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CN111162317A - Electrolyte and lithium ion battery - Google Patents

Electrolyte and lithium ion battery Download PDF

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Publication number
CN111162317A
CN111162317A CN201911304215.1A CN201911304215A CN111162317A CN 111162317 A CN111162317 A CN 111162317A CN 201911304215 A CN201911304215 A CN 201911304215A CN 111162317 A CN111162317 A CN 111162317A
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China
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lithium
electrolyte
negative electrode
ion battery
lithium ion
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朱振涛
赵新新
马俊青
张勇
苗力孝
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Shandong Haike Innovation Research Institute Co Ltd
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Shandong Haike Innovation Research Institute Co Ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/056Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564Accumulators 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
    • H01M10/0566Liquid materials
    • H01M10/0567Liquid materials characterised by the additives
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
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  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides an electrolyte, which comprises phthalimide and vinylene carbonate. According to the invention, phthalimide and vinylene carbonate are compounded for use, and the phthalimide and vinylene carbonate composition forms a stable Solid Electrolyte Interface (SEI) on the surface of an electrode, wherein the SEI has a lithium ion fast channel, reduces internal resistance, and can effectively improve the cycle performance of a battery. The phthalimide and the vinylene carbonate provided by the invention are common industrial chemicals, and the cheap raw materials are compounded to develop the electrolyte for the long-life battery system, so that the method is more suitable for large-scale production and commerce, and also achieves a key challenge faced by the research work of the existing energy storage battery.

Description

Electrolyte and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery.
Background
A lithium ion battery is a secondary battery (rechargeable battery) that mainly operates by movement of lithium ions between a positive electrode and a negative electrode. During charging and discharging, Li+Intercalation and deintercalation to and from two electrodes: upon charging, Li+The lithium ion battery is extracted from the positive electrode and is inserted into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. The battery generally adopts a material containing lithium element as an electrode, and is a representative of modern high-performance batteries. The lithium ion battery generally comprises a positive electrode, a negative electrode, a diaphragm, electrolyte and a shell, has the advantages of high working voltage, high specific energy, long cycle life, light weight, less self-discharge, no memory effect, high cost performance and the like, and becomes a main selection object of a rechargeable power supply in the fields of high-power electric vehicles, artificial satellites, aerospace and the like. With the strong support given by various governments in China and places, various supporting policies and matching policies emerge endlessly, and good environment and opportunity are provided for the development of new energy industry. In recent years, the global new energy industry has seen explosive growth. According to the prediction of ' market prospect and investment prediction analysis report of the Chinese energy storage industry ' of the industry research institute of prospect ', the investment construction scale of the Chinese energy storage industry in 2016-2020 is 1500-2400 billion yuan.
Lithium battery electrolytes are carriers for ion transport in batteries. Generally consisting of a lithium salt and an organic solvent. The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode of the lithium battery, and is a guarantee for the lithium battery to obtain the advantages of high voltage, high specific energy and the like. The electrolyte is prepared from high-purity organic solvent, electrolyte lithium salt, necessary additives and other raw materials according to a certain proportion under a certain condition. With the continuous development of lithium ion batteries in the application field, batteries with high safety and long service life are the basis of energy storage systems. In many research directions, a passivation film, called a solid electrolyte interface film (SEI), is formed on the surface of the negative electrode of the electrolyte during the first charging process of the battery, and the properties of the passivation film greatly determine the electrochemical performance of the battery. Therefore, the improvement of the cycle performance of the battery by adjusting the formula of the electrolyte and the advantage of low comprehensive development cost thereof become one of the main directions of the development of the battery with high safety and long service life.
Currently, the most successful and commonly used electrolyte formulation adjustments in improving battery cycle performance are the addition of small amounts of film-forming additives to the electrolyte formulation. For example, Vinylene Carbonate (VC) is a film-forming additive widely used in commercial lithium ion battery electrolytes at present, because it is most likely to undergo a two-electron reduction reaction and can promote the formation of an SEI film. However, the addition of VC to the lithium ion battery has the disadvantage of increasing the internal resistance of the battery, thereby causing the problem of electrochemical reduction of the battery.
Therefore, how to find a more suitable lithium ion battery electrolyte formula to improve the battery cycle performance and solve the above problems, especially to satisfy the commercial requirements of wide applications, has become one of the problems to be solved urgently by many front-line researchers and research and development type enterprises.
Disclosure of Invention
In view of the above, the invention provides an electrolyte and a lithium ion battery, and particularly provides an electrolyte for a lithium ion battery.
