CN114024028A

CN114024028A - Secondary battery

Info

Publication number: CN114024028A
Application number: CN202111115198.4A
Authority: CN
Inventors: 邓永红; 胡时光; 钱韫娴; 张永; 向晓霞
Original assignee: Shenzhen Capchem Technology Co Ltd
Current assignee: Shenzhen Capchem Technology Co Ltd
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2022-02-08
Also published as: WO2023045948A1

Abstract

In order to overcome the problem of insufficient high-temperature electrochemical performance of the existing battery, the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a solvent, an electrolyte salt and a compound shown in a structural formula 1:

wherein R is₁、R₂、R₃Each independently selected from the group consisting of Cl-C6 alkyl or haloalkyl, C2-C6 unsaturated hydrocarbyl or unsaturated halohydrocarbyl, and R₁、R₂At least one of the unsaturated alkyl or unsaturated halogenated alkyl is C2-C6; the secondary battery satisfies the following conditions: AW/100S is not less than 0.02 and not more than 3, wherein A is the mass percentage of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is; s is theSpecific surface area of negative electrode active material in m²(ii)/g; w is the surface density of the negative electrode material layer and the unit is g/m². The battery provided by the invention improves the cycle performance and the storage performance at high temperature, and simultaneously ensures that the battery has higher energy density.

Description

Secondary battery

Technical Field

The invention belongs to the technical field of energy storage electronic parts, and particularly relates to a secondary battery.

Background

The electrolyte is an important component of the lithium ion battery, and the performance of the electrolyte and the compatibility of the electrolyte with two electrodes directly influence the performance of the lithium ion battery. Therefore, research and development of the electrolyte are crucial to research and development of the performance of the lithium ion battery. Researches show that the use of the additive can obviously improve certain performances of the battery, including electrode capacity, rate charge and discharge performance, positive and negative electrode matching performance, low-temperature discharge performance, cycle performance, high-temperature storage performance or safety performance and the like. However, the conventional electrolyte still has the problems of compatibility with the positive electrode and the negative electrode, safety and the like.

Due to the expansion of the application field of the battery, higher requirements are provided for the performance stability of the battery at high temperature and low temperature, wherein the negative active material has important influence on the working stability of the battery, under the condition of high temperature, lithium ions are easy to form deposition on the surface of the negative material layer, so that lithium dendrites are formed, the existence of the lithium dendrites is easy to pierce a diaphragm to cause internal short circuit, the safety and the cycle life of the battery are influenced, meanwhile, the wetting performance of the electrolyte on the negative material layer influences the ionic conductivity in the negative material layer, and if the ionic conductivity is too low, the improvement of the internal resistance of the negative electrode is easy to cause, and the discharge performance of the battery is influenced.

Therefore, it is important to develop a battery that can improve high temperature performance.

Disclosure of Invention

The invention provides a secondary battery aiming at the problem that the existing battery has insufficient high-temperature electrochemical performance.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a solvent, an electrolyte salt and a compound shown in a structural formula 1:

wherein R is₁、R₂、R₃Each independently selected from the group consisting of Cl-C6 alkyl or haloalkyl, C2-C6 unsaturated hydrocarbyl or unsaturated halohydrocarbyl, and R₁、R₂At least one of the unsaturated alkyl or unsaturated halogenated alkyl is C2-C6;

the secondary battery satisfies the following conditions:

0.02≤AW/100S≤3

wherein A is the mass percentage of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is,

s is the specific surface area of the negative active material and has a unit of m²/g，

W is the surface density of the negative electrode material layer and the unit is g/m²。

Optionally, the secondary battery satisfies the following condition:

0.05≤AW/100S≤2；

preferably, the secondary battery satisfies the following conditions:

0.08≤AW/100S≤1.5。

optionally, the mass percent A of the compound shown in the structural formula 1 in the nonaqueous electrolyte is 0.01-5% based on 100% of the total mass of the nonaqueous electrolyte;

preferably, the mass percentage A of the compound represented by the formula 1 in the nonaqueous electrolytic solution is 0.01-2% based on 100% of the total mass of the nonaqueous electrolytic solution.

Optionally, the compound shown in formula 1 is at least one selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl phosphate, trifluoromethyl dipropargyl phosphate, dipropargyl 2,2, 2-trifluoroethyl phosphate, dipropargyl 3,3, 3-trifluoropropyl phosphate, hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, trifluoromethyl diallyl phosphate, 2,2, 2-trifluoroethyl diallyl phosphate, diallyl 3,3, 3-trifluoropropyl phosphate and diallyl hexafluoroisopropyl phosphate.

Optionally, the specific surface area S of the negative active material is 0.5-15 m²/g；

Preferably, the specific surface area of the negative electrode active material is 0.8-2 m²/g。

Optionally, the area density W of the negative electrode material layer is 5g/m²～150g/m²；

Preferably, the area density W of the negative electrode material layer is 20g/m²～120g/m²。

Optionally, the negative electrode material layer includes a negative electrode active material selected from at least one of a silicon-based negative electrode, a carbon-based negative electrode, and a tin-based negative electrode.

Optionally, the compacted density of the negative electrode material layer is 0.8-2.0 g/cc;

preferably, the compacted density of the negative electrode material layer is 1.55-1.85 g/ccc.

Optionally, the electrolyte salt is selected from LiPF₆、LiBOB、LiDFOB、LiPO₂F₂、LiBF₄、LiSbF₆、LiAsF₆、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiC(SO₂CF₃)₃、LiN(SO₂F)₂、LiClO₄、LiAlCl₄、LiCF₃SO₃、Li₂B₁₀Cl₁₀And a lower aliphatic carboxylic acid lithium salt.

Optionally, the nonaqueous electrolyte further comprises an auxiliary additive, wherein the auxiliary additive comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound and a nitrile compound;

preferably, the cyclic sulfate compound is at least one selected from vinyl sulfate, allyl sulfate or vinyl methyl sulfate;

the sultone compound is selected from at least one of 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;

the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,

in the formula 2, R₂₁、R₂₂、R₂₃、R₂₄、R₂₅、R₂₆Each independently selected from one of hydrogen atom, halogen atom, C1-C5 group;

the nitrile compound comprises one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.

