WO2024007267A1

WO2024007267A1 - Negative electrode sheet and manufacturing method therefor, secondary battery, battery module, battery pack, and electric device

Info

Publication number: WO2024007267A1
Application number: PCT/CN2022/104465
Authority: WO
Inventors: 何晓宁; 刘成勇; 薛文文; 胡波兵; 钟成斌; 廖赏举; 谢张荻
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-07-07
Filing date: 2022-07-07
Publication date: 2024-01-11
Also published as: CN117941090A

Abstract

The present application provides a negative electrode sheet and a manufacturing method therefor, a secondary battery, a battery module, a battery pack, and an electric device. The negative electrode sheet comprises a negative electrode active material layer and an ion transport layer located on at least one surface of the negative electrode active material layer, wherein the electronic conductivity of the ion transport layer is not higher than 1×10-7 S/cm, and the ionic conductivity is not less than 1×10-4 S/cm. The negative electrode sheet has a low expansion rate after being recycled, thereby improving the cycle performance of a battery.

Description

Negative electrode plate, manufacturing method thereof, secondary battery, battery module, battery pack and electrical device

Technical field

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

Background technique

In recent years, the application range of secondary batteries has become more and more extensive, and has been deeply used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and many other fields.

During the recycling process of lithium-ion batteries, the negative electrode plates are prone to expansion, thereby reducing the performance of the lithium-ion batteries and even causing battery failure or safety accidents.

Contents of the invention

This application was made in view of the above problems, and its purpose is to provide a negative electrode piece with a low expansion rate after repeated use, thereby improving the cycle performance of the battery.

A first aspect of the present application provides a negative electrode sheet, which includes: a negative active material layer, and an ion transport layer located on at least one surface of the negative active material layer. The electron conductivity of the ion transport layer is not higher than 1× 10 ^-7 S/cm, and the ionic conductivity is not less than 1×10 ^- ⁴ S/cm.

Therefore, this application solves the problem of lithium metal preferentially precipitating on the surface of the negative electrode, causing serious volume expansion of the battery core, by arranging an ion transport layer on the surface of the negative electrode active material layer. The ion transport layer makes it difficult for lithium ions to be electron-deposited into lithium metal on the surface of the negative active layer. The diffusion of lithium ions allows the lithium ions inside the negative electrode active layer to be continuously replenished, thereby achieving the deposition of lithium metal in the pores inside the pole piece. The negative electrode piece of the present application reduces the expansion rate of the electrode piece and greatly improves the cycle life of the battery.

In any embodiment, the ion transport layer includes an ion conducting polymer and an electrolyte salt. Using ion-conducting polymers and electrolyte salts to form an ion transport layer can reduce the negative electrode plate’s

Expansion rate, improve battery cycle life.

In any embodiment, the ion transport layer further includes at least one of an inorganic fast ion conductor and an inorganic ceramic. The addition of inorganic fast ion conductors can further improve the ion conductivity of the ion transport layer. The addition of inorganic ceramics can improve the strength of the ion transport layer, thereby further reducing the expansion rate of the negative electrode piece and improving the cycle performance of the battery core.

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

In any embodiment, the inorganic fast ion conductor is selected from the group consisting of garnet-type lithium lanthanum zirconium oxide (LLZO), perovskite-structured lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphate (LATP), and sulfide solid electrolytes, or It is doped with one or more types of modified materials.

In any embodiment, based on the total mass of the ion transport layer, the mass content of the ion conductive polymer is 20% to 90%, optionally 50% to 80%; or the mass content of the electrolyte salt is 10% to 50% , optionally 10% ~ 30%; or the mass content of inorganic fast ion conductors is 0% ~ 20%, optionally 5% ~ 10%; or the mass content of inorganic ceramics is 0% ~ 10%, optionally 5%~10%.

In any embodiment, the ion transport layer is a composite material formed by cross-linking components including a first polymerized monomer, a plasticizer, and an electrolyte salt.

The continuous phase of the composite material is formed through the cross-linking of the first polymerized monomer, which provides a base skeleton with a certain mechanical strength for the ion transport layer, and the ionic conductivity of the composite material is improved through the plasticizer and electrolyte salt in the composite material. The composite material has high ionic conductivity and low electronic conductivity, which can reduce the expansion rate of the negative electrode plate and improve the cycle performance of the battery.

In any embodiment, the first polymerized monomer is selected from one or more of ester monomers, sulfone monomers, amide monomers, nitrile monomers or ether monomers; or the plasticizer is selected from One or more types of ester or sulfone monomers.

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

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

In composite materials, adding a second polymerized monomer can improve the polymerization efficiency and degree of polymerization of the first polymerized monomer; adding a thickener can adjust the viscosity of the components and prevent the ion transport layer from penetrating into the pores inside the negative active material layer. Reduce the performance of the negative electrode plate; adding inorganic ceramics can further improve the strength of the ion transport layer and improve the safety performance and cycle performance of the battery.

In any embodiment, based on the total mass of the ion transport layer, the mass content of the first polymerized monomer is 0% to 30%, optionally 5% to 30%, or the mass content of the second polymerized monomer is 0 %~30%, optionally 5%~20%, or the mass content of plasticizer is 30%~80%, optionally 40%~70%, or the mass content of electrolyte salt is 10%~20%, Or the mass content of the thickener is 0% to 10%, optionally 3% to 10%, or the mass content of the inorganic ceramic is 0% to 50%, optionally 0% to 20%.

In any embodiment, the component further includes an active site initiator selected from one or more peroxides or azos.

In any embodiment, the inorganic ceramic is selected from one or more of alumina, boehmite, zirconia, aluminum nitride, titanium dioxide, magnesium oxide, silicon carbide, calcium carbonate, and diatomaceous earth.

