P 0.5 O 12 , abbreviated as LZSP.

[0132] In some embodiments, the solid-state electrolyte is Li3La(PO4)2(LLPO).

[0133] In the embodiments of the present application, when the solid-state electrolyte is selected from the above range, the thermal safety performance, kinetic performance and energy density of the battery monomer are further improved.

[0134] In some embodiments, the oligomer is formed in situ by curing a solidified monomer with an initiator, the solidified monomer includes one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl 2-cyanoacrylate, isocyanate, and the initiator includes one or more of azobisisobutyronitrile (AIBN), polypropylene (elastic modulus greater than or equal to 1500 MPa), hexafluorophosphate, aluminum triflate, 2-hydroxy-2-methylpropiophenone (HMPP).

[0135] In some embodiments, the mass percentage of the initiator based on the mass of the functional layer is 0.05%-5%.

[0136] In this paper, "initiator" refers to a compound that can generate free radicals or other active centers under certain conditions (such as heat, light or chemical action), thereby initiating the polymerization reaction of monomers or oligomers.

[0137] In some embodiments, the mass percentage of the initiator based on the mass of the functional layer is 0.05%-5%, such as 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or any numerical range between any two of them.

[0138] In the embodiments of the present application, when the oligomer is formed in situ by curing a solidified monomer with an initiator, the thermal safety performance, kinetic performance and energy density of the battery monomer are further improved.

[0139] In some embodiments, the functional layer further includes a flame retardant.

[0140] In the embodiments of the present application, when the functional layer includes a flame retardant, the thermal safety performance of the battery monomer is further improved.

[0141] In some embodiments, the flame retardant comprises one or more of tributyl phosphate, cresyl-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, dibromomethane, trichlorobromomethane, dichlorobromomethane, octabromodiphenyl ether, pentabromoethylbenzene, tetrabromobisphenol A, aluminum hydroxyl oxide, magnesium hydroxide, antimony trioxide, aluminum hydroxide.

[0142] In the embodiments of the present application, when the flame retardant is selected from the above range, the thermal safety performance of the battery monomer is further improved.

[0143] In some embodiments, the mass percentage of the flame retardant in the functional layer is 5%-20%.

[0144] In some embodiments, the mass percentage of the flame retardant in the functional layer is 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, or any numerical range between any two of them.

[0145] In the embodiments of the present application, when the mass percentage of the flame retardant is in the above range, the thermal safety performance of the battery monomer is improved while the kinetic performance of the battery monomer is taken into account.

[0146] In some embodiments, the functional layer further comprises a lithium salt.

[0147] In the embodiments of the present application, when the functional layer further comprises a lithium salt, the lithium ions in the lithium salt are dispersed in the oligomer, improving the ionic conductivity of the functional layer, and further improving the kinetic performance of the battery monomer.

[0148] In some embodiments, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide, lithium carbonate.

[0149] In the embodiments of the present application, when the lithium salt is selected from the above types, the kinetic performance of the battery monomer is further improved.

[0150] In some embodiments, the mass percentage of the lithium salt in the functional layer is 2%-20%.

[0151] In some embodiments, the mass percentage of the lithium salt in the functional layer is 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, or any numerical range between any two of them.

[0152] In the embodiments of the present application, when the mass percentage of the lithium salt is in the above range, the thermal safety performance, kinetic performance, and energy density of the battery monomer are further improved.

[0153] In some embodiments, the functional layer further comprises a high polymer.

[0154] In the embodiments of the present application, the high polymer in the functional layer plays the role of a binder, which helps to improve the bonding strength between components, improve the mechanical stability and adhesion of the film layer, reduce the risk of particle shedding, and thus improve the film forming consistency of the battery during the processing process and the structural integrity during the cycling process.

[0155] In some embodiments, the high polymer includes one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene acrylic acid copolymer, ethylene vinyl acetate copolymer, and acrylonitrile multivariate copolymer.

[0156] In some embodiments, the mass percentage of the high polymer is 0.5%-5% based on the mass of the functional layer.

[0157] In some embodiments, the mass percentage of the high polymer is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any numerical range between any two of them, based on the mass of the functional layer.

