CN117096433A - Electrolyte and battery comprising same - Google Patents

Electrolyte and battery comprising same Download PDF

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Publication number
CN117096433A
CN117096433A CN202210519601.8A CN202210519601A CN117096433A CN 117096433 A CN117096433 A CN 117096433A CN 202210519601 A CN202210519601 A CN 202210519601A CN 117096433 A CN117096433 A CN 117096433A
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electrolyte
additive
battery
alkyl group
formula
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王海
李素丽
李俊义
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)

Abstract

The application provides an electrolyte and a battery comprising the electrolyte, wherein an SEI film of a polymer skeleton containing naphthyl with anhydride functional groups is formed on the surface of a positive electrode and a negative electrode after charge and discharge, the naphthyl has the property of being easy to polymerize into a film, the formed film has better two-dimensional property so as to have better protectiveness, in addition, the anhydride functional groups on the protective film have the capability of inhibiting HF corrosion, so that the SEI film has an excellent function of inhibiting acid corrosion, further, a negative electrode active material can better adapt to the HF corrosion formed by FEC under the high temperature condition, the effect of improving the cycle performance of the battery is achieved, and meanwhile, the formed SEI film with the function of inhibiting acid corrosion can also reduce the content of byproduct HF, thereby improving the stability of the positive electrode and obviously improving the high temperature performance of the battery.

Description

Electrolyte and battery comprising same
Technical Field
The application relates to an electrolyte and a battery comprising the same, and belongs to the technical field of batteries.
Background
Lithium ion batteries have a series of advantages of longer cycle life, higher energy density, lower manufacturing cost, and the like, and are therefore increasingly used in various electronic products, electric vehicles, various electric tools, and energy storage devices in recent years. With further development of technology, higher and higher requirements are also put on the energy density of the battery, and the current improvement of the energy density of the battery can be realized by changing the cathode material with higher energy density or increasing the voltage of the anode.
The traditional battery cathode material is graphite, and the silicon-based material is the hottest cathode material in recent years, and has a gram capacity improvement which is several times higher than that of the graphite cathode. The use of higher and higher amounts of silicon-based materials in the negative electrode is a major trend in the next generation of high energy density batteries. However, compared with a common graphite anode, the volume expansion and shrinkage of the silicon-based anode are more remarkable in the charge and discharge process, and the SEI film on the surface of the anode is continuously broken, so that a large amount of fluoroethylene carbonate (FEC) is required to be added into the electrolyte to continuously repair the broken SEI film. Moreover, even if a battery assembled with a pure graphite negative electrode and a high-voltage lithium cobalt oxide positive electrode is employed, FEC is becoming an indispensable additive or solvent and there is a trend to partially replace Ethylene Carbonate (EC).
However, under high temperature conditions, FEC is easily decomposed to generate HF, which can corrode the SEI film and the CEI film, and the positive and negative electrode active materials, resulting in easy breakage of the positive and negative electrode protective films and even loss of the positive and negative electrode active materials, which further results in significant deterioration of high temperature performance (including high temperature storage, intermittent cycle, high temperature cycle, etc.) of the battery.
Disclosure of Invention
In order to solve the problem that the corrosion of HF causes the rupture of the surface protection film of the positive electrode and the negative electrode in the existing battery containing FEC, the application aims to provide an electrolyte and the battery comprising the electrolyte, wherein the electrolyte and the battery comprising the electrolyte have the function of inhibiting the corrosion of acid (particularly hydrofluoric acid), the electrolyte can form the protection film with the function of inhibiting the corrosion of acid on the surface of the positive electrode and the negative electrode and can resist the corrosion of HF, so that the stability of an SEI film and the stability of a negative electrode can be obviously improved, the rupture of the SEI film of the battery and the loss of the negative electrode under the high-temperature condition can be reduced, the content of HF by-product can be reduced, the stability of the positive electrode can be further improved, and the high-temperature performance of the battery can be obviously improved.
The application aims at realizing the following technical scheme:
an electrolyte comprising an organic solvent, an electrolyte salt and a functional additive, wherein the functional additive comprises an additive A selected from diaryl naphtho acid anhydride compounds.
