Battery cell and manufacturing method therefor, battery, electrical device, and pre-lithiated positive electrode sheet and manufacturing method therefor

Abstract

A battery cell and a manufacturing method therefor, a battery, an electrical device, and a pre-lithiated positive electrode sheet and a manufacturing method therefor. The preparation method for the battery cell comprises the steps of: providing a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, an insulating coating slurry and lithium metal simple substance material; coating the surface of a positive electrode active material layer with the insulating coating slurry, and drying same to form an insulating coating; attaching the lithium metal simple substance material to the surface of the insulating coating so as to obtain a pretreated positive electrode sheet; assembling the obtained pretreated positive electrode sheet, the separator and the negative electrode sheet to obtain an electrode assembly; and assembling the obtained electrode assembly and the electrolyte to obtain the battery cell. Under the function of the electrolyte, the pretreated positive electrode sheet realizes a pre-lithiation reaction by means of a self-discharge effect and forms a pre-lithiated positive electrode sheet. The battery cell has a high initial coulombic efficiency, good cycle performance and good processability.

Description

Battery monomer and preparation method thereof, battery, electric device, pre-lithiated positive electrode sheet and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311616661.2 filed on November 28, 2023, entitled “Battery cell and preparation method thereof, battery, electrical device, pre-lithiation positive electrode sheet and preparation method thereof,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0003] The present application relates to a battery cell and a preparation method thereof, a battery, an electrical device, a pre-lithiated positive electrode plate and a preparation method thereof. Background Art

[0004] During the first cycle of charging a lithium-ion battery, a solid electrolyte interface (SEI) film forms on the negative electrode surface, consuming the active lithium in the positive electrode. This loss of active lithium can lead to reduced battery capacity, lower coulombic efficiency, and a shorter cycle life. By pre-supplementing some active lithium in existing lithium-ion electrochemical systems, since the active lithium can be transferred to the negative electrode along with the electrolyte, this can compensate for the loss of active lithium caused by SEI film formation at the negative electrode, thereby improving the battery's coulombic efficiency, cycle life, and specific energy.

[0005] At present, the pre-lithiation process of lithium-ion batteries mainly includes electrochemical pre-lithiation process, chemical pre-lithiation process and self-discharge pre-lithiation process. The electrochemical pre-lithiation process is a process in which metallic lithium is introduced into the battery as the third electrode, and the metallic lithium and the negative electrode form a counter electrode, and the pre-lithiation is completed by controlling the depth of electrochemical charge and discharge. The process is complicated to operate and is not conducive to large-scale implementation. The chemical pre-lithiation process is usually a process in which lithium-rich compounds are added to the positive electrode or the negative electrode to complete the pre-lithiation. This process often has the problem of residual products, thereby reducing the specific energy of the battery. The self-discharge pre-lithiation process is a process in which the potential difference between the elemental metallic lithium material and the positive electrode active material is used to make the elemental metallic lithium material and the positive electrode active material directly contact in the electrolyte to complete the pre-lithiation. The process is simple to operate and has no residual products, but there are problems with the pre-lithiation reaction rate being too fast and difficult to control the process. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0006] Summary of the Invention

[0007] The present application provides a battery cell and a preparation method thereof, a battery, an electrical device, a pre-lithiation positive electrode plate and a preparation method thereof, which can adjust the pre-lithiation reaction rate and also enable the battery cell to have a high first coulombic efficiency, good cycle performance and good processability.

[0008] In a first aspect, the present application provides a method for preparing a battery cell, comprising the steps of: providing a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, an insulating coating slurry and a single metallic lithium material, wherein the positive electrode sheet comprises a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and forming an insulating coating after drying; attaching the single metallic lithium material to the surface of the insulating coating to obtain a pretreated positive electrode sheet; assembling the obtained pretreated positive electrode sheet with the separator and the negative electrode sheet to obtain an electrode assembly; assembling the obtained electrode assembly with the electrolyte to obtain a battery cell, wherein under the action of the electrolyte, the pretreated positive electrode sheet realizes a pre-lithiation reaction through a self-discharge effect and forms a pre-lithiation positive electrode sheet.

[0009] The method for preparing the battery cell provided in the embodiment of the present application has a simple process and can be integrated into the current battery cell preparation process and production equipment without the need for additional steps.

[0010] The preparation method provided in the embodiment of the present application provides an insulating coating on the surface of the positive electrode active material layer before pre-lithiation of the positive electrode plate, thereby performing a certain insulation treatment on the positive electrode active material layer. The insulating coating can reduce the contact area between the positive electrode active material layer and the elemental metallic lithium material, and can also reduce the pre-lithiation reaction rate, thereby reducing the expansion of the positive electrode plate caused by the pre-lithiation process, thereby improving the structural stability of the pre-lithiation positive electrode active material layer, and reducing the problems of pulverization and shedding of the positive electrode active material layer. Therefore, the preparation method provided in the embodiment of the present application can improve the machinability of the positive electrode plate and the battery cell, which is conducive to the large-scale production of battery cells.

[0011] The battery cell prepared by the preparation method provided in the embodiments of the present application can have high first coulombic efficiency, good cycle performance and good processability.

[0012] In some embodiments, the insulating coating slurry is coated on the surface of the positive electrode active material layer, and the porosity of the insulating coating formed after drying is 30%-90%, and optionally 45%-80%.

[0013] By adjusting the porosity of the insulating coating within the above range, the structural stability of the pre-lithiation positive electrode active material layer can be improved, and the problems of pulverization and falling off of the positive electrode active material layer can be reduced, thereby optimizing the battery performance; a good electrolyte path can also be formed between the elemental metallic lithium material and the positive electrode active material layer, thereby facilitating the realization of self-discharge pre-lithiation, and also enabling the battery cell to have good cycle performance.

[0014] In some embodiments, the insulating coating slurry is coated on the surface of the positive electrode active material layer, and the thickness of the insulating coating formed after drying is less than or equal to 20 μm, and can be optionally 1 μm-10 μm.

[0015] By adjusting the thickness of the insulating coating within the above range, the structural stability of the pre-lithiation positive electrode active material layer can be improved, and the problems of pulverization and falling off of the positive electrode active material layer can be reduced, thereby optimizing the battery performance; the preparation process of the positive electrode sheet can also be optimized, and the processing performance of the positive electrode sheet can be improved.

[0016] By adjusting the thickness of the insulating coating within the above range, a good lithium ion transmission path and electrolyte path can be formed between the single metallic lithium material and the positive electrode active material layer, thereby enabling the battery cell to have good cycle performance.

[0017] In some embodiments, the insulating coating slurry includes insulating particles, a binder, and a solvent.

[0018] In some embodiments, the weight content of the insulating particles is 8 wt % to 60 wt %, optionally 10 wt % to 30 wt %, based on the total weight of the insulating coating slurry.

[0019] In some embodiments, the weight content of the binder is 0.5 wt %-20 wt %, optionally 1 wt %-10 wt %, based on the total weight of the insulating coating slurry.

[0020] In some embodiments, the weight content of the solvent is 38 wt % to 95 wt %, optionally 60 wt % to 88 wt %, based on the total weight of the insulating coating slurry.

[0021] In some embodiments, the volume distribution particle size Dv50 of the insulating particles is less than or equal to 20 μm, and can be optionally 0.1 μm-10 μm.

[0022] In some embodiments, the insulating particles include one or more of organic particles and inorganic particles.

[0023] In some embodiments, the organic particles include one or more of resin particles, metal organic framework materials, covalent organic framework materials, hyper-crosslinked polymers, intrinsic microporous polymers, and conjugated microporous polymers.