[0158] In the embodiments of the present application, when the mass percentage of the high polymer is within the above range, the density and interface adhesion of the functional layer can be maintained while taking into account the mechanical strength and ion transmission efficiency.

[0159] In some embodiments, the thickness of the functional layer is 2-10 μm.

[0160] In some embodiments, the thickness of the functional layer is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any numerical range between any two of them.

[0161] In the embodiments of the present application, when the thickness of the functional layer is within the above range, the thermal safety and high energy density of the battery cell can be taken into account.

[0162] The embodiments of the second aspect of the present application provide a preparation method of a battery cell, including the following steps: coating a positive electrode slurry on at least one side of a positive electrode current collector surface to form a positive electrode film layer; coating a functional layer slurry on the surface of the positive electrode film layer away from the positive electrode current collector, wherein the functional layer slurry includes a solid-state electrolyte and a solidified monomer and an initiator; in-situ curing the solidified monomer to obtain a functional layer, and obtaining a positive electrode sheet; making a bare cell by the positive electrode sheet, a separator film and a negative electrode sheet; and performing electrolyte injection, packaging and formation steps on the bare cell to obtain the battery cell.

[0163] In the embodiments of the present application, the battery monomer prepared by the above method has good thermal safety performance, kinetic performance and high energy density. Although the mechanism is not clear, experiments show that this may be because the in-situ solidification of the solidified monomer forms oligomers, which fill the gaps between the solid electrolyte particles, reduce the path of oxygen release, and more efficiently separate the oxygen released from the positive electrode from the electrolyte and the negative electrode, so that the functional layer can achieve good thermal safety performance with a lower thickness, thereby achieving the balance of battery monomer thermal safety performance, high energy density and kinetic performance.

[0164] As an implementation manner, the solidified monomer can be used as a solvent of the functional layer slurry to dissolve other solid components, and after being initiated by an initiator, the solidified monomer is in-situ solidified into oligomers, so that the oligomers fill the gaps between the solid component particles.

[0165] In some embodiments, the in-situ solidification of the solidified monomer includes in-situ solidification of the solidified monomer by heating or ultraviolet irradiation.

[0166] In some embodiments, the mass percentage of the solid electrolyte is 40%-80% and the mass percentage of the solidified monomer is 9%-33% based on the mass of the functional layer.

[0167] In some embodiments, the mass percentage of the solid electrolyte is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% and the mass percentage of the solidified monomer is 9%, 12%, 15%, 18%, 21%, 24%, 27%, 31%, 32%, 33% or any numerical range between any two of them based on the mass of the functional layer.

[0168] In the embodiments of the present application, when the mass percentages of the solid electrolyte and the solidified monomer are within the above range, the thermal safety performance, kinetic performance and energy density of the battery monomer are further improved. Although the mechanism is not completely clear, experiments show that this may be because the oligomers formed by the in-situ solidification of the solidified monomer fill the gaps between the solid electrolyte particles, effectively reducing the porosity of the functional coating and enhancing the effect of mutual isolation between the oxygen released from the positive electrode film layer and the electrolyte and the negative electrode. Although the solidified monomer does not have or only has a lower ionic conductivity, the solid electrolyte particles in the functional layer can be in sufficient contact to form a continuous ionic conduction network, so that the functional layer as a whole has good ionic conduction ability, thereby improving the thermal safety performance of the battery monomer while balancing the kinetic performance of the battery.

[0169] In some embodiments, the mass percentage of the solid electrolyte is 50%-70% based on the mass of the functional layer.

[0170] In the embodiments of the present application, when the mass ratio of the solid-state electrolyte and the solidified monomer is within the above range, the thermal safety performance, the kinetic performance and the energy density of the battery monomer are further improved.

[0171] In some embodiments, the solidified monomer comprises one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl 2-cyanoacrylate, isocyanate, and the initiator comprises one or more of azobisisobutyronitrile, polypropylene (elastic modulus greater than or equal to 1500 MPa), hexafluorophosphate, aluminum triflate, 2-hydroxy-2-methylpropyl phenone (HMPP).

[0172] In some embodiments, the mass ratio of the initiator is 0.05%-5% based on the mass of the functional layer.

