CN114373980A - Secondary battery - Google Patents

Secondary battery Download PDF

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CN114373980A
CN114373980A CN202111485468.0A CN202111485468A CN114373980A CN 114373980 A CN114373980 A CN 114373980A CN 202111485468 A CN202111485468 A CN 202111485468A CN 114373980 A CN114373980 A CN 114373980A
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secondary battery
positive electrode
material layer
compound
negative electrode
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CN114373980B (en
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钱韫娴
刘中波
邓永红
王勇
黄雄
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Shenzhen Capchem Technology Co Ltd
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Shenzhen Capchem Technology Co Ltd
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Priority to PCT/CN2022/136962 priority patent/WO2023104038A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

In order to overcome the problem of insufficient high-temperature performance of the conventional secondary battery, the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, the positive electrode active material comprises a cobalt-containing compound, the negative electrode comprises a negative electrode material layer, and the non-aqueous electrolyte comprises a solvent, an electrolyte salt and a compound shown in a structural formula 1:
Figure DDA0003396341000000011
wherein R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, and n is 1 or 2; the secondary battery satisfies the following conditions:

Description

Secondary battery
Technical Field
The invention belongs to the technical field of energy storage battery devices, and particularly relates to a secondary 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 products such as mobile phones, notebook computers and the like and new energy automobiles. In recent years, with the development of thinning and thinning of 3C digital products, the demand of the battery industry for high energy density of lithium ion batteries is increasing, and fast charging has become a basic demand of batteries in consideration of clients. Therefore, it is highly desirable to increase the energy density and the fast charge performance of the lithium ion battery.
In the aspect of the positive electrode, by adopting the positive active material containing cobalt element, the volume energy density of the battery can be effectively improved, and better rate performance is kept, but along with the gradual increase of the battery voltage, the positive material enters a higher lithium removal state, the structural stability of the material can be worsened, the disproportionation reaction of Co in the positive electrode is easy to occur, the Co is dissolved in the electrolyte in the form of ions and migrates to the negative electrode interface, the ion exchange is carried out with lithium in the negative electrode, the position of lithium insertion of the negative electrode is occupied, and the lithium insertion position is not easy to be removed, the lithium storage capacity of the negative electrode is reduced, the capacity loss is caused, the performance of the lithium ion secondary battery is worsened, and the specific expression is that: the battery generates gas, the internal resistance is rapidly increased, and the capacity is sharply reduced. The generation of gas from the battery may increase the internal pressure, which may further lead to dangerous situations such as explosion and burning of the battery, and thus the high voltage battery needs to be matched with an electrolyte with better high voltage resistance.
The negative pole angle, for promoting energy density, high compaction has become the commonly adopted means in the industry, through the porosity that reduces the negative pole, reaches the purpose of bearing more active material. However, the higher the compaction density of the lithium ion battery negative electrode material is, the higher the requirement on the electrolyte is. The electrolyte suitable for the conventional compacted negative electrode is in a high-pressure physical system, a series of problems of lithium precipitation, cycle life reduction, rate performance reduction and the like of the battery easily occur, and the damage of Co ions dissolved out of the positive electrode to the negative electrode is more serious under the high-pressure actual condition, so that the high-temperature cycle performance of the battery is greatly reduced.
Therefore, in a battery system using a high-voltage positive electrode containing cobalt element in combination with a high-compaction negative electrode, how to configure an electrolyte to ensure normal operation of the battery at high temperature is an urgent problem to be solved.
Disclosure of Invention
The invention provides a secondary battery, aiming at the problem that the prior secondary battery has insufficient high-temperature performance.
The technical scheme adopted by the invention for solving the technical problems is as follows:
in one aspect, the present invention provides a secondary battery including a positive electrode material layer including a positive electrode active material including a cobalt-containing compound, a negative electrode including a negative electrode material layer, and a nonaqueous electrolyte including a solvent, an electrolyte salt, and a compound represented by structural formula 1:
Figure RE-GDA0003530790850000021
wherein R1 is selected from unsaturated hydrocarbon group with 3-6 carbon atoms, R2 is selected from alkylene group with 2-5 carbon atoms, and n is 1 or 2;
the secondary battery satisfies the following conditions:
Figure RE-GDA0003530790850000022
wherein a is a ratio of a mass of an electrolyte in the secondary battery to a total mass of the positive electrode material layer;
b is the mass percentage content of Co element in the positive electrode material layer, and the unit is;
m is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
p is the compacted density of the anode material layer and has a unit of g/cm3。
Optionally, the secondary battery satisfies the following condition:
Figure RE-GDA0003530790850000023
optionally, the compound shown in the structural formula 1 is selected from one or more of the following compounds:
Figure RE-GDA0003530790850000024
Figure RE-GDA0003530790850000031
optionally, a ratio a of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer is 0.10-0.70; preferably, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer in the secondary battery is 0.15 to 0.60.
