CN117941090A

CN117941090A - Negative electrode sheet, method for manufacturing same, secondary battery, battery module, battery pack, and electricity using device

Info

Publication number: CN117941090A
Application number: CN202280060213.6A
Authority: CN
Inventors: 何晓宁; 刘成勇; 薛文文; 胡波兵; 钟成斌; 廖赏举; 谢张荻
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-07-07
Filing date: 2022-07-07
Publication date: 2024-04-26
Also published as: WO2024007267A1

Abstract

The application provides a negative electrode plate, a manufacturing method thereof, a secondary battery, a battery module, a battery pack and an electric device. The negative electrode sheet includes: the negative electrode active material layer, and an ion transport layer on at least one surface of the negative electrode active material layer, the ion transport layer having an electron conductivity of not higher than 1X 10 ^‑7 S/cm and an ion conductivity of not lower than 1X 10 ^‑4 S/cm. The cathode pole piece has lower expansion rate after being recycled, thereby improving the cycle performance of the battery.

Description

Negative electrode sheet, method for manufacturing same, secondary battery, battery module, battery pack, and electricity using device

Technical Field

The application relates to the technical field of secondary batteries, in particular to a negative electrode plate, a manufacturing method, a secondary battery, a battery module, a battery pack and an electric device.

Background

In recent years, the application range of secondary batteries is becoming wider, and the secondary batteries are being deeply applied to energy storage power supply systems of hydraulic power, firepower, wind power, solar power stations and the like, and a plurality of fields of electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like.

In the cyclic use process of the lithium ion battery, the negative electrode plate is easy to expand so as to reduce the performance of the lithium ion battery, and even cause the battery failure or safety accident.

Disclosure of Invention

The present application has been made in view of the above problems, and an object of the present application is to provide a negative electrode tab having a low expansion ratio after recycling, and further to improve the cycle performance of a battery.

A first aspect of the present application provides a negative electrode tab comprising: the negative electrode active material layer, and an ion transport layer on at least one surface of the negative electrode active material layer, the ion transport layer having an electron conductivity of not higher than 1X 10 ^-7 S/cm and an ion conductivity of not lower than 1X 10 ^- ⁴ S/cm.

Therefore, the ion transmission layer is arranged on the surface of the anode active material layer, so that the problem that lithium metal is preferentially separated out on the surface of the anode, and the volume expansion of the battery cell is serious is solved. The ion transport layer makes it difficult for lithium ions to get electron deposition as lithium metal on the surface of the anode active layer. The lithium ions can be continuously supplemented in the negative electrode active layer through diffusion, so that deposition of lithium metal in pores in the electrode plate is realized. The negative pole piece reduces the expansion rate of the pole piece and greatly prolongs the cycle life of the battery.

In any embodiment, the ion transport layer comprises an ion conducting polymer and an electrolyte salt. The ion conductive polymer and electrolyte salt form ion transmission layer to reduce the negative electrode plate

The expansion rate is improved, and the cycle life of the battery is prolonged.

In any embodiment, the ion transport layer further comprises at least one of an inorganic fast ion conductor and an inorganic ceramic. The addition of the inorganic fast ion conductor can further improve the ion conductivity of the ion transport layer. The strength of the ion transmission layer can be improved by adding the inorganic ceramic, so that the expansion rate of the negative electrode plate is further reduced, and the cycle performance of the battery cell is improved.

In any embodiment, the ion conducting polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol, and polymethacrylate.

In any embodiment, the inorganic fast ion conductor is selected from one or more of garnet-type Lithium Lanthanum Zirconium Oxide (LLZO), perovskite-structured Lithium Lanthanum Titanium Oxide (LLTO), titanium aluminum phosphate (LATP), and sulfide solid state electrolytes or doping modified materials thereof.

In any embodiment, the mass content of the ion conducting polymer is 20% to 90%, optionally 50% to 80%, based on the total mass of the ion transport layer; or the mass content of the electrolyte salt is 10-50%, optionally 10-30%; or the mass content of the inorganic fast ion conductor is 0-20%, and optionally 5-10%; or the mass content of the inorganic ceramic is 0-10%, and optionally 5-10%.

In any embodiment, the ion transport layer is a composite material formed by crosslinking components comprising a first polymeric monomer, a plasticizer, and an electrolyte salt.

The continuous phase of the composite material is formed through crosslinking of the first polymerization monomer, a substrate framework with a certain mechanical strength is provided for the ion transmission layer, and the ion conductivity of the composite material is improved through the plasticizer and the electrolyte salt in the composite material. The composite material has higher ionic conductivity and lower electronic conductivity, can reduce the expansion rate of the negative pole piece and improve the cycle performance of the battery.

In any embodiment, the first polymeric monomer is selected from one or more of an ester monomer, a sulfone monomer, an amide monomer, a nitrile monomer, or an ether monomer; or the plasticizer is selected from one or more of esters or sulfones monomers.

In any embodiment, the plasticizer is selected from at least one of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

In any embodiment, the component further comprises one or more of a second polymeric monomer, a thickener, and an inorganic ceramic.

The addition of the second polymeric monomer to the composite material can improve the polymerization efficiency and the polymerization degree of the first polymeric monomer; the viscosity of the components can be adjusted by adding the thickener, so that the ion transmission layer is prevented from penetrating into the pores in the negative electrode active material layer, and the performance of the negative electrode plate is reduced; the strength of the ion transmission layer can be further improved by adding inorganic ceramics, and the safety performance and the cycle performance of the battery are improved.

In any embodiment, the first polymeric monomer is present in an amount of 0% to 30%, alternatively 5% to 30%, or the second polymeric monomer is present in an amount of 0% to 30%, alternatively 5% to 20%, or the plasticizer is present in an amount of 30% to 80%, alternatively 40% to 70%, or the electrolyte salt is present in an amount of 10% to 20%, or the thickener is present in an amount of 0% to 10%, alternatively 3% to 10%, or the inorganic ceramic is present in an amount of 0% to 50%, alternatively 0% to 20% based on the total mass of the ion transport layer.

In any embodiment, the component further comprises an active site initiator selected from one or more of peroxy compounds or azo species.

In any embodiment, the inorganic ceramic is selected from one or more of alumina, boehmite, zirconia, aluminum nitride, titania, magnesia, silicon carbide, calcium carbonate, diatomaceous earth.

In any embodiment, the electrolyte salt is selected from one or more of lithium salt, sodium salt.

