Battery monomer, preparation method of battery monomer, battery, power utilization device, pre-lithiated positive pole piece and preparation method of pre-lithiated positive pole piece

Abstract

The invention discloses a battery monomer, a preparation method of the battery monomer, a battery, an electric device, a pre-lithiated positive pole piece and a preparation method of the pre-lithiated positive pole piece. The preparation method of the battery monomer comprises the following steps: providing the positive pole piece, a negative pole piece, an isolating membrane, an electrolyte, insulating coating slurry and an elemental metal lithium material; coating the insulating coating slurry on the surface of the positive electrode active material layer, and drying to form an insulating coating; attaching an elemental metal lithium material to the surface of the insulating coating to obtain a pretreated positive pole piece; assembling the obtained pretreated positive pole piece, an isolating membrane and a negative pole piece to obtain an electrode assembly; and assembling the obtained electrode assembly and an electrolyte to obtain a battery monomer, and under the action of the electrolyte, realizing a pre-lithiation reaction on the pretreated positive pole piece through a self-discharge effect and forming a pre-lithiated positive pole piece. According to the invention, the battery monomer has high first coulombic efficiency, good cycle performance and good machinability.

Description

Technical Field

[0001] The present application relates to a battery cell, a preparation method thereof, a battery, an electrical device, a prelithiated positive electrode sheet and a preparation method thereof. Background Art

[0002] During the first charging process of a lithium-ion battery, a solid electrolyte interface (SEI) film is formed on the surface of the negative electrode. This process consumes the active lithium in the positive electrode, and the loss of active lithium will lead to problems such as reduced battery capacity, reduced Coulombic efficiency, and poor cycle life. In the existing lithium-ion electrochemical system, by pre-supplementing a part of active lithium, since the active lithium can transfer to the negative electrode along with the electrolyte, the loss of active lithium caused by the formation of the SEI film on the negative electrode can be filled, and the Coulombic efficiency, cycle life, and specific energy of the battery can be improved.

[0003] Currently, the prelithiation processes of lithium-ion batteries mainly include an electrochemical prelithiation process, a chemical prelithiation process, and a self-discharge prelithiation process. The electrochemical prelithiation process is a process of introducing metallic lithium as a third electrode into the battery and making the metallic lithium and the negative electrode form a counter electrode, and completing prelithiation by controlling the depth of electrochemical charge and discharge. This process has complex operations and is not conducive to large-scale implementation. The chemical prelithiation process is usually a process of adding a lithium-rich compound, etc. to the positive electrode or the negative electrode to complete prelithiation. This process often has the problem of residual products, which will reduce the specific energy of the battery. The self-discharge prelithiation process is a process of using the potential difference between the elemental metallic lithium material and the positive electrode active material to directly contact the elemental metallic lithium material and the positive electrode active material in the electrolyte to complete prelithiation. This process has simple operations and no residual products, but has the problems of too fast prelithiation reaction rate and difficult process control. The above statements are only used to provide background technical information related to the present application and do not necessarily constitute prior art. Summary of the Invention

[0004] The present application provides a battery cell, a preparation method thereof, a battery, an electrical device, a prelithiated positive electrode sheet and a preparation method thereof, which can adjust the prelithiation reaction rate and also enable the battery cell to have a high first Coulombic efficiency, good cycle performance, and good processability.

[0005] In a first aspect, the present application provides a method for preparing a battery cell, comprising the steps of: providing a positive electrode plate, a negative electrode plate, a separator, an electrolyte, an insulating coating slurry, and a metallic lithium material; the positive electrode plate comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector; coating the insulating coating slurry on the surface of the positive active material layer and drying to form an insulating coating; attaching the metallic lithium material to the surface of the insulating coating to obtain a pretreated positive electrode plate; assembling the obtained pretreated positive electrode plate with the separator and the negative electrode plate to obtain an electrode assembly; assembling the obtained electrode assembly with the electrolyte to obtain a battery cell, and under the action of the electrolyte, the pretreated positive electrode plate realizes a prelithiation reaction through a self-discharge effect and forms a prelithiated positive electrode plate.

[0006] The method for preparing a battery cell provided by the embodiments 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 processes.

[0007] Before prelithiation of the positive electrode plate, the insulating coating is provided on the surface of the positive active material layer in the preparation method provided by the embodiments of the present application, thereby performing a certain insulation treatment on the positive active material layer. The insulating coating can reduce the contact area between the positive active material layer and the metallic lithium material, and can also reduce the prelithiation reaction rate, thereby reducing the swelling of the positive electrode plate caused by the prelithiation process, improving the structural stability of the prelithiated positive active material layer, and reducing problems such as pulverization and shedding of the positive active material layer. Therefore, the preparation method provided by the embodiments of the present application can improve the processability of the positive electrode plate and the battery cell, which is beneficial to the large-scale production of the battery cell.

[0008] The battery cell prepared by the preparation method provided by the embodiments of the present application can have a high first Coulomb efficiency, good cycling performance, and good processability.

[0009] In some embodiments, when the insulating coating slurry is coated on the surface of the positive active material layer and dried, the porosity of the formed insulating coating is 30%-90%, and can be optionally 45%-80%.

[0010] By adjusting the porosity of the insulating coating within the above range, the structural stability of the prelithiated positive active material layer can be improved, problems such as pulverization and shedding of the positive active material layer can be reduced, and the battery performance can be optimized; a good electrolyte passage can also be formed between the metallic lithium material and the positive active material layer, which is beneficial to realizing self-discharge prelithiation and can also make the battery cell have good cycling performance.

[0011] In some embodiments, the insulating coating slurry is coated on the surface of the positive electrode active material layer, and after drying, the thickness of the formed insulating coating is less than or equal to 20 μm, and may be optionally 1 μm - 10 μm.

[0012] By adjusting the thickness of the insulating coating within the above range, the structural stability of the prelithiated positive electrode active material layer can be improved, problems such as pulverization and shedding of the positive electrode active material layer can be reduced, and thus the battery performance can be optimized; the preparation process of the positive electrode sheet can also be optimized, and the processing performance of the positive electrode sheet can be improved.

[0013] By adjusting the thickness of the insulating coating within the above range, a good lithium ion transport path and electrolyte path can also be formed between the elemental metal lithium material and the positive electrode active material layer, and thus the battery cell can also have good cycling performance.

[0014] In some embodiments, the insulating coating slurry includes insulating particles, a binder, and a solvent.

[0015] In some embodiments, the weight content of the insulating particles is 8 wt% - 60 wt%, and may be optionally 10 wt% - 30 wt%, based on the total weight of the insulating coating slurry.

[0016] In some embodiments, the weight content of the binder is 0.5 wt% - 20 wt%, and may be optionally 1 wt% - 10 wt%, based on the total weight of the insulating coating slurry.

[0017] In some embodiments, the weight content of the solvent is 38 wt% - 95 wt%, and may be optionally 60 wt% - 88 wt%, based on the total weight of the insulating coating slurry.

[0018] In some embodiments, the volume distribution particle size Dv50 of the insulating particles is less than or equal to 20 μm, and may be optionally 0.1 μm - 10 μm.

[0019] In some embodiments, the insulating particles include one or more of organic particles and inorganic particles.

