CN113659206B

CN113659206B - High-compaction lithium ion battery

Info

Publication number: CN113659206B
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: 2023-05-09
Anticipated expiration: 2041-08-13
Also published as: CN113659206A

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 is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently selected from one of a hydrogen atom, a fluorine atom or a group containing 1 to 5 carbon atoms; the positive electrode comprises a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material layer has a compacted density of 2.3g/cm ³ ～4.3g/cm ³ . The compound shown in the structural formula 1 in the electrolyte forms a layer of passivation film with high ion conduction and electronic insulation on the surfaces of the positive electrode and the negative electrode, and the passivation film inhibits side reactions of the positive electrode active material and the electrolyte, so that the high energy density of the high-compaction lithium ion battery can be ensured, and the high-low temperature performance of the high-compaction lithium ion battery is not weakened.

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 to the fields of 3C digital consumer and new energy automobiles. In recent years, both digital batteries and power batteries tend to develop in the direction of high energy density, and accordingly, the compaction of the design of the positive and negative electrodes of the batteries needs to be further improved. However, under high compaction, electrolyte infiltration is poor, lithium precipitation of the battery is easy to occur, low-temperature performance is deteriorated, and meanwhile, dissolution of metal ions under high compaction is increased, so that problems of poor cycle performance and the like are caused.

Currently, in terms of electrolytes, such problems are generally solved from two dimensions of solvent, additive. Specifically, the low-viscosity solvent is adopted to completely replace or partially replace the 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 infiltrate under 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 permeation, such as fluoroethylene carbonate (FEC), lithium difluorophosphate and the like, are added, and a positive and negative electrode interface film with low impedance and higher ion conductivity is formed in the initialization and capacity-dividing stage, so that the low-temperature discharge performance is improved. However, solvent replacement processes generally cause ballooning during high temperature storage and cycling, which in turn deteriorates the performance. Therefore, it is necessary to develop an electrolyte solution that can improve both the low-temperature performance and the high-temperature cycle performance of a high-pressure battery.

Disclosure of Invention

In order to solve the problems, the invention provides a high-compaction lithium ion battery, which comprehensively improves the comprehensive performance of the lithium ion battery by adding the compound shown in the 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 an anode, a cathode and electrolyte, wherein the electrolyte comprises electrolyte salt, an organic solvent and a compound shown in the following structural formula 1:

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each independently selected from one of a hydrogen atom, a fluorine atom or a group containing 1 to 5 carbon atoms;

the positive electrode comprises a positive electrode active material layer containing a positive electrode active material, and the positive electrode active material layer has a compacted density of 2.3g/cm ³ ～4.3g/cm ³ 。

Optionally, the positive electrode active material layer has a compacted density Dg/cm ³ The compound represented by the structural formula 1 is added in an amount of A% based on 100% of the total mass of the electrolyte, and the following relationships are satisfied between A and D: axD is more than or equal to 1.8 and less than or equal to 6.4; preferably, a and D satisfy the following relationship: axD is more than or equal to 1.8 and less than or equal to 3.6.

Optionally, the compound represented by the structural formula 1 is added in an amount of 0.05% -5% based on 100% of the total mass of the electrolyte.

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

lithium iron phosphate, or doping and/or cladding modified compounds thereof;

lithium-containing transition metal oxide Li _m Ni _x Co _y M _1-x-y O ₂ Or a doped and/or coated 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 at least one element selected from Mn and Al;

spinel lithium manganate Li ₂ Mn _2-z M _z O ₄ Or a doped and/or coated modified compound thereof, wherein z is more than or equal to 0 and less than or equal to 0.1, and M is at least one element selected from Ni, B, al, cr, fe, mg, zn, ti;

spinel lithium nickel manganese oxide LiNi _0.5-k M _k Mn _1.5 O ₄ Or a doping and/or cladding modifying compound thereof, wherein 0.ltoreq.k<0.5, M is selected from at least one element in Al, cr, fe, mg, zr, W, nb, si, ti;

lithium-rich manganese-based material Li _1.2+n [(Mn _a Co _b Ni _c M _1-a-b-c ) _1-d M' _d ] _0.8-n O ₂ Or a doping and/or cladding modifying 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.

Alternatively, the electrolyte salt is selected from LiPF ₆ 、LiPO ₂ F ₂ 、LiBF ₄ 、LiBOB、LiSbF ₆ 、LiAsF ₆ 、LiCF ₃ SO ₃ 、LiDFOB、LiN(SO ₂ CF ₃ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiN(SO ₂ C ₂ F ₅ ) ₂ 、LiN(SO ₂ F) ₂ 、LiCl、LiBr、LiI、LiClO ₄ 、LiBF ₄ 、LiB ₁₀ Cl ₁₀ 、LiAlCl ₄ At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenyl borate, and lithium iminoborate.

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

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Optionally, the anode comprises an anode active material layer containing an anode active material, the anode active material layer having a compacted density of 1.55g/cm ³ ～1.85g/cm ³ 。

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 cyclic sulfate compounds, cyclic sulfonate compounds, unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, nitrile compounds and phosphate compounds;

the cyclic sulfate compound comprises one or more of vinyl sulfate, propylene sulfate or vinyl methyl 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 ethylene carbonate (VC), ethylene carbonate (VEC), 4, 5-dimethyl ethylene carbonate, phenyl ethylene carbonate and 4, 5-divinyl ethylene carbonate;

The fluorinated cyclic carbonate compounds include one or more of 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, 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, hexanetrinitrile, adiponitrile, pimelic nitrile, suberonitrile, nonyldinitrile and decyldinitrile;

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

wherein R is ₇ 、R ₈ 、R ₉ Each independently selected from C ₁ -C ₅ Saturated, unsaturated or halogenated hydrocarbon groups, and R ₇ 、R ₈ 、R ₉ At 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, a layer of passivation film with high ion conduction and electronic insulation can be formed on the surfaces of the positive electrode and the negative electrode, the passivation film can inhibit side reactions of the positive electrode active material and the electrolyte, and the high-energy density of the high-compaction lithium ion battery can be ensured, and meanwhile, the high-low temperature performance of the high-compaction lithium ion battery is not weakened.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The embodiment of the invention provides a high-compaction lithium ion battery, which comprises an anode, a cathode 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 containing 1 to 5 carbon atoms is selected from one of a hydrocarbyl, a halocarbyl, an oxygenated hydrocarbyl, a siliceous hydrocarbyl, or a cyano-containing hydrocarbyl.