According to the electrolyte provided by the application, the diaryl naphthoanhydride compound is selected from at least one of compounds shown in the formula (1) and/or at least one of compounds shown in the formula (2):
in the formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-10 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-10 Alkyl, -C (=o) -C 1-10 Alkyl, -C (=o) -O-C (=o) -C 1-10 Alkyl, C 6-14 Aryl, 5-14 membered heteroaryl;
n1 is an integer between 0 and 6, and when n1 is 1 to 5, the substitution is carried out on any 1 to 5 sites of the naphthalene ring;
in the formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-10 An alkyl group; each R is b The same or different, independently of one another, are selected from halogen, C 1-10 Alkyl, -C (=o) -C 1-10 Alkyl, -C (=o) -O-C (=o) -C 1-10 Alkyl, C 6-14 Aryl, 5-14 membered heteroaryl;
n2 is an integer between 0 and 6, and when n2 is 1 to 5, the substitution is at any 1 to 5 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-6 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-6 An alkyl group; n1 is an integer between 0 and 4, and when n1 is 1 to 4, the substitution is at any 1 to 4 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-6 An alkyl group; each R is b The same or different, independently of one another, are selected from halogen, C 1-6 An alkyl group; n2 is an integer between 0 and 4, and when n2 is 1 to 4, the substitution is at any 1 to 4 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-3 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-3 An alkyl group; n1 is an integer between 0 and 2, and when n1 is 1 to 2, the substitution is at any 1 to 2 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-3 An alkyl group; each R is b The same or different, independently of one another, are selected from halogen, C 1-3 An alkyl group; n2 is an integer between 0 and 2, and when n2 is 1 to 2, the substitution is at any 1 to 2 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (1), n1 is 0, 1,2, 3, 4, 5 or 6.
According to the electrolyte of the present application, in formula (2), n2 is 0, 1,2, 3, 4, 5 or 6.
According to the electrolyte of the present application, the additive A may be prepared by methods known in the art or may be commercially available.
According to the electrolyte of the present application, the additive a is selected from at least one of compounds represented by the formulas (3) to (10):
according to the electrolyte of the present application, the additive A is contained in an amount of 0.1 to 5.0wt%, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt%, 3.8wt%, 4wt%, 4.2wt%, 4.5wt%, 4.8wt% or 5wt% based on the total mass of the electrolyte.
The electrolyte according to the application further comprises an additive B selected from fluoroethylene carbonate.
According to the electrolyte of the application, the additive B is present in an amount of 2-30 wt.%, for example 2 wt.%, 5 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.%, 21 wt.%, 22 wt.%, 23 wt.%, 24 wt.%, 25 wt.%, 26 wt.%, 27 wt.%, 28 wt.%, 29 wt.% or 30 wt.% of the total mass of the electrolyte.
According to the electrolyte of the present application, the electrolyte salt is selected from lithium salts.
According to the electrolyte of the present application, the lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorophosphate (LiPO) 2 F 2 ) One or more of lithium difluorooxalato borate (LiDFOB), lithium difluorosulfimide (LiTFSI), lithium bistrifluoromethylsulfonyl imide, lithium difluorobisoxalato phosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methyl or lithium bis (trifluoromethylsulfonyl) imide.
According to the electrolyte of the present application, the electrolyte salt is contained in an amount of 11-18wt%, for example 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt% or 18wt% based on the total mass of the electrolyte.
According to the electrolyte of the application, the organic solvent is selected from carbonates and/or carboxylic acid esters, and the carbonates are selected from one or more of the following solvents which are fluoro or unsubstituted: ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), ethylmethyl carbonate; the carboxylic acid ester is selected from one or more of the following solvents which are fluoro or unsubstituted: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, propyl Propionate (PP), ethyl Propionate (EP), methyl butyrate, ethyl n-butyrate.