[0020] In some embodiments, the organic particles include one or more of resin particles, metal-organic framework materials, covalent organic framework materials, hypercrosslinked polymers, intrinsically microporous polymers, and conjugated microporous polymers.

[0021] 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.

[0022] Optionally, the inorganic particles include one or more of ceramics, solid electrolyte materials with lithium ion conduction ability, molecular sieves, molecular sieve-like materials, and zeolites.

[0023] In some embodiments, the insulating particles include one or more of porous organic particles and porous inorganic particles.

[0024] Optionally, the porous organic particles include one or more of metal-organic framework materials, covalent organic framework materials, hypercrosslinked polymers, intrinsically microporous polymers, and conjugated microporous polymers.

[0025] Optionally, the porous inorganic particles include one or more of porous ceramics, molecular sieves, molecular sieve-like materials, and zeolites.

[0026] 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, acrylate resin, polyimide, polyamide, styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyacrylamide, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0027] In some embodiments, the solvent includes one or more of water, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran, and acetonitrile.

[0028] 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 nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, cobalt-free layered materials, lithium iron phosphate, lithium manganese phosphate, lithium nickel manganate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based materials, sulfurized polyacrylonitrile, sulfur-based materials, iron fluoride, and lithium vanadate, and is optionally one or more of nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, and cobalt-free layered materials.

[0029] In some embodiments, the elemental metallic lithium material includes at least one of lithium foil, lithium strip, and lithium mesh.

[0030] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one or more of carbon-based materials, silicon-based materials, lithium titanate, tin-based materials, germanium-based materials, antimony-based materials, aluminum-based materials, and magnesium-based materials. Optionally, the battery cell satisfies: ρ Li ×CE Li ×Q Li ≤Qn ×(CE p -CE n )×ρ n 。ρ Li is the areal density of the elemental lithium metal material, with the unit of g / cm 2 ; CE Li is the first Coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental lithium metal material, with the unit of mAh / g; Q n is the specific capacity of the negative electrode active material, with the unit of 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 areal density of the negative electrode active material layer, with the unit of g / cm 2 . Thus, the loss of active lithium caused by the formation of the SEI film on the negative electrode can be filled, thereby improving the first Coulombic efficiency, cycle life and specific energy of the battery cell; and the problem of lithium deposition on the negative electrode can also be reduced.

[0031] In some embodiments, the negative electrode tab includes a negative electrode current collector. Optionally, the negative electrode tab further includes an interfacial modification layer located on at least a part of the surface of the negative electrode current collector. Optionally, the battery cell satisfies: ρ Li ×CE Li ×Q Li ≥Q p ×(1 - CE′ n )×ρ p . ρ Li is the areal density of the elemental lithium metal material, with the unit of g / cm 2 ; CE Li is the first Coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental lithium metal material, with the unit of mAh / g; Q p is the specific capacity of the positive electrode active material, with the unit of mAh / g; CE′ n is the first Coulombic efficiency of the negative electrode tab; ρ p is the areal density of the positive electrode active material layer, with the unit of g / cm 2 . Thus, the loss of active lithium caused by the formation of the SEI film on the negative electrode can be filled, thereby improving the first Coulombic efficiency, cycle life and specific energy of the battery cell.

[0032] In some embodiments, the electrolyte includes an electrolyte salt and a non-aqueous organic solvent.

[0033] Optionally, the non-aqueous organic solvent includes one or more of carbonate solvents, carboxylate solvents, ether solvents, fluoroether solvents, and sulfone solvents.

[0034] Optionally, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorophosphate, lithium difluoro(oxalato)diphosphate, and lithium tetrafluoro(oxalato)phosphate.

[0035] Optionally, the concentration of the electrolyte solution is 0.5 mol / L - 8 mol / L.

[0036] 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.

[0037] 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 the battery cell of the second aspect of the present application.

[0038] In a fourth aspect, the present application provides an electrical device, which includes the battery of the third aspect of the present application, and the battery is used to provide electrical energy.

[0039] In a fifth aspect, the present application provides a method for preparing a prelithiated positive electrode sheet, including the steps of: providing a positive electrode sheet, an insulating coating slurry, and a metallic lithium material; the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and drying to form an insulating coating; contacting the metallic lithium material with the insulating coating under the infiltration of an electrolyte solution, and realizing a prelithiation reaction through a self-discharge effect to obtain a prelithiated positive electrode sheet.

[0040] In some embodiments, the insulating coating slurry includes the insulating coating slurry of the first aspect of the present application.

[0041] In a sixth aspect, the present application provides a prelithiated positive electrode sheet, which is prepared by the preparation method of the fifth aspect of the present application.

[0042] In a seventh aspect, the present application provides another prelithiated positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer provided 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 part of the positive electrode active material is a prelithiated positive electrode active material; the prelithiated positive electrode sheet further 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. Description of the Drawings

[0043] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for use in the embodiments of the present application. Obviously, the accompanying drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the accompanying drawings.

[0044] Figure 1 It is a schematic structural diagram of a vehicle provided by some embodiments of the present application.

[0045] Figure 2 It is an explosion schematic diagram of a battery provided by some embodiments of the present application.

[0046] Figure 3 For Figure 2 the schematic structural diagram of the battery module shown.

[0047] Figure 4 It is a schematic structural diagram of a battery cell provided by some embodiments of the present application.

[0048] Figure 5 It is an explosion schematic diagram of a battery cell provided by some embodiments of the present application.

[0049] In the accompanying drawings, the accompanying drawings are not necessarily drawn to actual scale.

[0050] The description of the reference numerals is as follows: 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Box; 5a. First box part; 5b. Second box part; 5c. Accommodating space; 6. Battery module; 7. Battery cell; 71. Shell; 72. Electrode assembly; 73. Cover plate. Detailed implementation manners

[0051] Hereinafter, the embodiments of the battery cell of the present application, its preparation method, battery, power-consuming device, pre-lithiated positive electrode sheet, and its preparation method will be specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where the detailed descriptions of well-known matters are omitted and the repeated descriptions of actually identical structures 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 accompanying 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.

[0052] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] If there is no special instruction, all embodiments and optional embodiments of this 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 this application.

[0054] If there is no special instruction, 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 considered to be included in the disclosure of this application.

[0055] If there is no special instruction, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0056] In this application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0057] In the description of the embodiments of the present application, unless otherwise specified, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply indicates that the horizontal height of the first feature is less than that of the second feature.

[0058] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art.

[0059] Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of the present application. Unless otherwise specified, the test temperature for each parameter is 25 °C.

[0060] The battery mentioned in the embodiments of the present application can 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 can include battery cells, battery modules, battery packs, etc. A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging. When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery can 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 can be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, part of the box body can become at least part of the vehicle's floor, or part of the box body can become at least part of the crossbeam and longitudinal beam of the vehicle.

[0061] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0062] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries.

[0063] The battery can be used as the power source of an electrical device or as the energy storage unit of an electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), a vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0064] The electrical device can select the type of battery according to its usage requirements, such as battery cells, battery modules, or battery packs.

[0065] For the convenience of description, the following embodiments take the electrical device as a vehicle as an example for illustration.

