CN113571769A - Electrolyte additive, secondary battery electrolyte, secondary battery and terminal - Google Patents

Electrolyte additive, secondary battery electrolyte, secondary battery and terminal Download PDF

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CN113571769A
CN113571769A CN202010349137.3A CN202010349137A CN113571769A CN 113571769 A CN113571769 A CN 113571769A CN 202010349137 A CN202010349137 A CN 202010349137A CN 113571769 A CN113571769 A CN 113571769A
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electrolyte
group
secondary battery
halogenated
lithium
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马强
秦德君
李阳兴
邓耀明
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Huawei Technologies 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
    • 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
    • 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

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Abstract

The embodiment of the application provides an electrolyte additive, which comprises a cyclotriphosphazene six-membered ring structure, wherein six substituent groups are totally arranged on three phosphorus atoms in the cyclotriphosphazene six-membered ring structure, and at least one of the six substituent groups is-N (Si R)1'R2'R3')(Si R4'R5'R6')，R1'、R2'、R3'、R4'、R5'、R6' are respectively selected from any one of alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy. The electrolyte additive is used under high voltage conditionAnd a stable interface film can be formed on the surface of the anode, and HF generated by the decomposition of the electrolyte can be captured, so that the influence of HF on the anode material can be effectively avoided from two layers of physics and chemistry, and the battery performance is improved. The embodiment of the application also provides a secondary battery electrolyte, a secondary battery and a terminal.

Description

Electrolyte additive, secondary battery electrolyte, secondary battery and terminal
Technical Field
The application relates to the technical field of secondary batteries, in particular to an electrolyte additive, a secondary battery electrolyte, a secondary battery and a terminal.
Background
Lithium secondary batteries have been widely used in terminal products (smart phones, digital cameras, notebook computers, electric vehicles, etc.) due to advantages of high energy density, high operating voltage, long service life, low self-discharge rate, environmental friendliness, etc. With the rapid development of the industry, the demand for the energy density of the battery is higher, wherein the development of a high-voltage cathode material (>4.4V) is one of effective technical means for improving the energy density of the lithium secondary battery.
However, the conventional electrolyte system at present is difficult to maintain the long-term cycle and high-temperature storage performance of the battery under the condition of more than 4.40V, and a series of side reactions can occur when the cathode material is contacted with the electrolyte under high voltage, so that the cycle degradation of the battery is caused, and even the safety problem is caused. Moreover, lithium hexafluorophosphate (LiPF) is mostly adopted in the conventional electrolyte system at present6) Is the dominant lithium salt due to LiPF6The self-chemical thermal stability is poor, the self-chemical thermal stability is sensitive to water, Hydrogen Fluoride (HF) is easily generated by decomposition, and the HF and a high-voltage positive electrode material generate serious side reaction to destroy the structure of the positive electrode material and accelerate the dissolution of transition metal in the positive electrode material, so that the battery performance is seriously deteriorated. In order to solve the above problems, it is necessary to develop a high voltage electrolyte system to effectively protect the positive electrode material.
Disclosure of Invention
The embodiment of the application provides an electrolyte additive, which can form a stable interface film on the surface of a positive electrode under a high-voltage condition and can capture HF generated by decomposition of electrolyte, so that the influence of HF on a positive electrode material can be effectively reduced from a physical layer and a chemical layer, and the performance of a battery is improved.
Specifically, in a first aspect, the embodiment of the present application provides an electrolyte additive, where a molecular structure of the electrolyte additive includes a cyclotriphosphazene six-membered ring structure, three phosphorus atoms in the cyclotriphosphazene six-membered ring structure have six substituent groups, and at least one of the six substituent groups is — N (Si R)1'R2'R3')(Si R4'R5'R6') wherein said R is1'、R2'、R3'、R4'、R5'、R6' are respectively selected from any one of alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.
In the embodiments of the present application, of the six substituents, the other than the-N (Si R)1'R2'R3')(Si R4'R5'R6') is independently selected from any one of fluorine, chlorine, bromine, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy, substituted sulfonic acid group, substituted phosphate group, substituted imide group and substituted sulfonylimide group.
In an embodiment of the present application, one or more of the remaining substituent groups are fluorine, chlorine, bromine, haloalkyl, haloalkoxy, haloalkenyl, haloalkenyloxy, haloaryl or haloaryloxy.
In an embodiment of the present application, one or more of the remaining substituent groups are fluorine, fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenoxy, fluoroaryl or fluoroaryloxy.
In one embodiment of the present application, one of the six substituent groups is-N (Si R)1'R2'R3')(Si R4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (I):
Figure BDA0002471309210000021
in the formula (I), R is1、R2、R3、R4、R5Are the remaining substituent groups.
In another embodiment of the present application, two of the six substituent groups are-N (Si R)1'R2'R3')(Si R4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (II):
Figure BDA0002471309210000022
in the formula (II), R is1、R2、R3、R5Are the remaining substituent groups.
In yet another embodiment of the present application, three of the six substituent groups are-N (Si R)1'R2'R3')(Si R4'R5'R6') said R2、R4And R6is-N (Si R)1'R2'R3')(Si R4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (III):
Figure BDA0002471309210000023
in the formula (III), the R1、R3、R5Are the remaining substituent groups.
In the embodiments of the present application, R is1'、R2'、R3'、R4'、R5'、R6In the item' above, the alkyl group, haloalkyl group, alkoxy group, haloalkoxy group have 1 to 20 carbon atoms; the carbon atom number of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy is 2-20; aryl, haloThe number of carbon atoms of the aryl, aryloxy and halogenated aryloxy groups is 6 to 20.
In the embodiments of the present application, R is1'、R2'、R3'、R4'、R5'、R6In the' case, the halogen in the haloalkyl group, the haloalkoxy group, the haloalkenyl group, the haloalkenyloxy group, the haloaryl group and the haloaryloxy group includes fluorine, chlorine, bromine and iodine, and the halogen is a perhalogenated or partially halogenated group.
In the embodiments, in the remaining substituent groups, the number of carbon atoms of the alkyl group, the haloalkyl group, the alkoxy group, and the haloalkoxy group is 1 to 20; the carbon atom number of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy is 2-20; the number of carbon atoms of the aryl, halogenated aryl, aryloxy and halogenated aryloxy is 6-20.