[0024] Optionally, the resin particles include one or more of vinylidene fluoride resin, olefin resin, styrene resin, styrene-conjugated diene resin, acrylic resin, acrylic-styrene resin, acrylic-conjugated diene resin, acrylic-styrene-conjugated diene resin, polyamide resin, polyurethane resin, and polysiloxane resin.

[0025] Optionally, the inorganic particles include one or more of ceramics, solid electrolyte materials with lithium ion conductivity, molecular sieves, molecular sieve-like materials, and zeolites.

[0026] In some embodiments, the insulating particles include one or more of porous organic particles and porous inorganic particles.

[0027] Optionally, the porous organic particles include one or more of metal organic framework materials, covalent organic framework materials, hyper-crosslinked polymers, intrinsic microporous polymers, and conjugated microporous polymers.

[0028] Optionally, the porous inorganic particles include one or more of porous ceramics, molecular sieves, molecular sieve-like particles, and zeolites.

[0029] In some embodiments, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylic resin, polyimide, polyamide, styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyacrylamide, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0030] In some embodiments, the solvent includes one or more of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and acetonitrile.

[0031] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of a nickel-cobalt-manganese-based ternary material, a nickel-cobalt-aluminum-based ternary material, a cobalt-free layered material, lithium iron phosphate, lithium manganese phosphate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based material, sulfided polyacrylonitrile, sulfur-based material, iron fluoride, and lithium vanadate, and can optionally include one or more of a nickel-cobalt-manganese-based ternary material, a nickel-cobalt-aluminum-based ternary material, and a cobalt-free layered material.

[0032] In some embodiments, the elemental metallic lithium material includes at least one of lithium foil, lithium ribbon, and lithium mesh.

[0033] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or more of a carbon-based material, a silicon-based material, a lithium titanate, a tin-based material, a germanium-based material, an antimony-based material, an aluminum-based material, and a magnesium-based material. Optionally, the battery cell satisfies: Li ×CE Li ×Q Li ≤Qn ×(CE p -CE n )×ρ n ρ Li is the surface density of the elemental metallic lithium material, in g / cm 2 ;CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental metallic lithium material, in mAh / g; Q n is the specific capacity of the negative electrode active material, in mAh / g; CE p is the first coulombic efficiency of the positive electrode active material; CE n is the first coulombic efficiency of the negative electrode active material; ρ n is the surface density of the negative electrode active material layer, in g / cm 2 This can make up for the loss of active lithium caused by the formation of SEI film on the negative electrode, thereby improving the initial coulombic efficiency, cycle life and specific energy of the battery cell; it can also reduce the problem of lithium plating on the negative electrode.

[0034] In some embodiments, the negative electrode plate includes a negative electrode current collector. Optionally, the negative electrode plate further includes an interface modification layer located on at least a portion of the surface of the negative electrode current collector. Optionally, the battery cell satisfies: Li ×CE Li ×Q Li ≥Q p ×(1-CE′ n )×ρ p ρ Li is the surface density of the elemental metallic lithium material, in g / cm 2 ;CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental metallic lithium material, in mAh / g; Q p is the specific capacity of the positive electrode active material, in mAh / g; CE′ n is the first coulombic efficiency of the negative electrode; ρ p is the surface density of the positive electrode active material layer, in g / cm 2 This can make up for the loss of active lithium caused by the formation of SEI film on the negative electrode, thereby improving the first coulombic efficiency, cycle life and specific energy of the battery cell.

[0035] In some embodiments, the electrolyte includes an electrolyte salt and a non-aqueous organic solvent.

[0036] Optionally, the non-aqueous organic solvent includes one or more of carbonate solvents, carboxylate solvents, ether solvents, fluoroether solvents, and sulfone solvents.

[0037] Optionally, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium difluorobisoxalatophosphate and lithium tetrafluorooxalatophosphate.

[0038] Optionally, the concentration of the electrolyte is 0.5 mol / L-8 mol / L.

[0039] In a second aspect, the present application provides a battery cell, which is prepared by the preparation method of the first aspect of the present application.

[0040] In a third aspect, the present application provides a battery, which includes a battery cell prepared by the preparation method of the first aspect of the present application, or includes a battery cell of the second aspect of the present application.

[0041] In a fourth aspect, the present application provides an electrical device comprising the battery according to the third aspect of the present application, wherein the battery is used to provide electrical energy.

[0042] In a fifth aspect, the present application provides a method for preparing a pre-lithiated positive electrode plate, comprising the steps of: providing a positive electrode plate, an insulating coating slurry and a single metallic lithium material, wherein the positive electrode plate comprises a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and forming an insulating coating after drying; contacting the single metallic lithium material with the insulating coating under electrolyte infiltration, realizing a pre-lithiation reaction through a self-discharge effect, and obtaining a pre-lithiated positive electrode plate.

[0043] In some embodiments, the insulating coating slurry includes the insulating coating slurry of the first aspect of the present application.

[0044] In a sixth aspect, the present application provides a pre-lithiated positive electrode plate, which is prepared by the preparation method of the fifth aspect of the present application.

[0045] In the seventh aspect, the present application provides another pre-lithiated positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, and at least a portion of the positive electrode active material is a pre-lithiated positive electrode active material; the pre-lithiated positive electrode plate also includes an insulating coating located on the surface of the positive electrode active material, and the insulating coating is formed by drying the insulating coating slurry of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0047] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application.

[0048] FIG2 is a schematic diagram of an explosion of a battery provided in some embodiments of the present application.

[0049] FIG3 is a schematic structural diagram of the battery module shown in FIG2 .

[0050] FIG4 is a schematic structural diagram of a battery cell provided in some embodiments of the present application.

[0051] FIG5 is a schematic diagram of an explosion of a battery cell provided in some embodiments of the present application.

[0052] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0053] The figure numbers are explained as follows: 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodation space; 6. Battery module; 7. Battery cell; 71. Shell; 72. Electrode assembly; 73. Cover plate. DETAILED DESCRIPTION

[0054] Below, the battery cell and its preparation method, battery, electrical device, pre-lithiation positive electrode sheet and its preparation method of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0055] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0057] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0058] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0059] In this application, the terms "plurality" and "multiple" refer to two or more.

[0060] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0061] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0062] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0063] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack, etc. A battery cell is the smallest unit that makes up a battery, which can independently realize the function of charging and discharging. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in mixed connection through a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a case and battery cells, and the battery cells or battery modules are housed in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least part of the floor of the vehicle, or part of the case may become at least part of the crossbeam and longitudinal beam of the vehicle.

[0064] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0065] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries.

[0066] Batteries can be used as power sources or energy storage units for electrical devices. Electrical devices include, but are not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0067] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0068] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device.

[0069] Figure 1 is a schematic diagram of the structure of a vehicle provided in some embodiments of the present application. As shown in Figure 1 , a battery 2 is disposed within vehicle 1. Battery 2 can be located at the bottom, front, or rear of vehicle 1. Battery 2 can be used to power vehicle 1, for example, as the operating power source of vehicle 1.

[0070] The vehicle 1 may further include a controller 3 and a motor 4 . The controller 3 is used to control the battery 2 to supply power to the motor 4 , for example, to meet the power requirements of the vehicle 1 during startup, navigation, and driving.

[0071] In some embodiments, the battery 2 can serve not only as an operating power source for the vehicle 1 , but also as a driving power source for the vehicle 1 , replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1 .

[0072] FIG2 is an exploded view of a battery according to some embodiments of the present application. As shown in FIG2 , the battery 2 includes a housing 5 and battery cells (not shown), which are housed in the housing 5 .