[0066] Figure 1 The structural schematic diagram of the vehicle provided by some embodiments of the present application is as follows. Figure 1 As shown, a battery 2 is provided inside the vehicle 1, and the battery 2 can be arranged at the bottom, head, or tail of the vehicle 1. The battery 2 can be used to supply power to the vehicle 1. For example, the battery 2 can be used as the operating power source of the vehicle 1.

[0067] 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, it is used for the working power requirements during the start, navigation, and driving of the vehicle 1.

[0068] In some embodiments, the battery 2 can not only be used as the operating power source of the vehicle 1 but also as the driving power source of the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0069] Figure 2 The explosion schematic diagram of the battery provided by some embodiments of the present application is as follows. Figure 2 As shown, the battery 2 includes a box body 5 and battery cells (not shown), and the battery cells are accommodated in the box body 5.

[0070] The box body 5 is used to accommodate the battery cells, and the box body 5 can have various structures. In some embodiments, the box body 5 can include a first box body part 5a and a second box body part 5b. The first box body part 5a and the second box body part 5b cover each other, and the first box body part 5a and the second box body part 5b jointly define an accommodation space 5c for accommodating the battery cells. The second box body part 5b can be a hollow structure with one end open, and the first box body part 5a is a plate-like structure. The first box body part 5a covers the open side of the second box body part 5b to form the box body 5 with the accommodation space 5c; both the first box body part 5a and the second box body part 5b can also be hollow structures with one side open, and the open side of the first box body part 5a covers the open side of the second box body part 5b to form the box body 5 with the accommodation space 5c. Of course, the first box body part 5a and the second box body part 5b can have various shapes, such as a cylinder, a cuboid, etc.

[0071] To improve the sealing performance after the connection between the first box body part 5a and the second box body part 5b, a sealing member, such as sealant, sealing ring, etc., can also be provided between the first box body part 5a and the second box body part 5b.

[0072] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body.

[0073] In the battery 2, the battery cells can be one or multiple. If there are multiple battery cells, they can be connected in series, parallel, or in a mixed connection. A mixed connection means that there are both series and parallel connections among multiple battery cells. Multiple battery cells can be directly connected in series, parallel, or in a mixed connection together, and then the whole formed by multiple battery cells is accommodated in the box body 5. Of course, it can also be that multiple battery cells are first connected in series, parallel, or in a mixed connection to form battery modules 6, and then multiple battery modules 6 are connected in series, parallel, or in a mixed connection to form a whole and are accommodated in the box body 5.

[0074] Figure 3 For Figure 2 the structural schematic diagram of the battery module shown. As Figure 3 shown, there are multiple battery cells 7. Multiple battery cells 7 are first connected in series, parallel, or in a mixed connection to form battery modules 6. Multiple battery modules 6 are then connected in series, parallel, or in a mixed connection to form a whole and are accommodated in the box body.

[0075] The multiple battery cells 7 in the battery module 6 can be electrically connected through a busbar component to achieve the parallel, series, or mixed connection of the multiple battery cells 7 in the battery module 6.

[0076] The battery cells mentioned in the embodiments of the present application can include at least one of lithium-ion battery cells, lithium metal battery cells without a negative electrode, etc.

[0077] An anode-free battery cell generally refers to a battery cell formed without actively disposing an anode active material layer on the anode side during the manufacturing process of the battery cell. For example, during the manufacturing process of the battery cell, no layer is disposed at the anode through processes such as coating or deposition, or the anode active material layer is formed by a carbonaceous active material layer. During the first charge, ions gain electrons on the anode side and deposit on the surface of the anode current collector to form a metal. During discharge, the metal can be converted into ions and return to the cathode, realizing cyclic charge and discharge. Compared with other battery cells, the anode-free battery cell can obtain a higher energy density due to the absence of a conventional anode active material layer. In some embodiments, in order to improve the performance of the battery cell, some substances that can be used as conventional anode active materials, such as carbon materials, can also be disposed on the anode side of the anode-free battery cell. Although these substances have a certain capacity, since their content is small and they are not used as the main anode active material in the battery cell, the battery cell thus formed can still be regarded as an anode-free battery cell. The CB (Cell Balance) value of the anode-free battery cell is usually very small. For example, in some embodiments, the CB value of the anode-free battery cell can be less than or equal to 0.1. The CB value is the unit area capacity of the anode in the battery cell divided by the unit area capacity of the cathode. Since the anode-free battery cell does not contain or only contains a small amount of anode active material, the unit area capacity of the anode is small, and thus the CB value is very small, usually less than or equal to 0.1 for example.

[0078] There is a potential difference between the elemental lithium metal material and the cathode active material. Under the action of the electrolyte, the elemental lithium metal material comes into contact with the cathode active material and undergoes a self-discharge reaction, thereby enabling prelithiation. However, this self-discharge reaction (prelithiation reaction) often has problems such as too fast reaction rate and difficult process control. After the cathode is prelithiated, its volume will expand. Too fast a prelithiation reaction rate easily causes the structure of the cathode electrode sheet to become unstable, and too much lithium is easily embedded in the surface layer position of the prelithiated cathode active material layer, resulting in a larger volume expansion difference between the surface layer position and the bottom layer position (i.e., the position close to the cathode current collector) of the cathode active material layer. As a result, problems such as pulverization and shedding of the cathode active material layer are likely to occur on the cathode electrode sheet, affecting the processability of the cathode electrode sheet and the battery, being not conducive to large-scale production, and also affecting the cycle performance of the battery. Especially for batteries that require a large amount of lithium supplementation (such as batteries with a relatively low initial Coulomb efficiency), the deterioration of their cycle performance is more obvious.

[0079] In the prior art, a pre-lithiation reaction is achieved and a pre-lithiated positive electrode sheet is formed by bringing the positive electrode sheet to be processed into contact with elemental lithium metal material under the infiltration of an organic solvent without electrolyte salt, and utilizing the self-discharge effect. Since an organic solvent without electrolyte salt is used, the rate of the pre-lithiation reaction is greatly reduced compared with that using an electrolyte solution. However, this pre-lithiation process requires an additional supply of an organic solvent without electrolyte salt, thereby increasing the raw material cost of the battery and the cost of recycling the organic solvent; at the same time, this pre-lithiation process cannot be integrated into the current battery manufacturing process and production equipment, and additional manufacturing processes are added, thereby increasing the manufacturing cost of the battery.

[0080] An embodiment of the present application provides a method for preparing a battery cell.

[0081] The preparation method includes the steps of: providing a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte solution, an insulating coating slurry, and an elemental lithium metal material, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and drying to form an insulating coating; attaching the elemental lithium metal 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; and assembling the obtained electrode assembly with the electrolyte solution to obtain a battery cell. Under the action of the electrolyte solution, the pretreated positive electrode sheet realizes a pre-lithiation reaction through the self-discharge effect and forms a pre-lithiated positive electrode sheet.

[0082] The method for preparing a battery cell provided by the embodiment of the present application has a simple process, can be integrated into the current battery cell preparation process and production equipment, and does not require additional processes, such as a solvent recovery process.

[0083] Before pre-lithiating the positive electrode sheet, the preparation method provided by the embodiment of the present application first sets an insulating coating on the surface of the positive electrode active material layer, 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 lithium metal material, and can also reduce the rate of the pre-lithiation reaction, thereby reducing the swelling of the positive electrode sheet caused by the pre-lithiation process, and thus improving the structural stability of the pre-lithiated positive electrode active material layer and reducing problems such as pulverization and shedding of the positive electrode active material layer. Therefore, the preparation method provided by the embodiment of the present application can improve the processability of the positive electrode sheet and the battery cell, which is beneficial to the large-scale production of the battery cell.

