CN112186256A - Electrolyte for lithium metal battery and preparation method and application thereof - Google Patents

Electrolyte for lithium metal battery and preparation method and application thereof Download PDF

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CN112186256A
CN112186256A CN201910593941.3A CN201910593941A CN112186256A CN 112186256 A CN112186256 A CN 112186256A CN 201910593941 A CN201910593941 A CN 201910593941A CN 112186256 A CN112186256 A CN 112186256A
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electrolyte
lithium
lithium metal
metal battery
carbonate
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李伟善
张乾魁
刘思
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South China Normal University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • 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

Abstract

The invention provides an electrolyte for a lithium metal battery, which comprises the following components: organic solvent and electrolyte lithium salt after water removal; the organic solvent comprises the following components: ethylene carbonate and bis (2,2, 2-trifluoroethyl) carbonate. The battery prepared by the electrolyte has the characteristics of preventing the electrolyte from burning and promoting the lithium metal cathode to form a film, and the electrolyte can form a stable SEI film on the surface of the lithium metal cathode, so that the reaction of the lithium and the electrolyte is effectively blocked, the interface stability of the lithium metal cathode/the electrolyte is obviously improved, and the cycle stability of the lithium metal battery is improved.

Description

Electrolyte for lithium metal battery and preparation method and application thereof
Technical Field
The invention belongs to the field of lithium metal batteries, and particularly relates to an electrolyte for a lithium metal battery, and a preparation method and application thereof.
Background
The metal lithium has a theoretical specific capacity as high as 3860mAh/g and an ultra-negative electrode potential of-3.04V (relative to a standard hydrogen electrode), and is an ideal negative electrode for constructing a high-specific-energy battery. With the increasing demand for energy density of batteries in the fields of advanced portable electronic products, electric vehicles and the like, the development of high specific energy secondary batteries based on metallic lithium cathodes has become a research hotspot in the field of chemical power sources in recent years. The negative electrode material used in the current research is mainly lithium metal, the electrolyte is widely prepared by adopting a mixed system of cyclic carbonate and linear carbonate, considering the physicochemical properties such as solvent viscosity, conductivity and the like, and adding different functional additive components to meet the requirements of various application scenes on the electrolyte properties.
The carbonate is capable of forming a relatively stable reduction product, alkyl lithium carbonate, at the lithium metal negative electrode, and is essential in the electrolyte composition. However, the mechanical strength of the alkyl lithium carbonate is low (less than 1GPa), so that the SEI film has poor mechanical strength, and is difficult to adapt to the volume expansion of the lithium metal battery in the circulation process, and finally the cycle life of the metal battery is shortened. In lithium metal batteries, however, the current strategies for constructing stable SEI films can be classified into the following categories: (1) an artificial SEI film (such as LiF, Li) is constructed on the surface of lithium metal3N,Li3PO4Etc.); (2) adopting organic or inorganic solid electrolyte as a lithium surface modification layer; (3) adopting a high-concentration lithium salt electrolyte; (4) the solvent composition is optimized to stabilize the lithium metal negative electrode. In contrast, optimizing the solvent composition to stabilize the lithium metal negative electrode is one of the simple and effective methods to solve this problem. Research shows that fluoroethylene carbonate is used in the electrolyte, and vinylene carbonate is used as a solvent to generate a stable SEI film and inhibit the reaction between lithium metal and the electrolyte. However, the solvent components reported at present have limited functions, and have major defects in particular in the aspects of constructing stable SEI films and flame retardance. Therefore, it is still very important to find new organic solvents with excellent electrochemical properties.
Disclosure of Invention
Accordingly, an object of the present invention is to provide an electrolyte for a lithium metal battery, which is used in the lithium metal battery to solve the problem of the combustion of a carbonate-based electrolyte of the lithium metal battery and to prolong the cycle life of the lithium metal battery.
In order to achieve the purpose, the specific technical scheme of the invention is as follows:
an electrolyte for a lithium metal battery, comprising the following components:
organic solvent and electrolyte lithium salt after water removal;
the organic solvent comprises the following components: ethylene carbonate and bis (2,2, 2-trifluoroethyl) carbonate.