According to the battery provided by the invention, the compound shown in the structural formula 1 is added as an additive, and the relationship between the specific surface area S and the surface density W of the negative active material and the addition A of the compound shown in the structural formula 1 is reasonably controlled, so that the compound shown in the structural formula 1 can fully play a role in improving the performance stability of the negative electrode under a high-temperature condition under the condition that the AW/100S is not less than 0.02 and not more than 3, specifically, the cycle performance and the storage performance of the battery under the high temperature are improved, and the battery is ensured to have higher energy density.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Embodiments of the present invention provide a secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolytic solution including a solvent, an electrolyte salt, and a compound represented by structural formula 1:

the secondary battery satisfies the following conditions:

0.02≤AW/100S≤3

wherein A is the mass percentage of the compound shown in the structural formula 1 in the non-aqueous electrolyte, and the unit is%

In the development of batteries, the selection of design parameters of a plurality of electrodes and nonaqueous electrolytic solutions, the type and addition amount of additives and the like have great influence on the electrochemical performance of the batteries, the existing mode is often a mode of obtaining an optimal combination mode by repeated trial and error through a large number of tests, however, the development mode of trial and error has great uncertainty, an optimal scheme is often difficult to obtain, only a scheme with relative advantages can be obtained, and the problems of long development time and high development cost exist. The inventor finds that when the compound shown in the structural formula 1 is used as the additive of the non-aqueous electrolyte of the battery, the performance improvement of the non-aqueous electrolyte of the battery has larger difference, and the obtained experimental effect is known in a reverse mode, in the aspect of improving the high-temperature performance of the battery, the addition amount A of the compound shown in the structural formula 1 and the specific surface area S and the surface density W of a negative active material have obvious correlation, and further experiments summarize an important relational expression that AW/100S is less than or equal to 3 and the obtained battery has better cycle performance and storage performance under the high-temperature condition and higher energy density when the battery meets the relational expression. When the battery containing the compound shown in the structural formula 1 is screened through the relational expression, a large number of unnecessary trial and error tests can be effectively eliminated, the battery with high energy density and excellent high-temperature cycle performance can be obtained more quickly, the development period is shortened, and the development cost is reduced.

In a preferred embodiment, the secondary battery satisfies the following conditions:

0.05≤AW/100S≤2。

in a more preferred embodiment, the secondary battery satisfies the following condition:

0.08≤AW/100S≤1.5。

the invention comprehensively designs the compound addition A shown in the structural formula 1 and intrinsic parameters (the specific surface area S of a negative electrode active material and the area density W of a negative electrode material layer) designed by a battery negative electrode material, reasonably quantifies the relevance of the parameters, and improves the high-temperature cycle performance of the battery under the condition of ensuring high energy density. It is presumed that the above parameter conditions of the battery negative electrode affect the permeability of the compound represented by the formula 1 in the negative electrode material layer and the stability of film formation, and that the compound represented by the formula 1 is decomposed in the negative electrode under the condition that the limitation of the above relational expression is satisfied to form a passivation film having an appropriate thickness and high conductivity of ions and electron insulation, and the passivation film is excellent in performance and suppresses the occurrence of side reactions of the active material and the electrolyte.

In the description of the present invention, the term "specific surface area of the anode active material" refers to the specific surface area before the anode active material is added to a solvent to form an anode slurry, that is, the specific surface area of the raw material.

In the description of the present invention, the term "areal density of the anode material layer" refers to the coating weight of the anode material layer per unit area on the anode, and the coating weight test method may be as follows: taking 30 current collector foils, wherein the area of each current collector foil is S1, respectively weighing the weight of each current collector foil, and taking the average value of the weight as W1; coating the same weight of slurry on one side of each current collector foil, drying at 120 ℃ for 1 hour after uniform coating, measuring the current collector foil which is basically free of solvent, respectively weighing the weight of the dried current collector foil with the slurry coated on one side, and taking the average value as W2; the area density W of the active material layer on one side of the current collector is (W2-W1)/S1.

In some embodiments, the mass percentage A of the compound shown in the structural formula 1 in the nonaqueous electrolytic solution is 0.01-5% based on 100% of the total mass of the nonaqueous electrolytic solution.

In a preferred embodiment, the mass percentage A of the compound shown in the structural formula 1 in the nonaqueous electrolytic solution is 0.01-2% based on 100% of the total mass of the nonaqueous electrolytic solution.

Specifically, the mass percentage a of the compound represented by the structural formula 1 in the nonaqueous electrolytic solution may be selected from 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.5%, 0.7%, 1%, 1.2%, 1.3%, 1.5%, 1.8%, or 2%.

The addition amount A of the compound shown in the structural formula 1 in the electrolyte plays a crucial role in the performance of a solid electrolyte interface film (SEI film) formed on a negative electrode. When the addition amount is too low, a passive film formed on the surface of the negative electrode by the additive cannot completely cover the surface, the electrolyte is easy to react on the surface of the negative electrode, irreversible capacity loss is generated, and gas is easy to generate to cause the expansion of the battery; when the amount of the added metal is too high, the formed passivation film becomes too thick to block the passage of lithium ions, thereby increasing the impedance and easily causing lithium precipitation.

In some embodiments, in the compound of formula 1, R₃Selected from the group consisting of Cl-C6 alkyl or haloalkyl, C2-C6 unsaturated hydrocarbon or unsaturated halohydrocarbon, R₁、R₂Are all selected from unsaturated alkyl or unsaturated halogenated alkyl of C2-C6.

In a preferred embodiment, in the compound shown in formula 1, the saturated alkyl group is selected from one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl; the unsaturated alkyl is selected from one of vinyl, allyl, 3-butenyl, isobutenyl, 4-pentenyl, ethynyl, propargyl, 3-butynyl and 1-methyl-2 propynyl; the halogenated hydrocarbon group is selected from one of monofluoromethyl, difluoromethyl, trifluoromethyl, 2,2, 2-trifluoroethyl, 2, 2-difluoroethyl, 2,2, 2-trifluoroethyl, 3, 3-difluoropropyl, 3,3, 3-trifluoropropyl and hexafluoroisopropyl.

In a preferred embodiment, the compound represented by structural formula 1 is selected from at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl phosphate, trifluoromethyl dipropargyl phosphate, dipropargyl 2,2, 2-trifluoroethyl phosphate, dipropargyl 3,3, 3-trifluoropropyl phosphate, hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, trifluoromethyl diallyl phosphate, 2,2, 2-trifluoroethyl diallyl phosphate, diallyl 3,3, 3-trifluoropropyl phosphate or diallyl hexafluoroisopropyl phosphate.