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

In any embodiment, the thickener and the plasticizer are mutually soluble, and the thickener is selected from the group consisting of polyvinyl formal, polyvinylidene fluoride and its copolymers, polyvinylidene fluoride, polyvinylidene fluoride, and trichlorethylene. , polytetrafluoroethylene, acrylic acid glue, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethylcellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide and one or more of polyvinylpyrrolidone.

A third aspect of the present application provides a method for manufacturing a negative electrode sheet. The manufacturing method includes the following steps: coating an ion transport layer on the surface of the negative electrode active material layer to obtain a negative electrode sheet, in which the electron conductivity of the ion transport layer is not high. is less than 1×10 ^-7 S/cm, and the lithium ion conductivity is not less than 1×10 ^-4 S/cm. The method is simple, low-cost and easy to promote and apply.

In any embodiment, the ion transport layer is composed of 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 sheet. The manufacturing method includes the following steps: synthesizing an ion transport layer in situ on the surface of the negative electrode active material layer to obtain a negative electrode sheet, in which the electron conductivity of the ion transport layer is not Higher than 1×10 ^-7 S/cm, and the lithium ion conductivity is not lower than 1×10 ^-4 S/cm.

In any embodiment, the ion transport layer is a composite material, and the composite material is cross-linked by each component of a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, a thickener, an inorganic ceramic, and an initiator. formed.

Through in-situ synthesis, this method can further improve the tightness of the connection between the ion transport layer and the negative active material layer, and reduce the deposition of negative metal on the surface of the negative active material layer.

A fifth aspect of the present application provides a secondary battery, including a positive electrode sheet, an electrolyte, and a negative electrode sheet of the first or second aspect of the present application or a negative electrode sheet 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, and can be selected from 0.3 to 0.7.

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

A seventh aspect of the present application provides a battery pack, including the battery module of the sixth aspect of the present application.

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

Description of the drawings

Figure 1 is a schematic diagram of the deposition of lithium ions on the surface of the negative electrode after the traditional negative electrode sheet is cycled.

Figure 2 is a scanning electron microscope image of lithium ions deposited on the surface of the negative electrode after cycling of a traditional negative electrode piece.

Figure 3 is a schematic diagram of lithium ions deposited in the negative active material layer after the negative electrode sheet of the present application is cycled.

FIG. 4 is a schematic diagram of a secondary battery according to an embodiment of the present application.

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

Figure 6 is a schematic diagram of a battery module according to an embodiment of the present application.

Figure 7 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 8 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 7 .

FIG. 9 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.

Explanation of reference symbols:

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

Detailed ways

Hereinafter, embodiments specifically disclosing the positive electrode active material and its manufacturing method, the positive electrode tab, the secondary battery, the battery module, the battery pack, and the electrical device of the present application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

"Ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may 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, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, 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 expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless stated otherwise, 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" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

If there is no special instructions, all steps of the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) 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 also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.

If there is no special explanation, the words "include" and "include" mentioned in this application represent open expressions, which may also be closed expressions. For example, "comprising" and "comprising" may mean that other components not listed may also be included or included, or only the listed components may be included or included.

In this application, the term "or" is inclusive unless otherwise stated. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).

Traditional lithium-ion batteries often adopt high CB value designs, that is, the negative electrode capacity is slightly higher than the positive electrode capacity. During the research process, the applicant unexpectedly discovered that the energy density of the battery can be improved by adopting a low CB battery design, that is, the negative electrode capacity is slightly lower than the positive electrode capacity. However, when electrodes with low CB values are used in battery systems containing liquid electrolyte, the negative electrode side expands greatly, which poses certain obstacles to the structural design and application of the battery core. As shown in FIG. 1 , the traditional negative electrode sheet 6 includes a current collector 61 and a negative active material layer 62 located on at least one surface of the current collector. Using a low CB design will cause excess lithium source of the positive electrode to be deposited on the negative active material layer 62 On the surface, a lithium metal layer 63 is formed, causing the negative electrode to expand, and its scanning electron microscope picture is shown in Figure 2. Based on the above technical problems, this application developed a negative electrode piece with low expansion rate, which can significantly improve the cycle performance of the battery.

[Negative pole piece]

Based on this, this application proposes a negative electrode sheet, which includes: a negative active material layer, and an ion transport layer located on at least one surface of the negative active material layer. The electronic conductivity of the ion transport layer is not higher than 1×10 ^-7 S/cm, and the ionic conductivity is not less than 1×10 ^-4 S/cm.

In this article, the term "electronic conductivity" is a parameter used to describe the ease with which electric charges flow through a substance, and is related inversely to resistivity.

In this article, the term "ionic conductivity" is used to describe the measure of the tendency for ionic conduction to occur in a substance. In some embodiments, the ionic conductivity is lithium ion conductivity. In some embodiments, the ionic conductivity is sodium ion conductivity.

In some embodiments, the ion transport layer has an ion conductivity of no less than 1×10 ⁻³ S/cm.

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

As shown in FIG. 3 , the negative electrode sheet of the present application solves the problem that lithium metal 63 preferentially precipitates on the surface of the negative electrode, causing serious volume expansion of the battery core, 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 be electron-deposited on the surface of the negative electrode active layer 62 as lithium metal 63. The diffusion of lithium ions allows the lithium ions inside the negative electrode active layer 62 to be continuously replenished, thereby realizing the lithium metal 63 in the electrode. Deposition of pores inside the sheet. The negative electrode piece of the present application reduces the expansion rate of the electrode piece and improves the cycle life of the battery.

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

In this article, the term "ion conductive polymer" refers to a conductive polymer material whose carriers are mainly positive and negative ions.