The invention provides an electrolyte, which comprises phthalimide and vinylene carbonate.
Preferably, the mass content of the phthalimide in the electrolyte is 0.1-5%;
the mass content of the vinylene carbonate in the electrolyte is 0.1-2%.
Preferably, the mass ratio of the phthalimide to the vinylene carbonate is (1-10): 1.
preferably, the electrolyte further includes a lithium salt.
Preferably, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide and lithium tris (trifluoromethylsulfonyl) methide;
the molar concentration of the lithium salt in the electrolyte is 0.2 mol/L-saturated concentration.
Preferably, the electrolyte further comprises a solvent.
Preferably, the solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl formate, ethyl formate, propyl formate, ethyl acetate, ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate and tetrahydrofuran.
The invention provides a lithium ion battery which comprises the electrolyte solution in any one of the technical schemes.
Preferably, the lithium ion battery further comprises a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.
Preferably, the active material of the positive electrode includes one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, polyanionic positive electrode material, lithium vanadium oxide, lithium iron oxide, NCM and NCA;
the negative electrode comprises one or more of a graphite negative electrode, a soft carbon negative electrode, a hard carbon negative electrode, a silicon carbon negative electrode, a nitride negative electrode and a nano negative electrode material;
the lithium ion battery comprises a ternary cathode material lithium ion battery.
The invention provides an electrolyte, which comprises phthalimide and vinylene carbonate. Compared with the prior art, the invention aims at the technical direction of adding the film-forming additive in the electrolyte formula in the aspect of improving the cycle performance of the battery, and the main additive Vinylene Carbonate (VC) has the defect of increasing the internal resistance of the battery and causing the cycle performance of the battery to be reduced. According to the invention, phthalimide and vinylene carbonate are creatively compounded for use, and the composition of Phthalimide (PI) and Vinylene Carbonate (VC) forms a stable Solid Electrolyte Interface (SEI) on the surface of an electrode, wherein the SEI has a lithium ion fast channel, reduces internal resistance and can effectively improve the cycle performance of a battery. Compared with a series of additives of cyclic dicarboximide, the cyclic dicarboximide can improve circulation and reduce internal resistance, but the cyclic dicarboximide has a complex molecular structure, is not an industrial common chemical product, is easy to obtain, is difficult to ensure high purity, and can obviously increase the cost of the electrolyte. The phthalimide provided by the invention is a common industrial chemical product, and the cheap raw materials are compounded to develop the electrolyte for a long-life battery system, so that the phthalimide is more suitable for large-scale production and commerce, and also achieves a key challenge in the research work of the existing energy storage battery.
Experimental results show that after the electrolyte containing VC and PI is adopted, the cycle life of the battery is prolonged by 10-20%, and the internal resistance of the battery is also reduced.
Drawings
FIG. 1 is a graph showing the cycle life of a lithium ion battery prepared from an electrolyte containing an additive and an electrolyte containing no additive according to example 9 of the present invention;
FIG. 2 is a graph comparing the internal DC resistances of lithium ion batteries prepared with the electrolyte containing the additive and the electrolyte without the additive in example 9 of the present invention.
Detailed Description
In order to further understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
All of the starting materials of the present invention, the source of which is not particularly limited, are preferably commercially available or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the present invention are not particularly limited in their purity, and the present invention preferably employs analytical purity or purity conventional in the field of lithium ion batteries.
The invention provides an electrolyte, which comprises phthalimide and vinylene carbonate.
The definition of the electrolyte in the present invention is not particularly limited, and a battery electrolyte well known to those skilled in the art may be used, and the present invention is preferably an electrolyte of a lithium ion battery. The electrolyte comprises phthalimide and vinylene carbonate.
The content of the phthalimide in the electrolyte is not particularly limited in principle, and can be selected and adjusted by those skilled in the art according to actual conditions, product performance and quality requirements, and in order to better reduce the internal resistance of the lithium ion battery and more effectively improve the cycle performance of the battery, the mass content of the phthalimide in the electrolyte is preferably 0.1% to 5%, more preferably 0.5% to 4.5%, more preferably 1% to 4%, more preferably 1.5% to 3.5%, and more preferably 2% to 3%.
The content of the vinylene carbonate in the electrolyte is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual conditions, product performance and quality requirements, and in order to better reduce the internal resistance of the lithium ion battery and more effectively improve the cycle performance of the battery, the content of the vinylene carbonate in the electrolyte is particularly preferably 0.1% to 2%, more preferably 0.3% to 1.8%, more preferably 0.5% to 1.5%, and more preferably 0.8% to 1.2%.
