CN110649318A - Electrolyte, preparation method thereof and lithium ion battery - Google Patents

Electrolyte, preparation method thereof and lithium ion battery Download PDF

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CN110649318A
CN110649318A CN201911035700.3A CN201911035700A CN110649318A CN 110649318 A CN110649318 A CN 110649318A CN 201911035700 A CN201911035700 A CN 201911035700A CN 110649318 A CN110649318 A CN 110649318A
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electrolyte
anhydride
lithium
additive
ion battery
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CN110649318B (en
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曾长安
王龙
李素丽
徐延铭
李俊义
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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
    • H01M10/058—Construction or manufacture
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The invention provides an electrolyte, a preparation method thereof and a lithium ion battery, wherein the electrolyte comprises lithium salt, a solvent, a nitrile additive shown in a formula 1 and an anhydride additive, wherein in the formula 1, R1、R2、R3、R4、R5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1‑6Alkyl and C1‑6Alkoxy, n is more than or equal to 1 and less than or equal to 5 and is an integer; r is C or Si. The electrolyte is used in the lithium ion battery, and the cycle performance and the high-temperature storage performance of the lithium ion battery can be improved under high voltage.

Description

Electrolyte, preparation method thereof and lithium ion battery
Technical Field
The invention relates to an electrolyte, a preparation method thereof and a lithium ion battery, and belongs to the technical field of lithium ion batteries.
Background
Since commercialization, lithium ion batteries have been widely used in the fields of digital, energy storage, power, military aerospace, communication equipment, etc. due to their advantages of portability, high specific energy, no memory effect, good cycle performance, etc. With the wide application of lithium ion batteries, consumers also put higher demands on the energy density, the cycle performance, the storage performance, the safety performance and the like of the lithium ion batteries.
Ways to increase the energy density of a lithium ion battery may include: the method has the advantages of improving the charging voltage of the battery, adopting the anode with higher charging voltage, adopting the process to improve the voltage of the existing battery or adopting a high-capacity high-nickel anode or a lithium-rich anode material, reducing the thickness of other main materials such as copper foil, aluminum foil, diaphragm and the like, improving the main content and compacted surface density of the anode and cathode main materials and the like.
However, the high-voltage or high-capacity high-nickel positive electrode or lithium-rich positive electrode material causes instability of the surface of the positive electrode, so that transition metal ions in a high oxidation state in the positive electrode are easy to dissolve out, the high-nickel positive electrode has the problems of oxygen evolution, particle breakage and the like, and the dissolved transition metal ions can damage an SEI film of the negative electrode when migrating to the negative electrode, so that the performances of the lithium ion battery such as cycle and storage are negatively affected.
The electrolyte is an important factor for improving the performance of the lithium ion battery, and the electrolyte additive is a key component of the electrolyte, so that the electrolyte with better performance is obtained by the combination optimization of the electrolyte solvent, the additive and the lithium salt so as to improve the cycle performance, the storage performance and the like of the lithium ion battery, and the method has important significance for the application of the lithium ion battery.
Disclosure of Invention
The invention provides an electrolyte which is simple in composition, and can be used in a lithium ion battery to improve the cycle performance and the high-temperature storage performance of the lithium ion battery under high voltage.
The invention also provides a preparation method of the electrolyte, which is simple and easy to operate and is beneficial to safely and efficiently preparing the electrolyte capable of improving the cycle performance and the high-temperature storage performance of the lithium ion battery under high voltage.
The invention provides an electrolyte, which comprises lithium salt, a solvent, a nitrile additive shown in a formula 1 and an anhydride additive,
Figure BDA0002251432510000021
in the formula 1, R1、R2、R3、R4、R5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-6Alkyl and C1-6Alkoxy, n is more than or equal to 1 and less than or equal to 5 and is an integer; r is C or Si.
The electrolyte solution as described above, wherein the acid anhydride additive is one or more selected from maleic anhydride, 2, 3-dimethylmaleic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, phthalic anhydride, citraconic anhydride, citric anhydride, fluoromaleic anhydride, 2, 3-dimethylfluoromaleic anhydride, fluorosuccinic anhydride, fluoroglutaric anhydride, fluoroadipic anhydride, fluoropimelic anhydride, fluorophthalic anhydride, fluorocitraconic anhydride, and fluorocitric anhydride.