In some embodiments, an ion-conducting polymer does not have ions itself, but is a polymer that can complex ionic compounds and allow the dissociated ions to move directionally therein under the influence of an electric field. In some embodiments, the ion-conducting polymer refers to itself assisting the diffusion of dissociated ions through chain segment movement. Such ion-conducting polymers often need to be used under swelling conditions and can better conduct dissociated ions.

As used herein, the term "electrolyte salt" refers to a salt that can be used as a liquid electrolyte in a battery.

In some embodiments, the electrolyte salt can be one or more of lithium salt and sodium salt, and can be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, bisfluorosulfonyl Lithium amine, lithium bistriflate, lithium triflate, lithium difluoromethanesulfonate, lithium difluoroborate, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, NaPF _6. One or more of NaClO ₄ , NaBCl ₄ , NaSO ₃ CF ₃ , Na(CH ₃ )C ₆ H ₄ SO ₃ .

Using ion conductive polymers and electrolyte salts to form an ion transport layer can reduce the expansion rate of the negative electrode and improve the cycle life of the battery.

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

In this article, the term "inorganic fast ion conductor" refers to inorganic compounds that are fast ion conductors, also known as solid electrolytes. It has an ionic conductivity (1×10 ^-6 S·cm ^-1 ) and a low ionic conductivity activation energy (≤0.40eV) that is comparable to that of liquid electrolytes within a certain temperature range.

In this article, the term "inorganic ceramics" refers to a class of inorganic non-metallic materials made from natural or synthetic compounds through shaping and high-temperature sintering. It has the advantages of high melting point, high hardness, high wear resistance, and oxidation resistance.

The addition of inorganic fast ion conductors can further improve the ion conductivity of the ion transport layer. The addition of inorganic ceramics can improve the strength of the ion transport layer, thereby further reducing the expansion rate of the negative electrode piece and improving the cycle performance of the battery core.

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

In some embodiments, the inorganic fast ion conductor is selected from the group consisting of garnet-type lithium lanthanum zirconium oxide (LLZO), perovskite-structured lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphate (LATP), and sulfide solid electrolytes or It is doped with one or more types of modified materials.

As used herein, the term "garnet type lithium lanthanum zirconium oxide" refers to a compound of the general formula Li ₇ La ₃ Zr ₂ O ₁₂ .

In this article, the term “perovskite structure lithium lanthanum titanium oxide” refers to a compound with the general formula Li _3x La _0.67- _x TiO ₃ .

In some embodiments, based on the total mass of the ion transport layer, the mass content of the ion conductive polymer is 20% to 90%, optionally 50% to 80%. In some embodiments, the upper or lower limit of the mass content of the ion conductive polymer can be selected from the group consisting of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, Either 70%, 75%.

In some embodiments, based on the total mass of the ion transport layer, the mass content of the electrolyte salt is 10% to 50%, optionally 10% to 30%. In some embodiments, the upper or lower limit of the mass content of the electrolyte salt may be selected from the group consisting of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

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

In some embodiments, based on the total mass of the ion transport layer, the mass content of the inorganic ceramic is 0% to 10%, optionally 5% to 10%.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a plasticizer, and an electrolyte salt. In some embodiments, the first polymerized monomer refers to the monomer that constitutes the structural unit of the continuous phase of the composite material. The first polymerized monomers are cross-linked to form the skeleton of the composite, and plasticizers and electrolyte salts are present in the cross-linked network for ion transport.

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

The continuous phase of the composite material is formed through the cross-linking of polymerized monomers, which provides a base skeleton with a certain mechanical strength for the ion transport layer. The plasticizer and electrolyte salt in the composite material are used to improve the ionic conductivity of the composite material. The composite material has high ionic conductivity and low electronic conductivity, which can reduce the expansion rate of the negative electrode plate and improve the cycle performance of the battery.

In some embodiments, the polymerized monomer is selected from one or more types of ester monomers, sulfone monomers, amide monomers, nitrile monomers or ether monomers.

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

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

As used herein, the term "amide 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, ester monomers include carbonate monomers, sulfate monomers, sulfonate monomers, phosphate monomers, and carboxylate monomers. In some embodiments, the carbonate monomer is selected from vinylene carbonate, ethylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, and chloroethylene carbonate. one or more. In some embodiments, the sulfate ester monomer is selected from one or more of vinyl vinyl sulfite, vinyl sulfite, 4-methyl vinyl sulfate, and 4-ethyl vinyl sulfate. In some embodiments, the sulfonate monomer is selected from 1,3-propene sultone, 1,3-propane sultone, 1,4-butane sultone, methane disulfonate One or more methylcycloesters. In some embodiments, the phosphate monomer is selected from dimethyl vinyl phosphate, diethyl vinyl phosphate, diethyl propenyl phosphate, diethyl butenyl phosphate, diethyl 1 -Buten-2-ylphosphonate, diethyl ethynyl phosphate, vinyl trifluoromethyl phosphate, vinyl-1-trifluoroethyl phosphate, diethyl fluorovinyl phosphate One or more of the esters and 1-trifluoropropenyl ethyl phosphate. In some embodiments, the carboxylate monomer is selected from vinyl acetate.

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

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

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

In some embodiments, the ether monomer includes 1,3-dioxane, ethylene oxide, 1,2-propylene oxide, 4-methyl-1,3-dioxane, and tetrahydrofuran. , 2-methyltetrahydrofuran, 1,4-dioxane, one or more of ethylene glycol dimethyl ether, ethylene glycol diglycidyl ether, and triethylene glycol divinyl ether.

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

In some embodiments, the plasticizer is selected from one or more types of ester or sulfone monomers.