In some embodiments, R ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ Each 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 of formula 1 is added in an amount of 0.01% to 10% based on 100% of the total mass of the electrolyte.

In a preferred embodiment, the compound of formula 1 is added in an amount of 0.05% to 5%, more preferably 0.1% to 2%, based on 100% of the total mass of the 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%, 8.5%, 9%, 9.5%, 10%.

In some embodiments, the positive electrode active material layer has a compacted density Dg/cm ³ The addition amount of the compound shown in the structural formula 1 is A% based on 100% of the total mass of the electrolyte, and the following relation is satisfied between A and D: axD 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: axD is more than or equal to 1.8 and less than or equal to 3.6.

The compaction density of the positive electrode active material layer is usually required to be in a proper range, so that on one hand, the volume energy density of the lithium ion battery can be ensured to be higher, and meanwhile, the compression deformation of the positive electrode active material is lower, thereby being beneficial to the rapid infiltration of electrolyte between the gaps of the pole pieces. The positive electrode adopts different active materials, and the achievable compaction densities are different. Specifically, the positive electrode active material layer may have a compacted density of 2.3 g/cm ³ ～4.3g/cm ³ 、2.3g/cm ³ ～2.7g/cm ³ 、2.3g/cm ³ ～2.8g/cm ³ 、2.4g/cm ³ ～2.7g/cm ³ 、2.7g/cm ³ ～2.8g/cm ³ 、2.8g/cm ³ ～2.9g/cm ³ 、2.9g/cm ³ ～3.2g/cm ³ 、2.9g/cm ³ ～3.1g/cm ³ 、3.1g/cm ³ ～3.2g/cm ³ 、3.2g/cm ³ ～3.6g/cm ³ 、3.2g/cm ³ ～3.4g/cm ³ 、3.4g/cm ³ ～3.7g/cm ³ 、3.4g/cm ³ ～3.6g/cm ³ 、3.6g/cm ³ ～3.7g/cm ³ 、3.8g/cm ³ ～3.9g/cm ³ 、3.9g/cm ³ ～4.1g/cm ³ 、4.1g/cm ³ ～4.3g/cm ³ 、4.1g/cm ³ ～4.2g/cm ³ Or 4.2g/cm ³ ～4.3g/cm ³ 。

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 battery energy density. However, the porosity is too high, and the charge efficiency or discharge efficiency is deteriorated. When the porosity is too low, the electrolyte is poorly soaked, lithium is easily separated from the battery, the low-temperature performance is deteriorated, and meanwhile, the dissolution of metal ions under high compaction is increased, so that the cycle performance is deteriorated. 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 electrode active material includes one or more of the following materials:

lithium iron phosphate, or doping and/or cladding modified compounds thereof;

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

In a preferred embodiment, the doping modification compound of the above material is doped with a cation, an anion or an anion and cation complex. Specifically, the cation doping element can be selected from one or more of Al, zr, ti, B, mg, V, cr, zn, Y; the anionic doping element can be selected from one or more of F, P, S, more preferably F. Preferably, the total amount of doping of the anions and cations is not more than 20%.

In a preferred embodiment, the material is coated with a modified compoundThe coating modification is that a coating layer is formed on the surface of the positive electrode active material, wherein the coating layer can be a carbon layer, a graphene layer, an oxide layer, an inorganic salt layer or a conductive polymer layer, and the oxide can be an oxide or fluoride formed by one or more elements in Al, ti, mn, zr, mg, zn, ba, mo, B, cr, ag, nb, Y, sr, W, mo, pb, cd, ca; the inorganic salt may be Li ₂ ZrO ₃ 、LiNbO ₃ 、Li ₄ Ti ₅ O ₁₂ 、Li ₂ TiO ₃ 、LiTiO ₂ 、Li ₃ VO ₄ 、LiSnO ₃ 、Li ₂ SiO ₃ 、LiAlO ₂ 、AlPO ₄ 、AlF ₃ One or more of the following; 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 _m Ni _x Co _y M _1-x-y O ₂ Can be specifically selected from LiCoO ₂ 、LiNi _0.33 Co _0.33 Mn _0.33 O ₂ 、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ 、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ 、LiNi _0.7 Co _0.1 Mn _0.2 O ₂ 、LiNi _1/ ₃ Co _1/3 Mn _1/3 O ₂ (NCM333)、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM523)、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (NCM622)、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM811)、LiNi _0.8 Co _0.1 Al _0.1 O ₂ 、LiNi _0.85 Co _0.10 Al _0.05 O ₂ 、LiNi _0.8 Co _0.2 O ₂ 、LiNi _0.80 Co _0.15 Al _0.05 O ₂ One or more of them.

In some embodiments, spinel lithium manganate Li ₂ Mn _2-z M _z O ₄ Can be specifically selected from Li ₂ Mn ₂ O ₄ 、Li ₂ Mn _1.95 Al _0.05 O ₄ 、Li ₂ Mn _1.95 Ni _0.05 O ₄ One or more of them.

In some embodiments, the spinel lithium nickel manganese oxide LiNi _0.5-k M _k Mn _1.5 O ₄ Can be specifically selected from LiNi _0.5 Mn _1.5 O ₄ 、LiNi _0.4 Al _0.1 Mn _1.5 O ₄ 、LiNi _0.3 Al _0.1 Fe _0.1 Mn _1.5 O ₄ 、LiNi _0.3 Mg _0.2 Mn _1.5 O ₄ 、LiNi _0.4 Ti _0.1 Mn _1.5 O ₄ One or more of them.