In any embodiment, the thickener and plasticizer are miscible, and the thickener is selected from one or more of polyvinyl formal, polyvinylidene fluoride and its copolymers, polyvinylidene fluoride, trichloroethylene, polytetrafluoroethylene, acrylic acid rubber, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide, and polyvinylpyrrolidone.

The third aspect of the present application provides a method for manufacturing a negative electrode sheet, the method comprising the steps of: and coating the ion transmission layer on the surface of the anode active material layer to obtain an anode piece, wherein the electron conductivity of the ion transmission layer is not higher than 1X10 ^-7 S/cm, and the lithium ion conductivity is not lower than 1X10 ^-4 S/cm. The method is simple, low in cost and easy to popularize and apply.

In any embodiment, the composition of the ion transport layer comprises an ion conducting polymer, an electrolyte salt, an inorganic fast ion conductor, and an inorganic ceramic.

The fourth aspect of the present application provides a method for manufacturing a negative electrode tab, the method comprising the steps of: and synthesizing the ion transmission layer on the surface of the negative electrode active material layer in situ to obtain a negative electrode plate, wherein the electron conductivity of the ion transmission layer is not higher than 1X 10 ^-7 S/cm, and the lithium ion conductivity is not lower than 1X 10 ^-4 S/cm.

In any embodiment, the ion transport layer is a composite material formed by crosslinking components of a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, a thickener, an inorganic ceramic, and an initiator.

The method can further improve the connection tightness of the ion transmission layer and the anode active material layer by in-situ synthesis, and reduce the deposition of anode metal on the surface of the anode active material layer.

A fifth aspect of the present application provides a secondary battery comprising a positive electrode tab, an electrolyte, and the negative electrode tab of the first or second aspect of the present application or the negative electrode tab manufactured by the manufacturing method of the third or fourth aspect of the present application. The battery has excellent cycle performance.

In any embodiment, the ratio of the lithium ion conductivity λ ₁ of the ion transport layer to the lithium ion conductivity λ ₂ of the electrolyte is less than 1, optionally from 0.3 to 0.7.

A sixth aspect of the application provides a battery module comprising the secondary battery of the fifth aspect of the application.

A seventh aspect of the application provides a battery pack comprising the battery module of the sixth aspect of the application.

An eighth aspect of the application provides an electric device comprising at least one selected from the secondary battery of the fifth aspect of the application, the battery module of the sixth aspect of the application, or the battery pack of the seventh aspect of the application.

Drawings

Fig. 1 is a schematic diagram of lithium ion deposition on the surface of a negative electrode after circulation of a conventional negative electrode sheet.

Fig. 2 is a scanning electron microscope image of lithium ions deposited on the surface of a negative electrode after the circulation of a conventional negative electrode plate.

Fig. 3 is a schematic view of lithium ions deposited in the negative active material layer after cycling of the negative electrode sheet of the present application.

Fig. 4 is a schematic view of a secondary battery according to an embodiment of the present application.

Fig. 5 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 4.

Fig. 6 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 7 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 8 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 7.

Fig. 9 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5a secondary battery; 51a housing; 52 electrode assembly; 53 a top cover assembly; 6, a negative pole piece; 61 current collector; 62 a negative electrode active material layer; 63 lithium metal; 64 ion transport layer.

Detailed Description

Hereinafter, embodiments of the positive electrode active material, the method for manufacturing the same, the positive electrode tab, the secondary battery, the battery module, the battery pack, and the electrical device according to the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand 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" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

Conventional lithium ion batteries often employ designs with high CB values, i.e., the negative electrode capacity is slightly higher than the positive electrode capacity. The inventors have unexpectedly found during the course of research that using a low CB battery design, i.e., a negative electrode capacity that is slightly lower than a positive electrode capacity, can increase the energy density of the battery. However, when the electrode with a low CB value is applied to a battery system containing a liquid electrolyte, the expansion of the negative electrode side is large, which causes a certain obstacle to the structural design and application of the battery cell. As shown in fig. 1, the conventional negative electrode tab 6 includes a current collector 61 and a negative electrode active material layer 62 on at least one surface of the current collector, and the use of a low CB design causes an excessive amount of positive lithium source to be deposited on the surface of the negative electrode active material layer 62, resulting in expansion of the negative electrode by forming a lithium metal layer 63, as shown in fig. 2. Based on the technical problems, the application develops the negative electrode plate with low expansion rate, and the cycle performance of the battery can be obviously improved.

[ Negative electrode sheet ]

Based on this, the application proposes a negative electrode tab comprising: the negative electrode active material layer, and an ion transport layer on at least one surface of the negative electrode active material layer, the ion transport layer having an electron conductivity of not higher than 1X 10 ^-7 S/cm and an ion conductivity of not lower than 1X 10 ^-4 S/cm.

In this context, the term "electron conductivity" is a parameter used to describe the ease of charge flow in a substance, and is inversely related to resistivity.

In this context, the term "ionic conductivity" is a measure used to describe the tendency of a substance to conduct ions. In some embodiments, the ionic conductivity is lithium ion conductivity. In some embodiments, the ionic conductivity is sodium ionic conductivity.

In some embodiments, the ion conductivity of the ion transport layer is not less than 1X 10 ^-3 S/cm.

In some embodiments, the ion transport layer is located on a surface of the anode active material layer that is in contact with the electrolyte.

As shown in fig. 3, the negative electrode tab of the present application solves the problem that lithium metal 63 is preferentially eluted on the surface of the negative electrode so that the volume expansion of the battery cell is serious by providing an ion transport layer 64 on the surface of the negative electrode active material layer 62. The ion transport layer 64 makes it difficult for lithium ions to get an electron deposition as lithium metal 63 on the surface of the anode active layer 62, and lithium ions by diffusion make the lithium ions inside the anode active layer 62 continuously replenished, thereby realizing the deposition of lithium metal 63 in the pores inside the electrode sheet. The negative pole piece reduces the expansion rate of the pole piece and improves the cycle life of the battery.

In some embodiments, the ion transport layer comprises an ion conducting polymer and an electrolyte salt.

As used herein, the term "ion conductive polymer" refers to a conductive polymeric material in which carriers are predominantly positive and negative ions.

In some embodiments, the ion-conducting polymer itself does not have ions, but can complex ionic compounds and allow dissociated ions to move directionally therein under the influence of an electric field. In some embodiments, the ion-conducting polymer refers to ion diffusion which itself assists in dissociating ions through segmental motion, and the ion-conducting polymer is more required to be used under swelling conditions and is better able to conduct dissociated ions.