According to the electrolyte of the application, the functional additive further comprises an additive C, wherein the additive C is at least one of the following compounds: 1, 3-propane sultone, 1, 3-propenesulfonic acid lactone, succinonitrile, adiponitrile, glycerotrigonitrile, 1,3, 6-hexanetrinitrile, lithium difluorooxalato borate, lithium difluorophosphate, lithium difluorodioxato phosphate.
According to the electrolyte of the application, the additive C is present in an amount of 0-10 wt.%, for example 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.% or 10 wt.% of the total mass of the electrolyte.
According to the electrolyte of the application, the electrolyte is suitable for high-voltage batteries.
According to the electrolyte disclosed by the application, the electrolyte is suitable for a lithium cobalt oxide battery.
The electrolyte is suitable for a battery with a silicon-based negative electrode.
The application also provides a battery, which comprises the electrolyte.
According to the battery provided by the application, the battery is a lithium ion battery.
The battery also comprises a positive plate containing positive electrode active materials, a negative plate containing negative electrode active materials and a separation film.
According to the battery of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both side surfaces of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder.
According to the battery of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both side surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
According to the battery provided by the application, the positive electrode active material layer comprises the following components in percentage by mass: 80-99.8wt% of positive electrode active material, 0.1-10wt% of conductive agent, and 0.1-10wt% of binder.
Preferably, the positive electrode active material layer comprises the following components in percentage by mass: 90-99.6wt% of positive electrode active material, 0.2-5wt% of conductive agent, and 0.2-5wt% of binder.
According to the battery, the mass percentage of each component in the anode active material layer is as follows: 80-99.8wt% of negative electrode active material, 0.1-10wt% of conductive agent, and 0.1-10wt% of binder.
Preferably, the mass percentage of each component in the anode active material layer is as follows: 90-99.6wt% of negative electrode active material, 0.2-5wt% of conductive agent, and 0.2-5wt% of binder.
According to the battery of the application, the conductive agent is at least one selected from conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube and metal powder.
According to the battery, the binder is at least one selected from sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.
According to the battery of the present application, the anode active material includes a carbon-based anode material and/or a silicon-based anode material.
According to the battery of the application, the silicon-based negative electrode material is selected from nano silicon, silicon oxygen negative electrode material (SiO x (0<x<2) At least one of a silicon carbon anode material).
According to the battery provided by the application, the carbon-based negative electrode material is at least one selected from artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon and soft carbon.
According to the battery, the mass ratio of the silicon-based anode material to the carbon-based anode material in the anode active material is 10:0-1:19, such as 1:19, 1:18, 1:17, 1:16, 1:15, 1:14, 1:13, 1:12, 1:11, 1:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 or 10:0.
According to the battery, the positive electrode active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate and lithium manganate; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O 2 Wherein, -0.1 is less than or equal to x is less than or equal to 1; y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y+z is more than or equal to 0 and less than or equal to 1; wherein M is one or more of Mg, zn, ga, ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr.
Definition and description of terms
Wherein "more" means three or more.
The term "halogen" refers to F, cl, br and I. In other words, F, cl, br, and I may be described as "halogen" in the present specification.
The term "C 1-10 Alkyl "is understood to mean preferably a straight-chain or branched saturated monovalent hydrocarbon radical having from 1 to 10 carbon atoms. Specifically, "C 1-10 Alkyl "is understood to mean preferably a straight-chain or branched saturated monovalent hydrocarbon radical having 1,2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-ethylpropyl, 1, 2-dimethylpropyl, neopentyl, 1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3-dimethylbutyl, 2-dimethylbutyl, 1-dimethylbutyl, 2, 3-dimethylbutyl, 1, 3-dimethylbutyl, or 1, 2-dimethylbutyl, or the like, or an isomer thereof. In particular, the radicals have 1,2, 3, 4, 5, 6 carbon atoms ("C 1-6 Alkyl "), such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, more particularly the radicals having 1,2 orOf 3 carbon atoms (' C) 1-3 Alkyl "), such as methyl, ethyl, n-propyl or isopropyl.