The electrolyte solution as described above, wherein R is1、R2、R3、R4And R5Each independently selected from hydrogen, halogen, methyl, ethyl, trimethylsiloxy, trifluoromethyl;
the electrolyte solution as described above, wherein the nitrile additive is selected from compounds having the following structures,
Figure BDA0002251432510000022
Figure BDA0002251432510000031
the electrolyte solution as described above, wherein the nitrile additive is present in the electrolyte solution in an amount of 0.1% to 10% by mass.
The electrolyte solution as described above, wherein the nitrile additive is present in the electrolyte solution in an amount of 1% to 7% by mass.
The electrolyte solution as described above, wherein the acid anhydride additive is present in the electrolyte solution in an amount of 0.1 to 5% by mass.
The electrolyte as described above, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), lithium difluoro (LiPO) phosphate2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2)、LiN(SO2C2F5)2Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more of (a).
The invention also provides a preparation method of any one of the above electrolytes, which comprises the following steps:
and mixing a solvent, a lithium salt, the nitrile additive shown in the formula 1 and an anhydride additive in an inert atmosphere to obtain the electrolyte.
The invention also provides a lithium ion battery, and the electrolyte of the lithium ion battery is any one of the above electrolytes.
The implementation of the invention has at least the following advantages:
1. according to the electrolyte provided by the invention, by adding the specific additive, the dissolution of transition metals in the positive active material under high voltage can be inhibited, and a stable SEI film can be formed on the surface of the negative electrode, so that the damage to the electrode material possibly caused can be avoided, and the cycle performance and the high-temperature storage performance of the lithium ion battery can be improved;
2. the preparation method of the electrolyte provided by the invention has the advantages of simple process, strong operability and convenience for practical popularization and large-scale application;
3. the lithium ion battery provided by the invention comprises the electrolyte, so that the lithium ion battery has better cycle performance and high-temperature storage performance under high voltage.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an electrolyte, which comprises lithium salt, solvent, nitrile additive shown in formula 1 and anhydride additive,
Figure BDA0002251432510000041
in the formula 1, R1、R2、R3、R4、R5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-6Alkyl and C1-6Alkoxy, n is more than or equal to 1 and less than or equal to 5 and is an integer; r is C or Si.
Specifically, when R is1、R2、R3、R4、R5When each is independently selected from halogen, the halogen is preferably a fluorine atom; when R is1、R2、R3、R4、R5Each independently selected from substituted C1-6Alkyl and C1-6When alkoxy, the substituent may be C1-6Alkyl and C1-6Alkoxy radical and R1、R2、R3、R4、R5The substituents may be different from each other.
Wherein halogen means F, Cl, Br and I; c1-6Alkyl is understood to preferably mean a straight-chain or branched, saturated monovalent hydrocarbon radical having from 1 to 6 carbon atoms, preferably C1-5An alkyl group. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexylIsopropyl, 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, and the like, or isomers thereof.
According to the technical scheme provided by the invention, the combination of the nitrile additive and the anhydride additive shown in the formula 1 is added into the electrolyte, so that the lithium ion battery has excellent normal-temperature and high-temperature cycle performance and high-temperature storage performance even under high voltage.
The inventors have analyzed based on this phenomenon and considered that it is possible to: the nitrile additive can be well complexed with transition metal ions of the anode material, inhibit the dissolution of the transition metal ions, stabilize the surface of the anode and avoid side reactions between the transition metal ions in a high oxidation state and electrolyte under high voltage, so that the cycle performance and the high-temperature storage performance of the lithium ion battery can be improved; in addition, the anhydride additive has high film forming potential, and can form a compact SEI film on the negative electrode to stabilize the negative electrode, so that the anhydride additive and the nitrile additive cooperate with each other to further optimize the cycle performance and the high-temperature storage performance of the lithium ion battery.
Specifically, the acid anhydride additive of the present invention may be one or more selected from maleic anhydride, 2, 3-dimethylmaleic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, phthalic anhydride, citraconic anhydride, citric anhydride, fluoromaleic anhydride, 2, 3-dimethylfluoromaleic anhydride, fluorosuccinic anhydride, fluoroglutaric anhydride, fluoroadipic anhydride, fluoropimelic anhydride, fluorophthalic anhydride, fluorocitraconic anhydride, and fluorocitric anhydride.
Further, R in nitrile additives1、R2、R3、R4And R5Each independently selected from hydrogen, halogen, methyl, ethyl, trimethylsiloxy, trifluoromethyl.