In some embodiments, lithium-rich manganese-based material Li _1.2+n [(Mn _a Co _b Ni _c M _1-a-b-c ) _1-d M' _d ] _0.8-n O ₂ Can be specifically selected from Li _1.2 [(Mn _0.667 Co _0.167 Ni _0.167 ) _0.8 ]O ₂ 、Li _1.25 [(Mn _0.75 Co _0.25 ) _0.75 ]O ₂ 、Li _1.5 [(Mn _0.5909 Co _0.0909 Ni _0.2273 Al _0.0909 ) _0.475 Ti _0.025 ]O ₂ 、Li[(Mn _0.6536 Ni _0.3268 Sr _0.0196 ) _0.97 Zr _0.02 Nb _0.01 ]O ₂ 、Li _1.3 [(Mn _0.6349 Co _0.1587 Ni _0.1587 Mg _0.0477 ) _0.686 La _0.007 W _0.007 ]O ₂ 、Li _1.2 [(Mn _0.6349 Co _0.1587 Ni _0.1587 Cr _0.0477 ) _0.796 Pr _0.004 ]O ₂ 、Li _1.3 [(Mn _0.6536 Co _0.1634 Ni _0.1634 Zn _0.0196 ) _0.693 Sc _0.007 ]O ₂ One or more of them.

In general, the average particle diameter D50 of the positive electrode active material, the gram capacity of the positive electrode active material, the coating weight W per unit area of the positive electrode active material layer, the thickness L of the positive electrode 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, the larger the gram capacity of the positive electrode active material, the larger the capacitance r per unit area of the positive electrode active material layer, the higher the actual energy density of the battery, but the worse the quick charge performance of the battery. Preferably, the average particle diameter D50 of the positive electrode active material is in the range of 0.5 μm.ltoreq.D50.ltoreq.15 μm, more preferably 1 μm.ltoreq.D50.ltoreq.7 μm, still more preferably 1 μm.ltoreq.D50.ltoreq.3 μm.

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

When the coating weight W of the unit area of the positive electrode active material layer is fixed, the larger the thickness L of the positive electrode active material layer is, the smaller the compaction density of the positive electrode active material layer is, the more beneficial to the liquid phase conduction of active ions during charge and discharge, 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 0.01 mm.ltoreq.L.ltoreq.0.5 mm, more preferably 0.015 mm.ltoreq.L.ltoreq.0.3 mm, still more preferably 0.02 mm.ltoreq.L.ltoreq.0.1 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-based material is carbon-based material such as conductive graphite, conductive carbon black, conductive carbon fiber or graphene; the metal oxide 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, any binder may be used in selecting the positive electrode binder as long as it is a material safe for the solvent and electrolyte used in manufacturing the electrode. Specifically, as a binder for a positive electrode, there are two main types, i.e., an oily binder and an aqueous binder, and in general, the former uses an organic solvent as a dispersant and the latter uses water as a dispersant. The oily binder is optional polyvinylidene fluoride; the water-based binder can be one or more of polyacrylic acid and salts thereof, carboxymethyl cellulose and salt complexes thereof, acrylonitrile multipolymer, xanthan gum, chitosan and water-soluble derivatives thereof, and polyvinyl acetate. Specifically, the polyacrylate comprises salts of metals such as Li, na, K, and the like, carboxymethyl cellulose and salt complexes thereof, wherein the salts comprise lithium carboxymethyl cellulose.

In some embodiments, 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. In preferred embodiments, the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, and the like. The graphite includes, but is not limited to, 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, for example, exfoliated graphite, flake graphite, soil graphite, or graphite particles obtained by using these as a raw material and subjecting the raw material to a treatment such as spheroidization or densification. The artificial graphite can be obtained by graphitizing organic matters such as coal tar pitch, coal heavy crude oil, atmospheric residuum, petroleum heavy crude oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenyl, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenyl ether, furfuryl alcohol resin, phenolic resin, imide resin and the like at high temperature. The amorphous carbon may be amorphous carbon particles obtained by heat-treating an easily graphitizable carbon precursor such as tar or pitch as a raw material for 1 or more times in a temperature range (400 to 2200 ℃) where graphitization does not occur, or amorphous carbon particles obtained by heat-treating an hardly graphitizable carbon precursor such as a resin as a raw material. 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, or resin, 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 amorphous carbon is used for coating the core graphite to obtain the 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 may be in a form in which a plurality of primary particles are combined with the carbon originating from the carbon precursor as a binder. Further, carbon may be deposited on the surface of graphite by reacting hydrocarbon gas such as benzene, toluene, methane, propane, or aromatic hydrocarbon with natural graphite and/or artificial graphite at high temperature to obtain a carbon-graphite composite. The graphite-coated graphite may be prepared by mixing natural graphite and/or artificial graphite with carbon precursor of easily graphitizable organic compound such as tar, pitch, resin, etc., and performing heat treatment at 2400-3200 deg.c for 1 or more times. 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 by graphitized matters, 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 lower than 400 ℃, and coating the core graphite with the resin or the like using the natural graphite and/or artificial graphite thus obtained as core graphite. Examples of the organic compounds such as tar and pitch resin include carbonizable organic compounds selected from the group consisting of 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, polystyrene, organic synthetic polymers, natural polymers, thermoplastic resins, and thermosetting resins.

In a preferred embodiment, the silicon-based anode 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 value of the addition amount of the silicon-based material is 5%, 10% or 15%. The silicon material is one or more of silicon nano particles, silicon nanowires, silicon nanotubes, silicon films, 3D porous silicon and hollow porous silicon.

In preferred embodiments, 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 composed of tin and one or more of Cu, ag, co, zn, sb, bi and In.

In a preferred embodiment, the lithium anode 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 viewpoints of capacity and cycle life of the nonaqueous electrolyte battery, the metal particles are preferably selected from, for example, metals in Fe, co, sb, bi, pb, ni, ag, si, sn, al, zr, cr, P, S, V, mn, as, nb, mo, cu, zn, ge, in, ti and W or compounds thereof. In addition, 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 a metal oxide, a metal nitride, and a metal carbide. In addition, an alloy formed of two or more metals may be used. Metal nitrides of the type of anti-fluorite or Li ₃ Compounds of N structure, in particular Li ₃ The compound of N structure comprises Li ₇ MnN ₄ 、Li ₇ FeN ₂ Etc.