[0073] The housing 5 is used to house battery cells and can have various structures. In some embodiments, the housing 5 can include a first housing portion 5a and a second housing portion 5b. The first housing portion 5a and the second housing portion 5b overlap each other, and the first housing portion 5a and the second housing portion 5b together define a storage space 5c for accommodating the battery cells. The second housing portion 5b can be a hollow structure with one end open. The first housing portion 5a is a plate-like structure, and the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. The first housing portion 5a and the second housing portion 5b can also be hollow structures with one end open. The open side of the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0074] In order to improve the sealing performance after the first box body 5a and the second box body 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body 5a and the second box body 5b.

[0075] Assuming that the first box body portion 5a covers the top of the second box body portion 5b, the first box body portion 5a can also be called an upper box cover, and the second box body portion 5b can also be called a lower box body.

[0076] In battery 2, there can be one or more battery cells. If there are multiple battery cells, they can be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections. Multiple battery cells can be directly connected in series, in parallel, or in a hybrid configuration, and then the entire battery cell structure can be housed within housing 5. Alternatively, multiple battery cells can be first connected in series, in parallel, or in a hybrid configuration to form a battery module 6, and then multiple battery modules 6 can be connected in series, in parallel, or in a hybrid configuration to form a single unit and housed within housing 5.

[0077] Figure 3 is a schematic diagram of the battery module shown in Figure 2. As shown in Figure 3, multiple battery cells 7 are first connected in series, parallel, or in series to form a battery module 6. Multiple battery modules 6 are then connected in series, parallel, or in series to form a single unit, which is then housed in a housing.

[0078] The multiple battery cells 7 in the battery module 6 can be electrically connected via a busbar component to achieve parallel connection, series connection, or mixed connection of the multiple battery cells 7 in the battery module 6 .

[0079] The battery cells mentioned in the embodiments of the present application may include at least one of lithium-ion battery cells, negative electrode-free lithium metal battery cells, and the like.

[0080] A negative electrode-free battery cell generally refers to a battery cell constructed without the active negative electrode layer being applied during the manufacturing process. For example, a negative electrode active material layer is not applied to the negative electrode through coating or deposition, or a carbonaceous active material layer is used to form the negative electrode active material layer. During initial charging, ions on the negative electrode side gain electrons and deposit on the surface of the negative electrode current collector to form metal. During discharge, the metal can be converted back to ions and returned to the positive electrode, enabling cyclic charge and discharge. Compared to other battery cells, negative electrode-free battery cells lack a conventional negative electrode active material layer, thus achieving higher energy density. In some embodiments, to improve battery cell performance, the negative electrode side of the negative electrode-free battery cell may also be provided with some conventional negative electrode active material, such as carbon materials. Although these materials have a certain capacity, their content is relatively low and they are not used as the primary negative electrode active material in the battery cell. Therefore, the battery cell constructed in this manner can still be considered a negative electrode-free battery cell. The CB (Cell Balance) value of a battery cell without a negative electrode is typically very small. For example, in some embodiments, the CB value of a battery cell without a negative electrode can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Because a battery cell without a negative electrode contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is relatively small, and thus the CB value is very small, for example, typically less than or equal to 0.1.

[0081] There is a potential difference between the elemental metallic lithium material and the positive electrode active material. Under the action of the electrolyte, the elemental metallic lithium material contacts the positive electrode active material to generate a self-discharge reaction, thereby achieving pre-lithiation. However, this self-discharge reaction (pre-lithiation reaction) often has the problem of too fast reaction rate and difficulty in process control. The volume of the positive electrode will expand after pre-lithiation. The too fast pre-lithiation reaction rate can easily cause the structure of the positive electrode sheet to become unstable. The surface position of the pre-lithiation positive electrode active material layer is prone to embedding too much lithium, thereby causing the volume expansion difference between the surface position and the bottom position (i.e., the position close to the positive electrode current collector) of the positive electrode active material layer to become larger, which in turn causes the positive electrode sheet to be prone to problems such as pulverization and shedding of the positive electrode active material layer, affecting the processability of the positive electrode sheet and the battery, which is not conducive to large-scale production and will also affect the cycle performance of the battery. In particular, for batteries that require a large amount of lithium replenishment (such as batteries with a relatively low initial coulombic efficiency), the deterioration of their cycle performance is more obvious.

[0082] Existing technologies use a self-discharge effect to achieve a pre-lithiation reaction and form a pre-lithiated positive electrode by bringing the cathode to be treated into contact with a single metallic lithium material while soaked in an organic solvent free of electrolyte salts. Because this organic solvent free of electrolyte salts is used, the rate of the pre-lithiation reaction is significantly reduced compared to using an electrolyte solution. However, this pre-lithiation process requires the additional supply of an organic solvent free of electrolyte salts, increasing both the raw material cost and the organic solvent recovery cost of the battery. Furthermore, this pre-lithiation process cannot be integrated into current battery manufacturing processes and production equipment, adding an additional manufacturing step and thus increasing the manufacturing cost of the battery.

[0083] An embodiment of the present application provides a method for preparing a battery cell.

[0084] The preparation method includes the following steps: providing a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, an insulating coating slurry and a single metallic lithium material, wherein the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector; coating the insulating coating slurry on the surface of the positive electrode active material layer and forming an insulating coating after drying; attaching the single metallic lithium material to the surface of the insulating coating to obtain a pretreated positive electrode sheet; assembling the obtained pretreated positive electrode sheet with the separator and the negative electrode sheet to obtain an electrode assembly; assembling the obtained electrode assembly with the electrolyte to obtain a battery cell, wherein under the action of the electrolyte, the pretreated positive electrode sheet realizes a pre-lithiation reaction through a self-discharge effect and forms a pre-lithiation positive electrode sheet.

[0085] The preparation method of the battery cell provided in the embodiment of the present application is simple in process and can be integrated into the current preparation process and production equipment of the battery cell without the need for additional steps, such as the need for a solvent recovery step.

[0086] The preparation method provided in the embodiment of the present application provides an insulating coating on the surface of the positive electrode active material layer before pre-lithiation of the positive electrode plate, thereby performing a certain insulation treatment on the positive electrode active material layer. The insulating coating can reduce the contact area between the positive electrode active material layer and the elemental metallic lithium material, and can also reduce the pre-lithiation reaction rate, thereby reducing the expansion of the positive electrode plate caused by the pre-lithiation process, thereby improving the structural stability of the pre-lithiation positive electrode active material layer, and reducing the problems of pulverization and shedding of the positive electrode active material layer. Therefore, the preparation method provided in the embodiment of the present application can improve the machinability of the positive electrode plate and the battery cell, which is conducive to the large-scale production of battery cells.

[0087] At the same time, insulating the positive electrode active material layer is also beneficial to improving the oxidation resistance of the surface of the positive electrode active material layer, which is beneficial to reducing the internal short circuit of the battery cell during the cycle process.

[0088] The battery cell prepared by the preparation method provided in the embodiments of the present application can have high first coulombic efficiency, good cycle performance and good processability.

[0089] In some embodiments, the coating method of the insulating coating slurry may include but is not limited to micro-gravure coating, submicron spraying, etc.

[0090] In some embodiments, the insulating coating slurry is coated on the surface of the positive electrode active material layer, and the porosity of the insulating coating formed after drying can be 30%-90%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or a range consisting of any of the above values.