The preferable compound is more beneficial to improving the high-temperature storage performance and the high-temperature cycle performance of the battery, and has better matching effect with the negative electrode material layer with specific surface area S and area density W.

In some embodiments, the specific surface area S of the negative active material is 0.5 to 15m²/g；

In a preferred embodiment, the specific surface area S of the negative electrode active material is 0.8-2 m²/g。

Specifically, the specific surface area S of the anode active material may be 0.5m²/g、0.7m²/g、0.8m²/g、1m²/g、1.5m²/g、2m²/g、2.5m²/g、3m²/g、5m²/g、8m²/g、10m²/g、12m²/g、13m²G or 15m²/g。

Electrode reaction is mostly concentrated on an electrode/electrolyte interface, the larger the specific surface area of an active material is, the larger the electrode/electrolyte interface is, the easier the electrode reaction is, the smaller the polarization is, the better the performance of the electrode is, but the structural strength of a negative electrode material layer is insufficient due to the increase of the specific surface area, the problems of material falling and electrolyte decomposition are caused, and meanwhile, the specific surface area S of the negative electrode active material also directly influences the area and the thickness of an SEI film formed on the surface of the negative electrode material by the compound shown in the structural formula 1 in unit mass, so that the film forming quality of the SEI film is influenced, and the performance of a battery is influenced.

In some embodiments, the anode material layer has an areal density W of 5g/m²～150g/m²；

In a preferred embodiment, the area density W of the negative electrode material layer is 20g/m²～120g/m²。

Specifically, the area density W of the negative electrode material layer may be 5g/m²、10g/m²、15g/m²、20g/m²、25g/m²、30g/m²、40g/m²、55g/m²、61g/m²、73g/m²、82g/m²、98g/m²、110g/m²、121g/m²、134g/m²、146g/m²Or 150g/m²。

The surface density W of the negative electrode material layer is the coating weight of the single surface of the negative electrode material layer in unit area, the smaller W is, the more easily the electrolyte wets the negative electrode material layer, and the better the surface dynamics is. However, when W is too small, energy density of the battery is directly affected, and the coating process of the negative electrode slurry is difficult to control. Therefore, when the coating weight per unit area of one side of the negative electrode material layer falls within the above preferred range, the dynamic performance of the battery can be better improved while a higher energy density is compatible.

The analysis is only based on the influence of each parameter on the battery when the parameter exists independently, but in the practical battery application process, the three parameters are related to each other and are inseparable. Specifically, when the specific surface area S of the electrode is larger with a fixed additive content, the larger the interfacial contact area between the compound represented by formula 1 in the nonaqueous electrolytic solution and the negative electrode is, the more the reaction is likely to form a film, but the thickness of the formed film becomes thinner, and even the distribution becomes uneven, and the negative electrode active material is partially exposed, so that the structure of the negative electrode active material cannot be completely protected. Similarly, when the specific surface area S of the negative active material is constant, the additive content a also directly affects the quality of the negative film formation. Therefore, under the condition of ensuring the wetting of the electrolyte and the energy density of the battery, a protective film with proper thickness can be formed on the interface of the negative electrode by selecting proper additive content and material specific surface area, so that the cycle life and the high-temperature performance of the battery are improved. In the battery circulation process, because the negative electrode continuously expands, the capacity of the active material is continuously lost, and the compound shown in the structural formula 1 is consumed, A, S and W parameters in the battery design are always in dynamic change, the relation provided by the invention relates the three, the three jointly influence the energy density and the high-temperature circulation performance of the battery, and the requirement that the battery with AW/100S being more than or equal to 0.02 and less than or equal to 3 can give consideration to better energy density and high-temperature circulation performance. If AW/100S is too high or too low, the battery will suffer from dynamic deterioration and poor cycling.

In some embodiments, the anode material layer includes an anode active material selected from at least one of a silicon-based anode, a carbon-based anode, and a tin-based anode.

In a preferred embodiment, the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, and the like. The graphite comprises one or more of natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite and resin-coated graphite. The natural graphite may be scale graphite, flake graphite, soil graphite, and/or graphite particles obtained by spheroidizing, densifying, or the like, using these graphites as a raw material. The artificial graphite can be obtained by graphitizing organic matters such as coal tar pitch, coal heavy crude oil, atmospheric residual oil, petroleum heavy crude oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenyl, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenolic resin, imide resin and the like at high temperature. The amorphous carbon may be one obtained by heat-treating an easily graphitizable carbon precursor such as tar or pitch at a temperature range (400 to 2200 ℃) where graphitization does not occur for 1 or more times, or one obtained by heat-treating an hardly graphitizable carbon precursor such as resin. The carbon-coated graphite may be a carbon-graphite composite obtained by mixing natural graphite and/or artificial graphite with a carbon precursor which is an organic compound such as tar, pitch, or resin, performing a heat treatment at 400 to 2300 ℃ for 1 or more times to obtain natural graphite and/or artificial graphite as core graphite, and coating the core graphite with amorphous carbon. The carbon graphite composite may be in a form in which the entire or part of the surface of the core graphite is coated with amorphous carbon, or in a form in which a plurality of primary particles are combined with carbon derived from the above-described carbon precursor as a binder. Further, a carbon-graphite composite can be obtained by reacting a hydrocarbon gas such as benzene, toluene, methane, propane, or an aromatic volatile component with natural graphite and/or artificial graphite at a high temperature to deposit carbon on the graphite surface. The graphite-coated graphite may be natural graphite and/or artificial graphite mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch, resin, etc., and subjected to heat treatment at 2400 to 3200 ℃ or more for 1 time. The obtained natural graphite and/or artificial graphite is used as core graphite, and the whole or part of the surface of the core graphite is coated with a graphitized material, so that graphite-coated graphite can be obtained. The resin-coated graphite may be obtained by mixing natural graphite and/or artificial graphite with a resin or the like, drying the mixture at a temperature of less than 400 ℃, using the natural graphite and/or artificial graphite obtained as core graphite, and coating the core graphite with a resin or the like. Examples of the organic compound such as the tar and the pitch resin include carbonizable organic compounds selected from coal-based heavy crude oil, direct-current-based heavy crude oil, decomposed petroleum-based heavy crude oil, aromatic hydrocarbons, N-ring compounds, S-ring compounds, polyphenyl, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins.

