CN113659206A

CN113659206A - High-compaction lithium ion battery

Info

Publication number: CN113659206A
Application number: CN202110934804.9A
Authority: CN
Inventors: 胡时光; 钱韫娴; 蓝广源; 向晓霞; 邓永红
Original assignee: Shenzhen Capchem Technology Co Ltd
Current assignee: Shenzhen Capchem Technology Co Ltd
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2021-11-16
Anticipated expiration: 2041-08-13
Also published as: CN113659206B

Abstract

The invention relates to the technical field of electrochemistry, in particular to a high-compaction lithium ion battery. A high-compaction lithium ion battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises electrolyte salt, an organic solvent and a compound shown in the following structural formula 1:

wherein R is₁、R₂、R₃、R₄、R₅、R₆Each independently selected from one of hydrogen atom, fluorine atom or group containing 1-5 carbon atoms; the positive electrode includes a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer having a compacted density of 2.3g/cm³～4.3g/cm³. The compound shown in the structural formula 1 in the electrolyte is on a positive electrode table and a negative electrode tableA layer of passivation film with high ion conduction and electronic insulation is formed on the surface, the passivation film inhibits the occurrence of side reaction of the anode active material and the electrolyte, and the high energy density of the high-compaction lithium ion battery can be ensured without weakening the high and low temperature performance of the high-compaction lithium ion battery.

Description

High-compaction lithium ion battery

Technical Field

The invention relates to the technical field of electrochemistry, in particular to a high-compaction lithium ion battery.

Background

The lithium ion battery has the advantages of high working voltage, wide working temperature range, high energy density and power density, no memory effect, long cycle life and the like, and is widely applied in the field of 3C digital consumption and the field of new energy automobiles. In recent years, both digital batteries and power batteries tend to have high energy density, and accordingly, the compaction of the design of the positive electrode and the negative electrode of the battery needs to be further improved. However, the high compaction causes problems such as poor electrolyte wetting, easy lithium deposition and deterioration of low-temperature performance of the battery, and increased metal ion elution at high compaction, resulting in poor cycle performance.

At present, in the aspect of electrolyte, the problems are generally solved from two dimensions of solvent and additive. Specifically, firstly, a low-viscosity solvent is adopted to completely or partially replace a high-viscosity solvent, such as Methyl Acetate (MA), Ethyl Acetate (EA) and the like, so that the overall viscosity of the electrolyte is reduced, the electrolyte is promoted to be soaked in a high-compaction material, and the performances of battery multiplying power, low-temperature discharge and the like are improved; and secondly, additives for reducing impedance and permeability, such as fluoroethylene carbonate (FEC), lithium difluorophosphate and the like, are added to form a positive and negative electrode interface film with low impedance and higher ion conductivity in the initial formation and capacity grading stages, so that the low-temperature discharge performance is improved. However, solvent replacement methods generally cause high temperature storage and cycling of the ballooning, which in turn degrades its performance. Therefore, it is urgent to develop an electrolyte capable of improving the low-temperature performance of a high-voltage battery and simultaneously achieving the high-temperature cycle performance.

Disclosure of Invention

In order to solve the problems, the invention provides a high-compaction lithium ion battery, and the comprehensive performance of the lithium ion battery is comprehensively improved by adding a compound shown in an additive structure 1 into electrolyte.

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

the invention provides a high-compaction lithium ion battery, which comprises a positive electrode, a negative electrode and electrolyte, wherein the electrolyte comprises electrolyte salt, an organic solvent and a compound shown in the following structural formula 1:

wherein R is₁、R₂、R₃、R₄、R₅、R₆Each independently selected from one of hydrogen atom, fluorine atom or group containing 1-5 carbon atoms;

the positive electrode includes a positive electrode active material layer containing a positive electrode active material, the positive electrode active material layer having a compacted density of 2.3g/cm³～4.3g/cm³。

Optionally, the compacted density of the positive electrode active material layer is Dg/cm³The addition amount of the compound shown in the structural formula 1 is A% based on 100% of the total mass of the electrolyte, and A and D satisfy the following relation: a multiplied by D is more than or equal to 1.8 and less than or equal to 6.4; preferably, a and D satisfy the following relationship: a multiplied by D is more than or equal to 1.8 and less than or equal to 3.6.

Optionally, the addition amount of the compound shown in the structural formula 1 is 0.05-5% based on 100% of the total mass of the electrolyte.

Optionally, the positive active material comprises one or more of the following materials:

lithium iron phosphate, or a doped and/or coated modified compound thereof;

lithium-containing transition metal oxide Li_mNi_xCo_yM_1-x-yO₂Or a doping and/or coating modified compound thereof, wherein M is more than or equal to 0.95 and less than or equal to 1.2, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, x + y is more than or equal to 0 and less than or equal to 1, and M is selected from at least one element of Mn and Al;

spinel lithium manganate Li₂Mn_2-zM_zO₄Or a doping and/or coating modified compound thereof, wherein z is more than or equal to 0 and less than or equal to 0.1, and M is selected from at least one element of Ni, B, Al, Cr, Fe, Mg, Zn and Ti;

spinel lithium nickel manganese oxide LiNi_0.5-kM_kMn_1.5O₄Or a doped and/or coated modified compound thereof, wherein k is 0. ltoreq. k<0.5, M is at least one element selected from Al, Cr, Fe, Mg, Zr, W, Nb, Si and Ti;

lithium-rich manganese-based material Li_1.2+n[(Mn_aCo_bNi_cM_1-a-b-c)_1-dM'_d]_0.8-nO₂Or a doping and/or coating modified compound thereof, wherein-0.2. ltoreq. n.ltoreq.0.3, 0.5. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.0.5, 0. ltoreq. c.ltoreq.0.5, 0. ltoreq. d.ltoreq.0.1, M and M' are each independently selected from at least one element of Al, B, Ba, Ce, Cr, Cu, Fe, K, La, Mg, Mo, Na, Nb, Os, Pr, Re, Ru, Sc, Sr, Sm, Ta, Ti, V, W, Y, Yb, Zn, Zr;

sulfur, or a complex thereof.

Optionally, the electrolyte salt is selected from 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.