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

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 includes one or more of a second polymeric monomer thickener and an inorganic ceramic.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a plasticizer, an electrolyte salt, and a thickener.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a plasticizer, an electrolyte salt, and an inorganic ceramic.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, and a thickener.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, and an inorganic ceramic.

In some embodiments, the composite material is formed by cross-linking components including a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, a thickener, and an inorganic ceramic.

In this article, the term "thickener" refers to a substance that increases the viscosity of a material system, keeps the material system in a uniform and stable suspension or turbid state, or forms a gel.

In some embodiments, each component forming the composite material also includes a second polymerized monomer. The second polymerized monomer can improve the cross-linking efficiency, cross-linking degree and strength of the composite material, thereby optimizing the plasticizer and electrolyte salt. The paths for diffusion and transport of ions in the cross-linked network further improve the ionic conductivity of the ion transport layer.

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

In some embodiments, the second polymerized monomer is selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate , butyl acrylate, isodecyl acrylate, isooctyl acrylate, lauryl acrylate, isobornyl acrylate, isobornyl methacrylate, ethoxyethoxyethyl acrylate, cyanoacrylate, caprolactone acrylic acid Ester, 2-phenoxyethyl acrylate, tetrahydrofuryl acrylate, ethoxylated tetrahydrofuran acrylate, cyclotrimethylolpropane acrylate, 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 dimethyl Acrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol Diol diacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, Propylene glycol dimethacrylate, tripropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 2 (propoxy) neopentyl Glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polycyclohexyl acrylate, methoxypolyethylene glycol acrylate, ethoxy Trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, methoxypolyethylene glycol methacrylate, pentaerythritol triacrylate, propoxylated glycerol triacrylate, tris( One of 2-hydroxyethyl)isocyanurate triacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol tetraacrylate, 4(ethoxy)pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate species or several species.

In composite materials, adding a second polymerized monomer can improve the polymerization efficiency and degree of polymerization of the first polymerized monomer. In composite materials, adding thickeners can adjust the viscosity of the components, prevent the ion transport layer from penetrating into the pores inside the negative active material layer, reduce the performance of the negative electrode sheet, and help further improve the cycle performance of the battery. In composite materials, adding inorganic ceramics can further improve the strength of the ion transport layer, helping to further improve the safety performance and cycle performance of the battery.

In some embodiments, based on the total mass of the ion transport layer, the mass content of the first polymerized monomer is 0% to 30%, optionally 5% to 30%, or the mass content of the second polymerized monomer is 0 %~30%, optionally 5%~20%, or the mass content of plasticizer is 30%~80%, optionally 40%~70%, or the mass content of electrolyte salt is 10%~20%, Or the mass content of the thickener is 0% to 10%, optionally 3% to 10%, or the mass content of the inorganic ceramic is 0% to 50%, optionally 0% to 20%. In some embodiments, the upper or lower limit of the mass content of the polymerized monomer can be selected as 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 polymerized monomer may 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 can be selected from 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 limit or upper limit of the mass content of the electrolyte salt can be selected as 10%, 15%, or 20%, based on the total mass of the ion transport layer. In some embodiments, the lower limit or upper limit of the mass content of the thickener may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, based on Total mass meter of the ion transport layer. In some embodiments, the lower limit or upper limit of the mass content of the inorganic ceramic can be selected from 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, based on ion The total mass of the transport layer.

In some embodiments, the component further includes an active site initiator, and the active site initiator is selected from one or more peroxy compounds or azo compounds. In some embodiments, peroxy compounds include, but are not limited to, acyl peroxides, such as benzoyl peroxide, lauroyl peroxide, persulfates, such as ammonium persulfate; azo initiators include, but are not limited to, azoyl peroxides. Azobisisobutyronitrile, azobisisoheptanitrile. In some embodiments, the active site initiator is thermally initiated, and the thermal initiation temperature can be selected from 50°C to 85°C.

In some embodiments, the inorganic ceramic is selected from one or more of alumina, boehmite, zirconia, aluminum nitride, titanium dioxide, magnesium oxide, silicon carbide, calcium carbonate, and diatomaceous earth.

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

In some embodiments, the thickener and the plasticizer are mutually soluble, and the thickener is selected from the group consisting of polyvinyl formal, polyvinylidene fluoride and its copolymers, polyvinylidene fluoride, polyvinylidene fluoride, and trichlorethylene. , polytetrafluoroethylene, acrylic acid glue, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethylcellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide and one or more of polyvinylpyrrolidone. By selecting a thickener that is miscible with the plasticizer, the thickening effect of the thickener can be further exerted.

The present application provides a method for manufacturing a negative electrode sheet. The manufacturing method includes the following steps: coating an ion transport layer on the surface of the negative electrode active material layer to obtain a negative electrode sheet, wherein the electronic conductivity of the ion transport layer is not higher than 1× 10 ^-7 S/cm, and the lithium ion conductivity is not less than 1×10 ^-4 S/cm.

It can be understood that coating can be carried out by any method, such as spray coating, glue coating, gravure coating, etc. This method is simple, low-cost, and easy to promote and apply.

In some embodiments, the ion transport layer is composed of an ion conductive polymer, an electrolyte salt, an inorganic fast ion conductor, and an inorganic ceramic.

The present application provides a method for manufacturing a negative electrode sheet. The manufacturing method includes the following steps: synthesizing an ion transport layer in situ on the surface of the negative electrode active material layer to obtain a negative electrode sheet, wherein the electronic conductivity of the ion transport layer is not higher than 1 ×10 ^-7 S/cm, and the lithium ion conductivity is not less than 1×10 ^-4 S/cm.

It can be understood that in-situ synthesis means that after the material is disposed on the surface of the negative electrode active material layer, the ion transport layer is synthesized in-situ on the surface of the negative electrode active material layer by initiating polymerization in situ.