Optionally, the mass percentage content b of the Co element in the positive electrode material layer is 5-60%; preferably, the mass percentage content b of the Co element in the positive electrode material layer is 5-30%.
Optionally, the mass percentage content m of the compound shown in the structural formula 1 in the non-aqueous electrolyte is 0.05-5%; preferably, the mass percentage content m of the compound shown in the structural formula 1 in the nonaqueous electrolytic solution is 0.1-3%.
Optionally, the compacted density p of the anode material layer is greater than or equal to 1.5g/cm3(ii) a Preferably, the compacted density p of the negative electrode material layer is 1.55-1.8 g/cm3。
Optionally, the nonaqueous electrolyte further includes an auxiliary additive, and the auxiliary additive includes at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, and a nitrile compound.
Optionally, the additive amount of the auxiliary additive is 0.01-30% based on 100% of the total mass of the nonaqueous electrolyte.
Optionally, the cyclic sulfate compound is selected from at least one of vinyl sulfate, allyl sulfate or vinyl methyl sulfate;
the sultone compound is selected from at least one of 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
Figure RE-GDA0003530790850000041
in the formula 2, R21、R22、R23、R24、R25、R26Each independently selected from one of hydrogen atom, halogen atom, C1-C5 group;
the unsaturated phosphate ester compound is selected from at least one of compounds shown in a structural formula 3:
Figure RE-GDA0003530790850000042
in the formula 3, R31、R32、R32Each independently selected from saturated alkyl, unsaturated alkyl, halogenated alkyl and Si (C1-C5)mH2m+1)3M is a natural number of 1 to 3, and R31、R32、R33At least one of them is an unsaturated hydrocarbon group;
the nitrile compound comprises one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
The secondary battery provided by the invention adopts the high-compaction cathode and the cobalt-containing anode, so that the secondary battery has higher initial energy density and simultaneously avoidsThe compound shown in the structural formula 1 is added into the non-aqueous electrolyte without the deterioration of the cycle performance of the battery, and the inventor finds that the improvement effect of the compound shown in the structural formula 1 on the high-temperature cycle performance is closely related to the addition amount of the compound, the ratio of the mass of the electrolyte to the total mass of the positive electrode material layer, the mass percentage content of Co in the positive electrode material layer and the compaction density of the negative electrode material layer through a large number of experiments, and when the positive electrode, the negative electrode and the electrolyte in the secondary battery meet the relational expression
Figure RE-GDA0003530790850000043
During the process, the dissolution of Co ions in the positive electrode in a high-temperature state can be effectively inhibited, and a more compact and stable SEI film is formed on the surface of the negative electrode, so that the damage of Co ions dissolved out by a cobalt-containing compound to a high-compaction negative electrode in the battery circulation process is effectively reduced, the capacity loss of the secondary battery in high-temperature circulation is reduced, and the high-temperature circulation performance of the secondary battery is improved.
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 secondary battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, the positive electrode active material comprises a cobalt-containing compound, the negative electrode comprises a negative electrode material layer, and the non-aqueous electrolyte comprises a solvent, an electrolyte salt and a compound shown in a structural formula 1:
Figure RE-GDA0003530790850000051
wherein R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, and n is 1 or 2;
the secondary battery satisfies the following conditions:
Figure RE-GDA0003530790850000052
wherein a is the ratio of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer;
b is the mass percentage content of Co element in the positive electrode material layer, and the unit is;
m is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
p is the compacted density of the anode material layer and has a unit of g/cm3。
The secondary battery adopts a high-compaction negative electrode and a cobalt-containing positive electrode, so that the secondary battery has higher initial energy density, and meanwhile, in order to avoid the deterioration of the cycle performance of the battery, the compound shown in the structural formula 1 is added into the non-aqueous electrolyte, and the inventor finds that the improvement effect of the compound shown in the structural formula 1 on the high-temperature cycle performance is closely related to the addition amount, the total mass percentage of the positive electrode and the electrolyte, the mass percentage of Co element in a positive electrode material layer and the compaction density of a negative electrode material layer through a large number of experiments, and when the positive electrode, the negative electrode and the electrolyte in the secondary battery meet the relational expression
Figure RE-GDA0003530790850000053
During the process, the dissolution of Co ions in the positive electrode in a high-temperature state can be effectively inhibited, and a more compact and stable SEI film is formed on the surface of the negative electrode, so that the damage of Co ions dissolved out by a cobalt-containing compound to a high-compaction negative electrode in the battery circulation process is effectively reduced, the capacity loss of the secondary battery in high-temperature circulation is reduced, and the high-temperature circulation performance of the secondary battery is improved.