In the present embodiment, the halogen in the haloalkyl group, the haloalkoxy group, the haloalkenyl group, the haloalkenyloxy group, the haloaryl group and the haloaryloxy group in the remaining substituent groups includes fluorine, chlorine, bromine and iodine, and the halogen is a perhalogenated or partially halogenated group.
A second aspect of embodiments herein provides a secondary battery electrolyte comprising an electrolyte salt, a non-aqueous organic solvent and an additive, the additive comprising an electrolyte additive as described in the first aspect of embodiments herein.
In the embodiment of the application, the electrolyte additive is 0.1-10% by mass of the electrolyte of the secondary battery.
In an embodiment of the present application, the electrolyte salt includes at least one of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt.
In an embodiment of the present application, the electrolyte salt includes MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2(MBOB)、MBF2C2O4(MDFOB)、M[(CF3SO2)2N]、M[(FSO2)2N]And M [ (C)mF2m+1SO2)(CnF2n+1SO2)N]Wherein M is Li, Na or K, and M and n are natural numbers.
In the embodiment of the present application, the molar concentration of the electrolyte salt in the electrolyte solution of the secondary battery is 0.01mol/L to 8.0 mol/L.
In the embodiment of the present application, the non-aqueous organic solvent includes one or more of a carbonate solvent, an ether solvent, and a carboxylate solvent.
In embodiments of the present application, the additive further comprises other additives including one or more of fluoroethylene carbonate, biphenyl, fluorobenzene, vinylene carbonate, trifluoroethylene carbonate, ethylene carbonate, 1, 3-propanesultone, 1, 4-butanesultone, vinyl sulfate, vinyl sulfite, succinonitrile, adiponitrile, 1, 2-bis (2-cyanoethoxy) ethane, and 1,3, 6-hexanetrinitrile.
A third aspect of the embodiments provides a secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution including the secondary battery electrolyte solution according to the second aspect of the embodiments.
In an embodiment of the present application, the negative electrode includes one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a lithium negative electrode, a sodium negative electrode, a potassium negative electrode, a magnesium negative electrode, a zinc negative electrode, and an aluminum negative electrode.
In an embodiment of the present application, the carbon-based negative electrode includes one or more of graphite, hard carbon, soft carbon, and graphene, the silicon-based negative electrode includes one or more of silicon, silicon carbon, silicon oxygen, and a silicon metal compound, the tin-based negative electrode includes one or more of tin, tin carbon, tin oxygen, and a tin metal compound, and the lithium negative electrode includes metallic lithium or a lithium alloy.
In an embodiment of the present application, the lithium alloy includes 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 the embodiments of the present application, the secondary battery includes a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, or an aluminum secondary battery.
The embodiment of the application further provides a terminal, including the casing, and accept in electronic components and batteries in the casing, the battery does electronic components supplies power, the battery includes the third aspect of the embodiment of the application secondary battery.
The electrolyte additive provided by the embodiment of the application has a cyclotriphosphazene structure and a silicon nitrogen structure-N (Si R) in a molecular structure1'R2'R3')(Si R4'R5'R6') wherein, cyclotriphosphazene structure is oxidized and decomposed under the condition of high voltage, a stable interfacial film can be formed on the surface of the anode, side reactions caused by direct contact of electrolyte and anode materials are effectively prevented, and the silicon nitrogen structure can effectively capture HF generated by decomposition of the electrolyte, so that the electrolyte additive in the embodiment of the application can reduce the influence of HF on the anode materials under high voltage from two physical and chemical layers, improve the performance of the battery, and enable the battery to maintain long-term circulation and high-temperature storage performance under the condition of more than 4.40V.
Drawings
Fig. 1 is a schematic structural diagram of a secondary battery provided in an embodiment of the present application;
FIG. 2 is a diagram showing the protective action mechanism of an electrolyte additive on a lithium cobaltate positive electrode in an example of the present application;
fig. 3 is a schematic structural diagram of a terminal according to an embodiment of the present application;
fig. 4 is a graph showing cycle profiles of the lithium secondary batteries in examples 1 to 4 of the present application and comparative examples 1 to 3.
Detailed Description
The embodiments of the present application will be described below with reference to the drawings.
As shown in fig. 1, a core component of a secondary battery (taking a lithium ion battery as an example) includes a positive electrode material 101, a negative electrode material 102, an electrolyte 103, a separator 104, and corresponding communication accessories and circuits. During charging, lithium ions are extracted from the crystal lattice of the positive electrode material 101, pass through the electrolyte 103 and then are deposited to the negative electrode; during discharge, lithium ions are extracted from the negative electrode, pass through the electrolytic solution 103, and are inserted into the crystal lattice of the positive electrode material 101. The electrolyte is a medium for transmitting lithium ions between a positive electrode and a negative electrode, and mainly comprises lithium salt, a nonaqueous organic solvent (generally a carbonate solvent) and an additive. In view of the fact that the conventional carbonate electrolyte is difficult to maintain the long-term circulation and high-temperature storage performance of the battery under the high-voltage condition of more than 4.40V, the embodiment of the application provides an electrolyte additive, a small amount of the electrolyte additive is added into the electrolyte, the high-voltage circulation performance of the battery can be remarkably improved, and the addition of the electrolyte additive has small influence on an electric core system.
Specifically, the molecular structure of the electrolyte additive provided in the embodiment of the present application includes a cyclotriphosphazene six-membered ring structure, and three phosphorus atoms in the cyclotriphosphazene six-membered ring structure have six substituent groups, which are R respectively1、R2、R3、R4、R5、R6，R1、R2、R3、R4、R5、R6In which at least one substituent group is a silicon nitrogen structural group-N (Si R)1'R2'R3')(Si R4'R5'R6') to a host; wherein R is1'、R2'、R3'、R4'、R5'、R6' are respectively selected from any one of alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.