In some embodiments, the ion transport layer is a composite material, and the composite material is cross-linked by each component of a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, a thickener, an inorganic ceramic, and an initiator. formed.

In some embodiments, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

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

In some embodiments, the negative active material may be a negative active material known in the art for batteries. As an example, the negative 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 selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.

In some embodiments, the negative active material layer optionally further includes a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative active material layer optionally further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative active material layer optionally also includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.

[Positive pole piece]

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

As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the cathode active material may be a cathode active material known in the art for batteries. As an example, the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (can also be abbreviated to NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (can also be abbreviated to NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (can also be abbreviated to NCM ₆₂₂ ), LiNi At least one of _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer optionally further 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 can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.

[electrolyte]

The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.

In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and solvents.

In some embodiments, the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting 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 At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

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

[Isolation film]

In some embodiments, the secondary battery further includes a separator film. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.

In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

[Secondary battery]

The present application provides a secondary battery, including a positive electrode sheet, an electrolyte, and a negative electrode sheet manufactured by a manufacturing method such as the negative electrode sheet in any embodiment or the negative electrode sheet 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, and can be selected 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 the group consisting of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9.

When a lithium-ion battery is charged, lithium ions are detached from the positive active material of the positive electrode piece and embedded in the negative active material of the negative electrode piece. When the lithium ions are fully embedded in the negative electrode body, the electrons from the lithium ions are deposited with lithium metal. Because the negative active material The high specific surface area inside the negative electrode plate causes the lithium ions inside the negative electrode plate to be quickly consumed, causing a short-term loss of internal lithium ions. When more lithium ions diffuse from the positive electrode to the negative electrode, electrons will be converted directly to the metallic state and precipitated on the surface of the negative electrode, causing almost all lithium metal to be deposited on the surface of the negative electrode.

When the surface of the negative electrode plate is covered with an ion transport layer, and 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, that is, the lithium ion conductivity of the ion transport layer is less than that of the electrolyte. Ion conductivity, the difference in ionic conductivity reduces the lithium ion conduction speed on the surface of the electrode piece, providing a time difference for the diffusion of lithium ions in the electrolyte inside the active material layer, making it easier for lithium ions to deposit inside the negative electrode piece and less easily in the negative electrode Electrons are deposited on the surface of the active layer as lithium metal. This can reduce the expansion rate of the battery and improve the cycle performance of the battery.

The ratio of the lithium ion conductivity λ ₁ of the ion transport layer to the lithium ion conductivity λ ₂ of the electrolyte can be selected from 0.3 to 0.7, which can ensure a suitable time difference for the diffusion of lithium ions inside the pole piece, further reduce the expansion rate of the battery, and improve Battery cycle performance.

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

In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 4 shows a square-structured secondary battery 5 as an 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 side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 . The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[Battery module]

In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number 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 arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.

[battery pack]

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

7 and 8 illustrate the battery pack 1 as an example. Referring to FIGS. 7 and 8 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3. The upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4. Multiple battery modules 4 can be arranged in the battery box in any manner.

[Electrical device]

In one embodiment of the present application, an electrical device is provided, including the battery in any embodiment.

The electrical device includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

As the power-consuming device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

Figure 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, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.

As another example, the device may be a mobile phone, a tablet, a laptop, etc. The device is usually required to be thin and light, and a secondary battery can be used as a power source.

Example

Example 1

1) Preparation of negative electrode piece

Prepare the negative active material layer: mix graphite, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system according to a weight ratio of 94:3:3. The surface of the copper foil is coated with a coating amount of 1.40mA·h/cm ² to make CB=0.4, and then dried and cold-pressed to obtain a negative active material layer.

Prepare the ion transport layer: Mix polymethyl methacrylate (PMMA), LiFSI, LLZO, and alumina in the NMP solvent system in a weight ratio of 6:2:1:1 to evenly prepare the slurry. Add the slurry to the prepared negative electrode. The surface of the active material layer is coated with slurry with a coating thickness of 10um. After coating, dry it in a vacuum oven at 80°C for 12 hours to obtain the negative electrode piece, which is cut into corresponding sizes for later use.

2) Preparation of positive electrode pieces

Mix NCM811, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. After mixing evenly, apply it on aluminum foil and dry it. After cold pressing, the positive electrode piece was obtained, with a coating amount of 3.5mAh/cm ² , and cut into corresponding sizes for later use.

3) Isolation film

Use polyethylene film (PE separator) as the isolation film.

4) Preparation of electrolyte

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

5) Preparation of battery

Use the double-sided positive electrode, separator, and single-sided negative electrode to assemble the laminated battery core. Assemble the bare battery core in the order of negative electrode, separator, positive electrode, separator, and negative electrode, so that the isolation film is between the positive and negative electrodes for isolation. Function, place the bare battery core in the outer packaging to obtain the dry battery core. Inject 0.3g of electrolyte into each cell, vacuum seal it after injection, and let it sit for infiltration.

In Comparative Examples 1 to 3, the ion transport layer is not coated on the negative electrode sheet, and other preparation methods are the same as in Example 1. The coating amount of the negative electrode active material layer is adjusted according to the designed CB value.

In Comparative Example 1, when the CB value is 0.7, the coating amount of the negative active material layer is 2.45 mA·h/cm ² . In Comparative Example 2, when the CB value is 0.4, the coating amount of the negative active material layer is 1.40 mA·h/cm ² . In Comparative Example 3, when the CB value is 1, the coating amount of the negative active material layer is 3.5 mAh/cm ² .

The forming method of the negative electrode piece of Comparative Example 4 is the same as that of Example 1, except that there is only PMMA polymer in the ion transport layer.