Optionally, the compound shown in the structural formula 1 is selected from at least one of the following compounds:

optionally, the negative electrode comprises a negative active material layer containing a negative active material, and the compacted density of the negative active material layer is 1.55g/cm³～1.85g/cm³。

Optionally, the negative electrode active material includes one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.

Optionally, the porosity of the positive electrode active material layer is less than or equal to 30%, and the porosity of the negative electrode active material layer is less than or equal to 30%.

Optionally, the electrolyte further comprises an auxiliary additive, wherein the auxiliary additive comprises one or more of a cyclic sulfate compound, a cyclic sulfonate compound, an unsaturated cyclic carbonate compound, a fluorinated cyclic carbonate compound, a nitrile compound and a phosphate compound;

the cyclic sulfate compound comprises one or more of vinyl sulfate, allyl sulfate or methyl vinyl sulfate;

the cyclic sulfonate compound comprises one or more of 1, 3-propane sultone (1,3-PS), 1, 4-Butane Sultone (BS) and 1, 3-Propylene Sultone (PST);

the unsaturated cyclic carbonate compound comprises one or more of Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), 4, 5-dimethyl vinylene carbonate, phenyl vinylene carbonate and 4, 5-divinyl ethylene carbonate;

the fluorinated cyclic carbonate compound includes fluoroethylene carbonate (FEC), 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) ethylene carbonate, 4- (difluoromethyl) ethylene carbonate, 4- (trifluoromethyl) ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, 4, one or more of 5-difluoro-4, 5-dimethylethylene carbonate, 4-difluoro-5, 5-dimethylethylene carbonate;

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

the phosphate ester compound comprises one or more compounds shown in a structural formula 2:

wherein R is₇、R₈、R₉Each independently selected from C₁-C₅A saturated hydrocarbon group, an unsaturated hydrocarbon group or a halogenated hydrocarbon group of (A), and R₇、R₈、R₉At least one of them is an unsaturated hydrocarbon group.

According to the high-compaction lithium ion battery provided by the invention, the electrolyte contains the compound shown in the structural formula 1, and a layer of passivation film with high ion conduction and electronic insulation can be formed on the surfaces of the anode and the cathode, and the passivation film can inhibit the occurrence of side reaction of an anode active material and the electrolyte, so that the high energy density of the high-compaction lithium ion battery can be ensured, and the high and low temperature performance of the high-compaction lithium ion battery can not be weakened.

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.

The embodiment of the invention provides a high-compaction lithium ion battery, which comprises a positive electrode, a negative electrode and electrolyte, wherein the electrolyte comprises electrolyte salt, an organic solvent and a compound shown in the following structural formula 1:

In some embodiments, the group having 1 to 5 carbon atoms is selected from one of a hydrocarbon group, a halogenated hydrocarbon group, an oxygen-containing hydrocarbon group, a silicon-containing hydrocarbon group, or a cyano-containing hydrocarbon group.

In some embodiments, R₁、R₂、R₃、R₄、R₅、R₆Each independently selected from one of a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a trimethylsiloxy group, a cyano group or a trifluoromethyl group.

In a preferred embodiment, the compound of formula 1 is selected from at least one of the following compounds:

in some embodiments, the compound represented by formula 1 is added in an amount of 0.01% to 10% based on 100% by mass of the total electrolyte.

In a preferred embodiment, the compound represented by the structural formula 1 is added in an amount of 0.05% to 5%, more preferably, the compound represented by the structural formula 1 is added in an amount of 0.1% to 2%, based on 100% by mass of the total electrolyte. Specifically, the compound represented by the structural formula 1 may be added in an amount of 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 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, the positive electrode active material layer has a compacted density of Dg/cm³The compound shown in the structural formula 1 is added in an amount of A% based on 100% of the total mass of the electrolyte, and A and D satisfy the following relation: a multiplied by D is more than or equal to 1.8 and less than or equal to 6.4.

In a preferred embodiment, a and D satisfy the following relationship: a multiplied by D is more than or equal to 1.8 and less than or equal to 3.6.

The compaction density of the positive active 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 active material is lower, and the electrolyte is favorably and rapidly infiltrated in gaps of the pole pieces. The positive electrode uses different active materials and can achieve different compaction densities. Specifically, the compacted density of the positive electrode active material layer may be 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 active material layer also affects the porosity of the positive electrode active 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 and the low-temperature performance of the battery are easy to generate, and simultaneously, the metal ion dissolution is increased under high compaction, so that the cycle performance is deteriorated and the like. In a preferred embodiment, the porosity of the positive electrode active material layer is 30% or less, for example, the porosity of the positive electrode active 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 active material comprises one or more of the following materials:

lithium iron phosphate, or a doped and/or coated modified compound thereof;

lithium-rich manganese-based material Li_1.2+n[(Mn_aCo_bNi_cM_1-a-b-c)_1-d M'_d]_0.8-nO₂Or a doping and/or coating modified compound thereof, wherein-0.2. ltoreq. n.ltoreq.0.3, 0.5. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.0.5, 0. ltoreq. c.ltoreq.0.5, 0. ltoreq. d.ltoreq.0.1, M and M' are each independently selected from at least one element of Al, B, Ba, Ce, Cr, Cu, Fe, K, La, Mg, Mo, Na, Nb, Os, Pr, Re, Ru, Sc, Sr, Sm, Ta, Ti, V, W, Y, Yb, Zn, Zr;

the sulfur or a composite thereof may be, for example, elemental sulfur, a sulfur/carbon composite, a sulfur/conductive polymer composite, or a sulfur/inorganic material composite. Specifically, the sulfur/carbon composite material is a composite of sulfur and a carbon nanotube, graphene or a porous carbon material; in the sulfur/conductive polymer composite material, conductive polymers mainly comprise polypyrrole, polyaniline, polythiophene, poly 3, 4-ethylenedioxythiophene and the like; in the sulfur/inorganic material composite material, the inorganic material is transition metal oxide, nitride, sulfide, or the like.

In a preferred embodiment, in the doping modification compound of the material, the doping modification is cation doping, anion doping or anion-cation composite doping. Specifically, the cation doping element can be one or more selected from Al, Zr, Ti, B, Mg, V, Cr, Zn and Y; the anion doping element can be one or more selected from F, P, S, and is preferably F. Preferably, the total doping of the anions and cations does not exceed 20%.