In this context, the term "electrolyte salt" refers to a salt that can be used as a liquid electrolyte for a battery.

In some embodiments, the electrolyte salt may be one or more selected from lithium salt and sodium salt, and may be one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorosulfimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium difluorophosphate, lithium tetrafluoro oxalato phosphate 、NaPF ₆、NaClO ₄、NaBCl ₄、NaSO ₃CF ₃、Na(CH ₃)C ₆H ₄SO ₃.

The ion conducting polymer and electrolyte salt form ion transmission layer to reduce the expansion rate of the negative pole piece and prolong the service life of the battery.

In some embodiments, the ion transport layer further comprises at least one of an inorganic fast ion conductor and an inorganic ceramic.

Herein, the term "inorganic fast ionic conductor" refers to an inorganic compound that is a fast ionic conductor, also referred to as a solid state electrolyte. It has ion conductivity (1X 10 ^-6S·cm ^-1) and low ion conductivity activation energy (less than or equal to 0.40 eV) which are comparable with that of liquid electrolyte in a certain temperature range.

As used herein, the term "inorganic ceramic" refers to a class of inorganic nonmetallic materials that are formed from natural or synthetic compounds by shaping and high temperature sintering. It has the advantages of high melting point, high hardness, high wear resistance, oxidation resistance, etc.

The addition of the inorganic fast ion conductor can further improve the ion conductivity of the ion transport layer. The strength of the ion transmission layer can be improved by adding the inorganic ceramic, so that the expansion rate of the negative electrode plate is further reduced, and the cycle performance of the battery cell is improved.

In some embodiments, the ion conducting polymer is selected from one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl alcohol (PVA), and Polymethacrylate (PMA).

In some embodiments, the inorganic fast ion conductor is selected from one or more of garnet-type Lithium Lanthanum Zirconium Oxide (LLZO), perovskite-structured Lithium Lanthanum Titanium Oxide (LLTO), titanium lithium aluminum phosphate (LATP), and sulfide solid state electrolytes or doping modified materials thereof.

In this context, the term "garnet-type lithium lanthanum zirconium oxide" refers to a compound of the general formula Li ₇La ₃Zr ₂O ₁₂.

Herein, the term "perovskite structured lithium lanthanum titanium oxide" refers to a compound having the general formula Li _3xLa _0.67- _xTiO ₃.

In some embodiments, the mass content of the ion conducting polymer is 20% to 90%, alternatively 50% to 80%, based on the total mass of the ion transport layer. In some embodiments, the upper or lower limit of the mass content of the ion conducting polymer may be selected from any one of 20%,25%,30%,35%,40%,45%,50%,55%,60%,65%,70%, 75%.

In some embodiments, the electrolyte salt is present in an amount of 10% to 50%, alternatively 10% to 30%, by mass based on the total mass of the ion transport layer. In some embodiments, the upper or lower limit of the mass content of the electrolyte salt may be selected from 10%,15%,20%,25%,30%,35%,40%,45%,50%.

In some embodiments, the mass content of the inorganic fast ion conductor is from 0% to 20%, alternatively from 5% to 10%, based on the total mass of the ion transport layer.

In some embodiments, the inorganic ceramic is present in an amount of 0% to 10%, alternatively 5% to 10%, by mass based on the total mass of the ion transport layer.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a plasticizer, and an electrolyte salt. In some embodiments, the first polymeric monomer refers to a monomer that comprises structural units of the continuous phase of the composite. The first polymeric monomer is crosslinked to form the backbone of the composite material, and the plasticizer and electrolyte salt are present in the crosslinked network for ion transport.

As used herein, the term "plasticizer" refers to a substance added to a polymeric material that increases the plasticity of the polymer.

The continuous phase of the composite material is formed by crosslinking the polymerized monomers, a substrate framework with a certain mechanical strength is provided for the ion transmission layer, and the ion conductivity of the composite material is improved by the plasticizer and the electrolyte salt in the composite material. The composite material has higher ionic conductivity and lower electronic conductivity, can reduce the expansion rate of the negative pole piece and improve the cycle performance of the battery.

In some embodiments, the polymeric monomer is selected from one or more of an ester monomer, a sulfone monomer, an amide monomer, a nitrile monomer, or an ether monomer.

As used herein, the term "ester monomer" refers to a monomer comprising an ester group,

As used herein, the term "sulfone-based monomer" refers to a monomer containing a sulfone group,

As used herein, the term "amide-based monomer" refers to a monomer containing an amide group,

As used herein, the term "nitrile monomer" refers to a monomer containing a cyano group,

As used herein, the term "ether monomer" refers to a monomer containing an ether group,

In some embodiments, the ester monomers include carbonate monomers, sulfate monomers, sulfonate monomers, phosphate monomers, carboxylate monomers. In some embodiments, the carbonate monomer is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, chloroethylene carbonate. In some embodiments, the sulfate monomer is selected from one or more of vinyl sulfite, vinyl 4-methylsulfate, vinyl 4-ethylsulfate. In some embodiments, the sulfonate monomer is selected from one or more of 1, 3-propenesulfonic acid lactone, 1, 3-propanesulfonic acid lactone, 1, 4-butanesulfonic acid lactone, and methane disulfonic acid methylene ester. In some embodiments, the phosphate monomer is selected from one or more of dimethylvinylphosphate, diethylvinylphosphate, diethylpropenyl phosphate, diethylbutenyl phosphate, diethyl 1-buten-2-yl phosphonate, diethylethynyl phosphate, vinyltrifluoromethyl phosphate, vinyl-1-trifluoroethyl phosphate, diethylfluorovinylphosphate, 1-trifluoropropenyl ethyl phosphate. In some embodiments, the carboxylate monomer is selected from vinyl acetate.

In some embodiments, the sulfone-based monomer is selected from one or more of methyl vinyl sulfone, ethyl vinyl sulfone, sulfolane, and ethylene sulfoxide.

In some embodiments, the amide monomer is selected from the group consisting of acrylamide.

In some embodiments, the nitrile monomer is selected from one or more of acrylonitrile, succinonitrile, glutaronitrile, adiponitrile.