The secondary batteries of Examples 2 to 14 and the secondary batteries of Comparative Examples 1 to 4 are similar to the secondary batteries of Example 1, but the composition and product parameters of the negative electrode plates are adjusted. The different product parameters are detailed in the table 1.

The relevant parameters of the cathode materials of the above-mentioned Examples 1 to 14 and Comparative Examples 1 to 4 are as shown in Table 1 below.

The preparation method of the secondary battery of Examples 15 to 28 is similar to that of the secondary battery of Example 1, but the composition and preparation method of the negative electrode sheet are adjusted. Taking Example 15 as an example, the preparation method of the negative electrode sheet is as follows:

Example 15

Preparation of negative electrode plate:

Prepare the negative active material layer: mix graphite, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system according to a weight ratio of 94:3:3. The surface of the copper foil is coated with a coating amount of 2.45mAh/cm ² to make CB=0.7, and is dried and cold-pressed to obtain a negative active material layer.

Prepare the ion transport layer: mix the first polymerized monomer vinylene carbonate (VC), the second polymerized monomer polyethylene glycol diacrylate (PEGDA), the mixture of plasticizer methyl ethyl carbonate and ethylene carbonate (EMC+EC ), thickener PVDF, electrolyte salt LiFSI, and inorganic ceramic alumina in a weight ratio of 20:5:40:5:20:10, stir thoroughly and mix evenly to prepare the slurry, and apply the slurry on the surface of the prepared negative active material layer , the coating thickness is 5um. Among them, the thickener PVDF can be dissolved in the plasticizer to achieve a thickening effect. The UV initiator diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide is added to the slurry before coating. (TPO), after coating, use a 365nm ultraviolet light source at a power of 2W/ ^cm2 for 1 minute to cause the slurry to solidify and form into a composite material to obtain the negative electrode piece, which is cut into corresponding sizes for later use.

The preparation method of the secondary batteries of Examples 15 to 28 is similar to that of the secondary battery of Example 15, but the composition and product parameters of the negative electrode sheet are adjusted. The different product parameters are detailed in Table 2.

In the step of preparing the ion transport layer in Comparative Example 5, a mixture of the polymerized monomer vinylene carbonate (VC), the second polymerized monomer polyethylene glycol diacrylate (PEGDA), the plasticizer methyl ethyl carbonate and ethylene carbonate was used. (EMC+EC), stir thoroughly and mix evenly to prepare the slurry according to the weight ratio of 20:5:75 to prepare the ion transport layer. Other steps are the same as in Example 15.

2. Performance test

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 testing method is as follows:

1. Calculation of CB value

Use the coated positive electrode sheet and negative electrode sheet to assemble the battery. Divide the area capacity of the negative electrode sheet by the area capacity of the positive electrode sheet in the battery system, which is the CB value of the battery, that is, CB = negative electrode area capacity / Positive surface capacity.

2. Lithium ion conductivity test

Coat the coating on the surface of the blank aluminum foil, cut it into small discs with a diameter of 20mm, and assemble the button battery in the order of positive electrode shell, small disc (coated side facing up), gasket, spring piece, and negative electrode shell, using Solartron 1470E CellTest multi-channel electrochemical workstation was used to test the electrochemical AC impedance method and draw the Nyquist diagram; the equivalent circuit curve fitting method was used to analyze the obtained Nyquist diagram, and the abscissa of the intersection of the semicircle and the oblique line in the Nyquist diagram was used as Resistor R, the test voltage can be 10mV, and the test frequency can be 0.1Hz~100K Hz.

According to the formula λ=d/RS, λ represents the ionic conductivity, d represents the thickness of the coating, R represents the resistance, and S represents the area of the coating, the ionic conductivity λ ₁ of the coating is calculated.

The ionic conductivity of the electrolyte is directly tested using a conductivity meter, and λ ₂ is obtained.

3. Electronic conductivity test

Coat the coating on the surface of the blank aluminum foil, cut it into small discs with a diameter of 20mm, and assemble the button battery in the order of positive electrode shell, small disc (coated side facing up), gasket, spring piece, and negative electrode shell, using Solartron 1470E CellTest multi-channel electrochemical workstation is tested in the potentiostatic mode. The voltage U is set to 1V and the time is set to 2h. The stable current in the final stage is recorded as I, and the formula λe=dI/SU is used, where d represents the coating's Thickness, S represents the area of the coating, I and U are the program setting values.

4. Expansion rate test

Before assembling the battery core, measure the thickness L ₀ of the negative electrode plate, let it sit for 5 minutes at an ambient temperature of 25°C, charge it to 4.25V at 1/3C, then charge it at a constant voltage of 4.25V until the current is ≤0.05mA, and let it stand. 5min, 1/3C discharge to 2.8V, let stand for 5min, charge at 1/3C to 4.25V, then charge at constant voltage at 4.25V to current ≤ 0.05mA, disassemble the battery, record the thickness of the negative electrode plate L ₁ , and calculate Expansion rate α = (L ₁ -L ₀ )/L ₁

5. Cell polarization voltage measurement

At an ambient temperature of 25°C, let it sit for 5 minutes, charge to 4.25V at 1/3C (46mA), then charge at a constant voltage of 4.25V to a current ≤ 0.05mA. Divide the charging energy by the charging capacity to calculate the average charging voltage. ; Let it stand for 5 minutes, discharge 1/3C to 2.8V, use the discharge energy divided by the discharge capacity to calculate the average discharge voltage, and subtract the discharge voltage from the average charge voltage to get the polarization voltage of the battery. This embodiment uses the data of the second cycle to calculate the polarization voltage.