The invention also provides a preparation method of the electrolyte for the lithium metal battery, which comprises the following steps:
a preparation method of electrolyte for a lithium metal battery comprises the following steps:
(1) purifying the organic solvent to remove impurities and water;
(2) mixing electrolyte lithium salt with the organic solvent in the step (1).
The invention also provides an application of the electrolyte for the lithium metal battery, which comprises the following specific steps:
the electrolyte for the lithium metal battery is applied to promoting the film formation of the negative electrode of the lithium metal battery.
The invention also provides a metal battery, which comprises the following components in part by weight:
a lithium metal battery comprising: the electrolyte for a lithium metal battery as described above.
Based on the technical scheme, the invention has the following beneficial effects:
the electrolyte for the lithium metal battery is prepared by reasonably matching ethylene carbonate, bis (2,2, 2-trifluoroethyl) carbonate and electrolyte lithium salt, wherein ethylene carbonate (VEC) in the electrolyte system can participate in the construction of an interface film on the surface of a lithium cathode to form a stable interface film, so that the parasitic reaction of lithium metal and the electrolyte is inhibited, and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) is matched to generate fluorine radicals under the heating condition, so that the fluorine radicals can be combined with electrolyte hydrogen radicals to prevent the generation of hydrogen, and the combustion of the electrolyte is prevented. The battery prepared by the electrolyte has the characteristics of preventing the electrolyte from burning and promoting the lithium metal cathode to form a film, and the electrolyte can form a stable SEI film on the surface of the lithium metal cathode, so that the reaction of the lithium and the electrolyte is effectively blocked, the interface stability of the lithium metal cathode/the electrolyte is obviously improved, and the cycle stability of the lithium metal battery is improved.
Drawings
FIG. 1 is a graph comparing the results of battery cycling tests for electrolyte assemblies of example 1 and comparative example 1;
FIG. 2 is a graph comparing the results of battery cycling tests for electrolyte assemblies of example 2 and comparative example 1;
FIG. 3 is a graph comparing the results of battery cycling tests for electrolyte assemblies of example 3 and comparative example 1;
FIG. 4 is a graph showing the results of a combustion test conducted on the electrolytes of example 1 and comparative example 1;
FIG. 5 shows the deposition of 2mAh cm on a copper foil in a general electrolyte of comparative example 1-2Low power plot of lithium amount;
FIG. 6 shows the deposition of 2mAh cm on a copper foil in a general electrolyte of comparative example 1-2A high power plot of lithium amount;
FIG. 7 shows the deposition of 2mAh cm on copper foil in the novel electrolyte prepared in example 1-2Low power plot of lithium amount;
FIG. 8 shows the deposition of 2mAh cm on copper foil in the novel electrolyte prepared in example 1-2High power plot of lithium amount.
Detailed Description
In order that the invention may be more readily understood, reference will now be made to the following more particular description of the invention, examples of which are set forth below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete. It is to be understood that the experimental procedures in the following examples, where specific conditions are not noted, are generally in accordance with conventional conditions, or with conditions recommended by the manufacturer. The various reagents used in the examples are commercially available.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
One of the inventionAn electrolyte for a lithium metal battery, comprising the following components: an organic solvent and an electrolytic lithium salt; the organic solvent comprises the following components: ethylene carbonate and bis (2,2, 2-trifluoroethyl) carbonate. Ethylene Carbonate (VEC) in the electrolyte system can participate in the construction of an interfacial film on the surface of a lithium negative electrode, and a layer rich in Li is formed on the surface of the negative electrode through reduction2CO3The SEI film of (1), the film containing Li2CO3The SEI film has a certain mechanical strength capable of effectively resisting breakage of lithium metal during a cycle, and simultaneously, the component facilitates diffusion of lithium ions and promotes uniform lithium deposition on the surface of the lithium metal, thereby inhibiting a parasitic reaction of the lithium metal with an electrolyte. The main substance generated on the surface of lithium metal by common ethylene carbonate is lithium alkyl carbonate (ROCO)2Li), generally such organic components are considered porous and brittle and do not have sufficient mechanical strength to accommodate the volume expansion of lithium during the precipitation dissolution process. Bis (2,2, 2-trifluoroethyl) carbonate (TFEC) is capable of generating fluorine radicals under heating, which can combine with electrolyte hydrogen radicals, preventing the generation of hydrogen gas, thus preventing the electrolyte from burning.