The electrolyte additive provided by the embodiment of the application is prepared by mixing silicon nitrogen structure-N (Si R)1'R2'R3')(Si R4'R5'R6') grafted to the cyclotriphosphazene structure through chemical bonds, so that the additive has the dual characteristics of a high-voltage film forming function and an HF capturing function, and can maintain the long-term cycle and high-temperature storage performance of the battery under the condition of more than 4.40V. Specifically, the cyclotriphosphazene structure in the electrolyte additive is oxidized and decomposed under the condition of high voltage, a stable interfacial film can be formed on the surface of a positive electrode, side reactions caused by direct contact of the electrolyte and a positive electrode material are effectively prevented, and the silicon nitrogen structure canEffectively captures HF generated by the decomposition of the electrolyte and effectively avoids the influence of the HF on the anode material. Therefore, the electrolyte additive provided by the embodiment of the application can reduce the influence of HF on the anode material under high voltage from two physical and chemical layers, and improves the battery performance.
In the embodiments of the present application, R1、R2、R3、R4、R5、R6In, except-N (Si R)1'R2'R3')(Si R4'R5'R6') may be independently selected from any one of fluorine, chlorine, bromine, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy, substituted sulfonic acid group, substituted phosphate group, substituted imide group and substituted sulfonylimide group.
In some embodiments of the present application, R1、R2、R3、R4、R5、R6Wherein one of the substituents is-N (Si R)1'R2'R3')(Si R4'R5'R6') e.g. R6is-N (Si R)1'R2'R3')(Si R4'R5'R6') and the remaining substituent groups R1、R2、R3、R4、R5Respectively selecting any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy, halogenated aryloxy, substituted sulfonic group, substituted phosphate group, substituted imide group and substituted sulfonyl imide group, wherein the chemical structural formula of the electrolyte additive is shown as the formula (I):
Figure BDA0002471309210000051
in other embodiments of the present application, R1、R2、R3、R4、R5、R6Two in the middleThe substituent group is-N (Si R)1'R2'R3')(Si R4'R5'R6') e.g. R4And R6is-N (Si R)1'R2'R3')(Si R4'R5'R6') and the remaining substituent groups R1、R2、R3、R5Respectively selecting any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy, halogenated aryloxy, substituted sulfonic group, substituted phosphate group, substituted imide group and substituted sulfonyl imide group, wherein the chemical structural formula of the electrolyte additive is shown as the formula (II):
Figure BDA0002471309210000052
of course, in other embodiments, there may be two-N (Si R)1'R2'R3')(Si R4'R5'R6') groups are attached to the same phosphorus atom in the cyclotriphosphazene structure.
In other embodiments of the present application, R1、R2、R3、R4、R5、R6Three of the substituent groups are-N (Si R)1'R2'R3')(Si R4'R5'R6') e.g. R2、R4And R6is-N (Si R)1'R2'R3')(Si R4'R5'R6') and the remaining substituent groups R1、R2、R3、R5Respectively selecting any one of fluorine, chlorine, bromine, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy, halogenated aryloxy, substituted sulfonic group, substituted phosphate group, substituted imide group and substituted sulfonyl imide group, wherein the chemical structural formula of the electrolyte additive is shown as the formula (III):
Figure BDA0002471309210000053
likewise, in other embodiments, there may be two-N (Si R)1'R2'R3')(Si R4'R5'R6') groups are attached to the same phosphorus atom in the cyclotriphosphazene structure.
In other embodiments of the present application, R1、R2、R3、R4、R5、R6In which there may also be four, five or even six substituents of-N (Si R)1'R2'R3')(Si R4'R5'R6'). Understandably, the substituent group-N (Si R)1'R2'R3')(Si R4'R5'R6') the more beneficial it is to improve its ability to capture HF in the electrolyte.
In some embodiments of the present application, R1、R2、R3、R4、R5、R6removing-N (Si R) in1'R2'R3')(Si R4'R5'R6') one or more of the remaining substituent groups other than fluorine, chlorine, bromine, haloalkyl, haloalkoxy, haloalkenyl, haloalkenyloxy, haloaryl or haloaryloxy. When one or more of the remaining substituent groups are the above-mentioned halogen-containing groups, a stable halide (e.g., lithium fluoride) is contained in a certain amount in the interfacial film formed on the surface of the positive electrode, thereby providing strong protection for the positive electrode material. Wherein when R is1、R2、R3、R4、R5、R6When a plurality of (two or more) substituent groups are the above-mentioned halogen-containing groups, the content of the halide in the interface film of the positive electrode can be increased, and the protective performance of the interface film can be improved. In some embodiments of the present application, R1、R2、R3、R4、R5、R6removing-N (Si R) in1'R2'R3')(Si R4'R5'R6') is any one of fluorine, fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenoxy, fluoroaryl and fluoroaryloxy. When the rest substituent groups are fluorine-containing groups, the interface film formed on the surface of the anode contains a certain content of stable fluoride, which is more beneficial to effectively protecting the anode.
In the embodiments of the present application, R1、R2、R3、R4、R5、R6And R1'、R2'、R3'、R4'、R5'、R6The alkyl group, the haloalkyl group, the alkoxy group, and the haloalkoxy group referred to in' have 1 to 20 carbon atoms, further, the carbon atom number may be 1 to 10, and specifically, the carbon atom number is, for example, 1,2, 3, 4, 5, 6, 7, 8, 9, 10; the number of carbon atoms of the alkenyl group, the haloalkenyl group, the alkenyloxy group, and the haloalkenyloxy group is 2 to 20, and further, the number of carbon atoms may be 2 to 10, and specifically, the number of carbon atoms is, for example, 2, 3, 4, 5, 6, 7, 8, 9, and 10; the number of carbon atoms of the aryl group, the halogenated aryl group, the aryloxy group, and the halogenated aryloxy group is 6 to 20, and further, the number of carbon atoms may be 7 to 10, and specifically, the number of carbon atoms is, for example, 7, 8, 9, and 10. The less carbon number is beneficial to controlling the molecular weight of the additive, so that the viscosity of the electrolyte is better controlled. In the embodiments of the present application, the halogen in the haloalkyl group, the haloalkoxy group, the haloalkenyl group, the haloalkenyloxy group, the haloaryl group and the haloaryloxy group may be fluorine, chlorine, bromine or iodine, and the halogen may be perhalogenated or partially halogenated. The alkyl group, haloalkyl group, alkoxy group, haloalkoxy group, alkenyl group, haloalkenyl group, alkenyloxy group, and haloalkenyloxy group may be linear or branched, or may be cyclic.