In some embodiments, the ether monomer comprises one or more selected from the group consisting of 1, 3-dioxolane, ethylene oxide, 1, 2-propylene oxide, 4-methyl-1, 3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 4-dioxane, ethylene glycol dimethyl ether, ethylene glycol diglycidyl ether, triethylene glycol divinyl ether.

In some embodiments, the polymeric monomer is selected from one or more of vinylene carbonate, vinyl sulfite, ethylene carbonate, 1, 3-propenyl-sultone, methyl vinyl sulfone, ethyl vinyl sulfone, methyl methacrylate, vinyl acetate, and acrylamide.

In some embodiments, the plasticizer is selected from one or more of an ester or sulfone type monomer.

In some embodiments, the plasticizer is selected from one or more of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

In some embodiments, the cross-linking polymerization is initiated by electron beam initiation, ultraviolet light initiation, or initiator initiation.

In some embodiments, the component further comprises one or more of a second polymeric monomeric thickener and an inorganic ceramic.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a plasticizer, an electrolyte salt, and a thickener.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a plasticizer, an electrolyte salt, and an inorganic ceramic.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, and a thickener.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, and an inorganic ceramic.

In some embodiments, the composite is formed from crosslinking components comprising a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, a thickener, and an inorganic ceramic.

As used herein, the term "thickener" refers to a substance that increases the viscosity of a system, maintains the system in a uniformly stable suspended or opaque state, or forms a gel.

In some embodiments, the components forming the composite further comprise a second polymeric monomer that can increase the crosslinking efficiency, degree of crosslinking, and strength of the composite, thereby optimizing the path of the plasticizer and electrolyte salt diffusing transport ions in the crosslinked network, further increasing the ionic conductivity of the ion transport layer.

In some embodiments, the second polymeric monomer is selected from one or more of acrylic or acrylate monomers.

In some embodiments of the present invention, in some embodiments, the second polymeric monomer is selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, hydroxyethyl methacrylate, butyl acrylate, isodecyl acrylate, isooctyl acrylate, lauryl acrylate, isobornyl methacrylate, ethoxyethoxyethyl acrylate, cyanoacrylate, caprolactone acrylate, 2-phenoxyethyl acrylate, tetrahydrofuranyl acrylate, ethoxylated tetrahydrofuranyl acrylate, cyclotrimethacrylate, 2-carboxyethyl acrylate, cyclohexyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, diethylene glycol diacrylate diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1, 4-butanediol diacrylate, 1, 4-butanediol dimethacrylate, 1, 3-butanediol diacrylate, 1, 3-butanediol dimethacrylate, 1, 6-hexanediol diacrylate, 1, 6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 2 (propoxylated) neopentyl glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, one or more of polycyclohexyl acrylate, methoxy polyethylene glycol acrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, methoxy polyethylene glycol methacrylate, pentaerythritol triacrylate, propoxylated glycerol triacrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, di (trimethylolpropane) tetraacrylate, pentaerythritol tetraacrylate, 4 (ethoxy) pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate.

In the composite material, the addition of the second polymeric monomer can increase the polymerization efficiency and the polymerization degree of the first polymeric monomer. The viscosity of the components can be adjusted by adding the thickener into the composite material, so that the ion transmission layer is prevented from penetrating into the pores inside the anode active material layer, the performance of the anode piece is reduced, and the cycle performance of the battery is further improved. The inorganic ceramic is added into the composite material, so that the strength of the ion transmission layer can be further improved, and the safety performance and the cycle performance of the battery can be further improved.

In some embodiments, the first polymeric monomer is present in an amount of 0% to 30%, alternatively 5% to 30%, or the second polymeric monomer is present in an amount of 0% to 30%, alternatively 5% to 20%, or the plasticizer is present in an amount of 30% to 80%, alternatively 40% to 70%, or the electrolyte salt is present in an amount of 10% to 20%, or the thickener is present in an amount of 0% to 10%, alternatively 3% to 10%, or the inorganic ceramic is present in an amount of 0% to 50%, alternatively 0% to 20% based on the total mass of the ion transport layer. In some embodiments, the upper or lower limit of the mass content of the polymerized monomer may be selected to be 5%, 10%, 15%, 20%, 25% and 30% based on the total mass of the ion transport layer. In some embodiments, the lower or upper limit of the mass content of the second polymeric monomer may be selected to be 5%, 10%, 15%, 20%, 25% or 30% based on the total mass of the ion transport layer. In some embodiments, the upper or lower limit of the mass content of the plasticizer may be selected to be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% based on the total mass of the ion transport layer. In some embodiments, the lower or upper limit of the mass content of the electrolyte salt may be selected to be 10%, 15%, 20% based on the total mass of the ion transport layer. In some embodiments, the lower or upper limit of the mass content of the thickener may be selected to be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% based on the total mass of the ion transport layer. In some embodiments, the lower or upper limit of the mass content of the inorganic ceramic may be selected to be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% based on the total mass of the ion transport layer.

In some embodiments, the component further comprises an active site initiator selected from one or more of peroxy compounds or azo species. In some embodiments, the peroxy compounds include, but are not limited to, acyl peroxides such as benzoyl peroxide, lauroyl peroxide, persulfates such as ammonium persulfate; azo-based initiators include, but are not limited to, azobisisobutyronitrile, azobisisoheptonitrile. In some embodiments, the active site initiator is initiated by heat, which may be selected from 50 ℃ to 85 ℃.

In some embodiments, the inorganic ceramic is selected from one or more of alumina, boehmite, zirconia, aluminum nitride, titania, magnesia, silicon carbide, calcium carbonate, diatomaceous earth.

In some embodiments, the electrolyte salt is selected from one or more of a lithium salt, a sodium salt.

In some embodiments, the thickener and plasticizer are miscible, the thickener being selected from one or more of polyvinyl formal, polyvinylidene fluoride and its copolymers, polyvinylidene fluoride, trichloroethylene, polytetrafluoroethylene, acrylic acid, epoxy, polyethylene oxide, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide, and polyvinylpyrrolidone. The thickening effect of the thickener can be further exerted by selecting the thickener which is miscible with the plasticizer,

The application provides a manufacturing method of a negative electrode plate, which comprises the following steps: and coating the ion transmission layer on the surface of the anode active material layer to obtain an anode piece, wherein the electron conductivity of the ion transmission layer is not higher than 1X 10 ^-7 S/cm, and the lithium ion conductivity is not lower than 1X 10 ^-4 S/cm.