In a preferred embodiment, among the metal particles capable of forming an alloy with Li, silicon or a silicon metal compound is preferred. 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 siliconThe metal compounds are collectively referred to as silicon compounds. As the silicon compound, siO is specifically mentioned _x 、SiN _x 、SiCx、SiZ _x O _y (z= C, N), and the like. The silicon compound is preferably a silicon metal oxide, which if represented by the general formula is SiO _x . SiO of the general formula _x Can be made of silicon dioxide (SiO ₂ ) And metallic silicon (Si) as a raw material, wherein x is usually 0.ltoreq.x < 2.SiO (SiO) _x The theoretical capacity of (a) is larger than that of graphite, and amorphous Si or nano-sized Si crystals easily allow alkali metal ions such as lithium ions to enter and exit, and a high capacity can be obtained. Specifically, the Si metal oxide is a metal oxide which can be expressed as SiO _x The compound (A) has x of 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 decrease due to the combination of Li and 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 anode active material, the larger the gram capacity of the anode active material, the larger the capacitance r per unit area of the anode active material layer, the higher the actual energy density of the battery, but the worse the quick charge performance of the battery. Preferably, the average particle diameter D50 of the negative electrode active material is in the range of 0.5 μm.ltoreq.D50.ltoreq.25μm, more preferably 4 μm.ltoreq.D50.ltoreq.15 μm, still more preferably 5 μm.ltoreq.D50.ltoreq.10μm.

The larger the coating mass W of the unit area of the anode active material layer is, the larger the capacitance gamma of the unit area of the anode active material layer is, the higher the actual energy density of the battery is, but the larger the liquid phase conduction resistance of active ions is during charge and discharge, and the worse the quick charge performance of the battery is. Preferably, the coating mass W per unit area of the anode active material layer is in the range of 2mg/cm ² ≤W≤20mg/cm ² Further preferably, 4mg/cm ² ≤W≤15mg/cm ² More preferably 6mg/cm ² ≤W≤10mg/cm ² 。

When the coating weight W of the unit area of the anode active material layer is fixed, the larger the thickness L of the anode active material layer is, the smaller the compaction density of the anode 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 anode active material layer is in the range of 0.01 mm.ltoreq.L.ltoreq.0.5 mm, more preferably 0.015 mm.ltoreq.L.ltoreq.0.15 mm, still more preferably 0.02 mm.ltoreq.L.ltoreq.0.1 mm.

In some embodiments, the negative electrode active material layer further comprises 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 may be the same as the positive electrode conductive agent or may be different from the positive electrode conductive agent, and a suitable conductive agent material may be selected by those skilled in the art according to the 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-based material is conductive graphite, conductive carbon black, conductive carbon fiber and graphene; the metal oxide 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 negative electrode binder as long as it is a material safe for the solvent and electrolyte used in manufacturing the electrode. In particular to 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 compacted density of the anode active material layer is generally adapted to the compacted density of the cathode active material layer, and the cathode active material layer is of high compacted density, then the anode active material layer is the same asThe sample is of high compacted density so that the desired energy density is achieved. The negative electrode adopts different active materials, and the achievable compaction densities are different. Preferably, the negative electrode active material layer may have a compacted density of 1.55g/cm ³ ～2.1g/cm ³ 、1.55g/cm ³ ～1.6g/cm ³ 、1.6g/cm ³ ～1.7g/cm ³ 、1.7g/cm ³ ～1.8g/cm ³ 、1.8g/cm ³ ～1.85g/cm ³ 、1.85g/cm ³ ～1.9g/cm ³ 、1.9g/cm ³ ～2.0g/cm ³ Or 2.0g/cm ³ ～2.1g/cm ³ More preferably 1.55g/cm ³ ～1.85g/cm ³ 。

In some embodiments, the compacted density of the anode active material layer also affects the porosity of the anode active material layer, with higher compacted density, lower porosity, and higher battery energy density. However, the porosity is too high, and the charge efficiency or discharge efficiency is deteriorated. When the porosity is too low, the electrolyte is poorly soaked, lithium is easily separated from the battery, the low-temperature performance is deteriorated, and meanwhile, the dissolution of metal ions under high compaction is increased, so that the cycle performance is deteriorated. Preferably, the porosity of the anode active material layer is not more than 30%, for example, the porosity of the anode 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 comprises a supplemental 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.

In a preferred embodiment, the cyclic sulfate compound includes one or more of vinyl sulfate, propylene sulfate, or vinyl methyl sulfate. When the nonaqueous electrolytic solution contains a cyclic sulfate compound, the addition amount of the cyclic sulfate compound is 0.1 to 5% based on 100% of the total mass of the nonaqueous electrolytic solution.

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 nonaqueous electrolytic solution 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 nonaqueous electrolytic solution.

In preferred embodiments, the unsaturated cyclic carbonate compound includes one or more of Vinylene Carbonate (VC), ethylene carbonate (VEC), 4, 5-dimethylvinylene carbonate, phenylvinylene carbonate, 4, 5-divinyl ethylene carbonate. When the unsaturated cyclic carbonate compound is contained in the nonaqueous electrolytic solution, the addition amount of the unsaturated cyclic carbonate compound is 0.1 to 5% based on 100% of the total mass of the nonaqueous electrolytic solution.

In preferred embodiments, the fluorinated cyclic carbonate compound includes one or more of 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, 5-difluoro-4, 5-dimethylethylene carbonate, 4-difluoro-5, 5-dimethylethylene carbonate. When the non-aqueous electrolyte contains a fluorinated cyclic carbonate compound, the fluorinated cyclic carbonate compound is added in an amount of 0.1 to 30% based on 100% of the total mass of the non-aqueous electrolyte.

In preferred embodiments, the nitrile compound includes one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelic nitrile, suberonitrile, nonyldinitrile, decyldinitrile. When the nonaqueous electrolytic solution contains a nitrile compound, the addition amount of the nitrile compound is 0.1 to 5% based on 100% of the total mass of the nonaqueous electrolytic solution.

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

In particular, the method comprises the steps of, the phosphate compound can be at least one of tripolyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2, 2-trifluoroethyl phosphate, dipropargyl-3, 3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2, 2-trifluoroethyl phosphate, diallyl-3, 3-trifluoropropyl phosphate and diallyl hexafluoroisopropyl phosphate. When the nonaqueous electrolytic solution contains a phosphate compound, the addition amount of the phosphate compound is 0.1 to 5% based on 100% of the total mass of the nonaqueous electrolytic solution.

In some embodiments, the auxiliary additive may further include at least one of an aromatic additive, a fluorine-containing anisole compound, a dicarboxylic anhydride, lithium difluorophosphate, lithium difluorosulfonimide (LiFSI).