In the embodiments of the present application, the substituted sulfonic acid group is represented by — O-S (═ O)2-R, wherein R may be selected from the group consisting of alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy, aryl, haloaryl, aryloxy, haloaryloxy, substituted phosphate, substituted imide andand (3) any one of the substituted sulfimide groups, wherein the substituted sulfonic group forms P-O bond chemical bonding with a phosphorus atom in the cyclotriphosphazene six-membered ring structure through an oxygen atom. The number of carbon atoms of R may be 1 to 20. Specifically, R may be selected from, but is not limited to, being-CH3(methyl), -CH2CH3(ethyl), -CH2CH2CH3(propyl), -CH (CH)3)2(isopropyl), -CH2CH2CH2CH3(butyl), -CH2CH2CH＝CH2(1-butenyl), -CF2CF2CF2CF3(perfluoro-substituted-butyl), -OCH2CF3(trifluoro-substituted ethoxy), methylphenyl, vinylphenyl, fluorophenyl or-OP ═ O (OCH)3)2(dimethylphosphate group), -OP ═ O (OCH)2CF3)2(bis-trifluoroethyl phosphate group), -NHC (═ O) CH3(acetyiimino), -NHS (═ O)2CF3(trifluoromethylsulfonylimino). The substituted sulfonic acid group has certain high-voltage film-forming property, and when the rest substituted groups comprise one or more substituted sulfonic acid groups, the high-voltage film-forming property of the electrolyte additive on the surface of the anode can be further improved.
In the embodiments of the present application, the substituted imide group may be represented by — NH — C (═ O) -X, where X may be selected from any one of alkyl groups, haloalkyl groups, alkoxy groups, haloalkoxy groups, alkenyl groups, haloalkenyl groups, alkenyloxy groups, haloalkenyloxy groups, aryl groups, haloaryl groups, aryloxy groups, and haloaryloxy groups. The number of carbon atoms of X may be 1 to 20.
In the embodiments of the present application, the substituted sulfonylimino group may be represented by — NH-S (═ O)2Y, wherein Y can be any one of alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy. The number of carbon atoms of Y may be 1 to 20.
In the embodiment of the present invention, the halogen-containing substituent group in the substituted sulfonic acid group, the substituted imide group and the substituted sulfonylimide group may be fluorine, chlorine, bromine or iodine, and the halogen may be a perhalogenated group or a partially halogenated group. The alkyl group, haloalkyl group, alkoxy group, haloalkoxy group, alkenyl group, haloalkenyl group, alkenyloxy group, and haloalkenyloxy group may be linear or branched, or may be cyclic.
In the embodiments of the present application, R1、R2、R3、R4、R5、R6removing-N (Si R) in1'R2'R3')(Si R4'R5'R6') the remaining substituent groups other than') may be the same or different groups.
In a specific embodiment of the present application, the electrolyte additive may have a molecular structure represented by formulas (a) to (I):
Figure BDA0002471309210000071
Figure BDA0002471309210000081
in the embodiments of the present application, the substituent group-N (Si R)1'R2'R3')(Si R4'R5'R6') form stable N-P covalent bonding with P atoms in the cyclotriphosphazene structure through N atoms, thereby forming a film on the anode along with the cyclotriphosphazene structure and reacting with HF to generate compounds such as fluorosilane and the like. Taking the electrolyte additive (a) as an example, a protection action mechanism diagram of the electrolyte additive to the lithium cobaltate positive electrode in the embodiment of the present application is shown in fig. 2, in a cell formation and/or charge-discharge process, the electrolyte additive (a) can form a film on the positive electrode due to the cyclotriphosphazene structure, so as to form a stable interface protection film, so as to form a physical protection barrier, and meanwhile, an outer layer of the protection film contains a large number of silicon nitrogen structure groups, which can react with a small amount of HF in the electrolyte, and in addition, the electrolyte additive existing in the electrolyte can capture HF, so as to play a role in removing HF and chemically protect the positive electrode.
The electrolyte additive provided by the embodiment of the application contains a cyclotriphosphazene structure and a silicon nitrogen structure in a molecular structure, so that the additive can form a powerful defense barrier for HF from dual actions of physics and chemistry, and the high-voltage characteristic and the high-temperature storage performance of the electrolyte are improved. The electrolyte additive provided by the embodiment of the application also has excellent flame retardant property due to the fact that the electrolyte additive contains a cyclotriphosphazene structure, and the safety of a battery can be improved. By adopting the electrolyte additive provided by the embodiment of the application, the adverse effects of the addition of various additives on the electrolyte performance, such as viscosity increase, poor compatibility with a negative electrode and the like, can be effectively avoided. In addition, the electrolyte additive provided by the embodiment of the application has good compatibility with positive and negative electrode materials, does not deteriorate other performances (such as low temperature and rate performance) of the battery, and has small influence on an electric core system.
In the embodiment of the application, the electrolyte additive can be prepared by different methods, the specific preparation method is not limited, and the electrolyte additive can be reasonably and comprehensively designed according to the conventional preparation process of the cyclotriphosphazene derivative and the property of the combined substituent group.
In some embodiments of the present application, taking the electrolyte additive (a) as an example, the electrolyte additive (a) can be prepared in the following manner:
adding triethylamine (as an acid-binding agent), hexafluorocyclotriphosphazene and acetonitrile (as a solvent) into a three-neck flask respectively, slowly adding hexamethyldisilazane into the three-neck flask at-20-30 ℃, stirring and reacting for 6-48 hours at 25-60 ℃, and performing post-treatment such as filtration and drying to obtain the electrolyte additive shown in the formula (A).
In other embodiments of the present application, the electrolyte additive (D) can be prepared as follows:
adding triethylamine (used as an acid-binding agent), pentafluorocyclotriphosphazene (ethoxy) and acetonitrile (used as a solvent) into a three-neck flask respectively, slowly adding hexamethyldisilazane into the three-neck flask at-20-30 ℃, stirring and reacting for 6-48 hours at 25-60 ℃, and performing post-treatment such as filtration and drying to obtain the electrolyte additive shown in the formula (D).