[0173] In this paper, "initiator" refers to a compound that can generate free radicals or other active centers under certain conditions (such as heat, light or chemical action), thereby initiating the polymerization reaction of monomers or oligomers.

[0174] In some embodiments, the mass ratio of the initiator is 0.05%-5%, such as 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or any numerical range between any two of them, based on the mass of the functional layer.

[0175] In the embodiments of the present application, when the solidified monomer and the initiator are selected from the above range, the thermal safety performance, the kinetic performance and the energy density of the battery monomer are further improved.

[0176] In some embodiments, the solid-state electrolyte comprises at least one of pyrochlore-type solid-state electrolyte, NASICON-type solid-state electrolyte, garnet-type solid-state electrolyte, halide-based solid-state electrolyte, Li3La(PO4)2.

[0177] In the embodiments of the present application, when the solid-state electrolyte is selected from the above range, the thermal safety performance, the kinetic performance and the energy density of the battery monomer are further improved.

[0178] In some embodiments, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a layered transition metal oxide comprising a component with a general formula of Li a M b O c wherein 0.8≤a≤1.3, 0.8

[0179] In some embodiments, the Dv50 of the particles of the solid-state electrolyte is 30nm-500nm.

[0180] In the present document, the term "volume average particle size Dv50" has the meaning commonly known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%. The volume distribution particle size Dv50 of the positive electrode active material can be tested using instruments and methods commonly known in the art. For example, it can be conveniently determined by using a laser particle size analyzer according to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. The positive electrode active material can be freshly prepared or scraped from the positive electrode film layer after disassembling the battery cell.

[0181] In some embodiments, the Dv50 of the particles of the solid-state electrolyte is 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 480 nm, 500 nm, or any numerical range between any two of them.

[0182] In the embodiments of the present application, when the Dv50 of the particles of the solid-state electrolyte is within the above range, the solid-state electrolyte has good dispersibility in the first slurry, and due to the lower particle size, the particles are more closely packed, further reducing the porosity of the functional layer, thereby further improving the thermal safety performance, kinetic performance, and energy density of the battery cell.

[0183] In some embodiments, the step of coating the functional layer slurry on the side of the positive electrode film layer away from the positive electrode current collector includes: coating a first slurry on the side of the positive electrode film layer away from the positive electrode current collector to prepare a first layer, wherein the first slurry comprises a solid-state electrolyte; coating a second slurry on the side of the first layer away from the positive electrode current collector, so that the second slurry penetrates into the first layer and solidifies in situ in the first layer to form a functional layer, thereby obtaining a positive electrode tab, wherein the second slurry comprises a solidified monomer and a solidified initiator.

[0184] In the embodiments of the present application, the battery cell prepared by the above method has good thermal safety performance, kinetic performance, and high energy density.

[0185] In some embodiments, the first slurry further comprises a solvent and a high polymer, wherein the solvent comprises one or more of N-methylpyrrolidone, N-dimethylacetamide, and N-dimethylformamide.

[0186] In the embodiments of the present application, when the first slurry includes the solvent, the processability of the first slurry is improved.

[0187] In some embodiments, the mass percentage of the solid component of the first slurry is 30%-60% based on the mass of the first slurry.

[0188] In some embodiments, the mass percentage of the solid component of the first slurry is 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any numerical range between any two of the above values.

[0189] In the embodiments of the present application, when the mass percentage of the solid component of the first slurry is within the above range, the processability of the first slurry is further improved.

[0190] The embodiments of the third aspect of the present application provide a battery device, which includes the battery cell of any one of the embodiments of the first aspect or the battery cell prepared by the preparation method of any one of the embodiments of the second aspect, and the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0191] The embodiments of the fourth aspect of the present application provide a power utilization device, which includes the battery device of any one of the embodiments of the third aspect, and the battery device is used to provide electric energy.

[0192] The embodiments of the fifth aspect of the present application provide an energy storage device, which includes the battery device of any one of the embodiments of the third aspect, and the battery device is used to store electric energy.

[0193] Generally, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, while allowing ions to pass through.