In a preferred embodiment, the silicon-based negative electrode may include a silicon material, an oxide of silicon, a silicon-carbon composite material, a silicon alloy material, and the like. The addition amount of the silicon-based material is more than 0 and less than 30 percent. Preferably, the upper limit value of the addition amount of the silicon-based material is 10%, 15%, 20%, or 25%; the lower limit of the addition amount of the silicon-based material is 5%, 10% or 15%. The silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon films, 3D porous silicon and hollow porous silicon.

In a preferred embodiment, the tin-based negative electrode may include tin, tin carbon, tin oxygen, tin-based alloys, tin metal compounds; the tin-based alloy refers to an alloy consisting of tin and one or more of Cu, Ag, Co, Zn, Sb, Bi and In.

In some embodiments, the anode material layer includes one or more of a lithium anode, a sodium anode, a potassium anode, a magnesium anode, a zinc anode, and an aluminum anode. The lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.

In some embodiments, the anode material layer has a compacted density of 0.8 to 2.0g/cm³。

In a preferred embodiment, the compacted density of the anode material layer is 1.55-1.85g/cm³。

Specifically, the compacted density of the anode material layer can be 0.8g/cm³、0.9g/cm³、1g/cm³、1.13g/cm³、1.21g/cm³、1.35g/cm³、1.4g/cm³、1.55g/cm³、1.60g/cm³、1.65g/cm³、1.70g/cm³、1.75g/cm³、1.85g/cm³、1.9g/cm³Or 2.0g/cm³。

The negative electrode material layer is of a porous structure, and the charge and discharge process of the battery actually comprises liquid phase conduction of ions in the negative electrode material layer, so that the abundance degree of pore channels in the negative electrode material layer directly influences the quick charge and service life performance of the battery. Under the same other conditions, the smaller the compaction density of the negative electrode material layer is, the more developed the pore structure is, and the more favorable the liquid phase conduction of active ions is, especially under the severe conditions that the battery undergoes repeated expansion of charge and discharge for many times. However, the compaction density is too low, so that the negative pole piece is subjected to demoulding and powder dropping, lithium precipitation is generated due to poor electronic conductivity during charging, the quick charging and service life performance of the battery are influenced, and the energy density of the battery is reduced. When the compacted density of the anode material layer is in the above range, the battery has the best performance.

The compaction density of the negative electrode material layer also affects the porosity of the negative electrode material layer, and the higher the compaction density, the lower the porosity, and the higher the energy density of the battery. However, the porosity is too high, and the charge efficiency or the discharge efficiency is deteriorated. The porosity of the negative electrode material layer is less than or equal to 30%, for example, the porosity of the negative electrode material layer can be 7% -30%, 7% -15%, 15% -18%, 18% -20%, 20% -24%, 24% -26%, 26% -30%, preferably 7% -25%.

In some embodiments, the negative electrode material layer has a capacitance γ of 1mAh/cm per unit area²≤γ≤7mAh/cm²。

γ represents the capacity per unit area of the negative electrode material layer, i.e., represents the total amount of active ions that can be received per unit area of the negative electrode material layer when the battery is fully charged. The design capacity of the battery is the same, and when the battery is charged with a certain fixed multiplying power, if the capacitance per unit area of the negative electrode material layer used by the battery core is larger, the number of active ions instantaneously reaching the surface of the negative electrode material layer per unit area is larger, and the quick charging performance and the cycle performance of the battery are poorer; however, the larger the capacitance per unit area of the negative electrode material layer, the smaller the area of the negative electrode material layer can accept all the active ions extracted from the positive electrode, and the higher the energy density of the battery. Preferably, the range of gamma is controlled to be 2mAh/cm²≤γ≤5mAh/cm²More preferably 2mAh/cm²≤γ≤3.8mAh/cm²。

In some embodiments, the thickness L of the negative electrode material layer satisfies 0.015mm L0.15 mm.

In some embodiments, the average particle diameter D50 of the anode active material is in a range of 0.5 μm < D50 < 25 μm.

In general, the larger the average particle diameter D50 of the negative electrode active material is, the larger the gram capacity of the negative electrode active material is, the larger the negative electrode material layer capacity γ per unit area is, the higher the actual energy density of the battery is, but the worse the quick charge performance of the battery is. Preferably, the average particle diameter D50 of the anode active material is in the range of 4 μm. ltoreq. D50. ltoreq.15 μm, and more preferably 5 μm. ltoreq. D50. ltoreq.10 μm.

In some embodiments, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector.

The negative electrode current collector is selected from metal materials capable of conducting electrons, preferably, the negative electrode current collector comprises one or more of Al, Ni, tin, copper and stainless steel, and in a more preferred embodiment, the negative electrode current collector is selected from aluminum foil.

In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer. The negative electrode binder comprises thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether, copolymers of ethylene and tetrafluoroethylene, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and trichloroethylene, copolymers of vinylidene fluoride and fluoroethylene, copolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, polyethylene, polypropylene and the like; an acrylic resin; sodium carboxymethylcellulose; and styrene butadiene rubber.

The negative electrode conductive agent comprises one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.

In some embodiments, the positive electrode includes a positive electrode material layer containing a positive electrode active material, the kind of the positive electrode active material is not particularly limited and may be selected according to actual needs as long as it is a positive electrode active material or a conversion-type positive electrode material capable of reversibly intercalating/deintercalating metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions, etc.).

In a preferred embodiment, the battery is a lithium ion battery, the positive electrode of which is activeThe material may be selected from LiFe_1-x’M’_x’PO₄、LiMn_2-y’M_y’O₄And LiNi_xCo_yMn_zM_1-x-y-zO₂Wherein M ' is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ≤ x ' < 1, 0 ≤ y ' ≦ 1, 0 ≤ y ≤ 1, 0 ≤ x ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1, and the positive electrode active material can be selected from one or more of sulfide, selenide, and halide. More preferably, the positive active material may be selected from LiCoO₂、LiFePO₄、LiFe_0.8Mn_0.2PO₄、LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂、LiNi_0.8Co_0.1Mn_0.1O₂、LiNi_0.5Co_0.2Mn_0.2Al_0.1O₂、LiMn₂O₄、LiNi_0.5Co_0.2Al_0.3O₂One or more of (a).