In a preferred embodiment, in the coating modified compound of the above material, the coating modification is to form a coating layer on the surface of the positive electrode active material, and the coating layer may be a carbon layer, a graphene layer, an oxide layer, an inorganic salt layer or a conductive polymer layer, wherein the oxide may be an oxide or a fluoride formed by one or more elements of Al, Ti, Mn, Zr, Mg, Zn, Ba, Mo, B, Cr, Ag, Nb, Y, Sr, W, Mo, Pb, Cd and Ca; the inorganic salt may be Li₂ZrO₃、LiNbO₃、Li₄Ti₅O₁₂、Li₂TiO₃、LiTiO₂、Li₃VO₄、LiSnO₃、Li₂SiO₃、LiAlO₂、AlPO₄、AlF₃One or more of the above; the conductive polymer can be polypyrrole (PPy), poly 3, 4-ethylenedioxythiophene (PEDOT) or Polyamide (PI); preferably, the mass of the coating layer does not exceed 20%.

In some embodiments, the lithium-containing transition metal oxide Li_mNi_xCo_yM_1-x-yO₂Can be selected from LiCoO₂、LiNi_0.33Co_0.33Mn_0.33O₂、LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂、LiNi_0.7Co_0.1Mn_0.2O₂、LiNi_1/ ₃Co_1/3Mn_1/3O₂(NCM333)、LiNi_0.5Co_0.2Mn_0.3O₂(NCM523)、LiNi_0.6Co_0.2Mn_0.2O₂(NCM622)、LiNi_0.8Co_0.1Mn_0.1O₂(NCM811)、LiNi_0.8Co_0.1Al_0.1O₂、LiNi_0.85Co_0.10Al_0.05O₂、LiNi_0.8Co_0.2O₂、LiNi_0.80Co_0.15Al_0.05O₂One or more of them.

In some embodiments, spinel lithium manganate Li₂Mn_2-zM_zO₄Can be selected in particular from Li₂Mn₂O₄、Li₂Mn_1.95Al_0.05O₄、Li₂Mn_1.95Ni_0.05O₄One or more of them.

In some embodiments, spinel lithium nickel manganese oxide LiNi_0.5-kM_kMn_1.5O₄May be selected in particular from LiNi_0.5Mn_1.5O₄、LiNi_0.4Al_0.1Mn_1.5O₄、LiNi_0.3Al_0.1Fe_0.1Mn_1.5O₄、LiNi_0.3Mg_0.2Mn_1.5O₄、LiNi_0.4Ti_0.1Mn_1.5O₄One or more of them.

In some embodiments, the lithium-rich manganese-based material, Li_1.2+n[(Mn_aCo_bNi_cM_1-a-b-c)_1-d M'_d]_0.8-nO₂Can be selected in particular from Li_1.2[(Mn_0.667Co_0.167Ni_0.167)_0.8]O₂、Li_1.25[(Mn_0.75Co_0.25)_0.75]O₂、Li_1.5[(Mn_0.5909Co_0.0909Ni_0.2273Al_0.0909)_0.475Ti_0.025]O₂、Li[(Mn_0.6536Ni_0.3268Sr_0.0196)_0.97Zr_0.02Nb_0.01]O₂、Li_1.3[(Mn_0.6349Co_0.1587Ni_0.1587Mg_0.0477)_0.686La_0.007W_0.007]O₂、Li_1.2[(Mn_0.6349Co_0.1587Ni_0.1587Cr_0.0477)_0.796Pr_0.004]O₂、Li_1.3[(Mn_0.6536Co_0.1634Ni_0.1634Zn_0.0196)_0.693Sc_0.007]O₂One or more of them.

In general, the average particle diameter D50 of the cathode active material, the gram capacity of the cathode active material, the coating weight W per unit area of the cathode active material layer, the thickness L of the cathode active material layer, and the like all affect the actual energy density of the battery.

Specifically, the larger the average particle diameter D50 of the positive electrode active material is, the larger the gram capacity of the positive electrode active material is, the larger the capacity per unit area r of the positive electrode active material layer 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 positive electrode active material is in the range of 0.5 μm < D50 < 15 μm, more preferably 1 μm < D50 < 7 μm, and still more preferably 1 μm < D50 < 3 μm.

The larger the coating mass W of the positive electrode active material layer per unit area is, the larger the capacity γ of the positive electrode active material layer per unit area is, the higher the actual energy density of the battery is, but the larger the liquid phase conduction resistance of active ions during charge and discharge is, the worse the quick charge performance of the battery is. Preferably, the positive electrode active material layer has a coating mass W per unit area in the range of 2mg/cm²≤W≤20mg/cm²Further preferably, 4mg/cm²≤W≤15mg/cm²More preferably 6mg/cm²≤W≤10mg/cm²。

When the coating weight W of the positive electrode active material layer per unit area is constant, the larger the thickness L of the positive electrode active material layer is, the smaller the compacted density of the positive electrode active material layer is, the more favorable the liquid phase conduction of active ions during charge and discharge is, the better the quick charge performance of the battery is, but the lower the actual energy density of the battery is. Preferably, the thickness L of the positive electrode active material layer is in the range of 0.01mm L0.5 mm, more preferably 0.015mm L0.3 mm, and still more preferably 0.02mm L0.1 mm.

In some embodiments, the positive electrode active 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 active material layer. In some embodiments, the positive electrode conductive agent is one or more of a metal conductive agent, a carbon-based material, a metal oxide-based conductive agent, and a composite conductive agent. Specifically, the metal conductive agent can be copper powder, nickel powder, silver powder and other metals; the carbon material is conductive graphite, conductive carbon black, conductive carbon fiber or graphene and other carbon materials; the metal oxide-based conductive agent may be tin oxide, iron oxide, zinc oxide, or the like; the composite conductive agent can be composite powder, composite fiber and the like. More specifically, the conductive carbon black may be one or more of acetylene black, 350G, ketjen black, carbon fiber (VGCF), and Carbon Nanotubes (CNTs).