In particular embodiments, the additive of the present invention may be selected from at least one compound represented by formula a1 to formula a 10:
Figure BDA0002251432510000051
the nitrile additives of formula 1 of the present invention may be obtained by commercial or any feasible method of preparation.
In the implementation process of the invention, the mass content of the nitrile additive in the electrolyte is generally controlled to be more than 0.01%. The additive adding amount in the nitrile electrolyte is reasonably controlled, which is beneficial to further improving the performance of the lithium ion battery, so that the mass fraction of the nitrile additive in the electrolyte can be controlled to be 0.1-10%. The inventor researches and discovers that as the dosage of the nitrile additive is increased within a certain range, the cycle performance and the high-temperature storage performance of the lithium ion battery tend to increase, and then the low-temperature discharge performance and the capacity retention rate slightly decrease, so that the mass content of the nitrile additive in the electrolyte is generally controlled to be 1-7% in consideration of balancing the various performances of the lithium ion battery. The content of the nitrile additive in the specific electrolyte can be further determined according to lithium salt, a solvent, a positive electrode material, a negative electrode material and a diaphragm adopted by the lithium ion battery, so that different lithium ion batteries have excellent cycle performance and high-temperature storage performance under high pressure.
In addition, in order to achieve better synergistic effect with the nitrile additive shown in the formula 1, the mass content of the acid anhydride additive in the electrolyte is 0.1-5%.
Furthermore, the solvent in the electrolyte of the present invention may be: carbonate and/or carboxylate compounds, wherein the carbonate is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; the carboxylic acid ester is selected from one or more of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, ethyl propionate, n-propyl propionate, methyl butyrate, ethyl n-butyrate or fluoro solvents of the above solvents.
The lithium salt of the present invention is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), lithium difluoro (LiPO) phosphate2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2)、LiN(SO2C2F5)2Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more of (a).
The mass fractions of the lithium salt and the solvent in the electrolyte are not particularly limited, and can be limited according to the mass fractions of the lithium salt and the solvent in the electrolyte commonly used by the lithium ion battery at present, or further reasonably determined according to factors such as a positive electrode material, a negative electrode material and a diaphragm in the lithium ion battery. In the specific implementation process of the invention, the nitrile additive and the anhydride additive are as described above, the mass fraction of the lithium salt in the electrolyte is generally controlled to be 8-18%, and the balance is the solvent.
The invention also provides a preparation method of any one of the lithium ion batteries, which comprises the following steps: and mixing a solvent, a lithium salt, the nitrile additive shown in the formula 1 and an anhydride additive in an inert atmosphere to obtain the electrolyte.
In particular, it can be carried out in an argon-filled glove box (moisture < 10ppm, oxygen < 1 ppm).
In the preparation process, lithium salt, nitrile additive and anhydride additive can be added into the solvent, and the electrolyte of the invention is obtained after stirring. Specifically, the lithium salt is added to the solvent, and then the additive is added, wherein the order of adding the nitrile additive and the acid anhydride additive is not limited in the present invention.
The preparation method of the electrolyte is simple and convenient to operate, and can be completed only by mixing and stirring the raw materials, so that the preparation of the electrolyte can be completed with high efficiency and low cost.
The invention also provides a lithium ion battery, and the electrolyte of the lithium ion battery is any one of the above electrolytes.
The working voltage of the lithium ion battery is 4.2V or more.
The lithium ion battery of the present invention may further include a positive electrode, a negative electrode, and a separator in addition to the electrolyte solution.
In the lithium ion battery of the present invention, the positive electrode specifically includes a positive electrode current collector layer and a positive electrode sheet formed of a positive electrode active material provided on the surface of the positive electrode current collector layer. Wherein the positive active substance is one or more of layered lithium composite oxide, lithium manganate and lithium cobaltate mixed ternary material, and the general formula of the layered lithium composite oxide is Li1+xNiyCozM(1-y-z)Y2Wherein x is more than or equal to-0.1 and 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 and Zr, and Y is one or more of O, F, P.
Specifically, when the positive electrode is prepared, at least one positive electrode active material, a conductive agent (such as acetylene black) and a binder (such as polyvinyl fluoride PVDF) can be dispersed in a proper amount of N-methyl pyrrolidone (NMP) solvent, and stirred under the action of a vacuum stirrer until a positive electrode slurry with uniform fluidity is formed; and uniformly coating the anode slurry on an anode current collector layer (such as an aluminum foil with the thickness of 10-13 mu m), baking the anode current collector layer by 5 sections of baking ovens with different temperature gradients, drying the anode current collector layer for 9 hours by an oven at 120 ℃, and rolling and slitting the anode current collector layer to obtain the anode.