In a preferred embodiment, the aromatic additive comprises an aromatic compound such as biphenyl, alkyl biphenyl, terphenyl, a partial hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-pentylbenzene, diphenyl ether, dibenzofuran, and the like; 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene. When the non-aqueous electrolyte contains an aromatic additive, the aromatic additive is added in an amount of 0.1 to 5% based on 100% of the total mass of the non-aqueous electrolyte.

In a preferred embodiment, the fluorine-containing anisole compound comprises one or more of 2, 4-difluoroanisole, 2, 5-difluoroanisole, 2, 6-difluoroanisole. When the non-aqueous electrolyte contains a fluorine-containing anisole compound, the addition amount of the fluorine-containing anisole compound is 0.1 to 5% based on 100% of the total mass of the non-aqueous electrolyte.

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 addition amount of the dicarboxylic anhydride is 0.1 to 5% based on 100% of the total mass of the nonaqueous electrolytic solution. When the nonaqueous electrolytic solution contains lithium difluorophosphate, the addition amount of the lithium difluorophosphate is 0.1-2% based on 100% of the total mass of the nonaqueous electrolytic solution;

In a preferred embodiment, when 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% of the total mass of the nonaqueous electrolytic solution.

In some embodiments, the auxiliary additive further comprises a nitrogen-containing compound such as 1-methyl-2-pyrrolidone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 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 benzotrifluoride.

In general, the addition amount of any one of the optional substances in the auxiliary additive to the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, and more preferably 0.1 to 2%, unless otherwise specified. Specifically, the addition 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%, 8.5%, 9%, 9.5%, 10%.

In particular, 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% of the total mass of the electrolyte.

The nonaqueous electrolyte solution of the highly compacted lithium ion battery of the present invention generally contains a nonaqueous solvent for dissolving the above electrolyte as a main component, as in the case of a general nonaqueous electrolyte 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, carboxylic acid esters, 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 usually a cyclic carbonate having an alkylene group having 2 to 4 carbon atoms, and from the viewpoint of improving the degree of dissociation of lithium ions and improving the battery characteristics, a cyclic carbonate having 2 to 3 carbon atoms can be preferably used.

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 less susceptible to oxidation/reduction is more preferable. The cyclic carbonate may be used alone, or two or more kinds may be used in any combination and ratio.

The content of the cyclic carbonate is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the highly compacted lithium ion battery of the present invention, but in the case of using one of them 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 the range, it is possible to avoid a decrease in conductivity due to a decrease in dielectric constant of the nonaqueous electrolyte solution, and it is easy to achieve a good range of high-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the range, the oxidation/reduction resistance of the nonaqueous electrolytic solution can be improved, thereby contributing to improvement of stability at high-temperature storage.

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

In addition, a chain carbonate having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonate") 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. In the case where the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.

The chain carbonate may be used alone, or two or more kinds may be used in any combination and ratio. The content of the chain carbonate is not particularly limited, but 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. In addition, the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. By setting the content of the chain carbonate in the above range, the viscosity of the nonaqueous electrolytic solution can be easily set to an appropriate range, and the decrease in the ionic conductivity can be suppressed, thereby contributing to the improvement in the output characteristics of the battery. 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 these 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 used. Since the chain ether has high solvation ability with lithium ions and can improve ion dissociation properties, dimethoxymethane, diethoxymethane and ethoxymethoxymethane, which have low viscosity and can impart high ion conductivity, are particularly preferable.

The ether compound may be used alone, or two or more of them may be used in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the highly compacted lithium ion battery of the present invention, and is usually 1% or more, preferably 2% or more, more preferably 3% or more in terms of the volume ratio of the nonaqueous solvent of 100%, and is usually 30% or less, preferably 25% or less, more preferably 20% or less in terms of the volume ratio. 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 is within the above preferred range, the effect of improving the ionic conductivity due to the increase in the dissociation degree of lithium ions and the decrease in the viscosity of the chain ether can be easily ensured. In addition, when the negative electrode active material is a carbon material, co-intercalation of the chain ether and lithium ions can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be brought into appropriate ranges.

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

The amount of the sulfone compound to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the highly compacted lithium ion battery of the present invention, and is usually 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume, and is usually 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume, based on the total amount of the solvent of the nonaqueous electrolytic solution. When two or more sulfone compounds are used in combination, the total amount of 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 excellent in high-temperature storage stability tends to be obtained.

In some embodiments, the carboxylate solvent may be, in particular but 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 be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.

In some embodiments, the electrolyte salt comprises 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 LiPF ₆ 、LiPO ₂ F ₂ 、LiBF ₄ 、LiBOB、LiSbF ₆ 、LiAsF ₆ 、LiCF ₃ SO ₃ 、LiDFOB、LiN(SO ₂ CF ₃ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiN(SO ₂ C ₂ F ₅ ) ₂ 、LiN(SO ₂ F) ₂ 、LiCl、LiBr、LiI、LiClO ₄ 、LiBF ₄ 、LiB ₁₀ Cl ₁₀ 、LiAlCl ₄ At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenyl borate, and lithium iminoborate. Specifically, the electrolyte salt may be LiBF ₄ 、LiClO ₄ 、LiAlF ₄ 、LiSbF ₆ 、LiTaF ₆ 、LiWF ₇ An inorganic electrolyte salt; liPF (LiPF) ₆ An isophosphoric acid electrolyte salt; liWOF ₅ Isopolytics electrolyte salts; HCO (hydrogen chloride) ₂ Li、CH ₃ CO ₂ Li、CH ₂ FCO ₂ Li、CHF ₂ CO ₂ Li、CF ₃ CO ₂ Li、CF ₃ CH ₂ CO ₂ Li、CF ₃ CF ₂ CO ₂ Li、CF ₃ CF ₂ CF ₂ CO ₂ Li、CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Carboxylic acid electrolyte salts such as Li; CH (CH) ₃ SO ₃ Sulfonic acid electrolyte salts such as Li; liN (FCO) ₂ ) ₂ 、LiN(FCO)(FSO ₂ )、LiN(FSO ₂ ) ₂ 、LiN(FSO ₂ )(CF ₃ SO ₂ )、LiN(CF ₃ SO ₂ ) ₂ 、LiN(C ₂ F ₅ SO ₂ ) ₂ Cyclic 1, 2-perfluoroethanedisulfonimide lithium, cyclic 1, 3-perfluoropropanedisulfonylimide lithium, and LiN (CF) ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) Imide electrolyte salts; liC (FSO) ₂ ) ₃ 、LiC(CF ₃ SO ₂ ) ₃ 、LiC(C ₂ F ₅ SO ₂ ) ₃ Isomethyl 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; liPF (liquid crystal display) and LiPF ₄ (CF ₃ ) ₂ 、LiPF ₄ (C ₂ F ₅ ) ₂ 、LiPF ₄ (CF ₃ SO ₂ ) ₂ 、LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ 、LiBF ₃ CF ₃ 、LiBF ₃ C ₂ F ₅ 、LiBF ₃ C ₃ F ₇ 、LiBF ₂ (CF ₃ ) ₂ 、LiBF ₂ (C ₂ F ₅ ) ₂ 、LiBF ₂ (CF ₃ SO ₂ ) ₂ 、LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ And fluorine-containing organic electrolyte salts.