6. Energy density test

Assemble the processed negative electrode sheet, positive electrode sheet and separator into a large soft-pack battery by winding, inject liquid according to the injection coefficient of 2g/Ah, charge according to 0.33C constant current to 4.25V, and let it stand for 5 minutes. , discharge to 2.8V at a constant current of 0.33C, read the discharge energy Q during the discharge stage, use a balance to weigh the cell mass m, and the energy density = Q/m.

7. Cycle life

Let the soft pack battery stand for 5 minutes, then charge it to 4.25V with a constant current of 0.33C (46mA), and then charge it with a constant voltage of 4.25V until the current is less than 0.05C (7mA). After letting it stand for 5 minutes, charge it with a constant current of 0.33C (46mA). Discharge to 2.8V to obtain the first-cycle discharge capacity C0 of the battery; repeat the above cycle until Cn is less than or equal to C0, and the number of cycles is recorded as the cycle life.

8. Discharge capacity test in the first week

After the soft-pack battery is left to stand for 5 minutes, charge it to 4.25V with a constant current of 0.33C (46mA), and then charge it with a constant voltage of 4.25V until the current is less than 0.05C to obtain the first-week charging capacity of the battery; after leaving it to stand for 5 minutes, charge it again Discharge to 2.8V at a constant current of 0.33C to obtain the first-week discharge capacity of the battery.

Batteries of each example and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 3 and Table 4.

In Comparative Example 3, when the CB value of the battery is 1, the energy density of the battery is 302Wh/kg. For the comparative example and embodiment with a CB value of 0.7, the energy density of the battery is 333Wh/kg. For the battery with a CB value of 0.4, the energy density of the battery is 333Wh/kg. According to the proportions and examples, the energy density of the battery is further improved to 369Wh/kg. It can be seen that the design of low CB value is conducive to improving the energy density of the battery.

The negative electrode sheet in Examples 1 to 28 includes a negative active material layer and an ion transport layer located on the surface where the negative active material layer is in contact with the electrolyte. The electronic conductivity of the ion transport layer is not higher than 1×10 ^{- 7} S/cm, and the ionic conductivity is not less than 1×10 ^-4 S/cm. From the comparison between Examples 1 to 14 and Comparative Examples 1, 2, and 4, and from the comparison between Examples 15 to 28 and Comparative Examples 1, 2, and 5, it can be seen that the negative electrode sheet is formed by locating the negative active material layer and the electrolyte phase. An ion transport layer is provided on the contact surface, which reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. When the ionic conductivity is not less than 1×10 ^-3 S/cm, the expansion rate of the negative electrode plate decreases and the cycle life of the battery increases more significantly. Compared with Comparative Example 4, the ion conductivity of the ion transport layer in Examples 1 to 14 is not less than 1×10 ^-4 S/cm, so that the battery can maintain a high first-cycle discharge capacity while improving cycle life.

In Examples 9 and 10, the ion transport layer only contains ion conductive polymer and electrolyte salt. Compared with Comparative Example 1, the negative electrode sheet reduces the expansion rate of the negative electrode sheet and improves the cycle life of the battery.

In Examples 1 to 8 and 11 to 13, in addition to ion conductive polymers and electrolyte salts, the ion transport layer also contains at least one of inorganic fast ion conductors and inorganic ceramics. Compared with Comparative Examples 1, 2, and 4, The negative electrode piece reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. Compared with Example 10, Examples 11 and 12 further improve the cycle life of the battery by adding inorganic fast ion conductors or inorganic ceramics.

The negative electrode sheet in Examples 15 to 28 includes a negative active material layer and an ion transport layer located on at least one surface of the negative active material layer. The electronic conductivity of the ion transport layer is not higher than 1×10 ^-7 S/cm. And the lithium ion conductivity is not less than 1×10 ^-4 S/cm, and the ion transport layer is a composite material. The composite material consists of various components including a first polymerized monomer, a second polymerized monomer, a plasticizer and an electrolyte salt. formed by cross-linking. Compared with Comparative Examples 1, 2, and 5, the negative electrode piece reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. Compared with Comparative Example 5, the ion conductivity of the ion transport layer in Examples 15 to 28 is higher than 1×10 ^-3 S/cm, which enables the battery to maintain a high first-cycle discharge capacity while improving cycle life.

The negative electrode plates in Embodiments 18-22 and 26-28 include a negative active material layer and an ion transport layer located on at least one surface of the negative active material layer. The electronic conductivity of the ion transport layer is not higher than 1×10 ^-7 S/cm, and the lithium ion conductivity is not less than 1×10 ^-4 S/cm. The ion transport layer is a composite material. The composite material consists of a first polymerized monomer, a second polymerized monomer, a plasticizer, and an electrolyte salt. , formed by cross-linking of various components of the thickener. Compared with Comparative Examples 1, 2, and 5, this negative electrode piece reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. Compared with Example 24, the addition of the thickener prevents the negative active material layer from seeping down during coating, further improving the cycle performance of the battery.

The negative electrode sheet in Examples 15 to 17, 23, and 25 includes a negative active material layer and an ion transport layer located on at least one surface of the negative active material layer. The electronic conductivity of the ion transport layer is not higher than 1×10 ^-7 S/cm, and the lithium ion conductivity is not less than 1×10 ^-4 S/cm. The ion transport layer is a composite material. The composite material consists of a first polymerized monomer, a second polymerized monomer, a plasticizer, and an electrolyte salt. , thickener and inorganic ceramic components are cross-linked. Compared with Comparative Examples 1, 2, and 5, this negative electrode piece reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. Compared with Example 20, the addition of inorganic ceramics in Example 25 further improves the cycle life of the battery.