[0194] [Positive electrode sheet]

[0195] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0196] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0197] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0198] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0199] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0200] [Negative electrode tab]

[0201] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0202] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0203] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0204] In some embodiments, the negative active material can employ a negative active material for a battery cell known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material can also be used. These negative active materials can be used alone or in combination of two or more.

[0205] In some embodiments, the negative film layer can also optionally include a binder. The binder can 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), and carboxymethyl chitosan (CMCS).

[0206] In some embodiments, the negative film layer can also optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0207] In some embodiments, the negative film layer can also optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0208] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after drying, cold pressing, and the like, the negative electrode sheet can be obtained.

[0209] [Electrolyte]

[0210] The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0211] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0212] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0213] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0214] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0215] [Separator]

[0216] In some embodiments, the battery cell further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0217] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0218] The battery cell disclosed in the embodiments of the present application can be used in, but is not limited to, an electric device or an energy storage device for a vehicle, a ship, or an aircraft. A power system having the battery cell, the battery device, etc. disclosed in the present application can be used to constitute the electric device or the energy storage device, so that the negative electrode lithium precipitation of the high-energy-density battery can be alleviated, and the stability of the battery performance and the battery life can be improved.

[0219] The embodiments of the present application provide a power consumption device using a battery device as a power supply. The power consumption device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric car, an electric vehicle, a ship, a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, an electric plane toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0220] The embodiments of the present application also provide an energy storage device using a battery device as a power supply. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0221] The following embodiments are described by taking a power consumption device of an embodiment of the present application as a vehicle 1000 for example for convenience of description.

[0222] Please refer to Figure 1 , Figure 1 The vehicle structure diagram provided by some embodiments of the present application is shown in FIG. 1. The vehicle 1000 can be a fuel automobile, a gas automobile, or a new energy automobile. The new energy automobile can be a pure electric vehicle, a hybrid electric vehicle, or a range extended vehicle, etc. The vehicle 1000 is internally provided with a battery device 100. The battery device 100 can be arranged at the bottom, the head, or the tail of the vehicle 1000. The battery device 100 can be used for power supply of the vehicle 1000. For example, the battery device 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300. The controller 200 is used to control the battery device 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation, and driving.

[0223] In some embodiments of the present application, the battery device 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0224] Please refer to Figure 2 , Figure 2The exploded structural diagram of the battery device is provided for some embodiments of the present application. The battery device 100 comprises a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. The box 10 is used to provide a containing space for the battery cell 20, and the box 10 can adopt various structures. In some embodiments, the box 10 can comprise a first part 11 and a second part 12, and the first part 11 and the second part 12 are mutually covered. The first part 11 and the second part 12 jointly define a containing space for containing the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate structure, which is covered on the open side of the second part 12 to jointly define the containing space with the second part 12. The first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 is covered on the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0225] In the battery device 100, the battery cell 20 can be multiple, and the multiple battery cells 20 can be connected in series, in parallel or in a mixed manner. The mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel or in a mixed manner, and then the whole of the multiple battery cells 20 is contained in the box 10. Of course, the battery device 100 can also be that the multiple battery cells 20 are first connected in series, in parallel or in a mixed manner to form a battery module, and then the multiple battery modules are connected in series, in parallel or in a mixed manner to form a whole, which is contained in the box 10. The battery device 100 can also comprise other structures, for example, the battery device 100 can also comprise a current collecting component for realizing the electrical connection between the multiple battery cells 20.

[0226] Each battery cell 20 can be a secondary battery or a primary battery, and can also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid or other shapes, etc.

[0227] Please refer to Figure 3 , Figure 3 The exploded structural diagram of the battery cell is provided for some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes a battery device. As Figure 3 , the battery cell 20 comprises an end cover 21, a shell 22, an electrode assembly 23 and other functional components.

[0228] The end cover 21 refers to a component that covers the opening of the housing 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cover 21 can be adapted to the shape of the housing 22 to fit the housing 22. Optionally, the end cover 21 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 21 is not easily deformed when subjected to extrusion collision, allowing the battery cell 20 to have higher structural strength and improved safety performance. The end cover 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect with the electrode assembly 23 for outputting or inputting the electrical energy of the battery cell 20. In some embodiments, the end cover 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold value. The material of the end cover 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. In some embodiments, an insulating member can also be provided on the inner side of the end cover 21, which can be used to isolate the electrical connection components in the housing 22 from the end cover 21 to reduce the risk of short circuit. For example, the insulating member can be plastic, rubber, etc.