In other embodiments of the present application, the electrolyte additive (F) can be prepared as follows:
adding triethylamine (used as an acid-binding agent), pentafluorocyclotriphosphazene (phenoxy) and acetonitrile (used as a solvent) into a three-neck flask respectively, slowly adding hexamethyldisilazane into the three-neck flask at the temperature of-20-30 ℃, stirring and reacting for 6-48 hours at the temperature of 25-60 ℃, and carrying out post-treatment such as filtration and drying to obtain the electrolyte additive shown in the formula (F).
The embodiment of the application also provides a secondary battery electrolyte, which comprises electrolyte salt, a non-aqueous organic solvent and an additive, wherein the additive comprises the electrolyte additive.
In the embodiment of the application, the mass percentage of the electrolyte additive in the electrolyte of the secondary battery can be 0.1-10%. Further, the electrolyte additive can be 0.5-8%, 1-6%, 2-5% and 0.5-1% by mass in the electrolyte of the secondary battery. In the embodiment of the application, the high-voltage cycle performance of the battery can be effectively improved by adding the electrolyte additive with lower content. Meanwhile, the addition of the electrolyte additive with lower content can ensure that the viscosity of the electrolyte is not too high, so that the performance of the battery is not influenced.
In the embodiment of the present application, the electrolyte salt may be a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, an aluminum salt, or the like, depending on the secondary battery system. Specifically, the lithium salt, sodium salt, potassium salt may be MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2(MBOB)、MBF2C2O4(MDFOB)、M[(CF3SO2)2N]、M[(FSO2)2N]And M [ (C)mF2m+1SO2)(CnF2n+1SO2)N]Wherein M is Li, Na or K, and M and n are natural numbers. Similarly, the magnesium salt, zinc salt, and aluminum salt may be salts of magnesium ion, zinc ion, and aluminum ion with anions of the lithium salt, sodium salt, and potassium salt.
In the embodiment of the present application, the molar concentration of the electrolyte salt in the electrolyte solution of the secondary battery is 0.01mol/L to 8.0 mol/L. Further, it may be 0.05mol/L to 2mol/L, 0.5mol/L to 1.0 mol/L.
In the embodiment of the present application, the non-aqueous organic solvent includes one or more of a carbonate solvent, an ether solvent, and a carboxylate solvent. The non-aqueous organic solvent may be mixed in any proportion. The carbonate solvent comprises cyclic carbonate or chain carbonate, and the cyclic carbonate can be specifically but not limited to one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), gamma-butyrolactone (GBL) and Butylene Carbonate (BC); the chain carbonate may be one or more of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC) and dipropyl carbonate (DPC). The ether solvent includes cyclic ether or chain ether, and the cyclic ether can 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 be, but is not limited to, one or more of Dimethoxymethane (DMM), 1, 2-Dimethoxyethane (DME), and diglyme (TEGDME). The carboxylic ester solvent may be, but not limited to, one or more of Methyl Acetate (MA), Ethyl Acetate (EA), propyl acetate (EP), butyl acetate, Propyl Propionate (PP), and butyl propionate.
In the embodiment of the present invention, in addition to the above-mentioned electrolyte additives, other additives may be added to the electrolyte of the secondary battery according to different performance requirements, and the other additives may be, but are not limited to, one or more of fluoroethylene carbonate, biphenyl, fluorobenzene, vinylene carbonate, ethylene trifluoromethyl carbonate, ethylene carbonate, 1, 3-propane sultone, 1, 4-butane sultone, vinyl sulfate, vinyl sulfite, succinonitrile, adiponitrile, 1, 2-bis (2-cyanoethoxy) ethane, and 1,3, 6-hexane trinitrile.
Correspondingly, the embodiment of the application also provides a preparation method of the electrolyte of the secondary battery, which comprises the following steps:
and dissolving the fully dried electrolyte salt in a non-aqueous organic solvent in an inert environment or a closed environment (such as an argon-filled glove box), stirring and mixing uniformly, then adding the electrolyte additive into the solution, and mixing uniformly to obtain the electrolyte of the secondary battery.
The operations in the preparation method can be implemented according to the existing conventional electrolyte preparation process, wherein the specific selection of the raw materials such as the electrolyte salt, the non-aqueous organic solvent, the electrolyte additive and the like is as described above and is not repeated herein. When the electrolyte further includes other additives, the additives may be added together with the electrolyte additives according to the embodiments of the present application.
The embodiment of the application also provides a secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the electrolyte adopts the electrolyte of the secondary battery provided by the embodiment of the application. According to the secondary battery provided by the embodiment of the application, the electrolyte additive is added into the electrolyte, so that good circulation stability can be obtained. In the embodiment of the present application, the secondary battery may be a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, an aluminum secondary battery, or the like. The secondary battery provided by the embodiment of the application can be used for terminal consumer products, such as mobile phones, tablet computers, mobile power supplies, portable computers, notebook computers, other wearable or movable electronic equipment, automobiles and other products, so as to improve the product performance.
In an embodiment of the present application, the negative electrode may include one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a lithium negative electrode, a sodium negative electrode, a potassium negative electrode, a magnesium negative electrode, a zinc negative electrode, and an aluminum negative electrode. Wherein the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, and the like; the silicon-based negative electrode can comprise silicon, silicon carbon, silicon oxygen, silicon metal compound and the like; the tin-based negative electrode may include tin, tin carbon, tin oxide, tin metal compounds; 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 an embodiment of the present application, the positive electrode comprises a reversible intercalationThe positive electrode active material for inserting/extracting metal ions (lithium ions, sodium ions, potassium ions, magnesium ions, zinc ions, aluminum ions and the like) has no special limitation on the selection of the positive electrode active material, and can be the positive electrode active material conventionally used by the conventional secondary battery. Taking a lithium secondary battery as an example, the positive electrode active material may be, but is not limited to, lithium cobaltate (LiCoO)2) Lithium iron phosphate (LiFePO)4) Lithium nickel cobalt manganese oxide (LiNi)0.6Co0.2Mn0.2) Polyanionic lithium compound LiMx(PO4)y(M is Ni, Co, Mn, Fe, Ti, V, x is more than or equal to 0 and less than or equal to 5, y is more than or equal to 0 and less than or equal to 5), and the like.