[0091] By adjusting the porosity of the insulating coating, the pre-lithiation reaction rate between the elemental metallic lithium material and the positive electrode active material layer can be adjusted. When other conditions are the same, the porosity of the insulating coating decreases, the insulating coating's ability to reduce the pre-lithiation reaction rate becomes stronger, and the structural stability of the pre-lithiation positive electrode active material layer becomes better. However, the ion transmission resistance during the subsequent cycle charge and discharge of the battery cell increases, which is not conducive to further improving the cycle performance of the battery cell.

[0092] By adjusting the porosity of the insulating coating within the above range, the structural stability of the pre-lithiation positive electrode active material layer can be improved, and the problems of pulverization and falling off of the positive electrode active material layer can be reduced, thereby optimizing the battery performance; a good electrolyte path can also be formed between the elemental metallic lithium material and the positive electrode active material layer, thereby facilitating the realization of self-discharge pre-lithiation, and also enabling the battery cell to have good cycle performance.

[0093] Optionally, the porosity of the insulating coating may be 45%-80%, thereby enabling the battery cell to have better cycle performance.

[0094] The porosity of the insulating coating can be tested as follows: apply the insulating coating slurry directly to the positive electrode current collector using the same process, dry it, and then test the porosity of the sample. The porosity of the sample can be tested in accordance with GB / T 24586-2009.

[0095] The porosity of the sample P = 1-ρ1 / ρ2, where ρ1 represents the apparent density of the sample, which can be calculated based on the weight and volume of the sample; ρ2 represents the true density of the sample, which can be measured using a true density tester using an inert gas (such as nitrogen) as a medium and a gas displacement method in accordance with GB / T 24586-2009.

[0096] In some embodiments, the insulating coating slurry is coated on the surface of the positive electrode active material layer, and the thickness of the insulating coating formed after drying can be less than or equal to 20 μm, for example, it can be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, or a range consisting of any of the above values.

[0097] The pre-lithiation reaction rate between the elemental metallic lithium material and the positive electrode active material layer can be adjusted by adjusting the thickness of the insulating coating. When other conditions are the same, as the thickness of the insulating coating increases, the insulating coating's ability to reduce the pre-lithiation reaction rate becomes stronger and the structural stability of the pre-lithiation positive electrode active material layer becomes better. However, the ion transmission path becomes longer during the subsequent cycle charge and discharge of the battery cell, which is not conducive to further improving the cycle performance of the battery cell.

[0098] By adjusting the thickness of the insulating coating within the above range, the structural stability of the pre-lithiation positive electrode active material layer can be improved, and the problems of pulverization and falling off of the positive electrode active material layer can be reduced, thereby optimizing the battery performance; the preparation process of the positive electrode sheet can also be optimized, and the processing performance of the positive electrode sheet can be improved.

[0099] By adjusting the thickness of the insulating coating within the above range, a good lithium ion transmission path and electrolyte path can be formed between the single metallic lithium material and the positive electrode active material layer, thereby enabling the battery cell to have good cycle performance.

[0100] Optionally, the thickness of the insulating coating layer may be 1 μm-10 μm, 1 μm-8 μm, 1 μm-5 μm, or 1 μm-3 μm, thereby enabling the battery cell to have better cycle performance.

[0101] In some embodiments, the insulating coating slurry may include insulating particles, a binder, and a solvent.

[0102] The binder is mainly used to play a bonding role, so that the insulating particles can be stably attached to the surface of the positive electrode active material layer.

[0103] The insulating particles are mainly used to provide contact sites between the elemental metallic lithium material and the positive electrode active material layer, and to form electrolyte paths and lithium ion transmission paths for self-discharge pre-lithiation.

[0104] By adjusting the type, form and / or content of each component in the insulating coating slurry, the porosity of the insulating coating can be adjusted, and then the pre-lithiation reaction rate can be adjusted, and the structural stability of the pre-lithiation positive electrode active material layer can be further improved, reducing the problems of pulverization and falling off of the positive electrode active material layer; the preparation process of the positive electrode plate can be further optimized, and the processing performance of the positive electrode plate can be improved; and a good lithium ion transmission path and electrolyte path can be formed between the elemental metallic lithium material and the positive electrode active material layer, and thus the battery cell can have good cycle performance.

[0105] Optionally, in some embodiments, the weight content of the insulating particles may be 8 wt %-60 wt %, optionally 10 wt %-30 wt %, based on the total weight of the insulating coating slurry.

[0106] Optionally, in some embodiments, the weight content of the binder may be 0.5 wt %-20 wt %, optionally 1 wt %-10 wt %, based on the total weight of the insulating coating slurry.

[0107] Optionally, in some embodiments, the weight content of the solvent may be 38 wt %-95 wt %, optionally 60 wt %-88 wt %, based on the total weight of the insulating coating slurry.

[0108] In some embodiments, the insulating coating slurry may further include a dispersant. The dispersant helps improve the uniformity of the insulating coating, thereby helping to improve the uniformity and structural stability of the pre-lithiated positive electrode active material layer, thereby reducing problems such as pulverization and shedding of the positive electrode active material layer.

[0109] Alternatively, the dispersant may include sodium carboxymethylcellulose (CMC).

[0110] Optionally, the weight content of the dispersant may be less than or equal to 2 wt %, based on the total weight of the insulation coating slurry.

[0111] In some embodiments, the volume distribution particle size Dv50 of the insulating particles may be less than or equal to 20 μm, and may be selected from 0.1 μm-10 μm, 0.5 μm-8 μm, 0.5 μm-5 μm, 0.5 μm-3 μm, and 1 μm-3 μm.

[0112] The volume distribution particle size Dv50 of a material is well known in the art and represents the particle size corresponding to 50% of the cumulative volume distribution percentage of the material. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, as described in GB / T 19077-2016, "Particle Size Distribution Laser Diffraction Method." The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0113] In some embodiments, the insulating particles may include one or more of organic particles and inorganic particles.

[0114] In some embodiments, the organic particles may include one or more of resin particles, metal organic frameworks (MOFs), covalent organic frameworks (COFs), hypercrosslinked polymers (HCPs), intrinsic microporous polymers (PIMs), and conjugated microporous polymers (CMPs).

[0115] Optionally, the resin particles may include but are not limited to one or more of vinylidene fluoride resins, olefin resins, styrene resins, styrene-conjugated diene resins, acrylic resins, acrylic-styrene resins, acrylic-conjugated diene resins, acrylic-styrene-conjugated diene resins, polyamide resins, polyurethane resins, and polysiloxane resins.

[0116] In some embodiments, the inorganic particles may include one or more of ceramics, solid electrolyte materials having lithium ion conductivity, molecular sieves, molecular sieve-like materials, and zeolites.

[0117] Alternatively, the ceramic may include, but is not limited to, one or more of aluminum oxide, zirconium oxide, silicon oxide, titanium oxide, magnesium oxide, vanadium oxide, zinc oxide, barium oxide, calcium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, hydrated aluminum oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, silicon nitride, boron carbide, boron nitride, aluminum nitride, gallium nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium titanate, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, calcium silicate, calcium phosphate, calcium carbonate, magnesium carbonate, calcium sulfate, forsterite, boehmite, mica, bentonite, hectorite, kaolin, talc, dolomite, cristobalite, wollastonite, and diatomaceous earth.