[0229] The housing 22 is a component for fitting the end cover 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, electrolyte and other components. The housing 22 and the end cover 21 can be independent components, and an opening can be provided on the housing 22, and the end cover 21 is covered on the opening to form the internal environment of the battery cell 20. Without limitation, the end cover 21 and the housing 22 can also be integrated, specifically, the end cover 21 and the housing 22 can form a common connection surface before other components enter the housing, and when it is necessary to seal the inside of the housing 22, the end cover 21 is covered on the housing 22. The housing 22 can be various shapes and various sizes, such as cuboid, cylinder, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0230] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 23 can be contained in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking the positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The positive and negative electrode sheets have a portion of active material constituting the main body of the electrode assembly, and the positive and negative electrode sheets each have a portion without active material constituting the tab 23a. The positive and negative tabs can be located together at one end of the main body or at two ends of the main body, respectively. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a are connected to the electrode terminals to form a current loop.

[0231] I. Examples

[0232] Hereinafter, the examples of the present application will be described. The examples described below are exemplary and are for the purpose of explanation of the present application and cannot be understood as a limitation of the present application. In the examples, the specific techniques or conditions not noted are performed in accordance with the techniques or conditions described in the literature in the field or in accordance with the product manual. The reagents or instruments not noted by the manufacturer are all conventional products that can be obtained on the market.

[0233] Example 1

[0234] 1) Preparation of positive electrode sheet

[0235] Preparation of positive electrode film layer slurry: LiNi 0.9 Co 0.05 Mn 0.05 O2, conductive agent (carbon nanotube, abbreviated as CNT), conductive agent (Super-P), binder (PVDF), surfactant (polyvinylpyrrolidone), solvent (N-methylpyrrolidone, abbreviated as NMP) were mixed uniformly in a weight ratio of 98.04:0.5:0.5:0.9:0.06:80.

[0236] Preparation of functional layer slurry: solid-state electrolyte (Li3La(PO4)2, abbreviated as LLPO, Dv50 of 100 nm), high polymer (polyvinylidene fluoride, abbreviated as PVDF), flame retardant (triphenyl phosphate), solidified monomer (polyethylene glycol diacrylate, abbreviated as PEGDA), lithium salt (LiPF6), initiator (azobisisobutyronitrile, abbreviated as AIBN) were mixed uniformly in a weight ratio of 60:1.7:13:20:5:0.3.

[0237] Using a multi-lip multi-slurry system, the positive electrode film layer slurry and the functional layer slurry were coated on both sides of the aluminum foil (the position relationship was that the functional layer was on the side of the positive electrode film layer surface away from the copper foil), and after heating at 60°C to in-situ solidification of the solidified monomer in the functional layer slurry, cold pressing, and cutting, the positive electrode sheet was obtained, and the thickness of the functional layer in the positive electrode sheet was 6 μm.

[0238] 2) Preparation of negative electrode sheet

[0239] Silicon-carbon material, conductive agent (conductive carbon black), conductive agent (CNT), binder (styrene-butadiene rubber, abbreviated as SBR), carboxymethyl cellulose (CMC), solvent (deionized water) were mixed uniformly in a weight ratio of 79.83:9.67:0.5:8.8:1.2:50, coated on both sides of the copper foil, and after cold pressing and cutting, the negative electrode sheet was obtained.

[0240] 3) Isolation film

[0241] A polyethylene film with a thickness of 13 μm was used as the separator film.

[0242] 4) Preparation of electrolyte

[0243] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), a lithium salt (lithium hexafluorophosphate LiPF6) was dissolved in organic solvents ethylene carbonate, diethyl carbonate, dimethyl carbonate (volume ratio 1:1:1), stirred uniformly, and an electrolyte with a LiPF6 concentration of 1 mol / L was obtained.