[0084] 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 and reducing internal short circuits in the battery cell during cycling.

[0085] The battery monomer prepared by the preparation method provided by the embodiments of the present application can have a high first Coulomb efficiency, good cycle performance, and good processability.

[0086] In some embodiments, the coating method of the insulating coating slurry may include, but is not limited to, microgravure coating, submicron spraying, etc.

[0087] In some embodiments, when the insulating coating slurry is coated on the surface of the positive electrode active material layer and dried, the porosity of the formed insulating coating may be 30%-90%, for example, it may be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range composed of the above arbitrary values.

[0088] By adjusting the porosity of the insulating coating, the prelithiation reaction rate between the elemental lithium metal material and the positive electrode active material layer can be adjusted. When other conditions are the same, the lower the porosity of the insulating coating, the stronger the ability of the insulating coating to reduce the prelithiation reaction rate, and the better the structural stability of the prelithiated positive electrode active material layer. However, the ion transport resistance increases during the subsequent charge and discharge cycles of the battery monomer, which is not conducive to further improving the cycle performance of the battery monomer.

[0089] By adjusting the porosity of the insulating coating within the above range, the structural stability of the prelithiated positive electrode active material layer can be improved, problems such as pulverization and shedding of the positive electrode active material layer can be reduced, and thus the battery performance can be optimized; a good electrolyte passage can also be formed between the elemental lithium metal material and the positive electrode active material layer, which is conducive to realizing self-discharge prelithiation and can also make the battery monomer have good cycle performance.

[0090] Optionally, the porosity of the insulating coating may be 45%-80%. This can enable the battery monomer to have better cycle performance.

[0091] The porosity of the insulating coating can be tested according to the following method: The insulating coating slurry is directly coated on the positive electrode current collector according to the same process, and the porosity of the sample is tested after the same drying process. The porosity of the sample can be tested with reference to GB / T 24586-2009.

[0092] The porosity P of the sample = 1 - ρ 1 / ρ 2 , ρ 1 represents the apparent density of the sample, which can be calculated based on the weight and volume of the sample; ρ 2 represents the true density of the sample, and can be tested by using an inert gas (such as nitrogen) as the medium and adopting the gas displacement method with a true density tester with reference to GB / T 24586-2009.

[0093] In some embodiments, an insulating coating slurry is coated on the surface of the positive electrode active material layer, and after drying, the thickness of the formed insulating coating 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 composed of any of the above values.

[0094] By adjusting the thickness of the insulating coating, the prelithiation reaction rate between the elemental lithium metal material and the positive electrode active material layer can be adjusted. When other conditions are the same, as the thickness of the insulating coating increases, the ability of the insulating coating to reduce the prelithiation reaction rate becomes stronger, and the structural stability of the prelithiated positive electrode active material layer becomes better. However, during the subsequent charge and discharge cycles of the battery cell, the ion transport path becomes longer, which is not conducive to further improving the cycle performance of the battery cell.

[0095] By adjusting the thickness of the insulating coating within the above range, the structural stability of the prelithiated positive electrode active material layer can be improved, problems such as pulverization and shedding of the positive electrode active material layer can be reduced, and thus the battery performance can be optimized; the preparation process of the positive electrode sheet can also be optimized, and the processing performance of the positive electrode sheet can be improved.

[0096] By adjusting the thickness of the insulating coating within the above range, a good lithium ion transport path and electrolyte path can also be formed between the elemental lithium metal material and the positive electrode active material layer, and thus the battery cell can also have good cycle performance.

[0097] Optionally, the thickness of the insulating coating can be 1 μm - 10 μm, 1 μm - 8 μm, 1 μm - 5 μm, 1 μm - 3 μm. This can enable the battery cell to have better cycle performance.

[0098] In some embodiments, the insulating coating slurry can include insulating particles, a binder, and a solvent.

[0099] 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.

[0100] The insulating particles are mainly used to provide contact sites between the elemental lithium metal material and the positive electrode active material layer, and to form an electrolyte path and a lithium ion transport path for self-discharge prelithiation.

[0101] By adjusting the types, morphologies, and / or contents of the various components in the insulating coating slurry, the porosity of the insulating coating can be adjusted, thereby the prelithiation reaction rate can be adjusted, and the structural stability of the prelithiated positive electrode active material layer can be further improved, reducing problems such as pulverization and shedding of the positive electrode active material layer; the preparation process of the positive electrode sheet can be further optimized, and the processing performance of the positive electrode sheet can be improved; a good lithium ion transmission path and electrolyte path can be formed between the elemental metal lithium material and the positive electrode active material layer, and further, the battery cell can have good cycling performance.

[0102] Optionally, in some embodiments, the weight content of the insulating particles can be 8 wt% - 60 wt%, optionally 10 wt% - 30 wt%, based on the total weight of the insulating coating slurry.

[0103] Optionally, in some embodiments, the weight content of the binder can be 0.5 wt% - 20 wt%, optionally 1 wt% - 10 wt%, based on the total weight of the insulating coating slurry.

[0104] Optionally, in some embodiments, the weight content of the solvent can be 38 wt% - 95 wt%, optionally 60 wt% - 88 wt%, based on the total weight of the insulating coating slurry.

[0105] In some embodiments, the insulating coating slurry may further include a dispersant. The dispersant helps to improve the uniformity of the insulating coating, thereby helping to improve the uniformity and structural stability of the prelithiated positive electrode active material layer, and further reducing problems such as pulverization and shedding of the positive electrode active material layer.

[0106] Optionally, the dispersant may include sodium carboxymethyl cellulose (CMC).

[0107] Optionally, the weight content of the dispersant can be less than or equal to 2 wt%, based on the total weight of the insulating coating slurry.

[0108] In some embodiments, the volume distribution particle size Dv50 of the insulating particles can be less than or equal to 20 μm, optionally 0.1 μm - 10 μm, 0.5 μm - 8 μm, 0.5 μm - 5 μm, 0.5 μm - 3 μm, 1 μm - 3 μm.

[0109] The volume distribution particle size Dv50 of the material has the meaning well-known in the art, which represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by the instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T19077 - 2016 Laser diffraction method for particle size distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0110] In some embodiments, the insulating particles may include one or more of organic particles and inorganic particles.

[0111] In some embodiments, the organic particles may include one or more of resin particles, metal-organic framework materials (MOFs), covalent organic framework materials (COFs), hypercrosslinked polymers (HCPs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs).

[0112] 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.

[0113] In some embodiments, the inorganic particles may include one or more of ceramics, solid electrolyte materials with lithium ion conduction ability, molecular sieves, zeotype molecular sieves, and zeolites.

[0114] Optionally, the ceramics may include, but are not limited to, one or more of alumina, zirconia, silica, titania, magnesia, vanadium oxide, zinc oxide, barium oxide, calcium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, hydrated alumina, 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, muscovite, bentonite, hectorite, kaolin, talc, dolomite, cristobalite, wollastonite, diatomaceous earth.