[0118] Alternatively, the solid electrolyte material having lithium ion conductivity may include but is not limited to lithium titanium phosphate Li xTi y (PO4)3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li x Al y Ti z (PO4)3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum germanium phosphate Li x Al y Ge z (PO4)3 (abbreviated as LAGP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum zirconium phosphate Li x Al y Zr z (PO4)3 (abbreviated as LAZP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate Li x Al y Cr z (PO4)3 (abbreviated as LACP, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -type glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate Li x La y TiO3 (0 < x < 2, 0 < y < 3), lithium lanthanum zirconium oxide Li7La3Zr2O 12 (abbreviated as LLZO), lithium lanthanum tantalum oxide Li5La3Ta2O 12 (abbreviated as LLTA), lithium zinc germanium oxide (Li 14 ZnGe4O 16 ), lithium thiogermanate electrolyte Li6PS5X (X includes one or more selected from Cl, Br, I), SiS2-type glass Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-type glass Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), lithium tetrathiophosphate Li3PS4, Li7P3S 11 , lithium germanium phosphorus sulfur sulfide Li 10 GeP2S 12 、and one or more of their respective doped compounds. The doped compound is usually a product obtained by doping other elements, such as metal elements, into the compound. The type of the doping element is not particularly limited as long as it does not damage the gist of this application.

[0119] The insulating particles can include one or more of non-porous insulating particles and porous insulating particles.

[0120] In some embodiments, the insulating particles may include one or more of porous organic particles and porous inorganic particles.

[0121] This is conducive to forming an insulating coating with a higher porosity between the elemental metallic lithium material and the positive electrode active material layer, thereby facilitating the formation of a good lithium ion transmission path and electrolyte path, thereby reducing the pre-lithiation reaction rate, and further improving the structural stability of the pre-lithiation positive electrode active material layer, reducing problems such as pulverization and shedding of the positive electrode active material layer; it can also further optimize the preparation process of the positive electrode sheet, improve the processing performance of the positive electrode sheet; and can also make the battery cell have good cycle performance.

[0122] In some embodiments, the porous organic particles may include, but are not limited to, one or more of metal organic frameworks (MOFs), covalent organic frameworks (COFs), hypercrosslinked polymers (HCPs), intrinsically microporous polymers (PIMs), and conjugated microporous polymers (CMPs).

[0123] In some embodiments, the porous inorganic particles may include, but are not limited to, one or more of porous ceramics, molecular sieves, molecular sieve-like particles, and zeolites.

[0124] In some embodiments, the binder may include but is not limited to one or more of polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylic resin, polyimide, polyamide, styrene-butadiene rubber (SBR), water-soluble unsaturated resin, water-based acrylic resin, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS), and may optionally include polytetrafluoroethylene.

[0125] Within the above range, the binder can have good film-forming and bonding properties, thereby allowing the insulating particles to adhere well to the surface of the positive electrode active material layer, reducing problems such as pulverization and falling off of the positive electrode active material layer; in addition, the binder also has good oxidation resistance and reduction ability, which is beneficial to avoid being reduced in the pre-lithiation reaction and avoiding being oxidized during the charge and discharge process.

[0126] In some embodiments, the solvent may include, but is not limited to, one or more of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and acetonitrile.

[0127] In some embodiments, the elemental metallic lithium material may include at least one of lithium foil, lithium ribbon, and lithium mesh.

[0128] In some embodiments, the process of attaching the elemental metallic lithium material to the surface of the insulating coating to obtain a pre-treated positive electrode sheet may include but is not limited to rolling.

[0129] [Positive electrode]

[0130] The positive electrode active material layer includes a positive electrode active material, which includes a material capable of extracting and inserting lithium.

[0131] Optionally, the positive electrode active material may include but is not limited to one or more of nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, cobalt-free layered materials, lithium iron phosphate, lithium manganese phosphate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based materials, sulfided polyacrylonitrile, sulfur-based materials, iron fluoride, and lithium vanadate, and may optionally include one or more of nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, and cobalt-free layered materials.

[0132] In some embodiments, the positive electrode active material layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the positive electrode active material layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). One or more.

[0134] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0135] The positive electrode active material layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0136] [Negative electrode]

[0137] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, and the negative electrode active material including one or more of a carbon-based material, a silicon-based material, lithium titanate, a tin-based material, a germanium-based material, an antimony-based material, an aluminum-based material, and a magnesium-based material.

[0138] Optionally, the carbon-based material may include, but is not limited to, one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0139] Optionally, the silicon-based material may include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0140] Optionally, the silicon-based material may further include one or more of an alkali metal element and an alkaline earth metal element. Optionally, the alkali metal element includes Li. Optionally, the alkaline earth metal element includes Mg. As an example, the silicon-based material may be a silicon-based material pre-embedded with Li.

[0141] Optionally, the battery cell satisfies: Li ×CE Li ×Q Li ≤Q n ×(CE p -CE n )×ρ n This can make up for the loss of active lithium caused by the formation of SEI film on the negative electrode, thereby improving the initial coulombic efficiency, cycle life and specific energy of the battery cell; it can also reduce the problem of lithium plating on the negative electrode.

[0142] ρ Li is the surface density of elemental metallic lithium material, in g / cm 2 ;CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental metallic lithium material, in mAh / g; Q n is the specific capacity of the negative electrode active material, in mAh / g; CE p The first coulombic efficiency of the positive electrode active material; CE n is the first coulombic efficiency of the negative electrode active material; ρ nis the surface density of the negative electrode active material layer, in g / cm 2 .

[0143] The surface density of elemental metallic lithium material ρ Li It refers to the ratio of the total mass of the single metallic lithium material on one side of the positive electrode current collector to the total area of ​​the positive electrode active material layer on one side of the positive electrode current collector.

[0144] The first coulombic efficiency CE of lithium metal Li It can be obtained by the following method: assemble lithium sheets into a symmetrical battery, using the same electrolyte and separator as the battery cell; after the assembled symmetrical battery is left to stand for 12 hours, charge it at a constant current of 0.1C, and then charge it at a constant voltage to a current of 50μA to obtain the charging capacity; after standing for 5 minutes, discharge the symmetrical battery at a constant current of 0.1C to obtain the discharge capacity. The ratio of the discharge capacity to the charging capacity is the first coulombic efficiency CE of lithium metal. Li .

[0145] The specific capacity Q of elemental lithium metal material Li It is 3860mAh / g.

[0146] Specific capacity Q of negative electrode active material n , the first coulombic efficiency CE of negative electrode active materials n It can be obtained by the following method: using a lithium sheet as the counter electrode and assembling it with a negative electrode sheet into a button battery, the negative electrode sheet used in the button battery (if the negative electrode sheet used in the battery cell is coated with a negative electrode active material layer on both sides, it needs to be adjusted to a single-side coating of the negative electrode active material layer), electrolyte and separator are the same as those of the battery cell; after the assembled button battery is left to stand for 12 hours, it is discharged at a constant current of 0.1C to obtain the discharge capacity; after standing for 5 minutes, the button battery is charged at a constant current of 0.1C, and then charged at a constant voltage to a current of 50μA to obtain the charge capacity. The ratio of the discharge capacity to the mass of the negative electrode active material is the specific capacity Q of the negative electrode active material. n The ratio of charge capacity to discharge capacity is the first coulombic efficiency CE of the negative electrode active material. n .

[0147] First coulombic efficiency CE of positive electrode active materials pIt can be obtained by the following method: use a lithium sheet as the counter electrode and assemble it with the positive electrode sheet into a button battery. The positive electrode sheet used in the button battery (if the positive electrode sheet used in the battery cell is double-sided coated, it needs to be adjusted to single-sided coating first), electrolyte and isolation membrane are the same as those of the battery cell; after the assembled button battery is left to stand for 12 hours, it is charged at a constant current of 0.1C, and then charged at a constant voltage to a current of 50μA to obtain the charging capacity; after standing for 5 minutes, the button battery is discharged at a constant current of 0.1C to obtain the discharge capacity. The ratio of the discharge capacity to the charging capacity is the first coulombic efficiency CE of the positive electrode active material. p .