[0244] 5) Preparation of battery monomer

[0245] The positive electrode sheet, the separator film, and the negative electrode sheet were stacked in order, with the separator film between the positive and negative electrode sheets to play a separating role, and then wound to obtain a battery core. The battery core was welded with tabs, and then put into an aluminum shell. Then, electrolyte was injected and sealed. After standing, cold pressing, formation, shaping, and capacity testing, a lithium ion secondary battery was obtained.

[0246] Examples 2-26 and Comparative Example 3

[0247] The preparation method of the battery monomer of Examples 2-26 and Comparative Example 3 was basically the same as that of Example 1, except that the thickness, type, or mass ratio of the functional layer was different. See Table 1-3 for details.

[0248] Example 27

[0249] The preparation method of the battery monomer of Example 27 was basically the same as that of Example 1, except that the preparation method of the functional layer was different. The specific steps are as follows.

[0250] First slurry: the solid-state electrolyte (LLPO, Dv50 of 100 nm), high polymer (PVDF), flame retardant (triphenyl phosphate), and solvent (NMP) were mixed uniformly.

[0251] Second slurry: the solidified monomer (PEGDA), lithium salt (LiPF6), and initiator (AIBN) were mixed uniformly.

[0252] Using a multi-lip multi-slurry system, the positive electrode film layer slurry and the first slurry were coated on both sides of the aluminum foil to form a positive electrode film layer and a surface coating layer covering the positive electrode film layer (the functional layer was located on the side of the positive electrode film layer away from the copper foil). After drying the coated sheet (i.e., complete evaporation of the solvent NMP), a micro-gravure transfer coating process was used to coat the solidified monomer solution on the surface of the positive electrode film layer at a thickness of 2 mg / 1540.25 mm 2The coating weight is coated on the surface of the surface coating layer, and standing allows the solidified monomer solution to infiltrate and fill the inside of the surface coating layer. Subsequently, the pole piece is heated at 60°C, allowing the solidified monomer to cure in situ to form a stable solidified structure, obtaining a functional layer. After curing, the positive pole piece is obtained after cold pressing and cutting. The mass percentage of each component in the functional layer is shown in Table 1, based on the mass of the functional layer.

[0253] Comparative Example 1

[0254] The preparation method of the battery cell of Comparative Example 1 is basically the same as that of Example 1, except that there is no functional layer.

[0255] Comparative Example 2

[0256] The preparation method of the battery cell of Comparative Example 2 is basically the same as that of Example 1, except that there is no flame retardant, oligomer, and lithium salt in the functional layer.

[0257] II. Battery Performance Test

[0258] 1) Thermal safety test:

[0259] At 25°C, the battery cell is charged at 0.5C constant current to the cut-off voltage of 4.35V, and then charged at 4.35V constant voltage to 0.05C. The fully charged battery cell is fixed with a heating plate (JK-HP-180A / 180B) on the large surface, and the heating plate is input with a signal of 220V / 3A, and the battery cell is heated at this constant power until the hard shell cell fails or the heating time reaches 2 hours. The thermal runaway judgment standard: the cell directs the safety valve to open, and there is no large surface or side surface shell rupture. Heating to 2 hours without thermal runaway is passed the thermal safety test.

[0260] 2) Kinetic performance test

[0261] At 25°C, the battery cell is charged at 0.5C constant current to the cut-off voltage of 4.35V, and then charged at 4.35V constant voltage to 0.05C. Then discharged at 0.02C constant current to the cut-off voltage of 2.5V, and record the full discharge capacity Co of the battery cell.

[0262] At 25°C, the battery cell is charged at 0.5C constant current to the cut-off voltage of 4.35V, and then charged at 4.35V constant voltage to 0.05C. Then discharged at 2C constant current to the cut-off voltage of 2.5V, and record the full discharge capacity C1 of the battery cell.

[0263] According to the formula: 2C discharge capacity retention rate = (C1 / C0) x 100%, the 2C discharge capacity retention rate of the battery cell is calculated to evaluate the kinetic performance of the battery cell.