The term "C 6-14 Aryl "is understood to mean preferably a mono-, bi-or tricyclic hydrocarbon ring of monovalent aromatic or partly aromatic nature having 6 to 14 carbon atoms. The term "C 6-14 Aryl "is understood to mean preferably a mono-, bi-or tricyclic hydrocarbon ring (" C ") having a monovalent aromatic or partially aromatic character of 6, 7, 8, 9, 10, 11, 12, 13 or 14 carbon atoms 6-14 Aryl), in particular a ring having 6 carbon atoms ("C) 6 Aryl "), such as phenyl; or biphenyl, or a ring having 9 carbon atoms ("C 9 Aryl "), e.g. indanyl or indenyl, or a ring having 10 carbon atoms (" C 10 Aryl "), such as tetralin, dihydronaphthyl or naphthyl, or a ring having 13 carbon atoms (" C " 13 Aryl "), e.g. fluorenyl, or a ring having 14 carbon atoms (" C) 14 Aryl "), such as anthracenyl.
The term "5-14 membered heteroaryl" is understood to include such monovalent monocyclic, bicyclic or tricyclic aromatic ring systems: having 5 to 14 ring atoms and containing 1 to 4 heteroatoms independently selected from N, O and S. The term "5-14 membered heteroaryl" is understood to include such monovalent monocyclic, bicyclic or tricyclic aromatic ring systems: it has 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and it contains 1 to 5, preferably 1 to 3 heteroatoms each independently selected from N, O and S and, in addition, can be benzo-fused in each case. In particular, the heteroaryl group is selected from thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl and the like and their benzo derivatives, such as benzofuryl, benzothienyl, benzoxazolyl, benzisoxazolyl, benzimidazolyl, benzotriazole, indazolyl, indolyl, isoindolyl and the like; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, and the like, and their benzo derivatives, such as quinolinyl, quinazolinyl, isoquinolinyl, and the like; or an axcinyl group, an indolizinyl group, a purinyl group, etc., and their benzo derivatives; or cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pteridinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, and the like.
The application has the beneficial effects that:
the application provides an electrolyte and a battery comprising the electrolyte, wherein an SEI film of a polymer skeleton containing naphthyl with anhydride functional groups is formed on the surface of a positive electrode and a negative electrode after charge and discharge, the naphthyl has the property of being easy to polymerize into a film, the formed film has better two-dimensional property so as to have better protectiveness, in addition, the anhydride functional groups on the protective film have the capability of inhibiting HF corrosion, so that the SEI film has an excellent function of inhibiting acid corrosion, further, a negative electrode active material can better adapt to the HF corrosion formed by FEC under the high temperature condition, the effect of improving the cycle performance of the battery is achieved, and meanwhile, the formed SEI film with the function of inhibiting acid corrosion can also reduce the content of byproduct HF, thereby improving the stability of the positive electrode and obviously improving the high temperature performance of the battery.
Detailed Description
The present application will be described in further detail with reference to specific examples. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the application. All techniques implemented based on the above description of the application are intended to be included within the scope of the application.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described in the following in conjunction with the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It is understood that the battery of the present application includes a negative electrode sheet, an electrolyte, a positive electrode sheet, a separator, and an exterior package. And stacking the positive plate, the isolating film and the negative plate to obtain a battery cell, or winding the positive plate, the isolating film and the negative plate to obtain the battery cell, placing the battery cell in an outer package, and injecting electrolyte into the outer package to obtain the battery.
Examples 1 to 9 and comparative examples 1 to 2
The batteries of examples 1 to 9 and comparative examples 1 to 2 were prepared by the following steps:
1) Preparation of positive plate
Lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) Mixing polyvinylidene fluoride (PVDF), SP (super P) and Carbon Nano Tube (CNT) according to the mass ratio of 96:2:1.5:0.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until the mixed system becomes anode active slurry with uniform fluidity; uniformly coating anode active slurry on two surfaces of an aluminum foil; and drying the coated aluminum foil, and then rolling and slitting to obtain the required positive plate.