In some embodiments, when the positive electrode binder is selected, any binder may be used as long as it is a material safe for a solvent and an electrolyte used in manufacturing an electrode. Specifically, the binder used for the positive electrode is classified into two types, i.e., an oil-based binder and an aqueous binder, and in general, the former is usually an organic solvent and the latter is usually water. Oily binder optionally polyvinylidene fluoride; the aqueous binder can be one or more selected from polyacrylic acid and its salts, carboxymethyl cellulose and its salt compound, acrylonitrile multipolymer, xanthan gum, chitosan and its water-soluble derivatives, and polyvinyl acetate. Specifically, the polyacrylate includes salts of metals such as Li, Na, K, etc., carboxymethyl cellulose and salt compound thereof, wherein the salts include lithium carboxymethyl cellulose.

In some embodiments, the anode active material comprises one or more of a carbon-based anode, a silicon-based anode, a tin-based anode, a lithium 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 obtained by mixing natural graphite and/or artificial graphite with a carbon precursor which is an organic compound such as tar, pitch, resin, or the like, and performing heat treatment at 400 to 2300 ℃ for 1 or more times. The obtained natural graphite and/or artificial graphite is used as core graphite, and the core graphite is coated with amorphous carbon to obtain a carbon graphite composite. 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 a preferred embodiment, the lithium negative electrode may include metallic lithium or a lithium alloy. As the metal particles capable of forming an alloy with Li, conventionally known arbitrary metal particles can be used, but from the viewpoint of the capacity and cycle life of the nonaqueous electrolyte battery, the metal particles are preferably selected from Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, As, Nb, Mo, Cu, and the likeZn, Ge, In, Ti and W, or a compound thereof. Further, an alloy formed of two or more metals may be used, and the metal particles may be alloy particles formed of two or more metal elements. Further, the metal particles are preferably a metal selected from Si, Sn, As, Sb, Al, Zn, and W, or a metal compound thereof. Examples of the metal compound include metal oxides, metal nitrides, and metal carbides. Further, an alloy formed of two or more metals may also be used. The metal nitride being of the inverse fluorite or Li family₃Compounds of N structure, in particular, Li₃The compound of N structure includes Li₇MnN₄、Li₇FeN₂And the like.

In a preferred embodiment, among the metal particles capable of forming an alloy with Li, silicon or a silicon metal compound is preferable. The silicon metal compound is preferably a silicon metal oxide. Silicon or a silicon metal compound is preferable from the viewpoint of increasing the capacity of the battery. In the present specification, silicon or a silicon metal compound is collectively referred to as a silicon compound. Specific examples of the silicon compound include SiO_x、SiN_x、SiCx、SiZ_xO_y(Z C, N), and the like. The silicon compound is preferably a silicon metal oxide, which if represented by the formula, is SiO_x. The general formula SiO_xCan be made of silicon dioxide (SiO)₂) And metallic silicon (Si) as a raw material, and the value of x is usually 0. ltoreq. x < 2. SiO 2_xHas a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals easily allow alkali metal ions such as lithium ions to enter and exit, and can obtain a high capacity. Specifically, the Si metal oxide can be expressed as SiO_xWherein x is 0. ltoreq. x < 2, more preferably 0.2 to 1.8, still more preferably 0.4 to 1.6, particularly preferably 0.6 to 1.4. Within this range, the battery has a high capacity, and irreversible capacity reduction due to Li bonding with oxygen can be avoided.

In general, the average particle diameter D50 of the anode active material, the gram capacity of the anode active material, the coating weight W per unit area of the anode active material layer, the thickness L of the anode active material layer, and the like all affect the actual energy density of the battery.

Specifically, 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 active material layer capacity per unit area r 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 0.5 μm < D50 < 25 μm, more preferably 4 μm < D50 < 15 μm, and still more preferably 5 μm < D50 < 10 μm.

The larger the coating mass W of the negative electrode active material layer per unit area is, the larger the capacity γ of the negative electrode active material layer per unit area is, the higher the actual energy density of the battery is, but the larger the liquid phase conduction resistance of active ions during charge and discharge is, the worse the quick charge performance of the battery is. Preferably, the negative electrode active material layer has a coating mass W per unit area in a range of 2mg/cm²≤W≤20mg/cm²Further preferably, 4mg/cm²≤W≤15mg/cm²More preferably 6mg/cm²≤W≤10mg/cm²。

When the coating weight W of the negative electrode active material layer per unit area is constant, the larger the thickness L of the negative electrode active material layer is, the smaller the compacted density of the negative electrode active material layer is, the more favorable the liquid phase conduction of active ions during charge and discharge is, the better the quick charge performance of the battery is, but the lower the actual energy density of the battery is. Preferably, the thickness L of the negative electrode active material layer is in the range of 0.01mm L0.5 mm, more preferably 0.015mm L0.15 mm, and still more preferably 0.02mm L0.1 mm.

In some embodiments, the negative electrode active 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 active material layer.

The negative electrode conductive agent and the positive electrode conductive agent can be the same or different, and a person skilled in the art can select a suitable conductive agent material according to a specific application. The negative electrode conductive agent may include a metal conductive agent, a carbon-based material, a metal oxide-based conductive agent, a composite conductive agent, and the like. Specifically, the metal conductive agent can be copper powder, nickel powder, silver powder and other metals; the carbon material is conductive graphite, conductive carbon black, conductive carbon fiber and graphene; the metal oxide-based conductive agent may be tin oxide, iron oxide, zinc oxide, or the like; the composite conductive agent can be composite powder, composite fiber and the like.

In a preferred embodiment, any binder may be used as the binder for the negative electrode as long as it is a material safe for the solvent and the electrolyte used in the production of the electrode. The rubber is one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer.

In a preferred embodiment, the compaction density of the negative electrode active material layer is generally matched to the compaction density of the positive electrode active material layer, the positive electrode active material layer is at a high compaction density, and the negative electrode active material layer is also at a high compaction density, so that a desired energy density is achieved. The negative electrodes are made of different active materials and have different compaction densities. Preferably, the anode active material layer may have a compacted density of 1.55g/cm³～2.1g/cm³、1.55g/cm³～1.6g/cm³、1.6g/cm³～1.7g/cm³、1.7g/cm³～1.8g/cm³、1.8g/cm³～1.85g/cm³、1.85g/cm³～1.9g/cm³、1.9g/cm³～2.0g/cm³Or 2.0g/cm³～2.1g/cm³More preferably 1.55g/cm³～1.85g/cm³。

In some embodiments, the compacted density of the negative active material layer also affects the porosity of the negative active material layer, with higher compacted densities leading to lower porosities and higher energy densities 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 and the low-temperature performance of the battery are easy to generate, and simultaneously, the metal ion dissolution is increased under high compaction, so that the cycle performance is deteriorated and the like. Preferably, the porosity of the negative electrode active material layer is less than or equal to 30%, for example, the porosity of the negative electrode active 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 electrolyte further includes an auxiliary additive including one or more of a cyclic sulfate-based compound, a cyclic sulfonate-based compound, an unsaturated cyclic carbonate-based compound, a fluorinated cyclic carbonate-based compound, a nitrile-based compound, and a phosphate-based compound.