In a preferred embodiment, the battery is a sodium ion battery, and the positive active material of the battery can be one or more selected from metal sodium, carbon materials, alloy materials, plated metal oxides, plated metal sulfides, phosphorus-based materials, titanate materials and Prussian blue materials. The carbon material can be selected from one or more of graphite, soft carbon and hard carbon, the alloy material can be selected from alloy materials consisting of at least two of Si, Ge, Sn, Pb and Sb, the alloy material can also be selected from alloy materials consisting of at least one of Si, Ge, Sn, Pb and Sb and C, and the chemical formula of the plated metal oxide and the plated metal sulfide is M1_xN_yM1 can be selected from one or more of Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb and V, N is selected from O or S, the phosphor-based material can be selected from one or more of red phosphor, white phosphor and black phosphor, and the titanate material can be selected from Na₂Ti₃O₇、Na₂Ti₆O₁₃、Na₄Ti₅O₁₂、Li₄Ti₅O₁₂、NaTi₂(PO₄)₃One or more than one of the Prussian blue materials, wherein the molecular formula of the Prussian blue materials is Na_xM[M′(CN)₆]_y·zH₂O, wherein M is a transition metal, M' is a transition metal, 0<x≤2，0.8≤y<1，0<z≤20。

In some embodiments, the positive electrode material layer has an areal density of 10g/m²～200g/m²。

In a preferred embodiment, the surface density W of the positive electrode material layer is 40g/m²≤W≤150g/m²More preferably 60g/m²≤W≤100g/m²。

Specifically, the surface density W of the positive electrode material layer may be 10g/m²、15g/m²、20g/m²、25g/m²、30g/m²、40g/m²、55g/m²、60g/m²、70g/m²、80g/m²、95g/m²、100g/m²、120g/m²、135g/m²、146g/m²、150g/m²、155g/m²、160g/m²、170g/m²、180g/m²、185g/m²、190g/m²、200g/m²。

If the surface density of the positive electrode material layer is too low, the lithium-embeddable positions of the positive electrode material layer are less, and the capacity is lower; if the surface density of the positive electrode material layer is too high, more solvent ethylene carbonate is needed, which increases the viscosity of the electrolyte, makes the electrolyte difficult to fully infiltrate the battery core, prolongs the migration path of lithium ions and electrons, increases the concentration polarization of the battery, and reduces the rate capability and the cycle performance of the battery.

The compaction density of the positive electrode material layer is generally required to be within a proper range, so that on one hand, the volume energy density of the lithium ion battery is ensured to be higher, and meanwhile, the compression deformation of the positive electrode active material is lower, and the electrolyte is favorably and rapidly infiltrated in gaps of the pole pieces. The active material adopted by the positive electrode is notLikewise, the compaction densities that can be achieved vary. Specifically, the positive electrode material layer may have a compacted density of 2.3g/cm³～4.3g/cm³、2.3g/cm³～2.7g/cm³、2.3g/cm³～2.8g/cm³、2.4g/cm³～2.7g/cm³、2.7g/cm³～2.8g/cm³、2.8g/cm³～2.9g/cm³、2.9g/cm³～3.2g/cm³、2.9g/cm³～3.1g/cm³、3.1g/cm³～3.2g/cm³、3.2g/cm³～3.6g/cm³、3.2g/cm³～3.4g/cm³、3.4g/cm³～3.7g/cm³、3.4g/cm³～3.6g/cm³、3.6g/cm³～3.7g/cm³、3.8g/cm³～3.9g/cm³、3.9g/cm³～4.1g/cm³、4.1g/cm³～4.3g/cm³、4.1g/cm³～4.2g/cm³Or 4.2g/cm³～4.3g/cm³。

The compacted density of the positive electrode material layer also affects the porosity of the positive electrode material layer, and the higher the compacted density, the lower the porosity, and the higher the energy density of the battery. However, the porosity is too high, and the charge efficiency or the discharge efficiency is deteriorated. When the porosity is too low, the electrolyte infiltration is poor, the lithium precipitation of the battery is easy to occur, and simultaneously, the dissolution of metal ions is increased under high compaction, so that the problem of poor cycle performance is caused. In a preferred embodiment, the porosity of the positive electrode material layer is less than or equal to 30%, for example, the porosity of the positive electrode material layer may be 7% to 30%, 7% to 15%, 15% to 18%, 18% to 20%, 20% to 24%, 24% to 26%, 26% to 30%, and more preferably 7% to 25%.

In some embodiments, the positive electrode has a resistivity of 3500 Ω · m or less, so that the lithium ion secondary battery has a low direct current resistance inside, thereby improving high-temperature storage performance and cycle performance of the lithium ion secondary battery.

Preferably, the resistivity of the positive electrode is 2500 Ω · m or less; more preferably, the resistivity of the positive electrode is 1200 Ω · m or less.

In some embodimentsThe OI value OI of the positive electrode material layer_c4 to 100, preferably 5 to 60; OI of the negative electrode material layer_c5 to 45, preferably 6 to 25. The OI value of the positive electrode material layer may reflect the degree of stacking orientation of the positive electrode active material in the positive electrode material layer, and the OI value of the negative electrode material layer may reflect the degree of stacking orientation of the negative electrode active material in the negative electrode material layer. OI value OI of positive electrode material layer_c＝C₀₀₃/C₁₁₀Wherein, C₀₀₃The peak area of 003 characteristic diffraction peak in the X-ray diffraction pattern of the positive pole piece, C₁₁₀Is the peak area of the 110 characteristic diffraction peak in the X-ray diffraction spectrum of the anode plate. OI value OI of negative electrode material layer_a＝C₀₀₄/C₁₁₀Wherein, C₀₀₄Is the peak area of 004 characteristic diffraction peak in X-ray diffraction pattern of the negative pole piece, C₁₁₀Is the peak area of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative pole piece.

In some embodiments, the positive electrode further comprises a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector.

The positive electrode current collector is selected from metal materials capable of conducting electrons, preferably, the positive electrode current collector comprises one or more of Al, Ni, tin, copper and stainless steel, and in a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

The positive electrode binder and the positive electrode conductive agent may be respectively the same as the negative electrode binder and the negative electrode conductive agent, and are not described herein again.

In some embodiments, the electrolyte salt includes one or more of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt. In a preferred embodiment, the electrolyte salt is selected from a lithium salt or a sodium salt.