In the embodiments of the present application, the separator may be an existing conventional separator, including but not limited to, a single PP (polypropylene), a single PE (polyethylene), a double PP/PE, a double PP/PP, and a triple PP/PE/PP separator.
As shown in fig. 3, the present embodiment further provides a terminal, where the terminal 200 may be a mobile phone, a tablet computer, a notebook computer, a portable device, an intelligent wearable product, an automobile, and the like, and includes a housing 201, and an electronic component and a battery (not shown in the figure) accommodated in the housing 201, where the battery supplies power to the electronic component, where the battery is the secondary battery provided in the present embodiment, and the housing 201 may include a front cover assembled on a front side of the terminal and a rear shell assembled on a rear side, and the battery may be fixed inside the rear shell.
The technical solution of the embodiments of the present application is further described below by specific examples.
Example 1
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (hexamethyldisilazane-based) pentafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (A) into the solution, and uniformly mixing the mixture to obtain the electrolyte disclosed by the embodiment 1 of the invention. Wherein, LiPF6Is 1.0mol/l, and the mass percentages of EC, DEC, PC and PP are respectively25:25:30:20, and the mass percentage of the additive (A) is 5 percent.
Figure BDA0002471309210000101
Production of lithium secondary batteries:
weighing 2% of polyvinylidene fluoride (PVDF), 2% of conductive agent super P and 96% of lithium cobaltate (LiCoO) in percentage by mass2) Sequentially adding the mixture into N-methylpyrrolidone (NMP), fully stirring and uniformly mixing, coating the slurry on an aluminum foil current collector, drying, cold pressing and cutting to obtain the positive pole piece.
Weighing 1.5% of CMC (sodium carboxymethylcellulose), 2.5% of SBR (styrene butadiene rubber), 1% of acetylene black and 95% of graphite in percentage by mass, sequentially adding the materials into deionized water, fully stirring and uniformly mixing, coating the slurry on a copper foil current collector, drying, cold pressing and slitting to obtain the negative pole piece.
And (3) preparing the prepared positive pole piece, negative pole piece and commercial PE diaphragm into a battery cell, packaging by adopting a polymer, filling the electrolyte prepared in the embodiment 1, and preparing the soft package lithium secondary battery by the processes of formation and the like.
Example 2
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) And lithium difluoroborate (LiDFOB) are dissolved in the solvent, the mixture is stirred and mixed into a uniform solution, then the (hexaethyldisilizalkyl) pentafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (B) is added into the solution, and the uniform mixing is carried out to prepare the electrolyte of the embodiment 2 of the invention. Wherein, LiPF6The concentration of (A) was 1.0 mol/liter, the concentration of LiDFOB was 0.05 mol/liter, the mass percentages of EC, DEC, PC and PP were 25:25:30:20, respectively, and the mass percentage of additive (B) was 3%.
Figure BDA0002471309210000111
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 2 was used and the other operations were the same as in example 1.
Example 3
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (hexa-trifluoromethyl disilizane alkyl) pentafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (C) into the solution, and uniformly mixing the mixture to obtain the electrolyte of the embodiment 3. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively, and the mass percentage of the additive (C) is 5%.
Figure BDA0002471309210000112
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 3 was used and the other operations were the same as in example 1.
Example 4
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, then adding the (1-ethoxy) (3-hexamethyldisilazane-based) tetrafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (D) and fluoroethylene carbonate (FEC) into the solution respectively, and uniformly mixing the solution to obtain the electrolyte of the embodiment 4 of the invention. Wherein, LiPF6Is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively, and the mass percentages of additive (D) and FEC are 25:30:20, respectively3% and 3%.
Figure BDA0002471309210000121
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 4 was used, and the other operations were the same as example 1.
Example 5
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (hexamethyldisilazane) (trifluoroethoxy) tetrafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (E) into the solution, and uniformly mixing the solution to obtain the electrolyte disclosed by the embodiment 5 of the invention. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively, and the mass percentage of the additive (E) is 3%.
Figure BDA0002471309210000122
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 5 was used, and the other operations were the same as example 1.
Example 6
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (hexamethyldisilazane) (phenoxy) cyclotriphosphazene tetrafluoride additive with the molecular structural formula shown as the formula (F) into the solution, and uniformly mixing the mixture to obtain the electrolyte of the embodiment 6 of the invention. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively, and the mass percentage of the additive (F) is 5%.
Figure BDA0002471309210000123
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 6 was used, and the other operations were the same as example 1.
Example 7
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (di-hexamethyldisilazane-based) cyclotriphosphazene tetrafluoride additive with the molecular structural formula shown as the formula (G) into the solution, and uniformly mixing the solution to obtain the electrolyte disclosed by the embodiment 7 of the invention. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively, and the mass percentage of the additive (G) is 3%.
Figure BDA0002471309210000131
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 7 was used, and the other operations were the same as example 1.
Example 8
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving in the solvent, stirring to obtain uniform solution, and mixing with (tri-hexamethyldisilazane) trifluorocyclotriazine with molecular structural formula shown as formula (H)And adding the phosphazene additive into the solution, and uniformly mixing to obtain the electrolyte of the embodiment 8 of the invention. Wherein, LiPF6The concentration of (A) was 1.0mol/l, the mass percentages of EC, DEC, PC and PP were 25:25:30:20, respectively, and the mass percentage of the additive (H) was 2%.
Figure BDA0002471309210000132
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 8 was used, and the other operations were the same as example 1.
Example 9
Preparing electrolyte: in an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving the mixture in the solvent, stirring and mixing the mixture to obtain a uniform solution, adding the (hexamethyldisilazane) (methylsulfonyl) tetrafluorocyclotriphosphazene additive with the molecular structural formula shown as the formula (H) into the solution, and uniformly mixing the solution to obtain the electrolyte of the embodiment 9 of the invention. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20 respectively, and the mass percentage of the additive (I) is 3%.
Figure BDA0002471309210000141
Production of lithium secondary batteries:
the only difference from example 1 is that the electrolyte prepared in example 9 was used, and the other operations were the same as example 1.