In a preferred embodiment, the cyclic sulfate compound comprises one or more of vinyl sulfate, propylene sulfate, or vinyl methylsulfate. When the non-aqueous electrolyte contains a cyclic sulfate compound, the addition amount of the cyclic sulfate compound is 0.1-5% based on 100% of the total mass of the non-aqueous electrolyte.

In a preferred embodiment, the cyclic sulfonate compound includes one or more of 1, 3-propane sultone (1,3-PS), 1, 4-Butane Sultone (BS), 1, 3-Propene Sultone (PST). When the non-aqueous electrolyte contains a cyclic sulfonate compound, the addition amount of the cyclic sulfonate compound is 0.1 to 5% based on 100% of the total mass of the non-aqueous electrolyte.

In a preferred embodiment, the unsaturated cyclic carbonate-based compound includes one or more of Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), 4, 5-dimethylvinylene carbonate, phenyl vinylene carbonate, 4, 5-divinylethylene carbonate. When the non-aqueous electrolyte contains an unsaturated cyclic carbonate compound, the amount of the unsaturated cyclic carbonate compound added is 0.1 to 5% based on 100% by mass of the total non-aqueous electrolyte.

In a preferred embodiment, the fluorocyclic carbonate compound includes fluoroethylene carbonate (FEC), 4-difluoroethylene carbonate, 4, 5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4, 5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, 4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) ethylene carbonate, 4- (difluoromethyl) ethylene carbonate, 4- (trifluoromethyl) ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4, 5-dimethylethylene carbonate, and, 4, 5-difluoro-4, 5-dimethyl ethylene carbonate, 4-difluoro-5, 5-dimethyl ethylene carbonate. When the non-aqueous electrolyte contains fluorinated cyclic carbonate compound, the addition amount of the fluorinated cyclic carbonate compound is 0.1-30% based on 100% of the total mass of the non-aqueous electrolyte.

In a preferred embodiment, the nitrile compound comprises one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile, sebaconitrile. When the non-aqueous electrolyte contains a nitrile compound, the amount of the nitrile compound added is 0.1 to 5% based on 100% by mass of the total non-aqueous electrolyte.

In a preferred embodiment, the phosphate ester based compound comprises one or more of the compounds represented by structural formula 2:

Specifically, the phosphate ester compound may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2, 2, 2-trifluoroethyl phosphate, dipropargyl-3, 3, 3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2, 2, 2-trifluoroethyl phosphate, diallyl-3, 3, 3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate. When the non-aqueous electrolyte contains a phosphate compound, the addition amount of the phosphate compound is 0.1-5% based on 100% of the total mass of the non-aqueous electrolyte.

In some embodiments, the supplemental additive may further include at least one of an aromatic additive, a fluoroanisole-containing compound, a dicarboxylic anhydride, lithium difluorophosphate, lithium bis-fluorosulfonylimide (LiFSI).

In a preferred embodiment, the aromatic additive includes aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partial hydride of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, dibenzofuran, etc.; one or more of 2-fluorobiphenyl, o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene. When the non-aqueous electrolyte contains an aromatic additive, the addition amount of the aromatic additive is 0.1-5% based on 100% of the total mass of the non-aqueous electrolyte.

In a preferred embodiment, the fluoroanisole-containing compound comprises one or more of 2, 4-difluoroanisole, 2, 5-difluoroanisole, and 2, 6-difluoroanisole. When the nonaqueous electrolytic solution contains the fluoroanisole-containing compound, the addition amount of the fluoroanisole-containing compound is 0.1-5% based on 100% of the total mass of the nonaqueous electrolytic solution.

In a preferred embodiment, the dicarboxylic anhydride comprises one or more of succinic acid, maleic acid, phthalic acid. When the nonaqueous electrolytic solution contains dicarboxylic anhydride, the amount of the dicarboxylic anhydride added is 0.1 to 5% based on 100% by mass of the nonaqueous electrolytic solution. When lithium difluorophosphate is contained in the nonaqueous electrolyte, the addition amount of the lithium difluorophosphate is 0.1-2% based on 100% of the total mass of the nonaqueous electrolyte;

in a preferred embodiment, when the lithium bis (fluorosulfonyl) imide (LiFSI) is contained in the nonaqueous electrolytic solution, the amount of the lithium bis (fluorosulfonyl) imide (LiFSI) added is 0.1 to 5% based on 100% by mass of the total of the nonaqueous electrolytic solution.

In some embodiments, the auxiliary additive further comprises nitrogen-containing compounds such as 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidone, 1, 3-dimethyl-2-imidazolidinone, N-methylsuccinimide, and the like; hydrocarbon compounds such as heptane, octane, and cycloheptane; fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene and trifluorotoluene.

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%.

Particularly, when the auxiliary additive is selected from fluorinated cyclic carbonate compounds, the fluorinated cyclic carbonate compounds are added in an amount of 0.05% to 30% based on 100% by mass of the total electrolyte.

The nonaqueous electrolytic solution of the high-pressure lithium ion battery of the present invention generally contains a nonaqueous solvent dissolving the above electrolyte as its main component, as in the case of a general nonaqueous electrolytic solution. The nonaqueous solvent used herein is not particularly limited, and a known organic solvent can be used. Examples of the organic solvent include cyclic carbonates, chain carbonates, carboxylates, ether compounds, sulfone compounds, and nitrile compounds, but are not limited to the above. These solvents may be used singly or in combination of two or more.