Preferably, the volume ratio of the ethylene carbonate in the organic solvent is more than 10%. More preferably, the volume fraction is between 10% and 90%.
Preferably, the volume ratio of the ethylene carbonate to the bis (2,2, 2-trifluoroethyl) carbonate is 1: 9-9: 1. More preferably, the concentration is 3: 7-7: 3.
Preferably, the electrolyte lithium salt has a concentration of 0.5 to 1.5mol/L in the electrolyte solution for a lithium metal battery. More preferably, the concentration is 0.8 to 1.2 mol/L. Further preferably 1 mol/L. Too high a lithium salt may result in a decrease in ionic conductivity and an increase in viscosity of the electrolyte.
Preferably, the electrolytic lithium salt is selected from: one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium hexafluoroarsenate, lithium bistrifluoromethylsulfonimide and lithium bistrifluoromethylsulfonimide.
Preferably, the organic solvent further comprises one or more of vinylene carbonate, fluoroethylene carbonate, dimethyl sulfite, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, gamma-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and butyl propionate.
The invention discloses a preparation method of electrolyte for a lithium metal battery, which comprises the following steps: (1) purifying the organic solvent to remove impurities and water; (2) mixing electrolyte lithium salt with the organic solvent in the step (1).
Preferably, the purification, impurity removal and water removal are preferably carried out by any one or more of molecular sieve, activated carbon, calcium hydride, lithium hydride, anhydrous calcium oxide, calcium chloride, phosphorus pentoxide and alkali metal or alkaline earth metal. More preferably, the molecular sieve can be used
Figure BDA0002117014460000041
The model is,
Figure BDA0002117014460000042
Type or
Figure BDA0002117014460000043
Type, preferably selected from
Figure BDA0002117014460000044
Type or
Figure BDA0002117014460000045
And (4) molding.
Specifically, the steps of purifying the organic solvent to remove impurities and removing water are as follows: the purification, impurity removal and water removal are preferably carried out by any one or more of molecular sieve, active carbon, calcium hydride, lithium hydride, anhydrous calcium oxide, calcium chloride, phosphorus pentoxide and alkali metal or alkaline earth metal. More preferably, the molecular sieve can be used
Figure BDA0002117014460000051
The model is,
Figure BDA0002117014460000052
Type or
Figure BDA0002117014460000053
Type, preferably selected from
Figure BDA0002117014460000054
Type or
Figure BDA0002117014460000055
And (4) molding. The purpose is to remove the water in the electrolyte and prevent the lithium hexafluorophosphate from being hydrolyzed to generate hydrofluoric acid and damage the electrode material. The water removal treatment should be such that the water content in the electrolyte is less than 10 ppm.
The invention also provides application of the electrolyte for the lithium metal battery in promoting film formation of a negative electrode of the lithium metal battery.
A lithium metal battery of the present invention includes: the electrolyte for a lithium metal battery as described above. Ethylene Carbonate (VEC) in the electrolyte system can participate in the construction of an interfacial film on the surface of the lithium negative electrode to form a stable interfacial film, so that the parasitic reaction of lithium metal and the electrolyte is inhibited. Therefore, the electrolyte which can not only prevent the electrolyte from burning but also promote the film formation of the lithium metal negative electrode and the lithium metal battery using the electrolyte are realized, and the obtained battery has excellent electrochemical performance.
Preferably, the battery further comprises: lithium metal, a positive pole piece, a diaphragm and a negative pole piece.