It will be appreciated that the coating may be carried out by any means, such as spraying, size coating, gravure coating, etc. The method is simple, low in cost and easy to popularize and apply.

In some embodiments, the composition of the ion transport layer contains an ion conducting polymer, an electrolyte salt, an inorganic fast ion conductor, and an inorganic ceramic.

The application provides a manufacturing method of a negative electrode plate, which comprises the following steps: and synthesizing the ion transmission layer on the surface of the negative electrode active material layer in situ to obtain a negative electrode plate, wherein the electron conductivity of the ion transmission layer is not higher than 1X 10 ^-7 S/cm, and the lithium ion conductivity is not lower than 1X 10 ^-4 S/cm.

It is understood that in-situ synthesis refers to in-situ synthesis of an ion transport layer on the surface of the anode active material layer by means of in-situ initiated polymerization after the material is disposed on the surface of the anode active material layer.

In some embodiments, the ion transport layer is a composite material formed from cross-linking components of a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, a thickener, an inorganic ceramic, and an initiator.

In some embodiments, the anode current collector has two surfaces opposing in a thickness direction thereof, and the anode active material layer is provided on either or both of the two surfaces opposing the anode current collector.

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

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the anode active material layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

In some embodiments, the anode active material layer may further optionally include a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the anode active material layer may also optionally include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

[ Positive electrode sheet ]

The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material of the first aspect of the application.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive electrode active material may employ a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of the olivine-structured lithium-containing phosphate may include, but are not limited to, at least one of lithium iron phosphate (e.g., liFePO ₄ (also simply LFP)), a composite of lithium iron phosphate and carbon, a composite of lithium manganese phosphate (e.g., liMnPO ₄), a composite of lithium manganese phosphate and carbon, a composite of lithium iron phosphate and manganese phosphate, and a composite of lithium manganese iron phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ Electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

[ Isolation Membrane ]

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability can be used.

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

Secondary battery

The application provides a secondary battery, which comprises a positive electrode plate, electrolyte and a negative electrode plate manufactured by the method for manufacturing the negative electrode plate in any embodiment or the negative electrode plate in any embodiment.

In some embodiments, the ratio of the lithium ion conductivity λ ₁ of the ion transport layer to the lithium ion conductivity λ ₂ of the electrolyte is less than 1, optionally from 0.3 to 0.7. In some embodiments, the upper or lower limit of the ratio of the lithium ion conductivity of the ion transport layer to the lithium ion conductivity of the electrolyte may be selected from 0.2,0.3,0.4,0.5,0.6,0.7,0.8 or 0.9.

When the lithium ion battery is charged, lithium ions are separated from the positive electrode active material of the positive electrode plate and are inserted into the negative electrode active material of the negative electrode plate, after the lithium ions are fully inserted into the negative electrode body, lithium ions are deposited as lithium metal, and the lithium ions in the negative electrode plate are rapidly consumed due to the high specific surface area in the negative electrode active material layer, so that the short loss of the lithium ions in the negative electrode plate is caused. When more lithium ions diffuse from the positive electrode to the negative electrode, electrons are directly obtained on the surface of the negative electrode and converted into metal state to be separated out, so that lithium metal is almost deposited on the surface of the negative electrode.

After the surface of the negative electrode plate is covered with the ion transmission layer, and the ratio of the lithium ion conductivity lambda ₁ of the ion transmission layer to the lithium ion conductivity lambda ₂ of the electrolyte is smaller than 1, namely the lithium ion conductivity of the ion transmission layer is smaller than the ion conductivity of the electrolyte, the difference of the ion conductivities reduces the lithium ion conduction speed of the surface of the plate, and provides a time difference for the lithium ion diffusion of the electrolyte inside the active material layer, so that lithium ions are easier to deposit inside the negative electrode plate, and electrons are not easy to deposit as lithium metal on the surface of the negative electrode active layer. Therefore, the expansion rate of the battery can be reduced, and the cycle performance of the battery can be improved.

The ratio of the lithium ion conductivity lambda ₁ of the ion transmission layer to the lithium ion conductivity lambda ₂ of the electrolyte can be selected to be 0.3-0.7, so that the proper time difference of the diffusion of lithium ions in the pole piece can be ensured, the expansion rate of the battery is further reduced, and the cycle performance of the battery is improved.

In some embodiments, the CB value of the battery is less than 1.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 4 is a secondary battery 5 of a square structure as one example.

In some embodiments, referring to fig. 5, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.

[ Battery Module ]

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 6 is a battery module 4 as an example. Referring to fig. 6, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.

[ Battery pack ]

In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 7 and 8 are battery packs 1 as an example. Referring to fig. 7 and 8, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[ Electric device ]

In one embodiment of the application, an electrical device is provided comprising a battery of any of the embodiments.

The power utilization device comprises at least one of a secondary battery, a battery module or a battery pack provided by the application. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 9 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples

Example 1

1) Preparation of negative electrode plate

Preparing a negative electrode active material layer: graphite and a conductive agent of acetylene black and a binder of polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of 94:3: and 3, fully stirring and uniformly mixing the mixture in an N-methyl pyrrolidone solvent system, coating the surface of the copper foil, wherein the coating weight is 1.40 mA.h/cm ², so that CB=0.4, drying and cold pressing to obtain the anode active material layer.

Preparing an ion transmission layer: polymethyl methacrylate (PMMA), liFSI, LLZO and alumina are mixed according to the weight ratio of 6:2:1:1 fully stirring and uniformly mixing the mixture in an NMP solvent system to prepare slurry, and coating the slurry on the surface of the prepared anode active material layer, wherein the coating thickness is 10um. After coating, drying for 12 hours at 80 ℃ in a vacuum oven to obtain a negative electrode plate, and cutting the plate into corresponding dimensions for later use.

2) Preparation of positive electrode plate

NCM811 and conductive agent acetylene black, binder polyvinylidene fluoride (PVDF) according to the weight ratio of 94:3: and 3, fully stirring and uniformly mixing the mixture in an N-methyl pyrrolidone solvent system, coating the mixture on an aluminum foil, drying and cold pressing the mixture to obtain a positive electrode plate, and cutting the positive electrode plate into corresponding sizes for later use, wherein the coating weight is 3.5mAh/cm ².

3) Isolation film

A polyethylene film (PE separator) was used as a separator.

4) Preparation of electrolyte

The electrolyte solvent is EC, EMC, DMC=1:1:1, lithium salt is LiFSI, and the concentration is 1M/L.