The cyclic carbonate is generally a cyclic carbonate having an alkylene group with 2 to 4 carbon atoms, and a cyclic carbonate with 2 to 3 carbon atoms is preferably used from the viewpoint of improving the battery characteristics by improving the dissociation degree of lithium ions.

Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, and butylene carbonate. Among them, ethylene carbonate and propylene carbonate are preferable, and ethylene carbonate which is not easily oxidized/reduced is more preferable. The cyclic carbonates may be used alone, or two or more of them may be used in combination in any combination and ratio.

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.

As the chain carbonate, a chain carbonate having 3 to 7 carbon atoms is usually used, and a chain carbonate having 3 to 5 carbon atoms is preferably used in order to adjust the viscosity of the electrolyte solution to an appropriate range.

Further, chain carbonates having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonates") can 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 chain carbonates may be used singly, or two or more kinds may be used in combination in any combination and ratio. 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 output characteristics of the battery can be favorably brought to a preferable 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.

The ether compound is preferably a chain ether having 3 to 10 carbon atoms or a cyclic ether having 3 to 6 carbon atoms.

Among the chain ethers having 3 to 10 carbon atoms, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether are mentioned. 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. When two or more ether compounds are used in combination, the total amount of the ether compounds may be set to satisfy 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 therefore the input/output characteristics and the charge/discharge rate characteristics can be set to appropriate ranges.

The sulfone compound is not particularly limited, and is preferably a compound having usually 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, in the case of a cyclic sulfone, and usually 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms, in the case of a chain sulfone.

The amount of the sulfone compound added is not particularly limited and is arbitrary within a range not significantly impairing the effect of the high-compacted 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, relative to the total amount of the solvent of the nonaqueous electrolytic solution. In the case where two or more sulfone compounds are used in combination, the total amount of the sulfone compounds may be set to satisfy the above range. When the amount of the sulfone compound added is within the above range, an electrolyte solution having excellent high-temperature storage stability tends to be obtained.

In some embodiments, the carboxylic ester solvent may be, but is not limited to, one or more of Methyl Acetate (MA), Ethyl Acetate (EA), propyl acetate (EP), butyl acetate, Propyl Propionate (PP), butyl propionate.

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

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 lithium salts.

In a preferred embodiment, the electrolyte salt is selected from 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 electrolyte salts such as lithium difluorooxalato borate, lithium bis (oxalato) borate, lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate and lithium tris (oxalato) phosphate; 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.

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; the excessively low concentration of the electrolyte salt can cause unstable film formation of the negative electrode, and an SEI film is easy to decompose and repair to generate a secondary electrolyteAnd the secondary SEI film is decomposed at high temperature, and generates a large amount of heat during decomposition and repair, so that a negative electrode interface is deteriorated, and 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 positive active material layer has an OI value OI_c4 to 100, preferably 5 to 60; OI of the negative electrode active material layer_c5 to 45, preferably 6 to 25. The OI value of the positive electrode active material layer may reflect the degree of stacking orientation of the positive electrode active material in the positive electrode active material layer, and the OI value of the negative electrode active material layer may reflect the degree of stacking orientation of the negative electrode active material in the negative electrode active material layer. OI value OI of positive electrode active 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 active 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 for extracting current, and the positive electrode active material layer covers the positive electrode current collector. Optionally, the positive current collector includes one of an aluminum current collector and a nickel current collector. In general, an aluminum current collector is often used as a positive current collector and LiCoO₂Lithium manganate, ternary material and LiFePO₄And matching the equal phases. The nickel as the current collector can be matched with positive active materials such as lithium iron phosphate and the like, and can also be matched with negative active materials such as nickel oxide, sulfur, carbon-silicon composite materials and the like.

In some embodiments, the negative electrode further comprises a negative electrode current collector for extracting current, and the negative electrode active material layer covers the negative electrode current collector. Optionally, the negative current collector includes one of a copper current collector, a stainless steel current collector, a nickel current collector, a carbon current collector, and a composite current collector. Copper is often used as a current collector for negative active materials such as graphite, silicon, tin, cobalt tin, and the like. The surface of the stainless steel current collector is also easy to form a passive film in strong corrosive media such as acid, alkali, salt and the like, so that the surface of the stainless steel current collector can be protected from being corroded. Common types of stainless steel current collectors are stainless steel mesh and porous stainless steel. The composite current collector comprises carbon-coated aluminum foil, conductive resin, titanium-nickel shape memory alloy and the like.

In a preferred embodiment, the separator is disposed between the positive electrode and the negative electrode, and the separator may be any known separator. Among them, resins, glass fibers, inorganic substances, and the like, which are formed of materials stable to the nonaqueous electrolytic solution of the present invention, can be used, and porous sheets, nonwoven fabrics, and the like having excellent liquid retention properties are preferably used. Examples of the material for the resin or glass fiber separator include polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, and glass filters. Among these, glass filters and polyolefins are preferable, and polyolefins are more preferable. These materials may be used alone, or two or more of them may be used in combination in any combination and ratio.

On the other hand, as the material of the inorganic substance, for example, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, sulfates such as barium sulfate and calcium sulfate; inorganic materials in particle form or fiber form may be used. The diaphragm can also be a polyimide lithium battery diaphragm, an organic/inorganic composite diaphragm and a nanofiber diaphragm. The organic/inorganic composite diaphragm is a composite material which is prepared by uniformly mixing an inorganic nano-particle material and an organic polymer and then coating the mixture on a polyolefin diaphragm substrate.

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

TABLE 1

Note: the compounds used in the following examples and comparative examples were selected from table 1.

Example 1

Preparation of battery for testing

(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) To a molar concentration of 1mol/L, the compound of formula 1 was added in an amount shown in example 1 of Table 2.

(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. Uniformly coating the slurry on two sides of an aluminum foil, drying, rolling and vacuum drying, and welding an aluminum outgoing line by using an ultrasonic welding machine to obtain a positive plate, wherein the thickness of the positive plate is 120-³。

(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 copper foil, drying, rolling and vacuum drying, and welding nickel outgoing line with ultrasonic welder to obtain negative plate with thickness of 120-m, the compacted density of the anode active material layer was 1.6g/cm³。

(4) Preparation of cell

And placing three layers of polypropylene microporous diaphragms 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 diaphragms, flattening the wound body, then placing the flattened wound body into an aluminum foil packaging bag, and baking the flattened wound body in vacuum at 75 ℃ for 48 hours 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.