2) Preparation of negative plate
Mixing negative electrode active materials of artificial graphite, silicon oxide, sodium carboxymethylcellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to the mass ratio of 79.5:15:2.5:1.5:1:0.5, adding deionized water, and obtaining negative electrode active slurry under the action of a vacuum stirrer; uniformly coating the anode active slurry on two surfaces of a copper foil; and (3) airing the coated copper foil at room temperature, transferring to an 80 ℃ oven for drying for 10 hours, and then carrying out cold pressing and slitting to obtain the negative plate.
3) Preparation of electrolyte
In a glove box filled with argon (H 2 O<0.1ppm，O 2 <0.1 ppm), EC/PC/DEC/PP was uniformly mixed in a mass ratio of 10/20/40/30, and then 1mol/L of sufficiently dried lithium hexafluorophosphate (LiPF) was rapidly added thereto 6 ) After dissolutionAdding 12wt% of fluoroethylene carbonate, 2wt% of 1, 3-propane sultone, 2wt% of 1,3, 6-hexanetrinitrile and a compound shown in formula (3) or a compound shown in formula (8) (the specific dosage is shown in table 1) based on the total mass of the electrolyte, stirring uniformly, and obtaining the required electrolyte after passing the detection of moisture and free acid.
4) Preparation of a Battery
Laminating the positive plate in the step 1), the negative plate in the step 2) and the isolating film according to the sequence of the positive plate, the isolating film and the negative plate, and then winding to obtain the battery cell; and (3) placing the battery cell in an outer packaging aluminum foil, injecting the electrolyte in the step (3) into the outer packaging, and performing the procedures of vacuum packaging, standing, formation, shaping, sorting and the like to obtain the battery. The charge and discharge range of the battery is 3.0-4.45V.
The batteries obtained in examples and comparative examples were subjected to a 60 ℃ high temperature storage performance test and a 45 ℃ cycle performance test, respectively, and the test results are shown in table 2.
1) 60 ℃ high-temperature storage performance test
The batteries of table 1 were charged to a cut-off voltage at 25 ℃ at a rate of 1C, a cut-off current of 0.025C, and left standing for 5 minutes, and the thickness of the lithium ion battery (this was taken as the thickness before storage) was measured. The fully charged battery is left open circuit for 35 days under the condition of (60+/-2) DEG C, and is left open circuit for 2 hours under the condition of room temperature after being stored for 35 days, the thickness after being stored is measured, and the thickness expansion rate of the lithium ion battery is calculated:
thickness expansion ratio = [ (thickness after storage-thickness before storage)/thickness before storage ] ×100%
2) 45 ℃ cycle performance test
The batteries in table 1 were subjected to charge-discharge cycles at 45 ℃ in a charge-discharge cut-off voltage range at a rate of 1C, and the discharge capacity at the 1 st week was measured as x1 mAh and the discharge capacity at the nth week was measured as y1 mAh; the capacity at week N was divided by the capacity at week 1 to obtain a cycle capacity retention rate r1=y1/x 1 at week N, and the number of cycles of the battery was recorded when the cycle capacity retention rate R1 was 80%.
Table 1 composition of electrolyte additives in the batteries of examples and comparative examples
Table 2 results of performance test of the batteries of examples and comparative examples
As can be seen from table 2, comparative example 1, to which no additive a that can form an acid-inhibiting SEI film was added, had a significantly larger storage thickness expansion ratio at 60 ℃ than that of the battery to which additive a was added, and the higher the content of additive a, the lower the thickness expansion ratio, but when the addition amount was more than 4%, further increase in the content of additive a had a smaller effect on the thickness expansion ratio.
As can be seen from table 2, comparative example 1, to which no additive a capable of forming an acid-inhibiting SEI film was added, had significantly less number of cycles at 45 ℃ than examples 1 to 7, to which an appropriate amount of additive a capable of forming an acid-inhibiting SEI film was added, demonstrating that additive a capable of forming an acid-inhibiting SEI film had a significant improvement effect on the cycle performance of a silicon-containing negative electrode.
Further, it can be seen from examples 1 to 4 that, as the amount of additive a capable of forming an acid suppression SEI film increases, the improvement of high temperature cycle performance thereof becomes stronger and then weaker, and thus it can be demonstrated that the addition of an appropriate amount of additive a capable of forming an acid suppression SEI film contributes to the improvement of battery cycle performance, but when it is excessively added, side effects such as an increase in impedance due to additive a become more remarkable, and further the performance of the battery is deteriorated.