In the negative electrode sheets in Examples 1 to 28, the ratio of the lithium ion conductivity of the ion transport layer to the lithium ion conductivity of the electrolyte is less than 1. The negative electrode piece reduces the expansion rate of the negative electrode piece and improves the cycle life of the battery. When the ratio of the lithium ion conductivity of the ion transport layer to the lithium ion conductivity of the electrolyte is 0.3 to 0.7, the expansion rate of the negative electrode piece is further reduced and the cycle life is further improved.

It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, within the scope that does not deviate from the gist of the present application, various modifications to the embodiments that can be thought of by those skilled in the art, and other forms constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application. .

Claims

A negative electrode piece, characterized in that it includes:

negative active material layer, and

an ion transport layer located on at least one surface of the negative active material layer,

The electronic conductivity of the ion transport layer is not higher than 1×10 -7 S/cm, and the ion conductivity is not lower than 1×10 -4 S/cm.
The negative electrode piece according to claim 1, characterized in that:

The ion transport layer includes an ion conductive polymer and an electrolyte salt.
The negative electrode piece according to claim 2, characterized in that:

The ion transport layer further includes at least one of an inorganic fast ion conductor and an inorganic ceramic.
The negative electrode piece according to claim 2 or 3, characterized in that:

The ion conductive polymer is selected from one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinyl alcohol and polymethacrylate.
The negative electrode piece according to claim 3 or 4, characterized in that:

The inorganic fast ion conductor is selected from the group consisting of garnet-type lithium lanthanum zirconium oxide (LLZO), perovskite structure lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphate (LATP) and sulfide solid electrolytes or doped modifications thereof. One or more types of sexual material.
The negative electrode piece according to any one of claims 3 to 5, characterized in that:

Based on the total mass of the ion transport layer, the mass content of the ion conductive polymer is 20% to 90%, optionally 50% to 80%; or

The mass content of the electrolyte salt is 10% to 50%, optionally 10% to 30%; or

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

Or the mass content of the inorganic ceramic is 0% to 10%, optionally 5% to 10%.
The negative electrode piece according to claim 1, characterized in that:

The ion transport layer is a composite material formed by cross-linking components including a first polymerized monomer, a plasticizer and an electrolyte salt.
The negative electrode piece according to claim 7, characterized in that:

The first polymerized monomer is selected from one or more types of ester monomers, sulfone monomers, amide monomers, nitrile monomers or ether monomers; or

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

The plasticizer is selected from the group consisting of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, methyl acetate, ethyl acetate, acetic acid At least one of propyl ester, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone kind.
The negative electrode piece according to any one of claims 7 to 9, characterized in that:

The component also includes one or more of a second polymerized monomer, a thickener, and an inorganic ceramic.
The negative electrode piece according to any one of claims 7 to 10, characterized in that:

Based on the total mass of the ion transport layer, the mass content of the first polymerized monomer is 0% to 30%, optionally 5% to 30%, or

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

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

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

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

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

The component further includes an active site initiator selected from one or more peroxy compounds or azo compounds.
The negative electrode piece according to any one of claims 3 to 12, characterized in that:

The inorganic ceramic is selected from one or more types of alumina, boehmite, zirconia, aluminum nitride, titanium dioxide, magnesium oxide, silicon carbide, calcium carbonate, and diatomite.
The negative electrode piece according to any one of claims 2 to 13, characterized in that:

The electrolyte salt is selected from one or more types of lithium salt and sodium salt.
The negative electrode piece according to any one of claims 10 to 14, characterized in that:

The thickener and the plasticizer are mutually soluble, and the thickener is selected from the group consisting of polyvinyl formal, polyvinylidene fluoride and its copolymers, polyvinylidene fluoride, polyvinylidene fluoride, and trichlorethylene , polytetrafluoroethylene, acrylic acid glue, epoxy resin, polyethylene oxide, polyacrylonitrile, sodium carboxymethylcellulose, styrene-butadiene rubber, polymethyl acrylate, polymethyl methacrylate, polyacrylamide and one or more of polyvinylpyrrolidone.
A method of manufacturing a negative electrode piece, characterized in that the manufacturing method includes the following steps:

Coating the ion transport layer on the surface of the negative active material layer to obtain the negative electrode piece,

The electronic conductivity of the ion transport layer is not higher than 1×10 -7 S/cm, and the lithium ion conductivity is not lower than 1×10 -4 S/cm.
The method for manufacturing a negative electrode piece according to claim 16, characterized in that:

The ion transport layer contains ion conductive polymer, electrolyte salt, inorganic fast ion conductor and inorganic ceramics.
A method of manufacturing a negative electrode piece, characterized in that the manufacturing method includes the following steps:

The ion transport layer is synthesized in situ on the surface of the negative active material layer to obtain the negative electrode piece,

The electronic conductivity of the ion transport layer is not higher than 1×10 -7 S/cm, and the lithium ion conductivity is not lower than 1×10 -4 S/cm.
The method for manufacturing a negative electrode piece according to claim 18, characterized in that:

The ion transport layer is a composite material formed by cross-linking components of a first polymerized monomer, a second polymerized monomer, a plasticizer, an electrolyte salt, a thickener, an inorganic ceramic, and an initiator. .
A secondary battery, characterized by comprising a positive electrode sheet, an electrolyte, and a negative electrode sheet as claimed in any one of claims 1 to 15 or a manufacturing method as described in any one of claims 16 to 19 Manufactured negative electrode plates.
The secondary battery according to claim 20, characterized in that

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, and can be selected from 0.3 to 0.7.
A battery module comprising the secondary battery according to claim 20 or 21.
A battery pack, characterized by comprising the battery module according to claim 22.
An electrical device, characterized by comprising at least one selected from the group consisting of the secondary battery according to any one of claims 20-21, the battery module according to claim 22, or the battery pack according to claim 23. kind.