In a preferred embodiment, the secondary battery satisfies the following conditions:
Figure RE-GDA0003530790850000061
in the secondary battery provided by the invention, the compound shown in the structural formula 1 is associated with the design parameters of the positive electrode and the negative electrode in the secondary battery (the total mass percentage of the positive electrode and the electrolyte, the mass percentage of the Co element in the positive electrode material layer and the compaction density of the negative electrode material layer), so that the influence of the positive electrode, the negative electrode and the compound shown in the structural formula 1 on the battery performance can be synthesized to a certain extent, and the secondary battery with higher initial energy density and better high-temperature cycle performance is obtained.
In some embodiments, the compound of formula 1 is selected from one or more of the following compounds:
Figure RE-GDA0003530790850000062
in some embodiments, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer is 0.10-0.70.
In a preferred embodiment, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer in the secondary battery is 0.15 to 0.60.
The capacity of the secondary battery depends on the interaction of the positive electrode material layer, the negative electrode material layer and the non-aqueous electrolyte, when the ratio of the quality of the electrolyte in the secondary battery to the total quality of the positive electrode material layer is too high, the content of the negative electrode material layer is correspondingly reduced, and when the ratio of the quality of the electrolyte in the secondary battery to the total quality of the positive electrode material layer is too low, the positive electrode material layer embedding sites for embedding electrolyte ions are lacked, so that the ratio of the quality of the electrolyte in the secondary battery to the total quality of the positive electrode material layer is too high or too low, which is not beneficial to the improvement of the capacity of the secondary battery.
In some embodiments, the mass percentage content b of the Co element in the positive electrode material layer is 5% to 60%.
In a preferred embodiment, the mass percentage content b of the Co element in the positive electrode material layer is 5% to 30%.
The mass percentage of the Co element in the positive electrode material layer can be correspondingly regulated and controlled by selecting the specific type of the cobalt-containing compound of the positive electrode active material and adjusting the content of the positive electrode active material in the positive electrode material layer. When the mass percentage content of the Co element in the positive electrode material layer reaches a certain value, the secondary battery can have better rate performance, but when the mass percentage content of the Co element in the positive electrode material layer is too large, the Co element is easily dissolved out due to the reaction of the positive electrode active material and the non-aqueous electrolyte under the condition of high voltage and migrates to a negative electrode interface, and is subjected to ion exchange with lithium in the negative electrode, occupies a negative electrode lithium-embedded position, and is not easy to be separated, so that the lithium storage capacity of the negative electrode is reduced, and the capacity loss is caused, and the performance of the lithium ion secondary battery is poor.
In a preferred embodiment, the secondary battery is a lithium ion battery.
In the present embodiment, the positive electrode active material includes a compound represented by the following formula;
Li1+xNiaCobM1-a-bO2-yAy
wherein, x is more than or equal to 0.1 and less than or equal to 0.2, a is more than or equal to 0 and less than or equal to 1, b 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 0.2, M comprises one or more of Mn and Al, and optionally comprises zero, one or more of Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe and Ce, and A comprises one or more of S, N, F, Cl, Br and I.
In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the compound represented by formula 1, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.
The mass percentage of the positive electrode binder is 1-2%, and the mass percentage of the positive electrode conductive agent is 0.5-2%, based on the total mass of the positive electrode material layer being 100%.
The positive binder comprises thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether, copolymers of ethylene and tetrafluoroethylene, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and trichloroethylene, copolymers of vinylidene fluoride and fluoroethylene, copolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, polyethylene, polypropylene and the like; an acrylic resin; sodium carboxymethylcellulose; polyvinyl butyral; ethylene-vinyl acetate copolymers; polyvinyl alcohol; and styrene butadiene rubber.
The positive electrode conductive agent comprises one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.
In some embodiments, the positive electrode sheet further comprises a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector. In the positive electrode of the present application, the portions other than the positive electrode current collector are referred to as positive electrode material layers.
The positive electrode current collector is selected from metal materials capable of conducting electrons, preferably, the positive electrode current collector comprises one or more of Al, Ni, tin, copper and stainless steel, and in a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.
In some embodiments, the mass percentage of the compound represented by formula 1 in the nonaqueous electrolyte solution is 0.05% to 5%.
In a preferred embodiment, the mass percentage content m of the compound shown in the structural formula 1 in the nonaqueous electrolytic solution is 0.1-3%.
The positive active material comprises a cobalt-containing compound, so that the secondary battery has better rate performance, when the mass percentage content of the Co element in the positive material layer is too large, the reaction of the positive active material and the non-aqueous electrolyte is easily caused under the condition of high voltage, so that the Co element is dissolved out, the stability of the non-aqueous electrolyte can be improved by adding the compound shown in the formula 1, and further the dissolution of the Co element in the positive active material is inhibited, but when the adding amount of the compound shown in the formula 1 is too large, some unnecessary side reaction products are generated, and further other performances of the secondary battery are deteriorated.