In a preferred embodiment, the electrolyte salt is selected from the group consisting of LiPF₆、LiPO₂F₂、LiBF₄、LiBOB、LiSbF₆、LiAsF₆、LiCF₃SO₃、LiDFOB、LiN(SO₂CF₃)₂、LiC(SO₂CF₃)₃、LiN(SO₂C₂F₅)₂、LiN(SO₂F)₂、LiCl、LiBr、LiI、LiClO₄、LiBF₄、LiB₁₀Cl₁₀、LiAlCl₄At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenylborate, and lithium imide. Specifically, the electrolyte salt may be LiBF₄、LiClO₄、LiAlF₄、LiSbF₆、LiTaF₆、LiWF₇And inorganic electrolyte salts; LiPF₆Isophosphoric acid electrolyte salts; LiWOF₅Tungstic acid electrolyte salts; HCO₂Li、CH₃CO₂Li、CH₂FCO₂Li、CHF₂CO₂Li、CF₃CO₂Li、CF₃CH₂CO₂Li、CF₃CF₂CO₂Li、CF₃CF₂CF₂CO₂Li、CF₃CF₂CF₂CF₂CO₂Carboxylic acid electrolyte salts such as Li; CH (CH)₃SO₃Sulfonic acid electrolyte salts such as Li; LiN (FCO)₂)₂、LiN(FCO)(FSO₂)、LiN(FSO₂)₂、LiN(FSO₂)(CF₃SO₂)、LiN(CF₃SO₂)₂、LiN(C₂F₅SO₂)₂Cyclic lithium 1, 2-perfluoroethanedisulfonimide, cyclic lithium 1, 3-perfluoropropanedisulfonimide, LiN (CF)₃SO₂)(C₄F₉SO₂) Imide electrolyte salts such as imide electrolyte salts; LiC (FSO)₂)₃、LiC(CF₃SO₂)₃、LiC(C₂F₅SO₂)₃And the like methyl electrolyte salts; oxalic acid such as lithium difluorooxalato borate, lithium bis (oxalato) borate, lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphateAn electrolyte salt; and LiPF₄(CF₃)₂、LiPF₄(C₂F₅)₂、LiPF₄(CF₃SO₂)₂、LiPF₄(C₂F₅SO₂)₂、LiBF₃CF₃、LiBF₃C₂F₅、LiBF₃C₃F₇、LiBF₂(CF₃)₂、LiBF₂(C₂F₅)₂、LiBF₂(CF₃SO₂)₂、LiBF₂(C₂F₅SO₂)₂Fluorine-containing organic electrolyte salts, and the like.

When the electrolyte salt is selected from other salts such as sodium salt, potassium salt, magnesium salt, zinc salt, aluminum salt, etc., lithium in the above lithium salt may be replaced with sodium, potassium, magnesium, zinc, aluminum, etc.

In a preferred embodiment, the sodium salt is selected from sodium perchlorate (NaClO)₄) Sodium hexafluorophosphate (NaPF)₆) Sodium tetrafluoroborate (NaBF)₄) Sodium triflate (NaFSI) and sodium bistrifluoromethylsulfonate (NaTFSI).

Generally, the electrolyte salt in the electrolyte is a transfer unit of lithium ions, the concentration of the electrolyte salt directly affects the transfer rate of the lithium ions, and the transfer rate of the lithium ions affects the potential change of the negative electrode. In the process of rapidly charging the battery, the moving speed of lithium ions needs to be improved as much as possible, the formation of lithium dendrites caused by the excessively fast decline of the negative electrode potential is prevented, potential safety hazards are brought to the battery, and the excessively fast decline of the cycle capacity of the battery can be prevented. Preferably, the total concentration of the electrolyte salt in the electrolyte solution may be 0.5 to 2.0mol/L, 0.5 to 0.6mol/L, 0.6 to 0.7mol/L, 0.7 to 0.8mol/L, 0.8 to 0.9mol/L, 0.9 to 1.0mol/L, 1.0 to 1.1mol/L, 1.1 to 1.2mol/L, 1.2 to 1.3mol/L, 1.3 to 1.4mol/L, 1.4 to 1.5mol/L, 1.5 to 1.6mol/L, 1.6 to 1.7mol/L, 1.7 to 1.8mol/L, 1.8 to 1.9mol/L, and further preferably 0.5 to 1.9mol/L, and further preferably 0.8 to 1.9mol/L, 0.7mol/L to 1.7mol/L, or 0.8mol/L to 1.5 mol/L.

The density of the electrolytic solution is closely related to the concentration of the electrolyte salt and the concentration of the organic solvent, and if the density of the electrolytic solution is too low, the density of the electrolyte salt may be too low or the density of the organic solvent may be too low. If the concentration of the electrolyte salt is too low, the interior of the battery does not have enough lithium ion transfer units, and when the battery is charged with a large multiplying power, the potential of the negative electrode is rapidly reduced, so that lithium dendrites are easy to grow on the surface of the negative electrode, reversible active lithium is consumed, and the lithium dendrites which continuously grow may pierce through an isolating membrane, so that the internal short circuit of the positive electrode and the negative electrode brings potential safety hazards to the battery; too low electrolyte salt concentration can also cause unstable film formation of the negative electrode, the SEI film is easy to decompose and repair to generate a secondary SEI film, the decomposition of the secondary SEI film is aggravated at high temperature, and a large amount of heat is generated during decomposition and repair to deteriorate the interface of the negative electrode, so that the cycle performance of the battery is further deteriorated. The organic solvent has too low a density, and the dielectric constant of the electrolyte is low, which may increase the lithium ion migration resistance. If the electrolyte density is too high, the electrolyte salt concentration is too high or the organic solvent density is too high, and the electrolyte salt is easily decomposed and releases heat at high temperature, so that the heat generation in the battery is aggravated by the higher electrolyte salt concentration, and the battery is easy to fail; too high electrolyte density can also cause too high electrolyte viscosity and large lithium ion shuttle resistance, thereby influencing the dynamic performance of the battery; too high electrolyte density can also lead to increased cell polarization and deterioration of cell cycling performance. Therefore, the density of the electrolyte is preferably 1.0g/cm³～1.3g/cm³More preferably 1.0g/cm³～1.2g/cm³。

In some embodiments, the nonaqueous electrolytic solution further includes an auxiliary additive including at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, and a nitrile-based compound;

In other embodiments, the supplemental additives may also include other additives that improve the performance of the battery: for example, resistance-reducing additives such as lithium difluorophosphate, lithium difluorooxalato borate, phosphorus-containing acid anhydride, lithium tetrafluoroborate, and the like; additives for inhibiting the growth of impedance, such as lithium bis (oxalato) difluorophosphate; and additives for improving the safety performance of the battery, such as fluoro phosphate, cyclophosphazene and other flame retardant additives, or tert-amylbenzene, tert-butylbenzene and other anti-overcharge additives.