More preferably, the positive electrode tab includes: the lithium-extracting active material, a conductive agent, a current collector and a binder, wherein the binder is used for combining the lithium-extracting active material with the current collector; and/or
The negative pole piece is a lithium metal electrode.
Further preferably, the lithium-deintercalated active material is one or more of metal oxides of lithium, Mg, Al, B, Ti, Sn, Ge, Fe, Sr, Ga, rare earth elements.
Example 1
The preparation method of the electrolyte for the lithium metal battery comprises the following steps:
mixing ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) according to a volume ratio of VEC to TFEC of 3:7, purifying by adopting a molecular sieve, calcium hydride and lithium hydride, removing impurities, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
at room temperature, adding LiPF serving as an electrolyte lithium salt6Dissolving in the mixed solvent to make the final concentration of electrolyte lithium salt be 1.0mol/L, stirring uniformly, standing to obtain the novel electrolyte for lithium metal battery.
Wherein, the chemical structural formulas of VEC and TFFEC are as follows:
Figure BDA0002117014460000061
example 2
Ethylene Carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) in a volume ratio VEC: TFEC ═ 1:1, mixing, purifying and removing impurities by adopting a molecular sieve, calcium hydride and lithium hydride, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
at room temperature, adding LiPF serving as an electrolyte lithium salt6Dissolving in the mixed solvent to make the final concentration of electrolyte lithium salt be 1.0mol/L, stirring uniformly, standing to obtain the novel electrolyte for lithium metal battery.
The difference from example 1 is that VEC and TFEC are mixed in a volume ratio VEC to TFEC of 1:1, and the rest of the procedure is the same.
Example 3
Mixing ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) according to the volume ratio of VEC to TFEC of 7:3, purifying by adopting a molecular sieve, calcium hydride and lithium hydride, removing impurities, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
at room temperature, adding LiPF serving as an electrolyte lithium salt6Dissolving in the mixed solvent to make the final concentration of electrolyte lithium salt be 1.0mol/L, stirring uniformly, standing to obtain the novel electrolyte for lithium metal battery.
The difference from the embodiment 1 is that,VEC and TFEC were mixed at a volume ratio of VEC to TFEC of 7:3, and the rest of the procedure was the same.
Example 4
Mixing ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) according to a volume ratio of VEC to TFEC of 3:7, purifying by adopting a molecular sieve, calcium hydride and lithium hydride, removing impurities, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
and dissolving electrolyte lithium salt LiFSI in the mixed solvent at room temperature to ensure that the final concentration of the electrolyte lithium salt is 1.0mol/L, uniformly stirring, and standing to obtain the novel electrolyte for the lithium metal battery.
The difference from example 1 is that the electrolytic lithium salt is LiFSI, and the rest of the procedure is the same.
Example 5
Mixing ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) according to a volume ratio of VEC to TFEC of 1:1, purifying by adopting a molecular sieve, calcium hydride and lithium hydride, removing impurities, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
and dissolving electrolyte lithium salt LiFSI in the mixed solvent at room temperature to ensure that the final concentration of the electrolyte lithium salt is 1.0mol/L, uniformly stirring, and standing to obtain the novel electrolyte for the lithium metal battery.
Differs from example 1 in that VEC and TFEC are mixed in a volume ratio of VEC to TFEC of 1:1, and the electrolyte lithium salt is LiFSI, the rest steps are the same.
Example 6
Mixing ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) according to the volume ratio of VEC to TFEC of 7:3, purifying by adopting a molecular sieve, calcium hydride and lithium hydride, removing impurities, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
and dissolving electrolyte lithium salt LiFSI in the mixed solvent at room temperature to ensure that the final concentration of the electrolyte lithium salt is 1.0mol/L, uniformly stirring, and standing to obtain the novel electrolyte for the lithium metal battery.
Differences from example 1In that VEC and TFEC are mixed in a volume ratio of VEC to TFEC of 7:3, and the electrolyte lithium salt is LiFSI, the rest steps are the same.