[0264] 3) Weight energy density

[0265] The battery cells were left to stand at 25°C for 2 hours. Then, at 25°C, they were charged at 0.33C (0.33C) to the charging cutoff voltage of 4.35V. After standing for 10 minutes, they were charged at a constant voltage of 4.35V until the current reached 0.05C, at which point charging was stopped. The battery cells were then left to stand at 25°C for 1 hour. Then, at 25°C, they were discharged at 0.33C to the discharge cutoff voltage of 2.5V. The total discharge energy of the battery cells was recorded as E0 (Wh). The weight of the battery cells was measured as M0 (kg). The weight energy density of the battery cells = discharge energy E0 / weight M0 (Wh / kg).

[0266] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0267] The performance parameters of the battery cells prepared in Examples 1-27 and Comparative Examples 1-3 were measured according to the above method. The results are shown in Tables 1-3 below. "Content" refers to the mass percentage based on the functional layer mass meter, and LATP represents Li 1.2 Al 0.2 Ti 1.8 (PO4)3, LLZTO is Li 6.4 La3Zr1Ta1O 12 LLZO is Li7La3Zr2O 12 LZSP is Li 10 Zr2Si 1.5 P 0.5 O 12 .

[0268] Table 1

[0269]

[0270] This application provides a battery cell including a positive electrode sheet. The positive electrode sheet includes a positive current collector, a positive electrode film layer disposed on at least one side of the surface of the positive current collector, and a functional layer disposed on the surface of the positive electrode film layer away from the positive current collector. The positive electrode film layer includes a positive active material, which includes a layered transition metal oxide, and the layered transition metal oxide includes materials with the general formula Li. a M b O c The components include 0.8≤a≤1.3, 0.8<b≤1, 1.5<c≤2, and M includes one or more of Ni, Co, Mn, and Al; wherein the functional layer includes a solid electrolyte and an oligomer, wherein the solid electrolyte accounts for 40%-80% by mass and the oligomer accounts for 9%-33% by mass.

[0271] The weight energy density of the battery cell of Example 1 measured according to the above method is 426 Wh / kg. Experimental results show that the battery cell in the application has high energy density.

[0272] According to Comparative Examples 1-3 and Examples 1-8, the battery cell provided in the application has better thermal safety performance.

[0273] According to Examples 1-3, when the solid-state electrolyte is LLPO (Young's modulus less than 25 GPa), the thermal safety performance of the battery cell can be improved while better considering the kinetic performance and energy density of the battery cell.

[0274] Table 2

[0275]

[0276] Table 3

[0277]

[0278] According to Examples 1-27, when the mass ratio of the solid-state electrolyte is 40%-80% and the mass ratio of the solidified cell is 9%-33% based on the mass of the functional layer, the thermal safety performance of the battery cell can be improved while better considering the kinetic performance of the battery cell.

[0279] According to Examples 9-16, when the mass ratio of the solid-state electrolyte is 50%-70% based on the mass of the functional layer, the thermal safety performance and kinetic performance of the battery cell are further improved.

[0280] It should be noted that the application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the application are all included in the technical scope of the application. In addition, within the scope of the main idea of the application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements of the embodiments are also included in the scope of the application.

Claims

1. A battery cell, characterized in that, The battery cell includes a positive electrode sheet, which includes a positive current collector, a positive electrode film layer disposed on at least one side of the surface of the positive current collector, and a functional layer disposed on the surface of the positive electrode film layer on the side away from the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes a layered transition metal oxide, and the layered transition metal oxide includes a material with the general formula Li. a M b O c The composition includes 0.8 ≤ a ≤ 1.3, 0.8 < b ≤ 1, 1.5 < c ≤ 2, and M includes one or more of Ni, Co, Mn, and Al. The functional layer comprises a solid electrolyte and oligomers. Based on the mass of the functional layer, the solid electrolyte accounts for 40%-80% of the total mass, and the oligomers account for 9%-33% of the total mass. The functional layer also includes a flame retardant, and the flame retardant accounts for 5%-20% of the mass based on the mass of the functional layer.

2. The battery cell according to claim 1, characterized in that, The oligomers include one or more of polyethylene glycol diacrylate oligomers, vinylene carbonate oligomers, cyclic ether oligomers, ethyl-2-cyanoacrylate oligomers, and isocyanate oligomers.