Comparative example 1
In an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) Dissolving in the above solvent, and stirring to obtain the final productThe electrolyte of comparative example 1 was noted. Wherein, LiPF6The concentration of (A) was 1.0mol/l, and the mass percentages of EC, DEC, PC and PP were 25:25:30:20, respectively.
Production of lithium secondary batteries:
the difference from example 1 is only that the electrolyte prepared in comparative example 1 was used and the other operations were the same as example 1.
Comparative example 2
In an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) And lithium difluoroborate (LiDFOB) were dissolved in the above solvent, and mixed with stirring to obtain an electrolyte solution of comparative example 2 of the present invention. Wherein, LiPF6Is 1.0mol/l, the concentration of LiDFOB is 0.05mol/l, and the mass percentages of EC, DEC, PC and PP are 25:25:30:20, respectively.
Production of lithium secondary batteries:
the difference from example 1 is only that the electrolyte prepared in comparative example 2 was used and the other operations were the same as example 1.
Comparative example 3
In an argon filled glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed to form an organic solvent, and fully dried lithium hexafluorophosphate (LiPF) was added6) The electrolyte of comparative example 3 of the present invention was prepared by dissolving the above-mentioned solvent in water, mixing with stirring to obtain a homogeneous solution, and then adding fluoroethylene carbonate (FEC) to the above-mentioned solution and mixing uniformly. Wherein, LiPF6The concentration of (A) is 1.0mol/l, the mass percentages of EC, DEC, PC and PP are 25:25:30:20 respectively, and the mass percentage of FEC is 3%.
Production of lithium secondary batteries:
the difference from example 1 is only that the electrolyte prepared in comparative example 3 was used and the other operations were the same as example 1.
The electrolytes and lithium secondary batteries of examples 1 to 9 of the present application and comparative examples 1 to 3 were subjected to the following performance tests:
1. electrolyte self-extinguishing performance test
1.0 g of electrolyte was placed in a 5.0 ml crucible and ignited to test the self-extinguishing time. The ignition device is used for quickly igniting, the ignition time is recorded, and the time from the ignition device being removed to the flame being automatically extinguished is recorded, namely the self-extinguishing time (SET). SET tests were performed 5 times and averaged for each electrolyte sample. And comparing the flame retardant performances of different electrolytes by taking the self-extinguishing time of the electrolyte in unit mass as a standard.
2. Lithium secondary battery performance test
2.1 testing of cycle Performance
The battery is subjected to charge-discharge cycle test at a charge-discharge rate of 1.0/1.0C, and the graphite/LiCoO2The voltage range of the battery was 3.0V to 4.48V, and the capacity retention ratio was recorded for 100 weeks.
2.2 high temperature storage Performance testing
Under the condition of the ambient temperature of 25 +/-3 ℃, the battery is charged and discharged for 1 time according to 0.2C/0.2C, and the capacity of the time is the initial capacity; the battery is fully charged again according to 0.2C, the charged battery is placed for 24 hours at the temperature of 70 ℃, then the battery is opened and placed for 2 hours at the room temperature, the battery is discharged to the end voltage at the constant current of 0.2C, and the voltage is recorded as the residual capacity, graphite/LiCoO2The voltage range of the battery was 3.0V-4.48V, and the remaining capacity retention ratio (remaining capacity/initial capacity 100%) was recorded.
The test results of examples 1 to 9 and comparative examples 1 to 3 are shown in Table 1 and FIG. 4.
TABLE 1 test data for examples 1-9 and comparative examples 1-3
Figure BDA0002471309210000151
As can be seen from table 1 and fig. 4, the electrolyte of examples 1 to 9 of the present application has certain flame resistance, because the electrolyte of examples 1 to 9 is added with an appropriate amount of the electrolyte additive of the present application, and when the electrolyte is heated, the cyclotriphosphazene structure in the electrolyte additive of the present application decomposes to generate P-based radicals to capture H or OH radicals generated by the electrolyte decomposition due to heating, and the chain reaction is cut off, so that the flame resistance of the electrolyte can be improved.
In addition, as can be seen from table 1 and fig. 4, the batteries of examples 1 to 9 of the present application have better high-voltage cycle performance, and the batteries exhibit higher capacity retention rate after 100 cycles and also exhibit better high-temperature storage performance, compared to comparative examples 1 to 3, because the electrolytes of examples 1 to 9 are added with appropriate amounts of the electrolyte additives of the examples of the present application. On the one hand, the electrolyte additive contains the silicon nitrogen structure, HF generated by decomposition of the electrolyte can be effectively captured, the influence of the HF on the anode material is avoided, meanwhile, the cyclotriphosphazene structure in the electrolyte additive can be subjected to oxidative decomposition under the high-voltage condition, a stable interface film can be formed on the surface of the anode, side reactions caused by direct contact of the electrolyte and the anode material are further prevented, and therefore the high-voltage cycle performance and the high-temperature storage performance of the battery are improved.

Claims (24)

1. The electrolyte additive is characterized in that the molecular structure of the electrolyte additive comprises a cyclotriphosphazene six-membered ring structure, six substituent groups are totally arranged on three phosphorus atoms in the cyclotriphosphazene six-membered ring structure, and at least one substituent group in the six substituent groups is-N (SiR)1'R2'R3')(SiR4'R5'R6') wherein said R is1'、R2'、R3'、R4'、R5'、R6' are respectively selected from any one of alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, alkenyl, halogenated alkenyl, alkenyloxy, halogenated alkenyloxy, aryl, halogenated aryl, aryloxy and halogenated aryloxy.
2. The electrolyte additive of claim 1 wherein of the six substituent groups, except the-N (SiR)1'R2'R3')(SiR4'R5'R6') are each independently selected from the group consisting of fluorine, chlorine, bromine, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkeneAny one of an oxy group, a haloalkenyloxy group, an aryl group, a haloaryl group, an aryloxy group, a haloaryloxy group, a substituted sulfonic acid group, a substituted phosphate group, a substituted imide group and a substituted sulfonylimide group.
3. The electrolyte additive of claim 2 wherein one or more of the remaining substituent groups is fluorine, chlorine, bromine, a haloalkyl, a haloalkoxy, a haloalkenyl, a haloalkenyloxy, a haloaryl, or a haloaryloxy.