Example 7
Mixing ethylene carbonate (VEC), bis (2,2, 2-trifluoroethyl) carbonate (TFEC) and Ethyl Methyl Carbonate (EMC) according to the volume ratio of VEC to TFEC to EMC (1: 1: 1), purifying and removing impurities by adopting a molecular sieve, calcium hydride and lithium hydride, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
at room temperature, adding LiPF serving as an electrolyte lithium salt6Dissolving in the mixed solvent to make the final concentration of electrolyte lithium salt be 1.0mol/L, stirring uniformly, standing to obtain the novel electrolyte for lithium metal battery. Comparative example 1
Mixing Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) in a volume ratio of EC to EMC of 3:7, purifying and removing impurities by adopting a molecular sieve, calcium hydride and lithium hydride, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
at room temperature, adding LiPF serving as an electrolyte lithium salt6Dissolving in the mixed solvent to make the final concentration of electrolyte lithium salt be 1.0mol/L, stirring uniformly, standing to obtain the novel electrolyte for lithium metal battery.
The difference from example 1 is that in example 1, ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) are mixed in the mixed solvent, and in comparative example 1, Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) are mixed in a volume ratio EC: EMC of 3:7, and the rest steps are the same.
Comparative example 2
Mixing Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) in a volume ratio of EC to EMC of 3:7, purifying and removing impurities by adopting a molecular sieve, calcium hydride and lithium hydride, and removing water (the water content is less than 10ppm) to obtain a mixed solvent;
and dissolving electrolyte lithium salt LiFSI in the mixed solvent at room temperature to ensure that the final concentration of the electrolyte lithium salt is 1.0mol/L, uniformly stirring, and standing to obtain the novel electrolyte for the lithium metal battery.
The difference from example 1 is that in example 1, ethylene carbonate (VEC) and bis (2,2, 2-trifluoroethyl) carbonate (TFEC) are mixed in the mixed solvent, in comparative example 2, Ethylene Carbonate (EC) and methyl ethyl carbonate (EMC) are mixed in a volume ratio EC: EMC of 3:7, and the electrolyte lithium salt is LiFSI for ratio 2, and the rest of the procedure is the same.
Example 7 Battery Performance testing
Example 1 and comparative example 1 the resulting Li/Cu cell was assembled separately and tested using standard methods for Li/Cu cell testing (1mA cm)-2Discharging and keeping constant current for 1 h; 1mA cm-2Voltage is more than or equal to 1V) are subjected to cycle test, and the results are shown in figures 1-3.
It can be seen that the average coulombic efficiency of the cells assembled with the common electrolyte of comparative example 1 was 62.9% after 200 cycles, whereas the average coulombic efficiency was as high as 98.1% after 700 cycles using the novel electrolyte cell prepared in example 1, and the average coulombic efficiency was as high as 97.4% and 97.8% after 700 cycles using the novel electrolyte cell prepared in examples 2 and 3. The results show that the common electrolyte prepared from Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) forms a solid electrolyte interface film (SEI) which is unstable and is not beneficial to the deposition and extraction of lithium. The novel electrolyte provided by the embodiments 1 to 3 of the invention can form a stable SEI film on the surface of the lithium metal cathode, effectively block the reaction of the bulk lithium and the electrolyte, and remarkably improve the interface stability of the lithium metal cathode/electrolyte, thereby improving the cycle stability of the lithium metal battery.
Example 8 Combustion test
The electrolyte of example 1 and the electrolyte of comparative example 1 were subjected to a combustion test, and the results are shown in fig. 4.
It can be seen that the left side is the normal electrolyte of comparative example 1 and the right side is the novel electrolyte of example 1. Ordinary electrolyte is very easily burnt, and novel electrolyte still can not burn through many times of ignition test. The main reason for the combustion of the common electrolyte is that the electrolyte generates a large amount of hydrogen radicals under the heating condition, and the hydrogen radicals react with each other to generate hydrogen gas, so that the electrolyte is combusted. The novel electrolyte can generate fluorine free radicals under the condition of heating, and the fluorine free radicals are combined with the hydrogen free radicals to prevent the generation of hydrogen, so that the flame retardant effect is achieved.