5) Preparation of a Battery

And assembling the laminated battery core by using a pole piece with a double-sided positive electrode, a diaphragm and a single-sided negative electrode, assembling the bare battery core according to the sequence of the negative electrode, the diaphragm, the positive electrode, the diaphragm and the negative electrode, so that the isolating film plays a role in isolating between the positive electrode and the negative electrode, and placing the bare battery core in an outer package to obtain the dry battery core. And injecting 0.3g of electrolyte into each cell, vacuum packaging after liquid injection, standing and soaking.

In comparative examples 1 to 3, the ion transport layer was not coated on the negative electrode sheet, and the coating amount of the negative electrode active material layer was adjusted according to the designed CB value in the same manner as in example 1.

In comparative example 1, when the CB value was 0.7, the coating amount of the anode active material layer was 2.45 mA.h/cm ². In comparative example 2, when the CB value was 0.4, the coating amount of the anode active material layer was 1.40 mA.h/cm ². In comparative example 3, when the CB value is 1, the coating amount of the anode active material layer is 3.5mAh/cm ².

The negative electrode sheet of comparative example 4 was formed in the same manner as in example 1, except that only PMMA polymer was used in the ion transport layer.

The secondary batteries of examples 2 to 14 and the secondary batteries of comparative examples 1 to 4 were similar to the secondary battery of example 1 in preparation method, but the composition of the negative electrode tab and the product parameters were adjusted, and the different product parameters are detailed in table 1.

The parameters related to the positive electrode materials of examples 1 to 14 and comparative examples 1 to 4 are shown in table 1 below.

The secondary batteries of examples 15 to 28 were similar to the secondary battery of example 1 in terms of the preparation method, but the composition and preparation method of the negative electrode tab were adjusted, taking example 15 as an example, and the preparation method of the negative electrode tab was as follows:

Example 15

Preparing a negative electrode plate:

Preparing a negative electrode active material layer: graphite and a conductive agent of acetylene black and a binder of polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of 94:3: and 3, fully stirring and uniformly mixing the mixture in an N-methylpyrrolidone solvent system, coating the surface of the copper foil with the coating weight of 2.45mAh/cm ² to ensure that CB=0.7, drying and cold pressing to obtain the anode active material layer.

Preparing an ion transmission layer: mixing a first polymerized monomer ethylene carbonate (VC), a second polymerized monomer polyethylene glycol diacrylate (PEGDA), a mixture of plasticizer ethylene methyl carbonate and ethylene carbonate (EMC+EC), a thickener PVDF, an electrolyte salt LiFSI and inorganic ceramic alumina according to the weight ratio of 20:5:40:5:20:10, fully stirring and uniformly mixing to prepare slurry, and coating the slurry on the surface of the prepared anode active material layer, wherein the coating thickness is 5um. The thickening agent PVDF can be dissolved in a plasticizer to play a thickening role, an ultraviolet initiator diphenyl (2, 4, 6-Trimethylbenzoyl) Phosphine Oxide (TPO) is added into the slurry before coating, after coating, a 365nm ultraviolet light source is used for irradiation for 1min under the condition of 2W/cm ² of power to initiate the slurry to solidify and form a composite material, a negative pole piece is obtained, and the pole piece is cut into corresponding sizes for standby.

The secondary batteries of examples 15 to 28 were similar to the secondary battery of example 15 in preparation method, but the composition of the negative electrode tab and the product parameters were adjusted, and the different product parameters are shown in table 2 in detail.

In the step of preparing the ion transport layer in comparative example 5, a mixture of a polymerized monomer Vinylene Carbonate (VC), a second polymerized monomer polyethylene glycol diacrylate (PEGDA), a plasticizer methyl ethyl carbonate and ethylene carbonate (emc+ec), in a weight ratio of 20:5:75, fully stirring and uniformly mixing to prepare the slurry, and preparing the ion transmission layer. Other steps are the same as in example 15.

2. Performance testing

The performance test data of examples 1 to 14 and comparative examples 1,2 and 4 are shown in Table 3. The performance test data of examples 15 to 28 and comparative examples 1,2 and 5 are shown in Table 4. The performance test method comprises the following steps:

1. calculation of CB values

And (3) assembling the battery by using the coated positive electrode plate and the coated negative electrode plate, and dividing the surface capacity of the negative electrode plate of the battery system by the surface capacity of the positive electrode plate to obtain the CB value of the battery, namely CB=negative electrode surface capacity/positive electrode surface capacity.

2. Lithium ion conductivity test

Coating a coating on the surface of a blank aluminum foil, cutting into small discs with the diameter of 20mm, assembling the button cell according to the sequence of an anode shell, the small discs (with the coating side upwards), a gasket, an elastic sheet and a cathode shell, testing by adopting an electrochemical alternating current impedance method of a Solartron 1470E CellTest multichannel electrochemical workstation, and drawing a Nyquist diagram; and analyzing the obtained Nyquist diagram by using an equivalent circuit curve fitting method, wherein the abscissa of the intersection point of the semicircle and the oblique line in the Nyquist diagram is used as a resistor R, the test voltage can be 10mV, and the test frequency can be 0.1 Hz-100K Hz.

The ionic conductivity of the coating, λ ₁, is calculated according to the formula λ=d/RS, λ representing the ionic conductivity, d representing the thickness of the coating, R representing the resistance, S representing the area of the coating.

The ionic conductivity of the electrolyte is directly tested by a conductivity meter to obtain lambda ₂.

3. Electronic conductivity test

Coating a coating on the surface of a blank aluminum foil, cutting into small discs with the diameter of 20mm, assembling the button cell according to the sequence of a positive electrode shell, the small discs (with the coating side upwards), a gasket, an elastic sheet and a negative electrode shell, testing by adopting a constant potential mode of a Solartron 1470E CellTest multichannel electrochemical workstation, setting the voltage U to be 1V, setting the time to be 2h, taking the stable current of the final stage to be recorded as I, and using a formula λe=dI/SU, wherein d represents the thickness of the coating, S represents the area of the coating, and I, U is a program setting value.