In general, the electrolyte salt in the electrolyte is a transfer unit of lithium ions, and the concentration of the electrolyte salt directly affects the transfer rate of lithium ions, which affects the potential change of the negative electrode. In the process of quick battery charging, the moving speed of lithium ions needs to be improved as much as possible, the formation of lithium dendrites caused by too fast negative electrode potential drop is prevented, potential safety hazards are brought to the battery, and meanwhile, the too fast attenuation of the circulating capacity of the battery can be prevented. Preferably, the total concentration of the electrolyte salt in the electrolyte 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, or 1.9 to 1.3mol/L, and preferably, 1.7 to 1.8mol/L, and more preferably, 0.7 to 1.8 mol/L.

The electrolyte density is closely related to the concentration of the electrolyte salt and the concentration of the organic solvent, and too small an electrolyte density may be too small an electrolyte salt concentration or too small an organic solvent density. If the concentration of electrolyte salt is too small, the internal part of the battery is not provided with enough lithium ion transfer units, and when the battery is charged at a high 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 are continuously grown and possibly puncture the isolating film, so that internal short circuit of the positive electrode and the negative electrode occurs to bring 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 can be aggravated at high temperature, and a large amount of heat is generated during the decomposition and repair, so that the interface of the negative electrode is worsened, and the cycle performance of the battery is further worsened. Too small a density of the organic solvent, a low dielectric constant of the electrolyte may increase lithium ion migration resistance. The electrolyte density is possibly too high, or the electrolyte salt density is too high, or the organic solvent density is too high, the electrolyte salt is easy to decompose and release heat at high temperature, so that the higher electrolyte salt concentration can increase the heat generation in the battery, and the battery is easy to fail; too high electrolyte density also causes too high electrolyte viscosity, so that lithium ion shuttle resistance becomes large, and the dynamic performance of the battery is affected; too high a density of the electrolyte also results in increased polarization of the battery, deteriorating the cycle performance of the battery. The density of the electrolyte is preferably 1.0g/cm ³ ～1.3g/cm ³ Further preferably 1.0g/cm ³ ～1.2g/cm ³ 。

In some embodiments, the positive electrode active material layer has an OI value OI of _c From 4 to 100, preferably5 to 60; OI of the negative electrode active material layer _c 5 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 ＝C ₀₀₃ /C ₁₁₀ Wherein C ₀₀₃ The peak area of 003 characteristic diffraction peak in the X-ray diffraction pattern of the positive plate is C ₁₁₀ Is the peak area of 110 characteristic diffraction peaks in the X-ray diffraction pattern of the positive pole piece. OI value OI of negative electrode active material layer _a ＝C ₀₀₄ /C ₁₁₀ Wherein C ₀₀₄ Is the peak area of 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode plate, C ₁₁₀ Is the peak area of 110 characteristic diffraction peaks in the X-ray diffraction pattern of the negative pole piece.

In some embodiments, the positive electrode further includes a positive electrode current collector for drawing current, and the positive electrode active material layer covers the positive electrode current collector. Optionally, the positive electrode current collector includes one of an aluminum current collector and a nickel current collector. In general, aluminum current collector is often used as positive electrode current collector and LiCoO ₂ Lithium manganate, ternary material and LiFePO ₄ And the like. Nickel may be used as a current collector to match with positive electrode active materials such as lithium iron phosphate, or may be used as a current collector to match with negative electrode active materials such as nickel oxide, sulfur and carbon silicon composite materials.

In some embodiments, the negative electrode further comprises a negative electrode current collector for drawing current, and the negative electrode active material layer covers the negative electrode current collector. Optionally, the negative current collector comprises 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 electrode active materials such as graphite, silicon, tin, cobalt tin, and the like. The surface of the stainless steel current collector is easy to form a passivation film in strong corrosive media such as acid, alkali, salt and the like, and the surface of the stainless steel current collector can be protected from corrosion. 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 a known separator may be optionally used. Among them, a resin, glass fiber, inorganic substance, or the like formed of a material stable to the nonaqueous electrolytic solution of the present invention can be used, and a porous sheet or a nonwoven fabric-like material excellent in liquid retention is preferably used. As materials for the resin and the glass fiber separator, for example, polyolefin such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filter, and the like can be used. Among them, glass filters and polyolefin are preferable, and polyolefin is more preferable. These materials may be used singly or in any combination and ratio.

On the other hand, as the inorganic material, for example, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate; a material of an inorganic substance in a particle shape or a fiber shape can be used. The membrane can also be polyimide lithium battery membrane, organic/inorganic composite membrane and nanofiber membrane. Wherein, the organic/inorganic composite membrane is a composite material which is coated on a polyolefin membrane substrate after inorganic nano particle materials and organic polymers are uniformly mixed.

The invention is further illustrated by the following examples.

TABLE 1

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

Example 1

1. Preparation of cells for testing

(1) Preparation of electrolyte

Mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) according to the mass ratio of EC: DEC: EMC=1:1:1, and then adding lithium hexafluorophosphate (LiPF) ₆ ) To a molar concentration of 1mol/L, the mixture was further added with a content as shown in example 1 of Table 2An amount of a compound represented by structural formula 1.