LiNi_0.5Co_0.3Mn_0.2O₂The battery is subjected to the first charging routine 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.

Second, testing the battery performance

(1) High temperature cycle performance test

LiNi_0.5Co_0.3Mn_0.2O₂The battery was charged to 4.35V at a constant current of 1C, then charged at a constant voltage until the current dropped to 0.02C, and then discharged to 3.0V at 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 (%) — discharge capacity of the last cycle/discharge capacity of the 1 st cycle × 100%;

(2) low temperature Performance test

At 25 ℃, the formed battery is charged to full-charge voltage (LiNi) by using 1C constant current and constant voltage_0.5Co_0.3Mn_0.2O₂4.35V) and then discharged to a full discharge voltage of 3V with a 1C constant current, and the discharge capacity was recorded. Then the 1C constant current and voltage is charged to full electric voltage (LiNi)_0.5Co_0.3Mn_0.2O₂4.35V), standing at-20 deg.C for 12h, and discharging at constant current of 0.5C toThe discharge capacity was recorded corresponding to a voltage of 2.5V.

A low-temperature discharge efficiency value of-20 ℃ was 0.5C discharge capacity (-20 ℃) per 1C discharge capacity (25 ℃) x 100%.

Examples 2-12 and comparative examples 1-3 illustrate a lithium ion battery of the present disclosure, including most of the operating steps of example 1, with the following exceptions:

the compound shown in the structural formula 1 with the content shown in the table 2 is added in the preparation process of the electrolyte. The test results are shown in Table 3.

TABLE 2 compositions of lithium ion batteries in examples 1-12 and comparative examples 1-3

TABLE 3 electrochemical Performance test results of the lithium ion batteries of examples 1 to 12 and comparative examples 1 to 3

As is clear from the test results of examples 1 to 12 and comparative examples 1 to 3, the addition of the compound represented by the formula 1 to the preparation of the nonaqueous electrolytic solution resulted in a high tap density (3.6 g/cm)³) The improvement effect of the low-temperature discharge efficiency and the high-temperature cycle performance of the lithium ion battery is more obvious, the low-temperature discharge efficiency is improved to 70.1 percent from 64.5 percent at most, the improvement range is about 6 percent, the high-temperature cycle capacity retention rate is improved to 80.1 percent from 63.2 percent at most, the improvement range can reach about 17 percent, although the low compaction density (3.2 g/cm)³) Improving effect of low-temperature discharge efficiency and high compaction density (3.6 g/cm) of lithium ion battery³) The lithium ion battery is almost the same, the low-temperature discharge efficiency is improved to 75.1 percent from 68.8 percent at most, the improvement range is about 6 percent, but the high-temperature cycle of the low-compaction-density lithium ion battery is realizedThe lifting amplitude is obviously lower than that of high compaction density (3.6 g/cm)³) The high-temperature circulation capacity retention rate is improved to 81.1% from 70.2% at most, and the improvement amplitude is about 10%. And finally, the lithium ion battery with high energy density can be obtained by regulating and controlling the compaction density of the positive active material layer and the addition amount of the compound shown in the structural formula 1, and particularly, the high-temperature cycle performance can be remarkably improved. In particular, when the compacted density D of the positive electrode active material layer and the addition amount a of the compound represented by formula 1 in the electrolyte satisfy the following relationship: when A multiplied by D is more than or equal to 1.8 and less than or equal to 3.6, the lithium ion battery with high energy density is obtained, and simultaneously, the low-temperature performance and the high-temperature cycle performance of the lithium ion battery are optimal, probably because the compound shown in the structural formula 1 is subjected to reduction decomposition reaction on a negative electrode in preference to solvent molecules, a reaction product forms a layer of passivation film on the surface of an electrode, the passivation film can inhibit the solvent molecules from further decomposition, the stability is better, the high-impedance LiF component is less, the lithium ions can pass through the passivation film, and the high-temperature cycle and the low-temperature performance of the battery can be obviously improved. When the relation between the compacted density D of the positive electrode active material layer and the addition amount A of the compound represented by the formula 1 in the electrolyte satisfies A x D<1.8, it is difficult to sufficiently form a passivation film on the surface of the negative electrode, and it is difficult to sufficiently improve the high-temperature and low-temperature performance of the nonaqueous electrolyte battery, and when A × D is used>3.6, the compound represented by the formula 1 cannot be completely dissolved in the nonaqueous electrolytic solution, and moreover, an excessively thick passivation film is formed on the surface of the negative electrode, which increases the internal resistance of the battery, thereby deteriorating the battery performance.

Comparative analysis of examples 1 to 4 with comparative example 1 revealed that the tap density was high (3.6 g/cm)³) When the relation between the compacted density D of the positive active material layer of the lithium ion battery and the addition A of the compound shown in the structural formula 1 in the electrolyte meets that A is more than or equal to 1.8 and less than or equal to 3.6, the low-temperature discharge efficiency and the capacity retention rate after 1C/1C circulation for 400 times at 45 ℃ of the lithium ion battery are both obviously improved.

Comparative analysis of examples 5 to 8 and comparative example 2 revealed that the compacted density (3.4 g/cm)³) The low-temperature discharge efficiency, the first discharge capacity and the capacity retention rate after 400 cycles of 1C/1C at 45 ℃ of the lithium ion battery are all obviously improved, and the low-temperature discharge efficiency and the first discharge capacity are lowThe maximum temperature discharge efficiency is improved from 66.3% to 72.5%, the improvement amplitude is about 6%, the maximum high-temperature circulation capacity retention rate is improved from 66.2% to 80.0%, the improvement amplitude is about 14%, and particularly, when the relation between the compaction density D of the positive electrode active material layer and the addition A of the compound shown in the structural formula 1 in the electrolyte meets 1.8<A×D<At 3.6, the magnitude of the lift is significantly better than out of range.