4. Expansion ratio test

Before the battery cell is assembled, the thickness L ₀ of the negative pole piece is measured, the battery is kept stand for 5min at the ambient temperature of 25 ℃, charged to 4.25V according to 1/3C, then charged to the current of less than or equal to 0.05mA under the constant voltage of 4.25V, kept stand for 5min, discharged to 2.8V according to 1/3C, kept stand for 5min, charged to 4.25V according to the 1/3C, then charged to the current of less than or equal to 0.05mA under the constant voltage of 4.25V, the battery is disassembled, the thickness L ₁ of the negative pole piece is recorded, and the expansion rate alpha= (L is calculated ₁-L ₀)/L ₁

5. Cell polarization voltage measurement

Standing for 5min at 25 ℃ and charging to 4.25V according to 1/3C (46 mA), then charging to current of less than or equal to 0.05mA at constant voltage under 4.25V, and calculating average charging voltage by dividing charging energy by charging capacity; standing for 5min, discharging to 2.8V at 1/3C, calculating average discharge voltage by dividing discharge energy by discharge capacity, and subtracting discharge voltage from average charge voltage to obtain polarization voltage of the battery. The present embodiment calculates the polarization voltage with the data of the second cycle.

6. Energy density testing

And assembling the processed negative pole piece, the positive pole piece and the diaphragm into a large soft package battery in a winding mode, injecting liquid according to an injection coefficient of 2g/Ah, charging to 4.25V according to a constant current of 0.33C, standing for 5 minutes, discharging to 2.8V according to a constant current of 0.33C, reading discharge energy Q in a discharge stage, weighing the mass m of the battery core by using a balance, and enabling energy density=Q/m.

7. Cycle life

After the soft-packed battery is kept stand for 5 minutes, the soft-packed battery is charged to 4.25V at a constant current of 0.33C (46 mA), and then is charged to a constant voltage of 4.25V until the current is less than 0.05C (7 mA); standing for 5 minutes, and discharging to 2.8V at a constant current of 0.33C to obtain the first-week discharge capacity C0 of the battery; the cycle is repeated until Cn is less than or equal to C0, and the cycle number is recorded as cycle life.

8. First week discharge capacity test

After the soft-packed battery is kept stand for 5 minutes, charging to 4.25V by 0.33C (46 mA) constant current, and then charging to current less than 0.05C by 4.25V constant voltage, so as to obtain the first-week charging capacity of the battery; after standing for 5 minutes, the battery was discharged to 2.8V at a constant current of 0.33C, thereby obtaining the first-week discharge capacity of the battery.

Batteries of each example and comparative example were prepared according to the above-described methods, and each performance parameter was measured, and the results are shown in tables 3 and 4.

In comparative example 3, when the CB value of the battery was 1, the energy density of the battery was 302Wh/kg, for the comparative example and example where the CB value was 0.7, the energy density of the battery was 333Wh/kg, and for the comparative example and example where the CB value was 0.4, the energy density of the battery was further improved to 369Wh/kg, whereby it was seen that the low CB value design was advantageous for improving the energy density of the battery.

The anode sheets in examples 1 to 28, comprising an anode active material layer, and an ion transport layer on a surface of the anode active material layer in contact with an electrolyte, the ion transport layer having an electron conductivity of not higher than 1×10 ^-7 S/cm and an ion conductivity of not lower than 1×10 ^-4 S/cm. From the comparison of examples 1 to 14 with comparative examples 1,2, and 4, and the comparison of examples 15 to 28 with comparative examples 1,2, and 5, it is apparent that the negative electrode tab has a reduced expansion rate and an improved cycle life of the battery by providing an ion transport layer on the surface of the negative electrode active material layer in contact with the electrolyte. When the ion conductivity is not lower than 1X10 ^-3 S/cm, the expansion rate of the negative electrode plate is reduced, and the cycle life of the battery is prolonged more obviously. Examples 1 to 14 have an ion conductivity of not less than 1×10 ^-4 S/cm in the ion transport layer compared to comparative example 4, so that the battery can maintain a high first-week discharge capacity while improving cycle life.

In examples 9 to 10, the ion transport layer contained only the ion conductive polymer and the electrolyte salt, and compared with comparative example 1, the negative electrode sheet reduced the expansion ratio of the negative electrode sheet and improved the cycle life of the battery.

In examples 1 to 8 and 11 to 13, the ion transport layer contained at least one of an inorganic fast ion conductor and an inorganic ceramic in addition to the ion conducting polymer and the electrolyte salt, and compared with comparative examples 1, 2 and 4, the expansion ratio of the negative electrode sheet was reduced, and the cycle life of the battery was improved. Examples 11 and 12 further improved the cycle life of the battery compared to example 10 by adding inorganic fast ion conductors or inorganic ceramics.

The negative electrode sheet in examples 15 to 28 comprises a negative electrode active material layer and an ion transport layer on at least one surface of the negative electrode active material layer, wherein the ion transport layer has an electron conductivity of not higher than 1×10 ^-7 S/cm and a lithium ion conductivity of not lower than 1×10 ^-4 S/cm, and the ion transport layer is a composite material formed by crosslinking components including a first polymer monomer, a second polymer monomer, a plasticizer and an electrolyte salt. Compared with comparative examples 1,2 and 5, the expansion rate of the negative electrode plate is reduced, and the cycle life of the battery is prolonged. Examples 15 to 28 have an ion conductivity higher than 1×10 ^-3 S/cm in the ion transport layer compared to comparative example 5, so that the battery can maintain a high initial discharge capacity while improving cycle life.

The anode sheet in examples 18 to 22, 26 to 28 comprises an anode active material layer and an ion transport layer on at least one surface of the anode active material layer, wherein the electron conductivity of the ion transport layer is not higher than 1×10 ^-7 S/cm, the lithium ion conductivity is not lower than 1×10 ^-4 S/cm, the ion transport layer is a composite material, and the composite material is formed by crosslinking components comprising a first polymer monomer, a second polymer monomer, a plasticizer, an electrolyte salt and a thickener. Compared with comparative examples 1, 2 and 5, the expansion rate of the negative electrode plate is reduced, and the cycle life of the battery is prolonged. The addition of the thickener prevents the negative electrode active material layer from bleeding down at the time of coating, further improving the cycle performance of the battery, compared with example 24.

The negative electrode sheet of examples 15 to 17, 23, 25 comprises a negative electrode active material layer and an ion transport layer on at least one surface of the negative electrode active material layer, wherein the ion transport layer has an electron conductivity of not higher than 1×10 ^-7 S/cm and a lithium ion conductivity of not lower than 1×10 ^-4 S/cm, the ion transport layer is a composite material formed by crosslinking components comprising a first polymeric monomer, a second polymeric monomer, a plasticizer, an electrolyte salt, a thickener, and an inorganic ceramic. Compared with comparative examples 1, 2 and 5, the expansion rate of the negative electrode plate is reduced, and the cycle life of the battery is prolonged. Example 25 the addition of inorganic ceramic further improved the cycle life of the battery compared to example 20.