In the lithium ion battery, the negative electrode specifically comprises a negative current collector layer and a negative plate which is arranged on the surface of the negative current collector layer and is formed by a negative active material. The negative active material is selected from one or more of carbon material, silicon-based material, tin-based material or their corresponding alloy materials.
Specifically, when the negative electrode is prepared, the negative electrode active material, the conductive agent, the binder (such as styrene butadiene rubber) and the thickening agent (such as sodium carboxymethylcellulose (CMC-Na)) can be dispersed in a proper amount of deionized water to form uniform negative electrode slurry under the action of a vacuum stirrer; and uniformly coating the negative electrode slurry on a negative electrode current collector layer (such as a copper foil with the thickness of 6-9 μm), drying at room temperature, drying (drying in an oven at 75-100 ℃ for 6-12h), cold pressing and slitting to obtain the negative electrode.
The material selection of the separator is not strictly limited, and the separator can be a separator material commonly used in the current lithium ion battery, such as one of a polypropylene separator (PP), a polyethylene separator (PE) and a polyvinylidene fluoride separator.
When a lithium ion battery is prepared, an anode, a diaphragm and a cathode are sequentially stacked, the diaphragm is positioned between the anode and the cathode to play a role in isolation, then the bare cell is obtained by winding, the bare cell is placed in an outer packaging shell, and after drying, the electrolyte of the invention is injected. The preparation of the lithium ion battery is completed through the working procedures of vacuum packaging, standing, formation, shaping, sorting and the like.
The lithium ion battery provided by the invention still has excellent cycle performance and high-temperature storage performance under high voltage due to the electrolyte.
Hereinafter, the electrolyte, the preparation method thereof and the lithium ion battery according to the present invention will be described in detail by specific examples.
Unless otherwise specified, the chemical materials and instruments used in the following examples and comparative examples are all conventional chemical materials and conventional instruments, and are commercially available. Wherein, A2 and A8 adopted in the examples are purchased from Beijing Bailingwei science and technology Limited, and A3 and A5 are purchased from Shenzhen Erikou chemical Limited.
Example 1
The electrolyte of the present example was prepared as follows (all mass fractions below are based on the mass of the electrolyte):
in a glove box filled with argon and with qualified water oxygen content, uniformly mixing ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate according to the mass ratio of 15:15:20:50 (the solvent, the following lithium salt and additives need to be normalized), and then quickly adding 14.5 wt% of fully dried lithium hexafluorophosphate (LiPF)6)，The resulting solution was dissolved in an organic solvent, and 1% of A2 and 0.2% of citraconic anhydride were added thereto and uniformly stirred to obtain an electrolyte solution of example 1.
The electrolyte of example 1 was assembled with a lithium cobaltate positive electrode, a polyethylene separator (asahi chemical company) and a graphite negative electrode to form a lithium ion battery # 1.
The preparation method of the lithium cobaltate positive electrode comprises the following steps: mixing a positive electrode active material 4.25V Lithium Cobaltate (LCO), a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black according to a weight ratio of 97:1.5:1.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a mixed system becomes a uniform and fluid positive electrode slurry; uniformly coating the positive electrode slurry on an aluminum foil with the thickness of 10 mu m; and baking the coated aluminum foil in 5 sections of baking ovens with different temperature gradients, drying the aluminum foil in a baking oven at 120 ℃ for 9 hours, and rolling and cutting to obtain the anode.
The preparation method of the graphite negative electrode comprises the following steps: mixing a negative electrode active material graphite, a thickening agent sodium carboxymethyl cellulose (CMC), a binder styrene butadiene rubber and a conductive agent acetylene black according to a weight ratio of 97.2:1:1:0.8, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer; uniformly coating the negative electrode slurry on a copper foil with the thickness of 8 mu m; and (3) airing the copper foil at room temperature, transferring the copper foil to an oven at 80 ℃ for drying for 12h, and then carrying out cold pressing and slitting to obtain the negative electrode.
Example 2
The electrolyte of this example was prepared in the same manner as in example 1, except that the nitrile additive in the electrolyte of example 1 was replaced with a 3.
And the electrolyte in the embodiment 2 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 2 #.