[0148] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. As examples, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0149] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. As examples, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0150] In some embodiments, the negative electrode active material layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0151] The negative electrode sheet can be prepared by dispersing the negative electrode active material, negative electrode binder, negative electrode conductive agent, and optional other additives in a solvent and stirring them uniformly to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector and, after drying and roll pressing, forms the negative electrode sheet. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0152] Alternatively, in some embodiments, the negative electrode sheet may include a negative electrode current collector but not the negative electrode active material layer, thereby assembling a negative electrode-free lithium metal battery cell.

[0153] In some embodiments, the negative electrode plate may further include an interface modification layer located on at least a portion of the surface of the negative electrode current collector.

[0154] Alternatively, the interface modification layer may include, but is not limited to, one or more of a solid electrolyte material, a metal oxide, a non-metal oxide, a metal sulfide, a non-metal sulfide, a metal nitride, a non-metal nitride, and a carbon-based material. This can regulate the deposition behavior of lithium metal at the negative electrode and reduce dendrite formation.

[0155] Optionally, the battery cell satisfies: Li ×CE Li ×Q Li ≥Q p ×(1-CE′ n )×ρ p This can make up for the loss of active lithium caused by the formation of SEI film on the negative electrode, thereby improving the first coulombic efficiency, cycle life and specific energy of the battery cell.

[0156] ρ Li is the surface density of elemental metallic lithium material, in g / cm 2 ;CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental metallic lithium material, in mAh / g; Q p is the specific capacity of the positive electrode active material, in mAh / g; CE′ n is the first coulombic efficiency of the negative electrode; ρ p is the surface density of the positive electrode active material layer, in g / cm 2 .

[0157] The first coulombic efficiency CE′ of the negative electrode n It can be obtained as follows: a lithium sheet is used as the counter electrode and assembled with a negative electrode sheet into a button battery. The negative electrode sheet used in the button battery (if the negative electrode sheet used in the battery cell is coated with an interface modification layer on both sides, it needs to be adjusted to a single-side interface modification layer), electrolyte, and separator are the same as those of the battery cell; after the assembled button battery is left to stand for 12 hours, it is discharged at a constant current of 0.1C to obtain the discharge capacity; after standing for 5 minutes, the button battery is charged at a constant current of 0.1C, and then charged at a constant voltage to a current of 50μA to obtain the charge capacity. The ratio of the charge capacity to the discharge capacity is the first coulombic efficiency CE' of the negative electrode sheet. n .

[0158] Specific capacity Q of the positive electrode active material pIt can be obtained by the following method: using a lithium sheet as the counter electrode, assembling it with a positive electrode sheet into a button cell. The positive electrode sheet used in the button cell (if the positive electrode sheet used in the battery cell is double-sided coated, it needs to be adjusted to single-sided coating first), electrolyte, and separator are the same as those of the battery cell; after the assembled button cell is left to stand for 12 hours, it is charged at a constant current of 0.1C, and then charged at a constant voltage to a current of 50μA to obtain the charging capacity; after standing for 5 minutes, the button cell is discharged at a constant current of 0.1C to obtain the discharge capacity. The ratio of the discharge capacity to the mass of the positive electrode active material is the specific capacity Q of the positive electrode active material. p .

[0159] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As examples of metal foils, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As examples of three-dimensional porous current collectors, copper mesh, nickel mesh, aluminum mesh, foam copper, foam nickel, and foam aluminum may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0160] [Electrolyte]

[0161] In some embodiments, the electrolyte includes an electrolyte salt and a non-aqueous organic solvent.

[0162] Optionally, the non-aqueous organic solvent may include one or more of a carbonate solvent, a carboxylate solvent, an ether solvent, a fluoroether solvent, and a sulfone solvent.

[0163] The carbonate solvent may include cyclic carbonate and / or chain carbonate. Alternatively, the carbonate solvent may include both cyclic carbonate and chain carbonate. The chain carbonate may include low-viscosity polar chain carbonate, aliphatic branched-chain carbonate, and the like.

[0164] As an example, the non-aqueous organic solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraglyceride alcohol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9OCH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, One or more of 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and 7-trifluoromethyl hexadecafluorooctyl propyl ether.

[0165] Alternatively, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP);

[0166] Optionally, the concentration of the electrolyte may be 0.5 mol / L-8 mol / L, or optionally 0.8 mol / L-4 mol / L. When the concentration of the electrolyte is within the above range, the electrolyte may have suitable ionic conductivity.

[0167] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0168] [Isolation film]

[0169] The separator is located between the positive electrode and the negative electrode, and mainly plays the role of preventing internal short circuit. The present application has no particular limitation on the type of separator, and any well-known porous structure separator with good chemical and mechanical stability can be selected.

[0170] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0171] The electrode assembly may be a wound structure or a laminated structure, which is not limited in the embodiments of the present application.

[0172] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The soft package can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0173] Figure 4 is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application. Figure 5 is an exploded schematic diagram of a battery cell provided in some embodiments of the present application. As shown in Figures 4 and 5, in some embodiments, the outer packaging may include a shell 71 and a cover plate 73. The shell 71 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 71 has an opening connected to the receiving cavity, and the cover plate 73 is used to cover the opening to close the receiving cavity. The electrode assembly 72 is encapsulated in the receiving cavity. The number of electrode assemblies 72 contained in the battery cell 7 may be one or more, which can be adjusted according to demand.

[0174] The embodiment of the present application also provides a battery cell prepared by the above preparation method.

[0175] The present application also provides a method for preparing a pre-lithiated positive electrode. The preparation method includes the following steps: providing a positive electrode, an insulating coating slurry, and a single metallic lithium material, wherein the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector; applying the insulating coating slurry to the surface of the positive active material layer, and forming an insulating coating after drying; contacting the single metallic lithium material with the insulating coating under electrolyte infiltration, achieving a pre-lithiation reaction through the self-discharge effect, and obtaining a pre-lithiated positive electrode. The insulating coating slurry can be the above-mentioned insulating coating slurry provided in the present application, and will not be described in detail here.

[0176] The preparation method provided in the embodiment of the present application provides an insulating coating on the surface of the positive electrode active material layer before pre-lithiation of the positive electrode plate, thereby performing a certain insulation treatment on the positive electrode active material layer. The insulating coating can reduce the contact area between the positive electrode active material layer and the elemental metallic lithium material, and can also reduce the pre-lithiation reaction rate, thereby reducing the expansion of the positive electrode plate caused by the pre-lithiation process, thereby improving the structural stability of the pre-lithiation positive electrode active material layer, and reducing the problems of pulverization and shedding of the positive electrode active material layer. Therefore, the preparation method provided in the embodiment of the present application can improve the machinability of the positive electrode plate and the battery cell, which is conducive to the large-scale production of battery cells.

[0177] The embodiment of the present application also provides a pre-lithiated positive electrode sheet prepared by the above preparation method.

[0178] An embodiment of the present application also provides another pre-lithiated positive electrode plate, which includes a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, and at least a portion of the positive electrode active material is a pre-lithiated positive electrode active material; the pre-lithiated positive electrode plate also includes an insulating coating located on the surface of the positive electrode active material, and the insulating coating is formed by drying the above-mentioned insulating coating slurry provided in the embodiment of the present application.

[0179] The insulating coating includes insulating particles and a binder.

[0180] Optionally, the weight content of the insulating particles in the insulating coating layer may be greater than or equal to 50 wt %, optionally greater than or equal to 70 wt %, based on the total weight of the insulating coating layer.