The ratio of the lithium ion conductivity of the ion transport layer to the lithium ion conductivity of the electrolyte was less than 1 for the negative electrode sheets in examples 1 to 28. The expansion rate of the negative electrode plate is reduced, and the cycle life of the battery is prolonged. When the ratio of lithium ion conductivity of the lithium ion conductivity electrolyte of the ion transmission layer is 0.3-0.7, the expansion rate of the negative electrode plate is further reduced, and the cycle life is further prolonged.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

A negative electrode tab, comprising:

A negative electrode active material layer, and

An ion transport layer on at least one surface of the anode active material layer,

The ion transport layer has an electron conductivity of not higher than 1X 10 ^-7 S/cm and an ion conductivity of not lower than 1X 10 ^-4 S/cm.
The negative electrode tab of claim 1, wherein,

The ion transport layer comprises an ion conducting polymer and an electrolyte salt.
The negative electrode tab of claim 2, wherein,

The ion transport layer further comprises at least one of an inorganic fast ion conductor and an inorganic ceramic.
The negative electrode tab of claim 2 or 3, wherein,

The ion conductive polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol and polymethacrylate.
The negative electrode tab of claim 3 or 4, wherein,

The inorganic fast ion conductor is selected from one or more of garnet-type Lithium Lanthanum Zirconium Oxide (LLZO), perovskite-structured Lithium Lanthanum Titanium Oxide (LLTO), titanium aluminum phosphate (LATP) and sulfide solid electrolyte or doping modified materials thereof.
The negative electrode sheet according to any one of claim 3 to 5, characterized in that,

The mass content of the ion conducting polymer is 20-90%, optionally 50-80%, based on the total mass of the ion transport layer; or (b)

The mass content of the electrolyte salt is 10% -50%, and optionally 10% -30%; or (b)

The mass content of the inorganic fast ion conductor is 0-20%, optionally 5-10%;

Or the mass content of the inorganic ceramic is 0-10%, optionally 5-10%.
The negative electrode tab of claim 1, wherein,

The ion transport layer is a composite material formed by crosslinking components including a first polymeric monomer, a plasticizer, and an electrolyte salt.
The negative electrode tab of claim 7, wherein,

The first polymerization monomer is selected from one or more of an ester monomer, a sulfone monomer, an amide monomer, a nitrile monomer or an ether monomer; or (b)

The plasticizer is selected from one or more of ester monomers or sulfone monomers.
The negative electrode tab according to claim 7 or 8, characterized in that,

The plasticizer is at least one selected from methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
The negative electrode tab according to any one of claims 7 to 9, characterized in that,

The component further comprises one or more of a second polymeric monomer, a thickener, and an inorganic ceramic.
The negative electrode tab according to any one of claims 7 to 10, characterized in that,

The mass content of the first polymeric monomer is 0% to 30%, alternatively 5% to 30%, or alternatively

The mass content of the second polymer monomer is 0-30%, optionally 5-20%, or

The mass content of the plasticizer is 30-80%, optionally 40-70%, or

The mass content of the electrolyte salt is 10-20%, or

The mass content of the thickener is 0-10%, optionally 3-10%, or

The mass content of the inorganic ceramic is 0% -50%, and optionally 0% -20%.
The negative electrode tab according to any one of claims 7 to 11, characterized in that,

The component further comprises an active site initiator selected from one or more of peroxy compounds or azo species.
The negative electrode sheet according to any one of claim 3 to 12, characterized in that,

The inorganic ceramic is selected from one or more of aluminum oxide, boehmite, zirconium oxide, aluminum nitride, titanium dioxide, magnesium oxide, silicon carbide, calcium carbonate and diatomite.
The negative electrode sheet according to any one of claim 2 to 13, characterized in that,

The electrolyte salt is selected from one or more of lithium salt and sodium salt.
The negative electrode tab of any one of claims 10 to 14, wherein,

The thickening agent and the plasticizer can be mutually soluble, and the thickening agent is one or more selected from polyvinyl formal, polyvinylidene fluoride and copolymers thereof, polyvinylidene fluoride, trichloroethylene, polytetrafluoroethylene, acrylic acid rubber, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide and polyvinylpyrrolidone.
A method of manufacturing a negative electrode sheet, the method comprising the steps of:

Coating an ion transmission layer on the surface of the anode active material layer to obtain the anode piece,

Wherein the electron conductivity of the ion transport layer is not higher than 1X 10 ^-7 S/cm and the lithium ion conductivity is not lower than 1X 10 ^-4 S/cm.
The method for manufacturing a negative electrode sheet according to claim 16, wherein,

The ion transport layer contains an ion conducting polymer, an electrolyte salt, an inorganic fast ion conductor and an inorganic ceramic.
A method of manufacturing a negative electrode sheet, the method comprising the steps of:

synthesizing an ion transmission layer on the surface of the negative electrode active material layer in situ to obtain the negative electrode plate,

Wherein the electron conductivity of the ion transport layer is not higher than 1X 10 ^-7 S/cm and the lithium ion conductivity is not lower than 1X 10 ^-4 S/cm.
The method for manufacturing a negative electrode sheet according to claim 18, wherein,

The ion transmission layer is a composite material, and the composite material is formed by crosslinking components of a first polymerized monomer, a second polymerized monomer, a plasticizer, electrolyte salt, a thickener, inorganic ceramic and an initiator.
A secondary battery comprising a positive electrode sheet, an electrolyte, and the negative electrode sheet according to any one of claims 1 to 15 or the negative electrode sheet manufactured by the manufacturing method according to any one of claims 16 to 19.
The secondary battery according to claim 20, wherein,

The ratio of the lithium ion conductivity lambda ₁ of the ion transmission layer to the lithium ion conductivity lambda ₂ of the electrolyte is less than 1, and can be selected to be 0.3-0.7.
A battery module comprising the secondary battery according to claim 20 or 21.
A battery pack comprising the battery module of claim 22.
An electric device comprising at least one selected from the secondary battery according to any one of claims 20 to 21, the battery module according to claim 22, and the battery pack according to claim 23.