3. The battery cell according to claim 1, characterized in that, Based on the mass meter of the functional layer, the mass ratio of the solid electrolyte is 50%-70%.

4. The battery cell according to claim 1, characterized in that, The porosity of the functional layer is greater than 0% and less than or equal to 10%.

5. The battery cell according to claim 1, characterized in that, The ionic conductivity of the solid electrolyte is greater than 10. -4 S / m.

6. The battery cell according to claim 1, characterized in that, At a pressure of 200 MPa, the Young's modulus of the solid electrolyte is 0.1 GPa-25 GPa.

7. The battery cell according to claim 1, characterized in that, The average major diameter of the solid electrolyte particles is 30 nm to 1 μm, and the aspect ratio of the solid electrolyte particles is greater than 1 and less than 50, wherein the average major diameter is the average of the longest diameters of the solid electrolyte particles.

8. The battery cell according to claim 1, characterized in that, The solid electrolyte includes at least one of pyrochlore-type solid electrolyte, NASICON-type solid electrolyte, garnet-type solid electrolyte, halide-based solid electrolyte, and Li3La(PO4)2.

9. The battery cell according to claim 8, characterized in that, The pyrochlore-type solid electrolyte includes Li x1 La x2 Q2O6F, where 0 < x1 ≤ 3, 0 < x2 ≤ 4, and Q includes Nb or Ta; The NASICON-type solid electrolyte includes one or more of lithium titanium aluminum phosphate and lithium silicon zirconium phosphate. The garnet-type solid electrolyte includes one or more of lithium lanthanum zirconium oxide and tantalum-doped lithium lanthanum zirconium oxide. The halide-based solid electrolyte includes one or more of oxygen-doped lithium aluminum chloride and lithium hexachloroindium oxide.

10. The battery cell according to claim 1, characterized in that, The solid electrolyte is Li3La(PO4)2.

11. The battery cell according to claim 1, characterized in that, The oligomer is formed by in-situ curing of solidified monomers with an initiator. The solidified monomers include one or more of polyethylene glycol diacrylate, vinylene carbonate, 1,3-dioxolane, ethyl-2-cyanoacrylate, and isocyanate. The initiator includes one or more of azobisisobutyronitrile, hexafluorophosphate, aluminum trifluoromethanesulfonate, and 2-hydroxy-2-methylphenylacetone.

12. The battery cell according to claim 11, characterized in that, Based on the mass of the functional layer, the mass percentage of the initiator is 0.05%-5%.

13. The battery cell according to claim 1, characterized in that, The flame retardant includes one or more of the following: tributyl phosphate, toluene-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, dibromomethane, trichlorobromomethane, dichlorobromomethane, octabromodiphenyl ether, pentabromoethylbenzene, tetrabromobisphenol A, aluminum hydroxide, magnesium hydroxide, antimony trioxide, and aluminum hydroxide.

14. The battery cell according to claim 1, characterized in that, The functional layer also includes lithium salt.

15. The battery cell according to claim 14, characterized in that, The lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium carbonate.

16. The battery cell according to claim 14, characterized in that, Based on the mass meter of the functional layer, the mass percentage of the lithium salt is 2%-20%.

17. The battery cell according to claim 1, characterized in that, The functional layer also includes polymers.

18. The battery cell according to claim 17, characterized in that, The polymers include one or more of the following: polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and acrylonitrile multi-element copolymer.

19. The battery cell according to claim 17, characterized in that, Based on the mass meter of the functional layer, the mass percentage of the polymer is 0.5%-5%.

20. The battery cell according to claim 1, characterized in that, The thickness of the functional layer is 2μm-10μm.

21. A battery device, characterized in that, The battery device includes one or more of the battery cells as described in any one of claims 1 to 20, and the battery device includes one or more of the battery modules and battery packs.

22. A battery device, characterized in that, The battery device includes a battery cell as described in any one of claims 1 to 20, and the battery device includes an energy storage battery.

23. An electrical appliance, characterized in that, The electrical device includes a battery device as described in claim 21 or 22, the battery device being used to provide electrical energy.

24. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 21 or 22, the battery device being used to store electrical energy.

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