In some embodiments, the negative electrodeThe material layer has a compacted density p of 1.5g/cm or more3(ii) a Preferably, the compacted density p of the negative electrode material layer is 1.55-1.8 g/cm3。
The compaction density p of the negative electrode material layer has a certain influence on the capacity of the secondary battery, generally, if the compaction density is too low, the quantity of negative electrode active materials capable of being embedded by lithium ions in the negative electrode of unit volume is less, which is not beneficial to improving the energy density, and if the compaction density of the negative electrode material layer is too high, the degree of compaction of a pore channel for embedding and extracting the lithium ions in the negative electrode is serious, a negative electrode plate is compact, and the porosity is smaller, so that the negative electrode active material particles are more closely attached to each other, active sites exposed in electrolyte are reduced, and the quantity of active sites of the negative electrode porous electrode capable of participating in reaction is less. In addition, the compaction density of the negative electrode material layer is related to the compound shown in the structural formula 1, and after the compound shown in the structural formula 1 is added into the non-aqueous electrolyte, the ionic conductivity, the viscosity and the like of the non-aqueous electrolyte are changed, so that the permeability of the non-aqueous electrolyte to the negative electrode material layer is influenced, and the intercalation and deintercalation efficiency of lithium ions is further influenced; the compaction density of the negative electrode material layer also influences the compactness of an SEI film formed by the decomposition of the compound shown in the structural formula 1 on the surface of the negative electrode material layer, and influences the protection effect of the SEI film on free Co.
The above analysis is based on the influence of each parameter or a plurality of parameters on the battery when the parameters exist independently, but in the practical battery application process, the above four parameters are correlated and inseparable. The relation formula provided by the invention relates the four, and the four influence the electrochemical performance of the battery together, so that the addition amount m of the compound shown in the structural formula 1, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer, the mass percentage content b of Co in the positive electrode material layer and the compaction density p of the negative electrode material layer are adjusted, so that
Figure RE-GDA0003530790850000091
The high-temperature cycle performance and the high-temperature storage performance of the secondary battery can be effectively improved on the premise of ensuring that the secondary battery has higher energy density. If it is
Figure RE-GDA0003530790850000092
At values that are too high or too low, the battery will experience dynamic degradation, leading to a shorter battery life at high temperatures and even safety issues.
In some embodiments, the anode material layer includes an anode active material selected from at least one of a silicon-based anode, a carbon-based anode, and a tin-based anode.
In a preferred embodiment, the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, and the like. The graphite comprises one or more of natural graphite, artificial graphite, amorphous carbon, carbon-coated graphite, graphite-coated graphite and resin-coated graphite. The natural graphite may be scale graphite, flake graphite, soil graphite, and/or graphite particles obtained by spheroidizing, densifying, or the like, using these graphites as a raw material. The artificial graphite can be obtained by graphitizing organic matters such as coal tar pitch, coal heavy crude oil, atmospheric residual oil, petroleum heavy crude oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenyl, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenolic resin, imide resin and the like at high temperature. The amorphous carbon may be one obtained by heat-treating an easily graphitizable carbon precursor such as tar or pitch at a temperature range (400 to 2200 ℃) where graphitization does not occur for 1 or more times, or one obtained by heat-treating an hardly graphitizable carbon precursor such as resin. The carbon-coated graphite may be 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 some embodiments, the anode material layer includes one or more of a lithium anode, a sodium anode, a potassium anode, a magnesium anode, a zinc anode, and an aluminum anode. The lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.
In some embodiments, the negative electrode further comprises a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. In the negative electrode of the present application, the portions other than the negative electrode current collector are referred to as negative electrode material layers.
The negative electrode current collector is selected from metal materials capable of conducting electrons, preferably, the negative electrode current collector comprises one or more of Al, Ni, tin, copper and stainless steel, and in a more preferred embodiment, the negative electrode current collector is selected from aluminum foil.
In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer. The negative electrode binder comprises thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether, copolymers of ethylene and tetrafluoroethylene, copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylidene fluoride and trichloroethylene, copolymers of vinylidene fluoride and fluoroethylene, copolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, thermoplastic polyimide, polyethylene, polypropylene and the like; an acrylic resin; sodium carboxymethylcellulose; and styrene butadiene rubber.
The negative electrode conductive agent comprises one or more of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide.
In some embodiments, the nonaqueous electrolytic solution further includes an auxiliary additive, and the auxiliary additive includes at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, and a nitrile compound.
Preferably, the cyclic sulfate compound is at least one selected from vinyl sulfate, allyl sulfate or vinyl methyl sulfate;
the sultone compound is selected from at least one of 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
Figure RE-GDA0003530790850000111
in the formula 2, R21、R22、R23、R24、R25、R26Each independently selected from one of hydrogen atom, halogen atom, C1-C5 group.