Unless otherwise specified, in general, the additive amount of any optional substance in the auxiliary additive in the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, more preferably 0.1 to 2%. Specifically, the additive amount of any optional substance in the auxiliary additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the fluoroethylene carbonate is added in an amount of 0.05% to 30% based on 100% by mass of the total mass of the nonaqueous electrolytic solution.

In some embodiments, the ionic conductivity of the nonaqueous electrolytic solution is preferably 6.0mS/cm or more, more preferably 7.6mS/cm or more, and still more preferably 8.0mS/cm or more.

In some embodiments, the weight percentage of the solvent with the viscosity of 0.7 mPas or less in the nonaqueous electrolytic solution is 40-80 wt%, so that the nonaqueous electrolytic solution has both low viscosity and high dielectric constant.

In some embodiments, the solvent includes one or more of an ether-based solvent, a nitrile-based solvent, a carbonate-based solvent, and a carboxylate-based solvent.

In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms, and the cyclic ether may be, but is not limited to, 1, 3-Dioxolane (DOL), 1, 4-Dioxan (DX), crown ether, Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH)₃-THF), 2-trifluoromethyltetrahydrofuran (2-CF)₃-THF); the chain ether may specifically be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferable because chain ethers have high solvating ability with lithium ions and can improve ion dissociation properties. The ether compound may be used alone, or two or more thereof may be used in combination in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-compaction lithium ion battery of the present invention, and is usually 1% by volume or more, preferably 2% by volume or more, and more preferably 3% by volume or more, and is usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less, based on 100% by volume of the nonaqueous solvent. In the presence of two or more ether compoundsWhen used in combination, the total amount of ether compounds may be within the above range. When the amount of the ether compound added is within the above-mentioned preferable range, the effect of improving the ionic conductivity by increasing the degree of dissociation of lithium ions and lowering the viscosity of the chain ether can be easily secured. In addition, when the negative electrode active material is a carbon material, the co-intercalation phenomenon of the chain ether and the lithium ion can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be set to appropriate ranges.

In some embodiments, the nitrile based solvent may specifically be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.

In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), γ -butyrolactone (GBL), Butylene Carbonate (BC); the chain carbonate may specifically be, but not limited to, one or more of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited and may be any within a range not significantly impairing the effect of the high-compacted lithium ion battery of the present invention, but in the case where one is used alone, the lower limit of the content is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of the solvent of the nonaqueous electrolytic solution. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the nonaqueous electrolytic solution, and it is easy to make the large-current discharge characteristic, the stability with respect to the negative electrode, and the cycle characteristic of the nonaqueous electrolyte battery fall within a favorable range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. Setting this range can improve the oxidation/reduction resistance of the nonaqueous electrolytic solution, and contributes to improvement of stability during high-temperature storage. The content of the chain carbonate is not particularly limited, and is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, based on the total amount of the solvent of the nonaqueous electrolytic solution. The volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. When the content of the chain carbonate is in the above range, the viscosity of the nonaqueous electrolytic solution is easily brought to an appropriate range, the decrease in the ionic conductivity is suppressed, and the content contributes to bringing the output characteristics of the nonaqueous electrolyte battery to a good range. When two or more kinds of chain carbonates are used in combination, the total amount of the chain carbonates may be set to satisfy the above range.

In some embodiments, chain carbonates having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonates") may also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, the fluorine atoms may be bonded to the same carbon atom or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.

The carboxylic ester solvent includes cyclic carboxylic ester and/or chain carbonate. Examples of the cyclic carboxylic acid ester include: one or more of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include: one or more of Methyl Acetate (MA), Ethyl Acetate (EA), propyl acetate (EP), butyl acetate, Propyl Propionate (PP), and butyl propionate.

In some embodiments, the sulfone-based solvent includes cyclic sulfones and chain sulfones, but preferably, in the case of cyclic sulfones, compounds having generally 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of chain sulfones, compounds having generally 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The amount of the sulfone solvent to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-performance lithium ion battery of the present invention, and is usually 0.3% by volume or more, preferably 0.5% by volume or more, and more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, and more preferably 30% by volume or less, based on the total amount of the solvent of the nonaqueous electrolytic solution. In the case where two or more sulfone solvents are used in combination, the total amount of the sulfone solvents may be set to satisfy the above range. When the amount of the sulfone solvent added is within the above range, an electrolyte excellent in high-temperature storage stability tends to be obtained.

In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.

In some embodiments, a separator is also included in the battery, the separator being positioned between the positive electrode and the negative electrode.

The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, and the like, including but not limited to a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP, and the like.

The present invention will be further illustrated by the following examples.

Examples 1 to 21

This example is used to illustrate the battery and the method for manufacturing the same disclosed in the present invention, and includes the following steps:

1) preparation of the electrolyte

Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) were mixed in a mass ratio of EC: DEC: EMC ═ 1:1:1, and then lithium hexafluorophosphate (LiPF) was added₆) Until the molar concentration is 1mol/L, and then adding the compound shown in the structural formula 1 with the mass content shown in the table 1.

2) Preparation of Positive plate

LiNi, a positive electrode active material, was mixed in a mass ratio of 93:4:3_0.5Co_0.3Mn_0.2O₂Conductive carbon black Super-P and a binder polyvinylidene fluoride (PVDF), and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. And uniformly coating the slurry on two surfaces of the aluminum foil, drying, rolling and vacuum drying to obtain anodes with various compaction densities, and welding aluminum outgoing lines by using an ultrasonic welding machine to obtain the positive plate, wherein the thickness of the positive plate is 120-150 mu m.

3) Preparation of negative plate

Mixing artificial graphite serving as a negative electrode active material, conductive carbon black Super-P, Styrene Butadiene Rubber (SBR) serving as a binder and carboxymethyl cellulose (CMC) according to a mass ratio of 94:1:2.5:2.5, and dispersing the materials in deionized water to obtain negative electrode slurry. Coating the slurry on two sides of a copper foil, drying, rolling and vacuum drying to obtain the negative electrodes with different specific surface areas and surface densities shown in the table 1, and welding a nickel leading-out wire by using an ultrasonic welding machine to obtain a negative plate, wherein the thickness of the negative plate is 120-150 mu m.

4) Preparation of cell

And placing three layers of isolating films with the thickness of 20 mu m between the positive plate and the negative plate, then winding the sandwich structure consisting of the positive plate, the negative plate and the diaphragm, flattening the wound body, then placing the wound body into an aluminum foil packaging bag, and baking for 48h at 75 ℃ in vacuum to obtain the battery cell to be injected with liquid.