The invention has no special limitation on the proportion between the phthalimide and the vinylene carbonate in principle, and a person skilled in the art can select and adjust the proportion according to the actual situation, the product performance and the quality requirement, in order to better reduce the internal resistance of the lithium ion battery and more effectively improve the cycle performance of the battery, the mass ratio of the phthalimide to the vinylene carbonate is more preferably (1-10): 1, more preferably (3-8): 1, more preferably (5-6): 1.
the invention is not limited to other components of the electrolyte in principle, and can be selected and adjusted by those skilled in the art according to the actual situation, product performance and quality requirements, and the electrolyte preferably further comprises a lithium salt in order to better reduce the internal resistance of the lithium ion battery and more effectively improve the cycle performance of the battery.
The specific selection and parameters of the lithium salt are not particularly limited in principle, and can be selected and adjusted by those skilled in the art according to actual conditions, product performance and quality requirements, so as to better reduce internal resistance of the lithium ion battery and more effectively improve the cycle performance of the battery, and the lithium salt preferably comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonyl, lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide and lithium tris (trifluoromethanesulfonyl) methide, and more preferably lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonyl, lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide or lithium tris (trifluoromethanesulfonyl) methide. The molar concentration of the lithium salt in the electrolyte is preferably 0.2mol/L to a saturated concentration, more preferably 0.5mol/L to a saturated concentration, and more preferably 0.8mol/L to a saturated concentration.
The invention is not particularly limited to other components of the electrolyte in principle, and can be selected and adjusted by a person skilled in the art according to actual conditions, product performance and quality requirements.
The specific selection and parameters of the solvent are not particularly limited in the present invention, and those skilled in the art can select and adjust the solvent according to the actual conditions, product performance and quality requirements, and the solvent preferably includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl formate, ethyl formate, propyl formate, ethyl acetate, ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate and tetrahydrofuran, and more preferably, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, gamma-butyrolactone, methyl formate, ethyl formate, propyl formate, ethyl acetate, and tetrahydrofuran, and the solvent is preferably selected and adjusted according to the actual conditions, product performance and quality requirements of the lithium ion battery, and the battery cycling performance is more effectively improved Ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate or tetrahydrofuran.
The invention uses a composition of Phthalimide (PI) and Vinylene Carbonate (VC), especially in specific proportions; the composition of the two forms a stable Solid Electrolyte Interface (SEI) on the surface of an electrode, and the SEI has a lithium ion fast channel, reduces the internal resistance and can improve the cycle performance of a battery; meanwhile, the prepared lithium ion battery has lower internal resistance and better cycle performance by matching with proper electrolyte.
The invention also provides a lithium ion battery which comprises the electrolyte solution in any one of the technical schemes.
The lithium ion battery of the present invention is not particularly limited in principle, and may be a lithium ion battery known to those skilled in the art, and those skilled in the art can select and adjust the lithium ion battery according to the actual situation, the product performance, and the quality requirement.
The specific selection of the positive electrode is not particularly limited in principle, and can be selected and adjusted by those skilled in the art according to actual conditions, product performance and quality requirements, and the active material of the positive electrode preferably includes one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, polyanion positive electrode material, lithium vanadium oxide, lithium iron oxide, NCM and NCA, and more preferably lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, polyanion positive electrode material, lithium vanadium oxide, lithium iron oxide, NCM or NCA. Specifically, the lithium iron phosphate, lithium cobaltate, lithium nickelate, lithium manganate, polyanionic positive electrode material, lithium vanadate, lithium ferrate, NCM or NCA, and more preferably, a ternary positive electrode material such as NCM or NCA. The electrolyte provided by the invention is more beneficial to forming a stable Solid Electrolyte Interface (SEI) on the surface of the electrode of the ternary cathode material, forming a lithium ion fast channel, reducing internal resistance and effectively improving the cycle performance of the battery.
The specific selection of the negative electrode is not particularly limited in principle, and can be selected and adjusted by those skilled in the art according to actual conditions, product performance and quality requirements, and the negative electrode preferably comprises one or more of a graphite negative electrode, a soft carbon negative electrode, a hard carbon negative electrode, a silicon carbon negative electrode, a nitride negative electrode and a nano negative electrode material, and more preferably comprises the graphite negative electrode, the soft carbon negative electrode, the hard carbon negative electrode, the silicon carbon negative electrode, the nitride negative electrode or the nano negative electrode material.