The unsaturated phosphate ester compound is selected from at least one of compounds shown in a structural formula 3:
Figure RE-GDA0003530790850000112
in the formula 3, R31、R32、R32Each independently selected from saturated alkyl, unsaturated alkyl, halogenated alkyl and Si (C1-C5)mH2m+1)3M is a natural number of 1 to 3, and R31、R32、R33At least one of them is an unsaturated hydrocarbon group.
In a preferred embodiment, the unsaturated 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.
The nitrile compound comprises one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
In other embodiments, the supplemental additives may also include other additives that improve the performance of the battery: for example, additives for improving the safety performance of the battery, such as a flame retardant additive such as fluorophosphate ester and cyclophosphazene, or an anti-overcharge additive such as tert-amylbenzene and tert-butylbenzene.
In some embodiments, the additive amount of the auxiliary additive is 0.01% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
Unless otherwise specified, in general, the additive amount of any optional substance in the auxiliary additive in the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, more preferably 0.1 to 2%. Specifically, the additive amount of any optional substance in the auxiliary additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.
In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the fluoroethylene carbonate is added in an amount of 0.05% to 30% based on 100% by mass of the total mass of the nonaqueous electrolytic solution.
In some embodiments, the electrolyte salt includes one or more of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt. In a preferred embodiment, the electrolyte salt is selected from a lithium salt or a sodium salt.
In a preferred embodiment, the electrolyte salt is selected from the group consisting of LiPF6、LiPO2F2、 LiBF4、LiBOB、LiSbF6、LiAsF6、LiCF3SO3、LiDFOB、LiN(SO2CF3)2、LiC(SO2CF3)3、 LiN(SO2C2F5)2、LiN(SO2F)2、LiCl、LiBr、LiI、LiClO4、LiBF4、LiB10Cl10、LiAlCl4At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenylborate, and lithium imide. Specifically, the electrolyte salt may be LiBF4、LiClO4、LiAlF4、LiSbF6、LiTaF6、LiWF7And inorganic electrolyte salts; LiPF6Isophosphoric acid electrolyte salts; LiWOF5Tungstic acid electrolyte salts; HCO2Li、CH3CO2Li、CH2FCO2Li、CHF2CO2Li、CF3CO2Li、 CF3CH2CO2Li、CF3CF2CO2Li、CF3CF2CF2CO2Li、CF3CF2CF2CF2CO2Carboxylic acid electrolyte salts such as Li; CH (CH)3SO3Sulfonic acid electrolyte salts such as Li; LiN (FCO)2)2、LiN(FCO)(FSO2)、 LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic lithium 1, 2-perfluoroethanedisulfonimide, cyclic lithium 1, 3-perfluoropropanedisulfonimide, LiN (CF)3SO2)(C4F9SO2) Imide electrolyte salts such as imide electrolyte salts; LiC (FSO)2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3Isomethyl electrolyteSalts; 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.
When the electrolyte salt is selected from other salts such as sodium salt, potassium salt, magnesium salt, zinc salt, aluminum salt, etc., lithium in the above lithium salt may be replaced with sodium, potassium, magnesium, zinc, aluminum, etc.
In a preferred embodiment, the sodium salt is selected from sodium perchlorate (NaClO)4) Sodium hexafluorophosphate (NaPF)6) Sodium tetrafluoroborate (NaBF)4) Sodium triflate (NaFSI) and sodium bistrifluoromethylsulfonate (NaTFSI).
Generally, the electrolyte salt in the electrolyte is a transfer unit of lithium ions, the concentration of the electrolyte salt directly affects the transfer rate of the lithium ions, and the transfer rate of the lithium ions affects the potential change of the negative electrode. In the process of rapidly charging the battery, the moving speed of lithium ions needs to be improved as much as possible, the formation of lithium dendrites caused by the excessively fast decline of the negative electrode potential is prevented, potential safety hazards are brought to the battery, and the excessively fast decline of the cycle capacity of the battery can be prevented. Preferably, the total concentration of the electrolyte salt in the electrolyte solution may be 0.5 to 2.0mol/L, 0.5 to 0.6mol/L, 0.6 to 0.7mol/L, 0.7 to 0.8mol/L, 0.8 to 0.9mol/L, 0.9 to 1.0mol/L, 1.0 to 1.1mol/L, 1.1 to 1.2mol/L, 1.2 to 1.3mol/L, 1.3 to 1.4mol/L, 1.4 to 1.5mol/L, 1.5 to 1.6mol/L, 1.6 to 1.7mol/L, 1.7 to 1.8mol/L, 1.8 to 1.9mol/L, and further preferably 0.5 to 1.9mol/L, and further preferably 0.8 to 1.9mol/L, 0.7mol/L to 1.7mol/L, or 0.8mol/L to 1.5 mol/L.