[0181] Optionally, the weight content of the binder in the insulating coating may be less than 50 wt %, optionally less than 30 wt %, based on the total weight of the insulating coating.

[0182] Example

[0183] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0184] Example 1

[0185] Preparation of positive electrode

[0186] The positive electrode active material Li[Ni 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2 to obtain a positive electrode slurry. The positive electrode slurry is then coated on the positive electrode current collector aluminum foil. The positive electrode sheet is obtained through drying, cold pressing, slitting, and cutting. The first coulombic efficiency CE of the positive electrode active material p The specific capacity Q of the positive electrode active material is 93%. p is 224 mAh / g, and the surface density of the positive electrode active material layer is p 0.025g / cm 2 .

[0187] Preparation of negative electrode sheet

[0188] The negative electrode active material SiC, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), and conductive agent carbon black (Super P) are thoroughly stirred and mixed in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil. After drying, cold pressing, slitting, and cutting, the negative electrode sheet is obtained. The first coulombic efficiency CE of the negative electrode active material n The specific capacity Q of the negative electrode active material is 80%. n is 1850mAh / g, and the surface density of the negative electrode active material layer is n 0.003g / cm 2 .

[0189] Preparation of electrolyte

[0190] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0191] Preparation of isolation membrane

[0192] A porous polyethylene film was used as the separator.

[0193] Preparation of insulating coating slurry

[0194] The insulating boehmite particles, the binder polytetrafluoroethylene, the dispersant sodium carboxymethyl cellulose (CMC), and the solvent deionized water were thoroughly stirred and mixed in a weight ratio of 16:4:0.5:79.5 to form a uniform insulating coating slurry. The volume distribution particle size Dv50 of the boehmite was 3 μm.

[0195] Preparation of battery cells

[0196] The insulating coating slurry is applied to the surface of the positive electrode active material layer and dried to form an insulating coating with a thickness of 3 μm and a porosity of 80%. Lithium foil is attached to the surface of the insulating coating to obtain a pre-treated positive electrode sheet. The surface density of the lithium foil is ρ Li 0.179×10 -3 g / cm 2 , the first coulombic efficiency CE of lithium metal Li The specific capacity Q of lithium foil is 99.6%. Li It is 3860mAh / g.

[0197] The pre-treated positive electrode sheet is stacked and wound in sequence with the separator and negative electrode sheet to form an electrode assembly. The electrode assembly is then placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. Under the action of the electrolyte, the pre-treated positive electrode sheet undergoes a pre-lithiation reaction through self-discharge, forming a pre-lithiated positive electrode sheet.

[0198] Example 2

[0199] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0200] The thickness of the insulating coating formed after drying was 1 μm.

[0201] Example 3

[0202] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0203] The thickness of the insulating coating formed after drying was 10 μm.

[0204] Example 4

[0205] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0206] The thickness of the insulating coating formed after drying was 20 μm.

[0207] Example 5

[0208] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0209] In the preparation step of the insulating coating slurry, the weight ratio of the insulating particle boehmite, the binder polytetrafluoroethylene, the dispersant sodium carboxymethyl cellulose (CMC), and the solvent deionized water is 10:4:0.5:85.5.

[0210] The volume distribution particle size Dv50 of the boehmite used in the step of preparing the insulating coating slurry was 0.5 μm.

[0211] The insulating coating formed after drying had a thickness of 3 μm and a porosity of 30%.

[0212] Example 6

[0213] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0214] The volume distribution particle size Dv50 of the boehmite used in the step of preparing the insulating coating slurry was 0.5 μm.

[0215] The insulating coating formed after drying has a thickness of 3 μm and a porosity of 45%.

[0216] Example 7

[0217] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0218] The volume distribution particle size Dv50 of the boehmite used in the step of preparing the insulating coating slurry was 1 μm.

[0219] The insulating coating formed after drying had a thickness of 3 μm and a porosity of 60%.

[0220] Example 8

[0221] The preparation of the battery cell was the same as that of Example 1 except for the following differences.

[0222] In the preparation step of the insulating coating slurry, the weight ratio of the insulating particle boehmite, the binder polytetrafluoroethylene, the dispersant sodium carboxymethyl cellulose (CMC), and the solvent deionized water is 20:4:0.5:75.5.

[0223] The insulating coating formed after drying had a thickness of 3 μm and a porosity of 90%.

[0224] Comparative Example 1

[0225] The preparation of the battery cell is the same as that of Example 1, except that the insulating coating slurry is not coated on the surface of the positive electrode active material layer and the positive electrode sheet is not pre-lithiated.

[0226] The positive electrode sheet is directly stacked and wound with the separator and the negative electrode sheet in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, injected with electrolyte after drying, and undergoes vacuum packaging, standing, formation, shaping and other processes to obtain a battery cell.

[0227] Comparative Example 2

[0228] The preparation of the battery cell was the same as that of Example 1, except that the insulating coating slurry was not coated on the surface of the positive electrode active material layer.

[0229] Lithium foil is attached to the surface of the positive electrode active material layer. The resulting positive electrode sheet, separator, and negative electrode sheet are then stacked and wound in sequence to form an electrode assembly. The electrode assembly is then placed in an outer packaging, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. Under the action of the electrolyte, the positive electrode sheet undergoes a pre-lithiation reaction through self-discharge, forming a pre-lithiated positive electrode sheet.

[0230] Performance Testing

[0231] (1) First Coulomb efficiency test

[0232] The prepared battery cell was left to rest for 3 hours at 25°C, then charged at a constant current of 0.1C to 4.25V, then charged at a constant voltage to a current of 50μA. After 5 minutes of rest, the battery cell was discharged at a constant current of 0.1C to 2.8V, and the initial charge and discharge capacities were obtained. The ratio of the initial discharge capacity to the initial charge capacity is the initial coulombic efficiency.

[0233] (2) Cyclic performance test

[0234] The prepared battery cell was allowed to stand for 10 minutes at 25° C., discharged at a constant current of 0.5 C to 2.8 V, and then allowed to stand for 10 minutes before performing the following cycle performance test.

[0235] The battery cell was charged at a constant current of 0.5C to 4.25V, then charged at a constant voltage to a current of 0.05C. After standing for 10 minutes, the battery cell was discharged at a constant current of 0.5C to 2.8V and allowed to stand for 10 minutes to obtain the first-cycle discharge capacity of the battery cell. The battery cell was subjected to cyclic charge and discharge testing according to the above method until the capacity of the battery cell after cycling decayed to 60% of the first-cycle discharge capacity. The test was stopped and the number of cycles of the battery cell was recorded.

[0236] The test results are shown in Table 1.

[0237] Table 1

[0238] It can be seen from the test results in Table 1 that by providing an insulating coating on the surface of the positive electrode active material layer before pre-lithiation of the positive electrode plate, the battery cell can have a high first coulombic efficiency and good cycle performance.

[0239] Comparative Example 2 does not provide an insulating coating on the surface of the positive electrode active material layer. Under the action of the electrolyte, the pre-lithiation reaction rate of the elemental metallic lithium material and the positive electrode active material is too rapid. At this time, the pre-lithiation of the positive electrode active material layer is uneven, and too much lithium is embedded in the surface layer. This leads to a larger difference in volume expansion between the surface and bottom layers of the positive electrode active material layer. At the same time, the pore structure of the positive electrode active material layer also deteriorates, which is not conducive to electrolyte infiltration. Therefore, compared with the battery cell prepared in Comparative Example 1 without pre-lithiation, the battery cell prepared in Comparative Example 2 can have a higher initial coulombic efficiency, but the cycle life of the battery cell is significantly reduced.