Comparative analysis of examples 9-12 with comparative example 3 reveals that, despite the low compacted density (3.2 g/cm)³) The low-temperature discharge efficiency of the lithium ion battery is improved to 75.1 percent from 68.8 percent at most, and the improvement amplitude is slightly higher than the high compaction density (3.6 g/cm)³) However, the improvement effect of the first discharge capacity and the capacity retention rate after 400 times of 1C/1C circulation at 45 ℃ is not obvious, the first discharge capacity is only improved to 1357.2mAh from 1297.5mAh to the maximum, the high-temperature circulation capacity retention rate is improved to 81.1% from 70.2% to the maximum, and the improvement effect is obviously lower than that of the high compaction density (3.6 g/cm)³) The improvement effect of the lithium ion battery.

From the test results of comparative examples 1 to 3, it can be seen that when the electrolyte does not contain the compound represented by the structural formula 1, the first discharge capacity of the lithium ion battery is lower as the compacted density of the positive electrode is reduced, but the low-temperature discharge efficiency and the high-temperature cycle performance are better, because the electrolyte is less infiltrated under high compaction, the battery is more likely to have lithium precipitation and deteriorated low-temperature performance, and meanwhile, the metal ion dissolution is increased under high compaction, which causes the cycle performance to be deteriorated.

Examples 13-15 are provided to illustrate a lithium ion battery of the present disclosure, including most of the operating steps of example 1, with the following differences:

during the preparation of the electrolyte, different compounds of formula 1 were added in the amounts shown in examples 13-15 in table 4. The results are shown in Table 5.

Table 4 lithium ion battery compositions of examples 3, 13-15, comparative example 1

TABLE 5 electrochemical Performance test results for lithium ion batteries of examples 3, 13-15, comparative example 1

As can be seen from the test data of comparative examples 3, 13 to 15 and comparative example 1, at a high tap density (3.6 g/cm)³) In the nickel-cobalt-manganese lithium ion battery, different compounds shown in the structural formula 1 are added into the electrolyte, so that the low-temperature discharge efficiency at minus 20 ℃ and the high-temperature cycle performance at 45 ℃ are improved to different degrees.

Examples 16 to 19

Examples 16-19 illustrate a lithium ion battery of the present disclosure, including most of the operating steps of example 1, with the following differences:

other compounds were added during the preparation of the electrolyte in the amounts shown in examples 16 to 19 in Table 6. The results are shown in Table 7.

TABLE 6 compositions of Li-ion batteries of examples 3, 16-19

Table 7 electrochemical performance test results of the lithium ion batteries of examples 3, 16 to 19

The results show that further additives (DTD, VC, FEC or tripropargyl phosphate) in the nonaqueous electrolyte system containing the compound represented by formula 1 of the present invention have further improving effects on the discharge efficiency and high-temperature cycle performance of the nickel-cobalt-manganese-lithium ion battery with high tap density.

Examples 20 to 30

Examples 20-30 are provided to illustrate a lithium ion battery of the present disclosure, including most of the operating steps of example 1, with the following differences:

the ingredients of the positive electrode active materials shown in examples 20 to 30 in table 8 were added during the preparation of the positive electrode plate. The results are shown in Table 9.

Table 8 compositions of lithium ion batteries in examples 20-30

Table 9 results of electrochemical performance tests of lithium ion batteries of examples 20 to 30

According to the test results, the high-compaction lithium ion battery provided by the invention can be suitable for various anode active materials due to the addition of the compound shown in the structural formula 1 in the electrolyte, and the lithium ion battery with high energy density and excellent high and low temperature performance can be obtained by only adjusting the compaction density of the anode active material and the addition amount of the compound shown in the structural formula 1, and particularly, the high-temperature cycle performance can be obviously improved.

In summary, the invention provides a high-compaction lithium ion battery, and an electrolyte is designed for a high-compaction positive electrode material, wherein the electrolyte contains a compound shown in a structural formula 1, and a passivation film can be generated on the surfaces of a positive electrode and a negative electrode to stabilize the performance of the positive electrode material, so that the high-low temperature performance of the lithium ion battery is improved.

The present invention has been further described with reference to specific embodiments, but it should be understood that the detailed description should not be construed as limiting the spirit and scope of the present invention, and various modifications made to the above-described embodiments by those of ordinary skill in the art after reading this specification are within the scope of the present invention.

Claims

1. A high-compaction lithium ion battery comprises a positive electrode, a negative electrode and electrolyte, and is characterized in that the electrolyte comprises electrolyte salt, an organic solvent and a compound shown in the following structural formula 1:

2. The high-compaction lithium ion battery according to claim 1, wherein the positive electrode active material layer has a compacted density of Dg/cm³The addition amount of the compound shown in the structural formula 1 is A% based on 100% of the total mass of the electrolyte, and A and D satisfy the following relation: a multiplied by D is more than or equal to 1.8 and less than or equal to 6.4;

preferably, a and D satisfy the following relationship: a multiplied by D is more than or equal to 1.8 and less than or equal to 3.6.

3. The high-compaction lithium ion battery according to claim 1, wherein the compound represented by the structural formula 1 is added in an amount of 0.05% to 5% based on 100% by mass of the total electrolyte.

4. The high-compaction lithium ion battery of claim 1, wherein the positive active material comprises one or more of the following materials:

lithium iron phosphate, or a doped and/or coated modified compound thereof;

sulfur, or a complex thereof.

5. The high-compaction lithium ion battery of claim 1, wherein the electrolyte salt is selected from 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、LiAlCl₄Boron chlorideAt least one of lithium alkane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenylborate, and lithium imide.

6. The high-compaction lithium ion battery according to claim 1, wherein the compound represented by the structural formula 1 is selected from at least one of the following compounds:

7. the high-compaction lithium ion battery of claim 1, wherein the negative electrode comprises a negative active material layer comprising a negative active material, the negative active material layer having a compacted density of 1.55g/cm³～1.85g/cm³。

8. The high-compaction lithium ion battery of claim 7, wherein the negative active material comprises one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a lithium negative electrode.

9. The high-compaction lithium ion battery according to claim 1, wherein the porosity of the positive electrode active material layer is 30% or less, and the porosity of the negative electrode active material layer is 30% or less.

10. The high-compaction lithium ion battery of claim 1, wherein the electrolyte further comprises an auxiliary additive comprising one or more of a cyclic sulfate compound, a cyclic sulfonate compound, an unsaturated cyclic carbonate compound, a fluorinated cyclic carbonate compound, a nitrile compound, a phosphate compound;