In some embodiments, the solvent includes one or more of an ether-based solvent, a nitrile-based solvent, a carbonate-based solvent, and a carboxylate-based solvent.
In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms, and the cyclic ether may be, but is not limited to, 1, 3-Dioxolane (DOL), 1, 4-Dioxan (DX), crown ether, Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH)3-THF), 2-trifluoromethyltetrahydrofuran (2-CF)3-THF); the chain ether may specifically be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferable because chain ethers have high solvating ability with lithium ions and can improve ion dissociation properties. The ether compound may be used alone, or two or more thereof may be used in combination in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-compaction lithium ion battery of the present invention, and is usually 1% by volume or more, preferably 2% by volume or more, and more preferably 3% by volume or more, and is usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less, based on 100% by volume of the nonaqueous solvent. 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 chain ether and lithium ion can be inhibited from being includedSince the co-insertion phenomenon occurs together, the input-output characteristics and the charge-discharge rate characteristics can be brought into appropriate ranges.
In some embodiments, the nitrile based solvent may specifically be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.
In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), γ -butyrolactone (GBL), Butylene Carbonate (BC); the chain carbonate may specifically be, but not limited to, one or more of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited and may be any within a range not significantly impairing the effect of the high-compacted lithium ion battery of the present invention, but in the case where one is used alone, the lower limit of the content is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of the solvent of the nonaqueous electrolytic solution. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the nonaqueous electrolytic solution, and it is easy to make the large-current discharge characteristic, the stability with respect to the negative electrode, and the cycle characteristic of the nonaqueous electrolyte battery fall within a favorable range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. Setting this range can improve the oxidation/reduction resistance of the nonaqueous electrolytic solution, and contributes to improvement of stability during high-temperature storage. The content of the chain carbonate is not particularly limited, and is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, based on the total amount of the solvent of the nonaqueous electrolytic solution. The volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. When the content of the chain carbonate is in the above range, the viscosity of the nonaqueous electrolytic solution is easily brought to an appropriate range, the decrease in the ionic conductivity is suppressed, and the content contributes to bringing the output characteristics of the nonaqueous electrolyte battery to a good range. When two or more kinds of chain carbonates are used in combination, the total amount of the chain carbonates may be set to satisfy the above range.
In some embodiments, chain carbonates having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonates") may also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, the fluorine atoms may be bonded to the same carbon atom or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.
The carboxylic ester solvent includes cyclic carboxylic ester and/or chain carbonate. Examples of the cyclic carboxylic acid ester include: one or more of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include: one or more of Methyl Acetate (MA), Ethyl Acetate (EA), propyl acetate (EP), butyl acetate, Propyl Propionate (PP), and butyl propionate.
In some embodiments, the sulfone-based solvent includes cyclic sulfones and chain sulfones, but preferably, in the case of cyclic sulfones, compounds having generally 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of chain sulfones, compounds having generally 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The amount of the sulfone solvent to be added is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-performance lithium ion battery of the present invention, and is usually 0.3% by volume or more, preferably 0.5% by volume or more, and more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, and more preferably 30% by volume or less, based on the total amount of the solvent of the nonaqueous electrolytic solution. In the case where two or more sulfone solvents are used in combination, the total amount of the sulfone solvents may be set to satisfy the above range. When the amount of the sulfone solvent added is within the above range, an electrolyte excellent in high-temperature storage stability tends to be obtained.
In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.
In some embodiments, a separator is also included in the battery, the separator being positioned between the positive electrode and the negative electrode.
The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, and the like, including but not limited to a single layer PP (polypropylene), a single layer PE (polyethylene), a double layer PP/PE, a double layer PP/PP, and a triple layer PP/PE/PP, and the like.
The present invention will be further illustrated by the following examples.
Figure RE-GDA0003530790850000151
Figure RE-GDA0003530790850000161
Table 1 design of parameters of examples and comparative examples
Figure RE-GDA0003530790850000162
Figure RE-GDA0003530790850000171
Note: LCO means LiCoO2NCM811 means LiNi0.8Co0.1Mn0.1O2And NCM622 denotes LiNi0.6Co0.2Mn0.2O2。
Example 1
This example is used to illustrate the battery and the method for manufacturing the same disclosed in the present invention, and includes the following steps:
(1) preparation of positive pole piece
LiCoO serving as a Co-containing positive electrode active material2(LCO is used for subsequent description), a conductive agent and a binder PVDF are dispersed into a solvent NMP to be uniformly mixed, so as to obtain anode slurry; uniformly coating the anode slurry on an anode current collector aluminum foil, drying, rolling and cutting into pieces to obtain an anodeThe mass ratio of the sheet, the positive electrode active material, the conductive carbon black and the binder PVDF is 96:2: 2.