[0115] Optionally, the solid electrolyte materials with lithium ion conduction ability may include, but are not limited to, lithium titanium phosphate Li x Ti y (PO 4 ) 3 (0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate Li x Al y Ti z (PO 4 ) 3 (abbreviated as LATP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum germanium phosphate Li x Al y Ge z (PO 4 ) 3 (abbreviated as LAGP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum zirconium phosphate Lix Al y Zr z (PO 4 ) 3 (abbreviated as LAZP, 0 < x < 2, 0 < y < 1, 0 < z < 3), lithium aluminum chromium phosphate Li x Al y Cr z (PO 4 ) 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 TiO 3 (0 < x < 2, 0 < y < 3), lithium lanthanum zirconium oxide Li 7 La 3 Zr 2 O 12 (abbreviated as LLZO), lithium lanthanum tantalum oxide Li 5 La 3 Ta 2 O 12 (abbreviated as LLTA), lithium zinc germanium oxide (Li 14 ZnGe 4 O 16 ), lithium thiargyrite electrolyte Li 6 PS 5 X (X includes one or more selected from Cl, Br, I), SiS 2 -type glass Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), P 2 S 5 -type glass Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), lithium tetrathiophosphate Li 3 PS 4 , Li 7 P 3 S 11 , lithium germanium phosphorus sulfur sulfide Li 10 GeP 2 S 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 doped element is not particularly limited as long as it does not damage the gist of the present application.

[0116] The insulating particles may include one or more of non-porous insulating particles and porous insulating particles.

[0117] In some embodiments, the insulating particles may include one or more of porous organic particles and porous inorganic particles.

[0118] This is conducive to forming an insulating coating with a higher porosity between the elemental lithium metal material and the positive electrode active material layer, thereby facilitating the formation of good lithium-ion transport pathways and electrolyte pathways, further reducing the pre-lithiation reaction rate, and further improving the structural stability of the pre-lithiated 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 and improve the processing performance of the positive electrode sheet; it can also endow the battery cell with good cycling performance.

[0119] In some embodiments, the porous organic particles may include, but are not limited to, one or more of metal-organic framework materials (MOFs), covalent organic framework materials (COFs), hyper-crosslinked polymers (HCPs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs).

[0120] In some embodiments, the porous inorganic particles may include, but are not limited to, one or more of porous ceramics, molecular sieves, zeotype molecular sieves, and zeolites.

[0121] 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, acrylate 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.

[0122] Within the above range, the binder can have good film-forming properties and adhesion, thereby enabling the insulating particles to adhere well to the surface of the positive electrode active material layer and reducing problems such as pulverization and shedding of the positive electrode active material layer; in addition, the binder also has good oxidation resistance and reduction resistance, which is conducive to avoiding being reduced during the pre-lithiation reaction and being oxidized during the charge and discharge process.

[0123] 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.

[0124] In some embodiments, the elemental lithium metal material may include at least one of lithium foil, lithium strip, and lithium mesh.

[0125] In some embodiments, the process of attaching the elemental lithium metal material to the surface of the insulating coating to obtain the pretreated positive electrode sheet may include, but is not limited to, rolling.

[0126] [Positive electrode sheet]

[0127] The positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes a material capable of deintercalating and intercalating lithium.

[0128] 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 manganate, lithium cobaltate, lithium manganate, lithium nickelate, lithium-rich manganese-based materials, sulfonated polyacrylonitrile, sulfur-based materials, iron fluoride, lithium vanadate, and may be optionally one or more of nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, and cobalt-free layered materials.

[0129] 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.

[0130] 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, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate 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).

[0131] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil can be used. The composite current collector can 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 can 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 can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0132] The positive electrode active material layer is generally formed by coating a positive electrode slurry on the positive electrode current collector and then drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional positive electrode conductive agent, an optional positive electrode binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0133] [Negative electrode tab]

[0134] In some embodiments, the negative electrode tab can include a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. 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, lithium titanate, a tin-based material, a germanium-based material, an antimony-based material, an aluminum-based material, and a magnesium-based material.

[0135] Optionally, the carbon-based material can include, but is not limited to, one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0136] Optionally, the silicon-based material can include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0137] Optionally, the silicon-based material can also include one or more of alkali metal elements and alkaline earth metal elements. Optionally, the alkali metal includes Li. Optionally, the alkaline earth metal includes Mg. As an example, the silicon-based material can be a silicon-based material pre-inserted with Li.

[0138] Optionally, the battery cell satisfies: ρ Li ×CE Li ×Q Li ≤Q n ×(CE p -CE n )×ρ n . Thus, the loss of active lithium caused by the formation of the SEI film on the negative electrode can be compensated, thereby improving the first Coulomb efficiency, cycle life, and specific energy of the battery cell; and the problem of lithium deposition on the negative electrode can also be reduced.

[0139] ρ Li is the areal density of the single-element metallic lithium material, with the unit of g / cm 2 ; CE Li is the initial Coulombic efficiency of the lithium metal; Q Li is the specific capacity of the single-element metallic lithium material, with the unit of mAh / g; Q n is the specific capacity of the negative electrode active material, with the unit of mAh / g; CE p is the initial Coulombic efficiency of the positive electrode active material; CE n is the initial Coulombic efficiency of the negative electrode active material; ρ n is the areal density of the negative electrode active material layer, with the unit of g / cm 2 .

[0140] The areal density ρ of the single-element metallic lithium material Li refers to the ratio of the total mass of the single-element 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.

[0141] The initial Coulombic efficiency CE of the lithium metal Li can be obtained by the following method: Assemble the lithium sheet into a symmetric cell, and the electrolyte and separator used in the symmetric cell are the same as those in the battery monomer; After standing the assembled symmetric cell for 12 h, perform constant current charging at 0.1C, and then perform constant voltage charging until the current is 50 μA to obtain the charging capacity; After standing for 5 min, discharge the symmetric cell at 0.1C with constant current to obtain the discharge capacity. The ratio of the discharge capacity to the charging capacity is the initial Coulombic efficiency CE of the lithium metal Li .

[0142] The specific capacity Q of the single-element metallic lithium material Li is 3860 mAh / g.

[0143] The specific capacity Q of the negative electrode active material n , the initial Coulombic efficiency CE of the negative electrode active material n can be obtained by the following method: Using the lithium sheet as the counter electrode, assemble it with the negative electrode sheet into a button cell, and the negative electrode sheet used in the button cell (if the negative electrode sheet used in the battery monomer is double-sided coated with the negative electrode active material layer, it needs to be adjusted to a single-sided coated negative electrode active material layer first), the electrolyte and separator are the same as those in the battery monomer; After standing the assembled button cell for 12 h, discharge it at 0.1C with constant current to obtain the discharge capacity; After standing for 5 min, charge the button cell at 0.1C with constant current, and then perform constant voltage charging until the current is 50 μA to obtain the charging 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 the charging capacity to the discharge capacity is the initial Coulombic efficiency CE of the negative electrode active material n .