(2) Preparation of positive plate

Mixing anode active material LiNi according to the mass ratio of 93:4:3 _0.5 Co _0.3 Mn _0.2 O ₂ Conductive carbon black Super-P and a binder polyvinylidene fluoride (PVDF) are 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, calendaring and vacuum drying, and welding an aluminum outgoing line by an ultrasonic welder to obtain a positive plate, wherein the thickness of the positive plate is 120-150 mu m, and the compaction density of the positive active material layer is 3.60g/cm ³ 。

(3) Preparation of negative plate

The negative electrode active material artificial graphite, conductive carbon black Super-P, binder Styrene Butadiene Rubber (SBR) and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94:1:2.5:2.5, and then dispersed in deionized water to obtain a negative electrode slurry. Coating the slurry on two sides of copper foil, oven drying, calendaring, vacuum drying, and welding nickel lead-out wire with ultrasonic welder to obtain negative plate with thickness of 120-150 μm and compacted density of 1.6g/cm ³ 。

(4) Preparation of the cell

And placing a three-layer polypropylene microporous membrane with the thickness of 20 mu m between the positive plate and the negative plate, winding a sandwich structure formed by the positive plate, the negative plate and the membrane, flattening the winding body, putting into an aluminum foil packaging bag, and baking for 48 hours at the temperature of 75 ℃ in vacuum to obtain the battery cell to be injected with the liquid.

(5) Injection and formation of battery cell

In a glove box with the dew point controlled below-40 ℃, the prepared electrolyte is injected into a battery cell, and the battery cell is subjected to vacuum packaging and is kept for 24 hours.

LiNi _0.5 Co _0.3 Mn _0.2 O ₂ The battery is conventionally formed by first charging according to the following steps: charging at 0.05deg.C for 180min, charging at 0.2deg.C to 3.95V, vacuum sealing, charging at 0.2deg.C to 4.35V, standing at normal temperature for 24hr, and charging at 0.2CConstant current discharge to 3.0V.

2. Battery performance test

(1) High temperature cycle performance test

LiNi _0.5 Co _0.3 Mn _0.2 O ₂ The battery was charged to 4.35V at a constant current of 1C, charged again 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 turn and the discharge capacity of the last turn were recorded in this cycle, and the capacity retention rate of the high temperature cycle was calculated as follows:

capacity retention (%) =discharge capacity of last round/discharge capacity of 1 st round×100%;

(2) Low temperature performance test

Charging the battery after formation with 1C constant current and constant voltage to full charge voltage (LiNi) _0.5 Co _0.3 Mn _0.2 O ₂ 4.35V) and then discharged to a full discharge voltage of 3V with a constant current of 1C, the discharge capacity was recorded. Then 1C constant current and constant voltage is charged to full charge voltage (LiNi _0.5 Co _0.3 Mn _0.2 O ₂ 4.35V), and after being placed in an environment of-20 ℃ for 12 hours, the constant current discharge of 0.5C is carried out until the corresponding voltage is 2.5V, and the discharge capacity is recorded.

-low temperature discharge efficiency value at 20 ℃ = 0.5C discharge capacity (-20 ℃)/1C discharge capacity (25 ℃) ×100%.

Examples 2-12 and comparative examples 1-3 are provided to illustrate the disclosed lithium ion batteries, including most of the operating steps of example 1, with the difference that:

the compound of formula 1 was added in an amount shown in table 2 during the preparation of the electrolyte. The test results are shown in Table 3.

TABLE 2 composition of lithium ion batteries in examples 1 to 12 and comparative examples 1 to 3

TABLE 3 electrochemical performance test results of 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 structural formula 1 in the preparation of the nonaqueous electrolytic solution was effective for a high compacted density (3.6 g/cm ³ ) The improvement effects of the low-temperature discharge efficiency and the high-temperature cycle performance of the lithium ion battery are more obvious, the highest low-temperature discharge efficiency is improved to 70.1 percent from 64.5 percent, the improvement range is about 6 percent, the highest high-temperature cycle capacity retention rate can be improved to 80.1 percent from 63.2 percent, 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) ³ ) The lithium ion battery has the highest low-temperature discharge efficiency from 68.8% to 75.1%, the lifting amplitude is about 6%, but the lifting amplitude of the high-temperature circulation of the lithium ion battery with low compaction density is obviously lower than that of the lithium ion battery with high compaction density (3.6 g/cm) ³ ) The high-temperature cycle capacity retention rate is improved from 70.2% to 81.1% at most, and the improvement range is about 10%. And the lithium ion battery with high energy density can be finally obtained by regulating and controlling the compaction density of the positive electrode 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 structural formula 1 in the electrolyte satisfy the following relationship: 1.8.ltoreq.AxD.ltoreq.3.6, the lithium ion battery with high energy density is obtained, and at the same time, 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 undergoes a reductive decomposition reaction in preference to solvent molecules at the negative electrode, and a passivation film is formed on the surface of the electrode by the reaction product, the passivation film can inhibit the solvent molecules from further decomposing, has better stability, has fewer LiF components with high impedance, is favorable for passing lithium ions, and can obviously improve the high temperature cycle and the low temperature performance of the battery. When the relationship between the compacted density D of the positive electrode active material layer and the addition amount A of the compound represented by the structural formula 1 in the electrolyte satisfies A×D <1.8, it is difficult to sufficiently form a passivation film on the surface of the negative electrode, thereby making it difficult to sufficiently improve the high-temperature and low-temperature performance of the nonaqueous electrolyte battery, while when A X D>3.6, the compound of formula 1 cannot be completely dissolved in the nonaqueous electrolyte, and an excessively thick passivation film is formed on the surface of the negative electrode, which increases the internal resistance of the battery, thereby degrading the battery performance.

Comparative analysis examples 1-4 and comparative example 1 show that when the high compaction density (3.6 g/cm ³ ) When the relation between the compaction density D of the positive electrode active material layer of the lithium ion battery and the addition amount A of the compound shown in the structural formula 1 in the electrolyte meets 1.8-A multiplied by D-3.6, the low-temperature discharge efficiency and the capacity retention rate after 400 cycles of 1C/1C at 45 ℃ of the lithium ion battery are both remarkably improved.

As can be seen from comparative analysis examples 5 to 8 and comparative example 2, the compacted density (3.4 g/cm ³ ) The low-temperature discharge efficiency, the first discharge capacity and the capacity retention rate of the lithium ion battery after the 1C/1C cycle for 400 times at 45 ℃ are obviously improved, the highest low-temperature discharge efficiency is improved to 72.5 percent from 66.3 percent, the improvement range is about 6 percent, the highest high-temperature cycle capacity retention rate is improved to 80.0 percent from 66.2 percent, the improvement range is about 14 percent, and particularly, when the relation between the compaction density D of the positive electrode active material layer and the addition amount A of the compound shown as the structural formula 1 in the electrolyte meets 1.8 <A×D<At 3.6, the boost amplitude is significantly better than out of range.