(2) Preparation of negative pole piece
Dispersing graphite serving as a negative electrode active material, a conductive agent, a binder CMC and SBR in deionized water according to a mass ratio of 96:1:1:2, and stirring to obtain negative electrode slurry; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector, drying, rolling and cutting into pieces to obtain the product with the compacted density of 1.6g/cm3The negative electrode plate of (1).
(3) Preparation of the electrolyte
Ethylene Carbonate (EC) and diethyl carbonate (DEC) are uniformly mixed in a mass ratio of 30:70, and 1mol/L LiPF6And dissolving the compound shown in the structural formula 1 accounting for 0.1 wt% of the electrolyte in the non-aqueous organic solvent to obtain the electrolyte.
(4) Preparation of lithium ion secondary battery
And (3) adopting a lamination process to sequentially laminate the positive pole piece, the isolating membrane and the negative pole piece, and then carrying out top side sealing, injecting a certain amount of electrolyte and other procedures to prepare the soft package battery.
Examples 2 to 28
Examples 2 to 28 are for explaining the battery and the method for manufacturing the same disclosed in the present invention, and include most of the operation steps in example 1, except that:
the anode parameters, cathode parameters and electrolyte additive components shown in table 1 were used.
Comparative examples 1 to 12
Comparative examples 1 to 12, which are used to illustrate the battery and the method for manufacturing the same disclosed in the present invention, include most of the operation steps in example 1, except that:
the anode parameters, cathode parameters and electrolyte additive components shown in table 1 were used.
Performance testing
And (3) carrying out high-temperature cycle performance test on the lithium ion battery prepared by the method:
and (3) at the temperature of 45 ℃, charging the formed battery to a cut-off voltage by using a 1C constant current and a constant voltage, then charging at the constant voltage until the current is reduced to 0.05C, then discharging to 3.0V by using a 1C current and a constant current, and thus cycling, and recording the 1 st discharge capacity and volume and the last 1 discharge capacity and volume.
The capacity retention for the high temperature cycle was calculated as follows:
capacity retention rate is the last 1 discharge capacity/1 st discharge capacity × 100%.
Volume growth rate (volume of last 1 time-volume of 1 st time)/volume of 1 st time x 100%
(1) The performance test results of the lithium ion batteries manufactured in examples 1 to 20 and comparative examples 1 to 7 are shown in table 2:
TABLE 2
Figure RE-GDA0003530790850000191
From the test results of the examples 1 to 20 and the comparative examples 1 to 7, it can be seen that, when the addition amount m of the compound shown in the structural formula 1, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer, the mass percentage content b of the Co element in the positive electrode material layer and the compaction density p of the negative electrode material layer of the lithium ion battery provided by the invention satisfy the relational expression
Figure RE-GDA0003530790850000192
In time, the lithium ion battery has better cycle performance at high temperature, and
Figure RE-GDA0003530790850000193
especially, from examples 13 to 20, when the cobalt content in the positive active material is increased, the high-temperature capacity retention rate and the volume increase rate of the battery can be maintained at similar levels by reducing the cathode compaction density, increasing the content of the compound shown in the structural formula 1 and the mass ratio of the electrolyte to the positive material layer, which indicates that the above factors have a mutual regulation relationship with the cobalt content adjustment of the positive active material, and the increase of the cobalt content in the positive electrode can be effectively inhibited by regulating the above factors to improve the battery cyclicityCan have negative effects.
Meanwhile, as can be seen from comparative examples 2 and 3, when the cobalt content in the positive electrode active material is low, the content of the compound represented by the structural formula 1 in the nonaqueous electrolyte is too high, which also causes the deterioration of the high-temperature cycle performance of the lithium ion battery; it can be seen from comparative examples 4 and 5 that, in the case where the content of cobalt in the positive electrode active material is high, the content of the compound having the structure 1 in the nonaqueous electrolytic solution is too low, which is also disadvantageous for improving the high-temperature cycle performance of the lithium ion battery, and it means that when the content of cobalt in the positive electrode active material is low or high, the compound having the structure 1 needs to be added to the nonaqueous electrolytic solution at a relatively low content or a relatively high content.
As is clear from the results of the tests of comparative examples 1 to 20, when the relation satisfies
Figure RE-GDA0003530790850000201
And meanwhile, the lithium ion battery has the best high-temperature storage performance and high-temperature cycle performance.
(2) The performance test results of the lithium ion batteries manufactured in examples 1 and 21 to 23 are shown in table 3:
TABLE 3
Figure RE-GDA0003530790850000202
As is clear from the test results of examples 1 and 21 to 23, when different compounds represented by the structural formula 1 were used as additives for nonaqueous electrolytic solutions, the relational expressions were satisfied as well
Figure RE-GDA0003530790850000203
The improvement effects of the compounds shown in the structural formula 1 on the high-temperature capacity retention rate and the high-temperature volume growth rate of the battery are similar, and the relationship definition provided by the invention has universality on the compounds shown in the structural formula 1.