As can be seen from examples 5 to 6, the compounds of formula (3) and formula (8) both have the same effect of improving the high-temperature storage property and the high-temperature cycle property, and the effect of improving the compound of formula (8) is slightly weaker than that of the compound of formula (3), probably because the acid anhydride group of the compound of unit formula (8) is located in a position relatively poor in the polymerization film-forming effect of the compound (3).
As can be seen from example 7, the compounds represented by formula (3) and formula (8) can be combined to improve the high temperature storage performance and the high temperature cycle performance of the battery.
It can be seen from examples 8 to 9 that the addition of an excessive amount of additive a capable of forming an acid-inhibiting SEI film no longer has an improvement effect on the high-temperature cycle performance of a battery, but rather deteriorates the cycle performance of a battery, because the formed acid-inhibiting SEI film has poor conductivity and excessive resistance, and is disadvantageous in terms of improvement of the cycle performance of a battery.
It can be seen from comparative example 2 and examples 1 to 7 that when phthalic anhydride is selected as an additive, the effect of improving the high-temperature storage property and the high-temperature cycle property of the battery is remarkably inferior to that of the addition amount of naphthalene anhydride, mainly because naphthalene group has a property of easily polymerizing into a film as compared with phenyl group, and the formed film has a better two-dimensional property and thus better protectiveness, but phenyl group cannot achieve the effect.
Example 10
Other operations are the same as in example 3, except that the composition of the electrolyte is:
in a glove box filled with argon (H 2 O<0.1ppm，O 2 <0.1 ppm), EC/PC/DEC/PP was uniformly mixed in a mass ratio of 10/20/40/30, and then 1mol/L of sufficiently dried lithium hexafluorophosphate (LiPF) was rapidly added thereto 6 ) After dissolution, 20wt% of fluoroethylene carbonate, 2wt% of 1, 3-propane sultone, 2wt% of 1,3, 6-hexane tri-nitrile and 2wt% of a compound shown in formula (3) are added, and the required electrolyte is obtained after water and free acid are detected to be qualified.
The battery of example 10 was subjected to performance using the method described above, and the test results were: the thickness expansion rate of the battery is 6.53% after the battery is stored at 60 ℃ for 35 days; the number of cycles at 45℃with a cycle capacity retention of 80% was 613 cycles.
Comparative example 3
Other operations are the same as example 10, except that the composition of the electrolyte is:
in a glove box filled with argon (H 2 O<0.1ppm，O 2 <0.1 ppm), EC/PC/DEC/PP in a mass ratio of 10/20/40/30Uniformly mixed, then 1mol/L of sufficiently dried lithium hexafluorophosphate (LiPF) was rapidly added thereto 6 ) After dissolution, 20wt% of fluoroethylene carbonate, 2wt% of 1, 3-propane sultone and 2wt% of 1,3, 6-hexane tri-nitrile are added, and the required electrolyte is obtained after water and free acid are detected to be qualified.
The battery of comparative example 3 was subjected to performance by the above method, and the test results were: the thickness expansion rate of the battery is 15.31% after being stored at 60 ℃ for 35 days; the number of cycles at 45℃with a cycle capacity retention of 80% was 431 cycles.
It can be seen that the electrolyte of the present application is also suitable for use in high FEC content electrolytes.
In summary, the electrolyte added with the additive A can form the SEI film of a polymer skeleton containing naphthyl with anhydride functional groups on the surface of a silicon-containing negative electrode after charge and discharge, the naphthyl has the property of being easy to polymerize into a film, the formed film has better two-dimensional property and better protectiveness, the SEI film has a large number of acid inhibiting functional groups, namely, the acid inhibiting SEI film is formed, and the formation of the acid inhibiting SEI film can delay the rupture of the SEI film under the etching of HF (HF is easy to form under the condition of high temperature of FEC), so that the electrolyte can better protect the negative electrode material in the charge and discharge process, and meanwhile, the content of byproducts HF can be reduced, thereby improving the stability of a positive electrode and remarkably improving the high temperature performance of a battery.