Example 3
The electrolyte of this example was prepared in the same manner as in example 1, except that the nitrile additive in the electrolyte of example 1 was replaced with a 5.
And the electrolyte in the embodiment 3 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 3 #.
Example 4
The electrolyte of this example was prepared in the same manner as in example 1, except that the acid anhydride-based additive in the electrolyte of example 1 was replaced with maleic anhydride.
And the electrolyte in the embodiment 4 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 4 #.
Example 5
The electrolyte of this example was prepared in the same manner as in example 2, except that the acid anhydride additive in the electrolyte of example 2 was replaced with maleic anhydride.
And the electrolyte in the embodiment 5 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 5 #.
Example 6
The electrolyte of this example was prepared in the same manner as in example 4, except that the nitrile additive in the electrolyte of example 4 was replaced with A8.
And 6# lithium ion battery is assembled by matching the electrolyte in example 6 with the positive electrode, the separator and the negative electrode in example 1.
Example 7
The preparation method of the electrolyte of the embodiment is the same as that of the embodiment 1, except that 0.2% of maleic anhydride is added into the electrolyte of the embodiment 1, and the matching of the solvent and the lithium salt in equal proportion by mass percentage is reduced.
And the electrolyte in the embodiment 7 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 7 #.
Example 8
The electrolyte of this example was prepared in the same manner as in example 7, except that 0.5% of A5 was added to the electrolyte of example 7, and the compatibility between the solvent and the lithium salt was reduced in terms of mass percentage.
And the electrolyte in the embodiment 8 is matched with the positive electrode, the diaphragm and the negative electrode in the embodiment 1 to assemble the lithium ion battery 8 #.
Comparative example 1
The electrolyte of this comparative example was prepared in the same manner as in example 1, except that the electrolyte of this comparative example did not contain a2 and citraconic anhydride, and the compatibility between the solvent and the lithium salt was improved in equal proportions by mass percentage.
And the electrolyte in the comparative example 1 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 9 #.
Comparative example 2
The electrolyte of this comparative example was prepared in substantially the same manner as in example 1, except that the electrolyte of this comparative example did not contain citraconic anhydride, and the compatibility between the solvent and the lithium salt was improved in equal proportions by mass percentage.
And the electrolyte in the comparative example 2 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 10 #.
Comparative example 3
The electrolyte of this comparative example was prepared in substantially the same manner as in example 2, except that the electrolyte of this comparative example did not contain citraconic anhydride, and the compatibility between the solvent and the lithium salt was improved in equal proportions by mass percentage.
And the electrolyte in the comparative example 3 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 11 #.
Comparative example 4
The electrolyte of this comparative example was prepared in substantially the same manner as in example 3, except that the electrolyte of this comparative example did not contain citraconic anhydride, and the compatibility between the solvent and the lithium salt was improved in equal proportions by mass percentage.
And the electrolyte in the comparative example 4 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 12 #.
Comparative example 5
The electrolyte of this comparative example was prepared in substantially the same manner as in example 6, except that the electrolyte of this comparative example did not contain maleic anhydride, and the solvent and lithium salt were more proportionally matched in mass%.
And the electrolyte in the comparative example 5 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 13 #.
Comparative example 6
The electrolyte of this comparative example was prepared in substantially the same manner as in example 1, except that the electrolyte of this comparative example did not contain a2, and the solvent and lithium salt were more proportionally matched in mass%.
And the electrolyte in the comparative example 6 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 14 #.
Comparative example 7
The electrolyte of this comparative example was prepared in substantially the same manner as in example 4, except that the electrolyte of this comparative example did not contain a2, and the solvent and lithium salt were found to have an improved compatibility in terms of mass percentage content and in terms of equivalent amount.
And the electrolyte in the comparative example 7 is matched with the positive electrode, the diaphragm and the negative electrode in the example 1 to assemble the lithium ion battery 15 #.