[0144] The initial Coulombic efficiency CE of the positive electrode active material p can be obtained by the following method: using a lithium sheet as the counter electrode, assembling it with the positive electrode sheet into a button cell. The positive electrode sheet used in the button cell (when the positive electrode sheet used in the battery monomer is double-sided coated, it needs to be adjusted to single-sided coating first), the electrolyte and the separator are the same as those of the battery monomer; after the assembled button cell is left standing for 12 h, it is charged at a constant current of 0.1 C, and then charged at a constant voltage until the current is 50 μA to obtain the charging capacity; after standing for 5 min, the button cell is discharged at a constant current of 0.1 C to obtain the discharging capacity. The ratio of the discharging capacity to the charging capacity is the initial Coulombic efficiency CE of the positive electrode active material p 。

[0145] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. As an example, 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

[0146] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. As an example, 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, water-based acrylic resins (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS)

[0147] In some embodiments, the negative electrode active material layer may further include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc

[0148] The negative electrode sheet can be prepared by the following method: dispersing the negative electrode active material, negative electrode binder, negative electrode conductive agent, optional other additives, etc. in a solvent and stirring evenly to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and rolling, a negative electrode sheet is formed. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto

[0149] Alternatively, in some embodiments, the negative electrode sheet may include a negative electrode current collector but does not include the above-mentioned negative electrode active material layer, and thus a lithium metal battery monomer without a negative electrode can be assembled

[0150] In some embodiments, the negative electrode sheet may further include an interface modification layer located on at least a part of the surface of the negative electrode current collector

[0151] Optionally, the interface modification layer may include, but is not limited to, one or more of solid electrolyte materials, metal oxides, non-metal oxides, metal sulfides, non-metal sulfides, metal nitrides, non-metal nitrides, and carbon-based materials. Thereby, the deposition behavior of lithium metal on the negative electrode can be adjusted, and the formation of dendrites can be reduced.

[0152] Optionally, the battery cell satisfies: ρ Li ×CE Li ×Q Li ≥Q p ×(1 - CE′ n )×ρ p . Thereby, the loss of active lithium caused by the formation of the SEI film on the negative electrode can be filled, and thus the first Coulombic efficiency, cycle life, and specific energy of the battery cell can be improved.

[0153] ρ Li is the areal density of the elemental lithium metal material, with the unit of g / cm 2 ; CE Li is the first Coulombic efficiency of lithium metal; Q Li is the specific capacity of the elemental lithium metal material, with the unit of mAh / g; Q p is the specific capacity of the positive electrode active material, with the unit of mAh / g; CE′ n is the first Coulombic efficiency of the negative electrode sheet; ρ p is the areal density of the positive electrode active material layer, with the unit of g / cm 2 .

[0154] The first Coulombic efficiency CE′ of the negative electrode sheet n can be obtained as follows: Using a lithium sheet as the counter electrode, assemble it with the negative electrode sheet into a coin cell. The negative electrode sheet used in the coin cell (when the negative electrode sheet used in the battery cell is double-sided coated with the interface modification layer, it needs to be adjusted to a single-sided coated interface modification layer first), the electrolyte, and the separator are the same as those of the battery cell; after standing the assembled coin cell for 12 h, discharge it at a constant current of 0.1C to obtain the discharge capacity; after standing for 5 min, charge the coin cell at a constant current of 0.1C, and then charge it at a constant voltage until the current is 50 μA 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 .

[0155] The 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 the positive electrode sheet into a coin cell. The positive electrode sheet used in the coin cell (when the positive electrode sheet used in the battery monomer is double-sided coated, it needs to be adjusted to single-sided coating first), the electrolyte, and the separator are the same as those in the battery monomer. After standing the assembled coin cell for 12 h, it is charged at a constant current of 0.1C, and then charged at a constant voltage until the current is 50 μA to obtain the charging capacity. After standing for 5 min, the coin 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 active material is the specific capacity Q of the positive active material. p 。

[0156] In some embodiments, the negative current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As an example of the metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, or aluminum alloy foil can be used. As an example of the three-dimensional porous current collector, copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, or aluminum foam can be used. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. 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 substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0157] [Electrolyte]

[0158] In some embodiments, the electrolyte includes an electrolyte salt and a non-aqueous organic solvent.

[0159] Optionally, the non-aqueous organic solvent may include one or more of carbonate solvents, carboxylate solvents, ether solvents, fluoroether solvents, and sulfone solvents.

[0160] The carbonate solvents may include cyclic carbonates and / or chain carbonates. Optionally, the carbonate solvents may include both cyclic carbonates and chain carbonates at the same time. The chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0161] 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), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF 2 ) 2 OCH 3 、C 4 F 9 OCH 3 、H(CF 2 ) 2 OCH 2 CH 3 、H(CF 2 ) 2 OCH 2 CF 3 、H(CF 2 ) 2 CH 2 O(CF 2 ) 2 H、CF 3 CHFCF 2 OCH 3 、CF 3 CHFCF 2 OCH 2 CH 3 、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, 5-trifluoromethyldodecafluorohexyl methyl ether, 5-trifluoromethyldodecafluorohexyl ethyl ether, 5-trifluoromethyldodecafluorohexyl propyl ether, 6-trifluoromethyltetradecafluoroheptyl methyl ether, 6-trifluoromethyltetradecafluoroheptyl ethyl ether, 6-trifluoromethyltetradecafluoroheptyl propyl ether, 7-trifluoromethylhexadecafluorooctyl methyl ether, 7-trifluoromethylhexadecafluorooctyl ethyl ether, 7-trifluoromethylhexadecafluorooctyl propyl ether, or one or more thereof.

[0162] Optionally, the electrolyte salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or one or more of them;

[0163] Optionally, the concentration of the electrolyte solution may be 0.5 mol / L - 8 mol / L, and may be optionally 0.8 mol / L - 4 mol / L. When the concentration of the electrolyte solution is within the above range, the electrolyte solution can have appropriate ionic conductivity.

[0164] In some embodiments, the electrolyte solution may also optionally include additives. For example, the additives may include negative electrode film-forming additives, may also include positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0165] [Separator membrane]

[0166] The separator membrane is located between the positive electrode and the negative electrode, mainly functioning to prevent internal short circuit. This application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0167] In some embodiments, the material of the separator membrane may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane may be a single-layer film or a multi-layer composite film. When the separator membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0168] The electrode assembly may be a wound structure or a stacked structure, and the embodiments of this application do not limit this.

[0169] The battery cell may further include an outer package, which can be used to encapsulate the electrode assembly and the electrolyte. The outer package can be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0170] Figure 4 Schematic structural diagram of the battery cell provided by some embodiments of the present application. Figure 5 Explosion schematic diagram of the battery cell provided by some embodiments of the present application. As Figure 4 and Figure 5 shown, in some embodiments, the outer package may include a housing 71 and a cover plate 73. The housing 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 housing 71 has an opening communicating with 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 included in the battery cell 7 can be one or more, which can be adjusted according to requirements.

[0171] The embodiments of the present application also provide a battery cell prepared by the above preparation method.

[0172] The embodiments of the present application also provide a preparation method for a prelithiated positive electrode sheet. The preparation method includes the steps of: providing a positive electrode sheet, an insulating coating slurry, and a metallic lithium material; the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and drying to form an insulating coating; contacting the metallic lithium material with the insulating coating under the infiltration of the electrolyte, and realizing a prelithiation reaction through a self-discharge effect to obtain a prelithiated positive electrode sheet. The insulating coating slurry can be the above-mentioned insulating coating slurry provided by the embodiments of the present application, which will not be elaborated here.