(3) The performance test results of the lithium ion batteries manufactured in examples 1, 24 to 28 and comparative examples 8 to 12 are shown in table 4:
TABLE 4
Figure RE-GDA0003530790850000211
From the test results of examples 1 and 24 to 28, it can be seen that the high-temperature cycle performance and the high-temperature storage performance of the battery can be further improved by adding the cyclic sulfate compound, the sultone compound, the cyclic carbonate compound, the unsaturated phosphate compound or the nitrile compound as the auxiliary additive to the lithium ion battery provided by the present invention, and it is presumed that a passivation film can be formed on the electrode together due to the interaction between the compound represented by the structural formula 1 and the cyclic sulfate compound, the sultone compound, the cyclic carbonate compound, the unsaturated phosphate compound or the nitrile compound, wherein when the auxiliary additive is vinyl sulfate, the performance improvement of the battery is most obvious.
From the comparison results of example 1 and comparative examples 8 to 12, it is understood that the effect achieved by adding the compound represented by the structural formula 1 cannot be achieved when the compound represented by the structural formula 1 in the nonaqueous electrolytic solution is replaced with a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, or a nitrile compound.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A secondary battery comprising a positive electrode including a positive electrode material layer including a positive electrode active material including a cobalt-containing compound, a negative electrode including a negative electrode material layer, and a nonaqueous electrolytic solution including a solvent, an electrolyte salt, and a compound represented by structural formula 1:
Figure FDA0003396340980000011
wherein R1 is selected from unsaturated hydrocarbon groups with 3-6 carbon atoms, R2 is selected from alkylene groups with 2-5 carbon atoms, and n is 1 or 2;
the secondary battery satisfies the following conditions:
Figure FDA0003396340980000012
wherein a is the ratio of the mass of the electrolyte in the secondary battery to the total mass of the positive electrode material layer;
b is the mass percentage content of Co element in the positive electrode material layer, and the unit is;
m is the mass percentage content of the compound shown in the structural formula 1 in the nonaqueous electrolyte, and the unit is;
p is the compacted density of the anode material layer and has a unit of g/cm3。
2. The secondary battery according to claim 1, wherein the secondary battery satisfies the following condition:
Figure FDA0003396340980000013
3. the secondary battery according to claim 1, wherein the compound represented by structural formula 1 is selected from one or more of the following compounds:
Figure FDA0003396340980000014
Figure FDA0003396340980000021
4. the secondary battery according to claim 1, wherein a ratio a of a mass of the electrolyte to a total mass of the positive electrode material layer in the secondary battery is 0.10 to 0.70; preferably, the ratio a of the mass of the electrolyte to the total mass of the positive electrode material layer in the secondary battery is 0.15 to 0.60.
5. The secondary battery according to claim 1, wherein the mass percentage content b of the Co element in the positive electrode material layer is 5% to 60%;
preferably, the mass percentage content b of the Co element in the positive electrode material layer is 5-30%.
6. The secondary battery according to claim 1, wherein the mass percentage m of the compound represented by the formula 1 in the nonaqueous electrolytic solution is 0.05% to 5%;
preferably, the mass percentage content m of the compound shown in the structural formula 1 in the nonaqueous electrolytic solution is 0.1-3%.
7. The secondary battery according to claim 1, wherein the anode material layer has a compacted density p of 1.5g/cm or more3；
Preferably, the compaction density p of the negative electrode material layer is 1.55-1.8 g/cm3。
8. The secondary battery according to claim 1, further comprising an auxiliary additive including at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, an unsaturated phosphate-based compound, and a nitrile-based compound.
9. The secondary battery according to claim 8, wherein the additive amount of the auxiliary additive is 0.01 to 30% based on 100% by mass of the total mass of the nonaqueous electrolytic solution.
10. The secondary battery according to claim 8, wherein the cyclic sulfate-based compound is at least one selected from vinyl sulfate, propylene sulfate, and vinyl methylsulfate;
the sultone compound is selected from at least one of 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate or a compound shown in a structural formula 2,
Figure FDA0003396340980000031
in the formula 2, R21、R22、R23、R24、R25、R26Each independently selected from one of hydrogen atom, halogen atom, C1-C5 group;
the unsaturated phosphate ester compound is selected from at least one of compounds shown in a structural formula 3:
Figure FDA0003396340980000032
in the formula 3, R31、R32、R32Each independently selected from saturated alkyl, unsaturated alkyl, halogenated alkyl and Si (C1-C5)mH2m+1)3M is a natural number of 1 to 3, and R31、R32、R33At least one of them is an unsaturated hydrocarbon group;
the nitrile compound comprises one or more of succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
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