Comparative analysis examples 9-12 and comparative example 3 show that, although the low compaction density (3.2 g/cm ³ ) The highest low-temperature discharge efficiency of the lithium ion battery is improved from 68.8% to 75.1%, and the improvement range is slightly higher than that of the high-compaction density (3.6 g/cm) ³ ) However, the effect of improving the first discharge capacity and the capacity retention rate after 400 cycles of 1C/1C at 45 ℃ is not obvious, the first discharge capacity is only increased to 1357.2mAh from 1297.5mAh, the high-temperature cycle capacity retention rate is increased to 81.1% from 70.2%, and the improvement effect is obviously lower than that of the high compaction density (3.6 g/cm) ³ ) Improving effect of lithium ion battery.

From the test results of comparative examples 1 to 3, it is understood that, when the compound represented by structural formula 1 is not contained in the electrolyte, the lower the first discharge capacity of the lithium ion battery is, but the better the low-temperature discharge efficiency and the high-temperature cycle performance are, as the positive electrode compaction density is reduced, because the electrolyte is less wetted under high compaction, the battery is more likely to be subjected to lithium precipitation, the low-temperature performance is deteriorated, and the dissolution of metal ions under high compaction is increased, resulting in deterioration of the cycle performance.

Examples 13-15 illustrate the disclosed lithium ion batteries, including most of the operating steps of example 1, with the difference that:

The electrolyte was prepared by adding various amounts of the compounds of formula 1 shown in examples 13 to 15 of Table 4. The test results are shown in Table 5.

TABLE 4 lithium ion battery compositions in 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

The test data of comparative examples 3, 13-15 and comparative example 1 demonstrate that at high compaction densities (3.6 g/cm ³ ) In the nickel-cobalt-manganese lithium ion battery, the electrolyte is added with different compounds shown in the structural formula 1, so that the low-temperature discharge efficiency at the temperature of minus 20 ℃ and the high-temperature cycle performance at the temperature of 45 ℃ are improved to different degrees.

Examples 16 to 19

Examples 16-19 illustrate the lithium ion batteries disclosed herein, including most of the operating steps of example 1, with the difference that:

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

TABLE 6 composition of lithium ion batteries in examples 3, 16-19

Table 7 electrochemical performance test results of lithium ion batteries in examples 3, 16-19

The results show that further additives (DTD, VC, FEC or tripropylester phosphate) in the nonaqueous electrolyte system containing the compound represented by structural 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 compacted density.

Examples 20 to 30

Examples 20-30 illustrate the lithium ion batteries disclosed herein, including most of the operating steps of example 1, with the difference that:

the components 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 test results are shown in Table 9.

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

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

As shown by test results, the high-compaction lithium ion battery provided by the invention can be suitable for various positive electrode active materials due to the fact that the compound shown in the structural formula 1 is added into the electrolyte, and the lithium ion battery with high energy density and excellent high-low temperature performance can be obtained by only adjusting the compaction density of the positive electrode 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, which designs an electrolyte 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 invention has been further described with reference to specific embodiments, but it should be understood that the detailed description is not to be construed as limiting the spirit and scope of the invention, but rather as providing those skilled in the art with the benefit of this disclosure with the benefit of their various modifications to the described embodiments.

Claims

1. A high-compaction lithium ion battery, comprising 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:

structure 1

the positive electrode includes a positive electrode active material layer containing a positive electrode active material, the positive electrode having at least one of the following features:

the positive electrode active material is selected from lithium-containing transition metal oxide Li _m Ni _x Co _y M _1-x-y O ₂ Or a doping and/or cladding modifying compound thereof, wherein 0.95.ltoreq.m.ltoreq.1.2, 0 < x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0 < x+y.ltoreq.1, and M is at least one element selected from Mn and Al, the compacted density of the positive electrode active material layer is 3.6g/cm ³ ~3.8g/cm ³ ；

The positive electrode active material is selected from LiCoO ₂ The positive electrode active material layer had a compacted density of 4.2g/cm ³ The compaction density is less than or equal to 4.3g/cm ³ ；

The positive electrode active material layer has a compacted density of 2.7g/cm when the positive electrode active material is selected from lithium iron phosphate or a doping and/or cladding modified compound thereof ³ ~2.8g/cm ³ ；

The positive electrode active material layer has a compacted density of Dg/cm ³ The compound represented by the structural formula 1 is added in an amount of A% based on 100% of the total mass of the electrolyte, and the following relationships are satisfied between A and D: axD is more than or equal to 1.8 and less than or equal to 3.6.

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

3. The high compaction lithium ion battery of claim 1, wherein the electrolyte salt is selected from LiPF ₆ 、LiPO ₂ F ₂ 、LiBF ₄ 、LiBOB、LiSbF ₆ 、LiAsF ₆ 、LiCF ₃ SO ₃ 、LiDFOB、LiN(SO ₂ CF ₃ ) ₂ 、LiC(SO ₂ CF ₃ ) ₃ 、LiN(SO ₂ C ₂ F ₅ ) ₂ 、LiN(SO ₂ F) ₂ 、LiCl、LiBr、LiI、LiClO ₄ 、LiB ₁₀ Cl ₁₀ 、LiAlCl ₄ At least one of lithium lower aliphatic carboxylate having 4 or less carbon atoms and lithium tetraphenyl borate.

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

/>

。

5. the high-compaction lithium ion battery according to claim 1, wherein the negative electrode comprises a negative electrode active material layer containing a negative electrode active material, the negative electrode active material layer having a compaction density of 1.55g/cm ³ ~1.85g/cm ³ 。

6. The high-compaction lithium ion battery of claim 5, wherein the negative electrode active material comprises one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.

7. The high-compaction lithium ion battery according to claim 5, wherein 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%.

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

structure 2

Wherein R is ₇ 、R ₈ 、R ₉ Each independently selectFrom C ₁ -C ₅ Saturated, unsaturated or halogenated hydrocarbon groups, and R ₇ 、R ₈ 、R ₉ At least one of them is an unsaturated hydrocarbon group.