[0173] Before prelithiation of the positive electrode sheet in the preparation method provided by the embodiments of the present application, an insulating coating is first provided on the surface of the positive electrode active material layer, 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 metallic lithium material, and can also reduce the prelithiation reaction rate, thereby reducing the swelling of the positive electrode sheet caused by the prelithiation process, and thus improving the structural stability of the prelithiated positive electrode active material layer and reducing problems such as pulverization and shedding of the positive electrode active material layer. Therefore, the preparation method provided by the embodiments of the present application can improve the processability of the positive electrode sheet and the battery cell, which is beneficial to the large-scale production of the battery cell.

[0174] The embodiments of the present application also provide a prelithiated positive electrode sheet prepared by the above preparation method.

[0175] Another pre-lithiated positive electrode sheet is also provided in an embodiment of the present application, which includes a positive current collector and a positive active material layer provided on at least one surface of the positive current collector. The positive active material layer includes a positive active material, and at least a part of the positive active material is a pre-lithiated positive active material; the pre-lithiated positive electrode sheet further includes an insulating coating located on the surface of the positive active material, and the insulating coating is formed by drying the above-mentioned insulating coating slurry provided in the embodiment of the present application.

[0176] The insulating coating includes insulating particles and a binder.

[0177] Optionally, the weight content of the insulating particles in the insulating coating may be greater than or equal to 50 wt%, and may be optionally greater than or equal to 70 wt%, based on the total weight of the insulating coating.

[0178] Optionally, the weight content of the binder in the insulating coating may be less than 50 wt%, and may be optionally less than 30 wt%, based on the total weight of the insulating coating.

[0179] Example

[0180] The following examples more specifically describe the content disclosed in the present application. These examples are only for illustrative purposes, because various modifications and variations within the scope of the present application disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0181] Example 1

[0182] Preparation of positive electrode

[0183] The positive active material Li[Ni 0.8 Co 0.1 Mn 0.1 O 2 , conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) according to a mass ratio of 96:2:2 to obtain a positive electrode slurry; the positive electrode slurry is coated on an aluminum foil positive current collector, and through processes such as drying, cold pressing, slitting, and cutting, a positive electrode sheet is obtained. The initial Coulombic efficiency CE p of the positive active material is 93%, the specific capacity Q p of the positive active material is 224 mAh / g, and the areal density ρ p of the positive active material layer is 0.025 g / cm2 .

[0184] Preparation of negative electrode

[0185] Mix the negative electrode active material SiC, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC), and conductive agent carbon black (Super P) in a mass ratio of 95.4:2:1.8:0.8 in an appropriate amount of deionized water solvent and stir well to form a uniform negative electrode slurry; uniformly coat the negative electrode slurry on the surface of the negative electrode current collector copper foil, and obtain the negative electrode plate through processes such as drying, cold pressing, slitting, and cutting. The initial Coulombic efficiency CE of the negative electrode active material n is 80%, and the specific capacity Q of the negative electrode active material n is 1850 mAh / g, and the areal density ρ of the negative electrode active material layer n is 0.003 g / cm 2 .

[0186] Preparation of electrolyte

[0187] Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolve the fully dried LiPF 6 in the above organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0188] Preparation of separator

[0189] Use a porous polyethylene film as the separator.

[0190] Preparation of insulating coating slurry

[0191] Mix insulating particles boehmite, binder polytetrafluoroethylene, dispersant sodium carboxymethyl cellulose (CMC), and solvent deionized water in a weight ratio of 16:4:0.5:79.5 and stir well to form a uniform insulating coating slurry. The volume distribution particle size Dv50 of boehmite is 3 μm.

[0192] Preparation of battery cell

[0193] Coat the insulating coating slurry on the surface of the positive electrode active material layer, and form an insulating coating after drying. The thickness of the insulating coating is 3 μm and the porosity is 80%. Attach a lithium foil to the surface of the insulating coating to obtain a pretreated positive electrode plate. The areal density ρ of the lithium foil Li is 0.179×10 -3 g / cm 2 , and the initial Coulombic efficiency CE of the lithium metal Li is 99.6%, and the specific capacity Q of the lithium foil LiIt is 3860 mAh / g.

[0194] The obtained pretreated positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, dried, and then electrolyte is injected. After vacuum packaging, standing, forming, shaping and other processes, a battery cell is obtained. Under the action of the electrolyte, the pretreated positive electrode sheet undergoes a prelithiation reaction through the self-discharge effect to form a prelithiated positive electrode sheet.

[0195] Example 2

[0196] The preparation of the battery cell is the same as that of Example 1 except for the following differences.

[0197] The thickness of the insulating coating formed after drying is 1 μm.

[0198] Example 3

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

[0200] The thickness of the insulating coating formed after drying is 10 μm.

[0201] Example 4

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

[0203] The thickness of the insulating coating formed after drying is 20 μm.

[0204] Example 5

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

[0206] In the preparation steps of the insulating coating slurry, the weight ratio of the insulating particles boehmite, binder polytetrafluoroethylene, dispersant sodium carboxymethylcellulose (CMC), and solvent deionized water is 10:4:0.5:85.5.

[0207] The volume distribution particle size Dv50 of the boehmite used in the preparation steps of the insulating coating slurry is 0.5 μm.

[0208] The thickness of the insulating coating formed after drying is 3 μm and the porosity is 30%.

[0209] Example 6

[0210] The preparation of the battery cell is the same as that of Example 1 except for the following differences.

[0211] The volume distribution particle size Dv50 of the boehmite used in the preparation steps of the insulating coating slurry is 0.5 μm.

[0212] The thickness of the insulating coating formed after drying is 3 μm, and the porosity is 45%.

[0213] Example 7

[0214] The preparation of the battery cell is the same as that of Example 1 except for the following differences.

[0215] In the preparation step of the insulating coating slurry, the volume distribution particle size Dv50 of boehmite used is 1 μm.

[0216] The thickness of the insulating coating formed after drying is 3 μm, and the porosity is 60%.

[0217] Example 8

[0218] The preparation of the battery cell is the same as that of Example 1 except for the following differences.

[0219] In the preparation step of the insulating coating slurry, the weight ratio of insulating particles boehmite, binder polytetrafluoroethylene, dispersant sodium carboxymethyl cellulose (CMC), and solvent deionized water is 20:4:0.5:75.5.

[0220] The thickness of the insulating coating formed after drying is 3 μm, and the porosity is 90%.

[0221] Comparative Example 1

[0222] 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 plate is not pre-lithiated.

[0223] The positive electrode plate is directly stacked and wound with the separator and the negative electrode plate in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, dried, and then electrolyte is injected. After processes such as vacuum packaging, standing, formation, and shaping, a battery cell is obtained.

[0224] Comparative Example 2

[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.

[0226] A lithium foil is attached to the surface of the positive electrode active material layer. Then, the obtained positive electrode plate is stacked and wound with the separator and the negative electrode plate in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, dried, and then electrolyte is injected. After processes such as vacuum packaging, standing, formation, and shaping, a battery cell is obtained. Under the action of the electrolyte, the positive electrode plate undergoes a pre-lithiation reaction through the self-discharge effect to form a pre-lithiated positive electrode plate.