[0240] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a battery cell, comprising the steps of: Providing a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, an insulating coating slurry and a single metal lithium material, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector; Applying the insulating coating slurry on the surface of the positive electrode active material layer to form an insulating coating after drying; Adhere the single metal lithium material to the surface of the insulating coating to obtain a pretreated positive electrode sheet; Assembling the obtained pretreated positive electrode sheet with the separator and the negative electrode sheet to obtain an electrode assembly; The obtained electrode assembly is assembled with an electrolyte to obtain a battery cell. Under the action of the electrolyte, the pretreated positive electrode plate realizes a pre-lithiation reaction through a self-discharge effect and forms a pre-lithiation positive electrode plate.

2. The preparation method according to claim 1, wherein The insulating coating slurry is coated on the surface of the positive electrode active material layer, and the porosity of the insulating coating formed after drying is 30%-90%, and can be optionally 45%-80%.

3. The preparation method according to any one of claims 1 to 2, wherein: The insulating coating slurry is coated on the surface of the positive electrode active material layer, and the thickness of the insulating coating formed after drying is less than or equal to 20 μm, and can be optionally 1 μm-10 μm.

4. The preparation method according to any one of claims 1 to 3, wherein: The insulating coating slurry comprises insulating particles, a binder and a solvent; Optionally, the weight content of the insulating particles is 8wt%-60wt%, optionally 10wt%-30wt%, based on the total weight of the insulating coating slurry; and / or, Optionally, the weight content of the binder is 0.5wt%-20wt%, optionally 1wt%-10wt%, based on the total weight of the insulating coating slurry; and / or, Optionally, the weight content of the solvent is 38 wt %-95 wt %, optionally 60 wt %-88 wt %, based on the total weight of the insulation coating slurry.

5. The preparation method according to claim 4, wherein: The volume distribution particle size Dv50 of the insulating particles is less than or equal to 20 μm, and can be selected to be 0.1 μm-10 μm.

6. The preparation method according to any one of claims 4 to 5, wherein: The insulating particles include one or more of organic particles and inorganic particles; Optionally, the organic particles include one or more of resin particles, metal organic framework materials, covalent organic framework materials, hyper-crosslinked polymers, intrinsic microporous polymers, and conjugated microporous polymers. More optionally, the resin particles include one or more of vinylidene fluoride resins, olefin resins, styrene resins, styrene-conjugated diene resins, acrylic resins, acrylic-styrene resins, acrylic-conjugated diene resins, acrylic-styrene-conjugated diene resins, polyamide resins, polyurethane resins, and polysiloxane resins. Optionally, the inorganic particles include one or more of ceramics, solid electrolyte materials with lithium ion conductivity, molecular sieves, molecular sieve-like materials, and zeolites.

7. The preparation method according to claim 6, wherein: The insulating particles include one or more of porous organic particles and porous inorganic particles; Optionally, the porous organic particles include one or more of metal organic framework materials, covalent organic framework materials, hyper-crosslinked polymers, intrinsic microporous polymers, and conjugated microporous polymers; Optionally, the porous inorganic particles include one or more of porous ceramics, molecular sieves, molecular sieve-like particles, and zeolites.

8. The preparation method according to any one of claims 4 to 7, wherein: The binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylic resin, polyimide, polyamide, styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyacrylamide, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan; and / or, The solvent includes one or more of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and acetonitrile.

9. The preparation method according to any one of claims 1 to 8, wherein: The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of a nickel-cobalt-manganese-based ternary material, a nickel-cobalt-aluminum-based ternary material, a cobalt-free layered material, lithium iron phosphate, lithium manganese phosphate, lithium nickel manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based material, sulfided polyacrylonitrile, sulfur-based material, iron fluoride, and lithium vanadate, and may be selected from one or more of a nickel-cobalt-manganese-based ternary material, a nickel-cobalt-aluminum-based ternary material, and a cobalt-free layered material; and / or, The single metallic lithium material includes at least one of lithium foil, lithium ribbon and lithium mesh.

10. The preparation method according to any one of claims 1 to 9, wherein: The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or more of a carbon-based material, a silicon-based material, a lithium titanate, a tin-based material, a germanium-based material, an antimony-based material, an aluminum-based material, and a magnesium-based material; Optionally, the battery cell satisfies: Li ×CE Li ×Q Li ≤Q n ×(CE p -CE n )×ρ n , ρ Li is the surface density of the single metal lithium material, in g / cm 2 ; CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the single metal lithium material, in mAh / g; Q n is the specific capacity of the negative electrode active material, in mAh / g; CE p is the first coulombic efficiency of the positive electrode active material; CE n is the first coulombic efficiency of the negative electrode active material; n is the surface density of the negative electrode active material layer, in g / cm 2 .

11. The preparation method according to any one of claims 1 to 10, wherein: The negative electrode plate includes a negative electrode current collector. Optionally, the negative electrode plate also includes an interface modification layer located on at least a portion of the surface of the negative electrode current collector.

12. The preparation method according to claim 11, wherein The battery cell satisfies: Li ×CE Li ×Q Li ≥Q p ×(1-CE′ n )×ρ p , ρ Li is the surface density of the single metal lithium material, in g / cm 2 ; CE Li is the first coulombic efficiency of lithium metal; Q Li is the specific capacity of the single metal lithium material, in mAh / g; Q p is the specific capacity of the positive electrode active material, in mAh / g; CE′ n is the first coulombic efficiency of the negative electrode; ρ p is the surface density of the positive electrode active material layer, in g / cm 2 .

13. The preparation method according to any one of claims 1 to 12, wherein: The electrolyte includes an electrolyte salt and a non-aqueous organic solvent. Optionally, the non-aqueous organic solvent includes one or more of carbonate solvents, carboxylate solvents, ether solvents, fluoroether solvents, and sulfone solvents; and / or, Optionally, the electrolyte salt includes lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium dioxalatoborate, One or more of lithium difluorophosphate, lithium difluorobisoxalate phosphate and lithium tetrafluorooxalate phosphate; and / or, Optionally, the concentration of the electrolyte is 0.5 mol / L-8 mol / L.

14. A battery monomer prepared by the preparation method according to any one of claims 1 to 13.

15. A battery, comprising a battery cell prepared by the preparation method according to any one of claims 1 to 13 or a battery cell according to claim 14.

16. An electrical device comprising the battery according to claim 15, wherein the battery is used to provide electrical energy.

17. A method for preparing a pre-lithiated positive electrode plate, comprising the steps of: Providing a positive electrode plate, an insulating coating slurry and a single metal lithium material, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector; Applying the insulating coating slurry on the surface of the positive electrode active material layer to form an insulating coating after drying; The single metallic lithium material is brought into contact with the insulating coating under the infiltration of an electrolyte, and a pre-lithiation reaction is achieved through a self-discharge effect to obtain a pre-lithiation positive electrode plate.

18. The preparation method according to claim 17, wherein: The insulating coating slurry comprises the insulating coating slurry according to any one of claims 1-13.

19. A pre-lithiated positive electrode sheet prepared by the preparation method according to any one of claims 17-18.

20. A pre-lithiated positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein: The positive electrode active material layer includes a positive electrode active material, at least a portion of which is a pre-lithiated positive electrode active material; The pre-lithiated positive electrode plate further comprises an insulating coating located on the surface of the positive electrode active material, wherein the insulating coating is formed by drying the insulating coating slurry according to any one of claims 1 to 13.

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