The lithium ion batteries of the above examples and comparative examples were subjected to electrochemical performance tests, as follows:
1. normal temperature cycle test at 25 deg.C
Thickness D of full-electricity cell before test0Placing the battery in an environment of (25 +/-3) DEG C, standing for 3 hours, charging the battery to 4.1V according to 1C when the battery core body reaches (25 +/-3) DEG C, then charging to 4.25V at 0.7C, then charging to cut-off current at constant voltage of 4.25V to 0.05C, then discharging to 3V at 1C, and recording initial capacity Q0When the cycle is 400 weeks, the previous discharge capacity is taken as the capacity Q of the battery1Then, the battery is fully charged, the battery core is taken out and then is kept stand for 3 hours at normal temperature, and the full charge thickness D is tested1。
Wherein the content of the first and second substances,
thickness change rate (%) - (D)1-D0)/D0*100％
Capacity retention (%) ═ Q1/Q0*100％
2. High temperature cycling experiment at 45 ℃:
thickness D of full-electricity cell before test0Placing the battery in an environment of (45 +/-3) DEG C, standing for 3 hours, charging and discharging the battery at 0.7C/0.5C when the battery core body reaches (45 +/-3) DEG C, and stopping current0.05C, and then discharged at 0.5C to record the initial capacity Q0When the cycle reaches 200 weeks, the previous discharge capacity is taken as the capacity Q of the battery1Then, the battery is fully charged, the core is taken out and is kept stand for 3 hours at normal temperature, and the full-charge thickness D is tested1。
Wherein the content of the first and second substances,
thickness change rate (%) - (D)1-D0)/D0*100％
Capacity retention (%) ═ Q1/Q0*100％
3. 60 ℃ high temperature storage test
The thickness D of the fully charged cell was measured at 25 deg.C0Charging the formed battery to 4.1V according to 1C, then charging to 4.25V by 0.7C, then charging to 0.05C by 4.25V constant voltage, then discharging to 3.0V by 0.5C constant current, then charging to 4.1V by 1C, then charging to 4.25V by 0.7C, then charging to 0.05C by 4.25V constant voltage, placing in 60 ℃ environment for 14 days, testing the full charge thickness D1。
Wherein the content of the first and second substances,
thickness change rate (%) - (D)1-D0)/D0*100％
The results of the above tests are shown in Table 1.
TABLE 1
Figure BDA0002251432510000131
From the results of table 1, it can be seen that:
1. compared with the corresponding comparative example, the embodiment of the invention has better cycle performance and high-temperature storage performance under high voltage by adding the specific nitrile additive and the anhydride additive into the electrolyte of the lithium ion battery under the condition of keeping the other factors the same.
2. Under the condition of keeping other factors the same, the circulation performance and the high-temperature storage performance can be obviously improved along with the increase of the mass content of the additive in a certain range, so that the addition amount of the additive can be further determined according to the target value of each performance parameter.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. An electrolyte solution, characterized by comprising a lithium salt, a solvent, a nitrile additive represented by formula 1, and an acid anhydride additive,
Figure FDA0002251432500000011
in the formula 1, R1、R2、R3、R4、R5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-6Alkyl and C1-6Alkoxy, n is more than or equal to 1 and less than or equal to 5 and is an integer; r is C or Si.
2. The electrolyte of claim 1, wherein the acid anhydride additive is selected from one or more of maleic anhydride, 2, 3-dimethylmaleic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, pimelic anhydride, phthalic anhydride, citraconic anhydride, citric anhydride, fluoromaleic anhydride, 2, 3-dimethylfluoromaleic anhydride, fluorosuccinic anhydride, fluoroglutaric anhydride, fluoroadipic anhydride, fluoropimelic anhydride, fluorophthalic anhydride, fluorocitraconic anhydride, and fluorocitric anhydride.
3. The electrolyte of claim 1 or 2, wherein R is1、R2、R3、R4And R5Each independently selected from hydrogen, halogen, methyl, ethyl, trimethylsiloxy, trifluoromethyl.
4. The electrolyte of claim 3, wherein the nitrile additive is selected from compounds of the following structures,
5. the electrolyte as claimed in any one of claims 1 to 4, wherein the nitrile additive is present in the electrolyte in a mass fraction of 0.1% to 10%.
6. The electrolyte of claim 5, wherein the nitrile additive is present in the electrolyte in an amount of 1-7% by weight.
7. The electrolyte according to claim 5, wherein the mass fraction of the acid anhydride additive in the electrolyte is 0.1% to 5%.
8. The electrolyte of claim 1, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), lithium difluoro (LiPO) phosphate2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2)、LiN(SO2C2F5)2Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more of (a).
9. The method of preparing the electrolyte of any of claims 1-8, comprising: and mixing a solvent, a lithium salt, the nitrile additive shown in the formula 1 and an anhydride additive in an inert atmosphere to obtain the electrolyte.
10. A lithium ion battery, characterized in that the electrolyte of the lithium ion battery is the electrolyte according to any one of claims 1 to 8.
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