4. The electrolyte additive of claim 3 wherein one or more of the remaining substituent groups are fluorine, fluoroalkyl, fluoroalkoxy, fluoroalkenyl, fluoroalkenoxy, fluoroaryl, or fluoroaryloxy.
5. The electrolyte additive of any of claims 2-4 wherein one of the six substituent groups is-N (SiR)1'R2'R3')(SiR4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (I):
Figure FDA0002471309200000011
in the formula (I), R is1、R2、R3、R4、R5Are the remaining substituent groups.
6. The electrolyte additive of any of claims 2-4 wherein two of the six substituent groups are-N (SiR)1'R2'R3')(SiR4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (II):
Figure FDA0002471309200000012
in the formula (II), R is1、R2、R3、R5Are the remaining substituent groups.
7. The electrolyte additive of any of claims 2-4 wherein three of the six substituent groups are-N (SiR)1'R2'R3')(SiR4'R5'R6') said R2、R4And R6is-N (SiR)1'R2'R3')(SiR4'R5'R6') the chemical structural formula of the electrolyte additive is shown as formula (III):
Figure FDA0002471309200000021
in the formula (III), the R1、R3、R5Are the remaining substituent groups.
8. The electrolyte additive of any one of claims 1-7 wherein R is1'、R2'、R3'、R4'、R5'、R6In the item' above, the alkyl group, haloalkyl group, alkoxy group, haloalkoxy group have 1 to 20 carbon atoms; the carbon atom number of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy is 2-20; the number of carbon atoms of the aryl, halogenated aryl, aryloxy and halogenated aryloxy is 6-20.
9. The electrolyte additive of any one of claims 1-8 wherein R is1'、R2'、R3'、R4'、R5'、R6In the' case, the halogen in the haloalkyl group, the haloalkoxy group, the haloalkenyl group, the haloalkenyloxy group, the haloaryl group and the haloaryloxy group includes fluorine, chlorine, bromine, and the like,Iodine, said halo being perhalo or partially halo.
10. The electrolyte additive according to any one of claims 2 to 9, wherein in the remaining substituent groups, the number of carbon atoms of the alkyl group, the halogenated alkyl group, the alkoxy group, the halogenated alkoxy group is 1 to 20; the carbon atom number of the alkenyl, the halogenated alkenyl, the alkenyloxy and the halogenated alkenyloxy is 2-20; the number of carbon atoms of the aryl, halogenated aryl, aryloxy and halogenated aryloxy is 6-20.
11. The electrolyte additive according to any one of claims 2 to 10 wherein the halogen in the haloalkyl, haloalkoxy, haloalkenyl, haloalkenyloxy, haloaryl and haloaryloxy groups in the remaining substituent groups comprises fluorine, chlorine, bromine, iodine, and the halogen is perhalogenated or partially halogenated.
12. A secondary battery electrolyte comprising an electrolyte salt, a non-aqueous organic solvent and an additive comprising the electrolyte additive of any one of claims 1-11.
13. The secondary battery electrolyte of claim 12 wherein the electrolyte additive is present in the secondary battery electrolyte in an amount of 0.1% to 10% by weight.
14. The secondary-battery electrolyte of claim 12 or 13 wherein the electrolyte salt comprises at least one of a lithium salt, a sodium salt, a potassium salt, a magnesium salt, a zinc salt, and an aluminum salt.
15. The secondary battery electrolyte of any of claims 12-14 wherein the electrolyte salt comprises MClO4、MBF4、MPF6、MAsF6、MPF2O2、MCF3SO3、MTDI、MB(C2O4)2、MBF2C2O4、M[(CF3SO2)2N]、M[(FSO2)2N]And M [ (C)mF2m+1SO2)(CnF2n+1SO2)N]Wherein M is Li, Na or K, and M and n are natural numbers.
16. The secondary-battery electrolyte of any of claims 12-15 wherein the molar concentration of the electrolyte salt in the secondary-battery electrolyte is from 0.01mol/L to 8.0 mol/L.
17. The secondary battery electrolyte as claimed in any one of claims 12 to 16 wherein the non-aqueous organic solvent comprises one or more of a carbonate-based solvent, an ether-based solvent, and a carboxylate-based solvent.
18. The secondary battery electrolyte of any of claims 12-17 wherein the additives further comprise other additives including one or more of fluoroethylene carbonate, biphenyl, fluorobenzene, vinylene carbonate, trifluoroethylene carbonate, ethylene carbonate, 1, 3-propanesultone, 1, 4-butanesultone, vinyl sulfate, vinyl sulfite, succinonitrile, adiponitrile, 1, 2-bis (2-cyanoethoxy) ethane, and 1,3, 6-hexanetrinitrile.
19. A secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, the electrolyte comprising the secondary battery electrolyte according to any one of claims 12 to 18.
20. The secondary battery of claim 19, wherein the negative electrode comprises one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a lithium negative electrode, a sodium negative electrode, a potassium negative electrode, a magnesium negative electrode, a zinc negative electrode, and an aluminum negative electrode.
21. The secondary battery of claim 20, wherein the carbon-based negative electrode comprises one or more of graphite, hard carbon, soft carbon, graphene; the silicon-based negative electrode comprises one or more of silicon, silicon carbon, silicon oxygen and silicon metal compounds; the tin-based negative electrode comprises one or more of tin, tin carbon, tin oxygen and tin metal compounds; the lithium negative electrode includes metallic lithium or a lithium alloy.
22. The secondary battery of claim 21, wherein the lithium alloy comprises 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.
23. The secondary battery according to claim 20, wherein the secondary battery comprises a lithium secondary battery, a potassium secondary battery, a sodium secondary battery, a magnesium secondary battery, a zinc secondary battery, or an aluminum secondary battery.
24. A terminal comprising a housing, and an electronic component and a battery housed in the housing, the battery supplying power to the electronic component, the battery comprising the secondary battery according to any one of claims 19 to 23.
CN202010349137.3A 2020-04-28 2020-04-28 Electrolyte additive, secondary battery electrolyte, secondary battery and terminal Pending CN113571769A (en)

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