The embodiments of the present application have been described above. However, the present application is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (10)

1. An electrolyte, characterized in that the electrolyte comprises an organic solvent, electrolyte salt and a functional additive, wherein the functional additive comprises an additive A, and the additive A is selected from diaryl naphtho acid anhydride compounds.
2. The electrolyte according to claim 1, wherein the diaryl naphthoanhydride compound is selected from at least one of compounds represented by formula (1) and/or at least one of compounds represented by formula (2):
in the formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-10 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-10 Alkyl, -C (=o) -C 1-10 Alkyl, -C (=o) -O-C (=o) -C 1-10 Alkyl, C 6-14 Aryl, 5-14 membered heteroaryl;
n1 is an integer between 0 and 6, and when n1 is 1 to 5, the substitution is carried out on any 1 to 5 sites of the naphthalene ring;
in the formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-10 An alkyl group; each R is b The same or different, independently of one another, are selected from halogen, C 1-10 Alkyl, -C (=o) -C 1-10 Alkyl, -C (=o) -O-C (=o) -C 1-10 Alkyl, C 6-14 Aryl, 5-14 membered heteroaryl;
n2 is an integer between 0 and 6, and when n2 is 1 to 5, the substitution is at any 1 to 5 positions of the naphthalene ring.
3. The electrolyte according to claim 2, wherein in formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-6 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-6 An alkyl group; n1 is an integer between 0 and 4, and when n1 is 1 to 4, the substitution is at any 1 to 4 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-6 An alkyl group; each R is b Identical or different, independently of one another, from halogenElement, C 1-6 An alkyl group; n2 is an integer between 0 and 4, and when n2 is 1 to 4, the substitution is at any 1 to 4 positions of the naphthalene ring.
4. The electrolyte according to claim 3, wherein in formula (1), R 1 Selected from unsubstituted or optionally substituted by one, two or more R a Substituted C 1-3 An alkyl group; each R is a The same or different, independently of one another, are selected from halogen, C 1-3 An alkyl group; n1 is an integer between 0 and 2, and when n1 is 1 to 2, the substitution is at any 1 to 2 positions of the naphthalene ring.
According to the electrolyte of the present application, in formula (2), R 2 Selected from unsubstituted or optionally substituted by one, two or more R b Substituted C 1-3 An alkyl group; each R is b The same or different, independently of one another, are selected from halogen, C 1-3 An alkyl group; n2 is an integer between 0 and 2, and when n2 is 1 to 2, the substitution is at any 1 to 2 positions of the naphthalene ring.
5. The electrolyte according to claim 4, wherein the additive a is selected from at least one of compounds represented by the formulas (3) to (10):
6. the electrolyte according to any one of claims 1 to 5, wherein the content of the additive a is 0.1 to 5.0wt% of the total mass of the electrolyte.
7. The electrolyte of any one of claims 1-5 wherein the functional additive further comprises additive B, the additive B selected from fluoroethylene carbonate;
and/or the content of the additive B is 10-30wt% of the total mass of the electrolyte.
8. The electrolyte according to any one of claims 1 to 5, wherein the functional additive further comprises an additive C selected from at least one of the following compounds: 1, 3-propane sultone, 1, 3-propenesulfonic acid lactone, succinonitrile, adiponitrile, glycerotrigonitrile, 1,3, 6-hexanetrinitrile, lithium difluorooxalato borate, lithium difluorophosphate, lithium difluorodioxato phosphate;
and/or the content of the additive C is 0-10wt% of the total mass of the electrolyte.
9. The electrolyte according to any one of claims 1 to 5, wherein the electrolyte is suitable for use in a lithium cobalt oxide battery;
and/or the electrolyte is suitable for a battery with a silicon-based negative electrode.
10. A battery comprising the electrolyte of any one of claims 1-9.
CN202210519601.8A 2022-05-12 2022-05-12 Electrolyte and battery comprising same Pending CN117096433A (en)

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