Similarly, the electrolyte of the embodiment 2-3 can not be combusted after a plurality of ignition tests by carrying out a combustion test, and has good flame retardant effect.
Example 9
The amount of lithium deposited on the copper foil in the electrolytes of example 1 and comparative example 1 was measured by scanning electron microscopy, and the results are shown in FIGS. 5 to 8.
Wherein, FIG. 5 shows that 2mAh cm is deposited on the copper foil in the general electrolyte of comparative example 1-2Low power of lithium amount, uneven surface, and many dendritic lithium formation.
FIG. 6 shows the deposition of 2mAh cm on a copper foil in a general electrolyte of comparative example 1-2High power plot of lithium amount, it can be seen that many dendritic lithium deposits, surface and attachment of many electrolyte decomposition products.
FIG. 7 shows the deposition of 2mAh cm on copper foil in the novel electrolyte prepared in example 1-2Low power plot of lithium amount, flat surface, and many block-like lithium generation.
FIG. 8 shows the deposition of 2mAh cm on copper foil in the novel electrolyte prepared in example 1-2High-power plot of the amount of lithium, many massive lithium deposits can be seen, the surface is relatively smooth, and no electrolyte decomposition products are produced.
The result shows that the novel electrolyte can obviously improve the cycle stability and the safety of the lithium metal battery.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, the scope of the present description should be considered as being described in the present specification.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (12)

1. An electrolyte for a lithium metal battery, comprising the following components:
organic solvent and electrolyte lithium salt after water removal;
the organic solvent comprises the following components: ethylene carbonate and bis (2,2, 2-trifluoroethyl) carbonate.
2. The electrolyte for a lithium metal battery according to claim 1, wherein the volume percentage of the ethylene carbonate in the anhydrous organic solvent is 10 to 90%.
3. The electrolyte for a lithium metal battery according to claim 2, wherein the volume ratio of ethylene carbonate to bis (2,2, 2-trifluoroethyl) carbonate is 3:7 to 7: 3.
4. The electrolyte solution for a lithium metal battery according to any one of claims 1 to 3, wherein the concentration of the electrolytic lithium salt in the electrolyte solution for a lithium metal battery is 0.5 to 1.5 mol/L.
5. The electrolyte for a lithium metal battery according to claim 4, wherein the electrolyte lithium salt is selected from the group consisting of: one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium hexafluoroarsenate, lithium bistrifluoromethylsulfonimide and lithium bistrifluorosulfonimide.
6. The electrolyte for a lithium metal battery according to any one of claims 1 to 3, wherein the organic solvent further comprises one or more of vinylene carbonate, fluoroethylene carbonate, dimethyl sulfite, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ -butyrolactone, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and butyl propionate.
7. A preparation method of electrolyte for a lithium metal battery is characterized by comprising the following steps:
(1) purifying the organic solvent according to any one of claims 1 to 6 to remove impurities and water;
(2) mixing electrolyte lithium salt with the organic solvent in the step (1).
8. Use of the electrolyte for a lithium metal battery as claimed in any one of claims 1 to 6 for promoting film formation of a negative electrode of a lithium metal battery.
9. A lithium metal battery, comprising: the electrolyte for a lithium metal battery as recited in any one of claims 1 to 6.
10. The lithium metal battery of claim 9, further comprising: lithium metal, a positive pole piece, a diaphragm and a negative pole piece.
11. The lithium metal battery of claim 10, wherein the positive electrode tab comprises: a lithium-deintercalating active material, a conductive agent, a current collector, and a binder; and/or
The negative pole piece is a lithium metal electrode.
12. The lithium metal battery of claim 11, wherein the lithium-deintercalating active material is one or more of a metal oxide of lithium, Mg, Al, B, Ti, Sn, Ge, Fe, Sr, Ga, and a rare earth element.
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Publication number Priority date Publication date Assignee Title
CN114039092A (en) * 2021-10-28 2022-02-11 湖南法恩莱特新能源科技有限公司 Lithium ion battery electrolyte and preparation method and application thereof

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