5) Liquid injection and formation of battery core

And (3) in a glove box with the dew point controlled below-40 ℃, injecting the prepared electrolyte into the battery cell, carrying out vacuum packaging, and standing for 24 hours.

The conventional formation of the first charge is carried out according to the following steps: charging at 0.05C for 180min, charging at 0.2C to 3.95V, vacuum sealing for the second time, further charging at 0.2C to 4.35V, standing at room temperature for 24hr, and discharging at 0.2C to 3.0V.

Comparative examples 1 to 12

This comparative example, which is used for comparative illustration of the battery and the method for manufacturing the same disclosed in the present invention, includes most of the operating steps of example 1, except that:

adopting a compound shown as a structural formula 1 in a mass percentage shown as comparative examples 1-12 in the table 1;

the negative electrodes having the specific surface areas and the surface densities shown in table 1 were used.

Performance testing

The following performance tests were performed on the batteries prepared in examples 1 to 21 and comparative examples 1 to 12: high temperature storage Performance test

The formed battery is charged to 4.35V at a constant current of 1C at normal temperature, then charged at a constant current and a constant voltage until the current is reduced to 0.05C, then discharged to 3.0V at a constant current of 1C, the initial discharge capacity D1 of the battery is measured, then the battery is charged to full charge and stored for 30 days at 60 ℃, then discharged to 3V at 1C, and the retention capacity D2 and the recovery capacity D3 of the battery are measured. The calculation formula is as follows:

battery capacity retention (%) — retention capacity D2/initial capacity D1 × 100%;

battery capacity recovery (%) — recovery capacity D3/initial capacity D1 × 100%;

high temperature cycle performance test

Charging to 4.35V with a constant current of 1C, constant voltage charging until the current drops to 0.02C, and discharging to 3.0V with a constant current of 1C. The discharge capacity of the 1 st cycle and the discharge capacity of the last cycle were recorded in this cycle, and the capacity retention rate in the high-temperature cycle was calculated as follows:

capacity retention (%) — the last discharge capacity/1 st discharge capacity × 100%;

the test results obtained are filled in Table 1.

TABLE 1

From the test results of the examples 1 to 17 and the comparative examples 1 to 12, it can be seen that in the invention, when the mass percentage a of the compound represented by the structural formula 1, the specific surface area S of the negative electrode active material and the surface density W of the negative electrode material layer satisfy the condition that AW/100S is not less than 0.02 and not more than 3, the high-temperature storage and high-temperature cycle performance of the lithium ion battery can be effectively improved, and the increase of the high-temperature performance of the battery is not facilitated by the excessively large or excessively small value of AW/100S.

As can be seen from the test results of comparative examples 1 to 17, with the increase of the AW/100S value, the high-temperature storage performance and the high-temperature cycle performance of the battery increase first and then decrease, and particularly, when the relationship formula satisfies that AW/100S is not less than 0.05 and not more than 2, the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery can be significantly improved, and the increase of the initial capacity of the battery can be effectively ensured, which indicates that by controlling the relationship between the compound represented by the structural formula 1 and the design parameters of the negative electrode material layer, both the superior high-temperature performance and the higher energy density of the battery can be achieved.

The test results of the comparative examples 6, 18 to 21 and 1 to 12 show that when different compounds shown in the structural formula 1 are adopted, the specific surface area S of the compounds, the specific surface area S of the negative active material and the surface density W of the negative material layer are similar, and the results show that the compounds shown in the structural formula 1 have universality improvement on the high-temperature performance of the lithium ion battery on the premise that the relational expression AW/100S is more than or equal to 0.02 and less than or equal to 3.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolytic solution, the negative electrode comprising a negative electrode material layer containing a negative electrode active material, the nonaqueous electrolytic solution comprising a solvent, an electrolyte salt and a compound represented by structural formula 1:

the secondary battery satisfies the following conditions:

0.02≤AW/100S≤3

s is the negative active materialSpecific surface area of (D) in m²/g，

2. The secondary battery according to claim 1, wherein the secondary battery satisfies the following condition:

0.05≤AW/100S≤2；

preferably, the secondary battery satisfies the following conditions:

0.08≤AW/100S≤1.5。

3. the secondary battery according to claim 1, wherein the mass percentage a of the compound represented by the structural formula 1 in the nonaqueous electrolytic solution is 0.01 to 5% based on 100% by mass of the total mass of the nonaqueous electrolytic solution;

preferably, the mass percentage A of the compound represented by the formula 1 in the nonaqueous electrolytic solution is 0.1-2% based on 100% of the total mass of the nonaqueous electrolytic solution.

4. The secondary battery according to claim 1, wherein the compound represented by structural formula 1 is at least one selected from the group consisting of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, trifluoromethyl dipropargyl phosphate, dipropargyl 2,2, 2-trifluoroethyl phosphate, dipropargyl 3,3, 3-trifluoropropyl phosphate, hexafluoroisopropyl dipropargyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, trifluoromethyl diallyl phosphate, 2,2, 2-trifluoroethyl diallyl phosphate, diallyl 3,3, 3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate.

5. The secondary battery according to claim 1, wherein the negative electrode active material has a specific surface area S of 0.5 to 15m²/g；

Preferably, the ratio of the negative electrode active materialThe surface area is 0.8-2 m²/g。

6. The secondary battery according to claim 1, wherein the negative electrode material layer has an areal density W of 5g/m²～150g/m²；

7. The secondary battery of claim 1, wherein the negative electrode active material is selected from at least one of a silicon-based negative electrode, a carbon-based negative electrode, and a tin-based negative electrode.

8. The secondary battery according to claim 1, wherein the anode material layer has a compacted density of 0.8 to 2.0 g/cc;

9. The secondary battery of claim 1, wherein the electrolyte salt is selected from LiPF₆、LiBOB、LiDFOB、LiPO₂F₂、LiBF₄、LiSbF₆、LiAsF₆、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiC(SO₂CF₃)₃、LiN(SO₂F)₂、LiClO₄、LiAlCl₄、LiCF₃SO₃、Li₂B₁₀Cl₁₀And a lower aliphatic carboxylic acid lithium salt.

10. The secondary battery according to claim 1, wherein the nonaqueous electrolytic solution further includes an auxiliary additive including at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, and a nitrile-based compound;