[0227] Performance test

[0228] (1) First Coulomb efficiency test

[0229] At 25 °C, the prepared battery monomer was left standing for 3 hours, charged at a constant current of 0.1C to 4.25V, and then charged at a constant voltage until the current reached 50 μA; after standing for 5 min, the battery monomer was discharged at a constant current of 0.1C to 2.8V to obtain the first charge capacity and the first discharge capacity. The ratio of the first discharge capacity to the first charge capacity is the first Coulombic efficiency.

[0230] (2) Cycle performance test

[0231] At 25 °C, the prepared battery monomer was left standing for 10 min, discharged at a constant current of 0.5C to 2.8V, and after standing for 10 min, the following cycle performance test was carried out.

[0232] The battery monomer was charged at a constant current of 0.5C to 4.25V, and then charged at a constant voltage until the current reached 0.05C; after standing for 10 min, the battery monomer was discharged at a constant current of 0.5C to 2.8V, and after standing for 10 min, the first-cycle discharge capacity of the battery monomer was obtained. The battery monomer was subjected to cyclic charge and discharge tests according to the above method until the capacity of the battery monomer after cycling decayed to 60% of the first-cycle discharge capacity, and the test was stopped, and the number of cycles of the battery monomer was recorded.

[0233] The test results are shown in Table 1.

[0234] Table 1

[0235] Serial number Initial Coulombic efficiency Number of cycles (cycles) Example 1 101.0％ 370 Example 2 96.5％ 339 Example 3 90.0％ 289 Example 4 87.5％ 269 Example 5 98.2％ 265 Example 6 102.6％ 383 Example 7 101.0％ 372 Example 8 100.0％ 360 Comparative example 1 79.8％ 204 Comparative example 2 99.0％ 50

[0236] It can be seen from the test results in Table 1 that by first providing an insulating coating on the surface of the positive electrode active material layer before pre-lithiation of the positive electrode sheet, the battery monomer can have a high first Coulombic efficiency and good cycle performance.

[0237] In Comparative Example 2, no insulating coating was provided on the surface of the positive electrode active material layer. Under the action of the electrolyte, the pre-lithiation reaction rate of the elemental metal lithium material and the positive electrode active material was too fast. At this time, the pre-insertion of lithium in the positive electrode active material layer was uneven, and too much lithium was inserted at the surface layer position, resulting in a larger volume expansion difference between the surface layer position and the bottom layer position of the positive electrode active material layer; at the same time, the pore structure of the positive electrode active material layer also deteriorated, which was also not conducive to the infiltration of the electrolyte. Therefore, compared with the battery monomer without pre-lithiation in Comparative Example 1, the battery monomer prepared in Comparative Example 2 can have a relatively high first Coulombic efficiency, but the cycle life of the battery monomer is greatly reduced.

[0238] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A preparation method of a battery cell, characterized in that, it includes steps: providing a positive electrode plate, a negative electrode plate, a separator, an electrolyte, an insulating coating slurry and elemental lithium metal material, wherein the positive electrode plate includes a positive current collector and a positive active material layer provided on at least one surface of the positive current collector; coating the insulating coating slurry on the surface of the positive active material layer, and drying to form an insulating coating; attaching the elemental lithium metal material to the surface of the insulating coating to obtain a pretreated positive electrode plate; assembling the obtained pretreated positive electrode plate with the separator and the negative electrode plate to obtain an electrode assembly; assembling the obtained electrode assembly with the electrolyte to obtain a battery cell, and under the action of the electrolyte, the pretreated positive electrode plate realizes a prelithiation reaction through a self-discharge effect and forms a prelithiated positive electrode plate.

2. The preparation method according to claim 1, characterized in that, when the insulating coating slurry is coated on the surface of the positive active material layer and dried, the porosity of the formed insulating coating is 30%-90%, and can be optionally 45%-80%.

3. The preparation method according to any one of claims 1-2, characterized in that, when the insulating coating slurry is coated on the surface of the positive active material layer and dried, the thickness of the formed insulating coating 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 1-3, characterized in that, the insulating coating slurry includes insulating particles, a binder and a solvent; optionally, the weight content of the insulating particles is 8 wt%-60 wt%, and can be optionally 10 wt%-30 wt%, based on the total weight of the insulating coating slurry; and / or, optionally, the weight content of the binder is 0.5 wt%-20 wt%, and can be optionally 1 wt%-10 wt%, based on the total weight of the insulating coating slurry; and / or, optionally, the weight content of the solvent is 38 wt%-95 wt%, and can be optionally 60 wt%-88 wt%, based on the total weight of the insulating coating slurry.

5. The preparation method according to claim 4, characterized in that, 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.

6. The preparation method according to any one of claims 4-5, characterized in that, 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, hypercrosslinked polymers, inherently microporous polymers, conjugated microporous polymers, and 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, polysiloxane resins. Optionally, the inorganic particles include one or more of ceramics, solid electrolyte materials with lithium ion conduction ability, 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, hypercrosslinked polymers, intrinsically microporous polymers, and conjugated microporous polymers; Optionally, the porous inorganic particles include one or more of porous ceramics, molecular sieves, molecular sieve-like materials, and zeolites.

8. The preparation method according to any one of claims 4-7, wherein, the binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylate 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 1-8, wherein, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes one or more of nickel-cobalt-manganese-based ternary materials, nickel-cobalt-aluminum-based ternary materials, cobalt-free layered materials, lithium iron phosphate, lithium manganese phosphate, lithium nickel manganate, lithium cobaltate, lithium manganate, lithium nickelate, lithium-rich manganese-based materials, sulfurized 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; and / or, the elemental lithium metal material includes at least one of lithium foil, lithium strip, and lithium mesh.

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

11. The preparation method according to any one of claims 1-10, wherein, the negative electrode sheet includes a negative electrode current collector, and optionally, the negative electrode sheet further includes an interface modification layer located on at least a part of the surface of the negative electrode current collector.

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

13. The preparation method according to any one of claims 1-12, 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 one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorophosphate, lithium difluoro(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate; and / or, Optionally, the concentration of the electrolyte solution is 0.5 mol / L - 8 mol / L.

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

15. A battery characterized in that it includes a battery cell prepared by the preparation method according to any one of claims 1 - 13 or the battery cell according to claim 14.

16. An electrical device characterized in that it includes the battery according to claim 15, and the battery is used to provide electrical energy.

17. A preparation method of a prelithiated positive electrode sheet characterized in that it includes the steps of: providing a positive electrode sheet, an insulating coating slurry, and a metallic lithium material, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector; coating the insulating coating slurry on the surface of the positive electrode active material layer, and drying to form an insulating coating; bringing the metallic lithium material into contact with the insulating coating under the infiltration of an electrolyte solution, and realizing a prelithiation reaction through a self-discharge effect to obtain a prelithiated positive electrode sheet.

18. According to the preparation method according to claim 17 characterized in that the insulating coating slurry includes the insulating coating slurry according to any one of claims 1 - 13.

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

20. A prelithiated positive electrode sheet, including a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, characterized in that the positive electrode active material layer includes a positive electrode active material, and at least a part of the positive electrode active material is a prelithiated positive electrode active material; the prelithiated positive electrode sheet further 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 according to any one of claims 1 - 13.

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