The preparation method of the lithium ion battery is not particularly limited, and the method for preparing the lithium ion battery, which is well known to those skilled in the art, can be adopted. The specific steps are preferably as follows: and (3) preparing the electrolyte in a glove box, and assembling the anode, the cathode, the diaphragm and the electrolyte into the lithium ion battery.
The invention provides an electrolyte and a lithium ion battery. According to the invention, phthalimide and vinylene carbonate are compounded for use, and particularly, a stable Solid Electrolyte Interface (SEI) is formed on the surface of an electrode by using the Phthalimide (PI) and Vinylene Carbonate (VC) composition in a specific proportion, and the SEI has a lithium ion fast channel, reduces internal resistance and can effectively improve the cycle performance of a battery. The invention combines the specially selected lithium salt electrolyte and solvent with the additive for use, and the obtained lithium ion electrolyte can further improve the battery cyclicity. The Phthalimide (PI) and the Vinylene Carbonate (VC) adopted by the invention are common industrial chemicals, are cheap and easily available, can effectively control the cost of the electrolyte, are compounded by using the cheap raw materials to develop the electrolyte for a long-life battery system, are more suitable for large-scale production and commerce, and also achieve a key challenge faced by the existing research work of energy storage batteries.
Experimental results show that after the electrolyte containing VC and PI is adopted, the cycle life of the battery is prolonged by 10-20%, and the internal resistance of the battery is also reduced.
For further illustration of the present invention, an electrolyte and a lithium ion battery provided by the present invention are described in detail below with reference to examples, but it should be understood that the examples are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, which are only for further illustration of the features and advantages of the present invention, but not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
The reagents used in the following examples are all commercially available.
Examples 1 to 8
Comparative examples 1 to 2
Preparing a positive plate: lithium iron phosphate LiFePO serving as positive active material4The conductive carbon black and the binder (PVDF) are uniformly dispersed in a solvent N-methyl pyrrolidone (NMP) to prepare the anode slurry. The solid component contains 96 wt% of lithium iron phosphate, 2 wt% of conductive carbon black and 2 wt% of binder. And (3) uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 16 mu m, drying at 90 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the positive plate.
Preparing a negative plate: the negative electrode active material artificial graphite, conductive carbon black, sodium carboxymethyl cellulose thickener (CMC) and binder Styrene Butadiene Rubber (SBR) are uniformly dispersed in deionized water to prepare negative electrode slurry. The solid component comprises 97.2 wt% of artificial graphite, 0.8 wt% of conductive carbon black, 0.8 wt% of CMC and 1.2 wt% of SBR. And uniformly coating the negative electrode slurry on a 12-micron copper foil of a negative electrode current collector, drying at 100 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the negative electrode plate.
Manufacturing a lithium ion battery:
and winding the positive plate, the 12 mu m polypropylene diaphragm and the negative plate to assemble the naked electric core. Filling the bare cell into an aluminum-plastic packaging bag, drying in vacuum for 10h, injecting electrolyte, vacuum packaging, standing for 24h, charging to 3.0V at a constant current of 0.1C, standing for 10min, charging to 3.65V at a constant current of 0.2C, standing for 10min, charging to 3.65V at a constant voltage, discharging to 2.5V at a constant current of 0.2C, repeating the charging and discharging for 2 times, and finally charging to 3.65V at a constant current of 0.1C, thereby completing the manufacture of the lithium ion battery.
The cycle performance of the lithium ion battery prepared by the embodiment of the invention is detected.
Testing the cycle performance of the lithium ion battery: discharging to 2.5V at constant current of 0.5C at 25 deg.C, standing for 1min, charging to 3.65V at constant voltage of 0.5C, charging to current of 0.05C at constant voltage of 3.65V, standing for 1min, repeating the charging and discharging, and recording the capacity retention rate and internal resistance change rate after 1000 cycles.
Referring to table 1, table 1 shows the formulations of the lithium ion battery electrolytes prepared in examples 1 to 8 of the present invention and comparative examples 1 to 2.
TABLE 1
Figure BDA0002322638200000081
Figure BDA0002322638200000091
Referring to table 2, table 2 shows the capacity retention rate and the internal resistance change rate after 1000 cycles of assembling the lithium ion batteries by the electrolytes prepared in examples 1 to 8 and comparative examples 1 to 2 of the present invention.
TABLE 2
Numbering Retention ratio of circulating Capacity (%) Rate of change of internal resistance (%)
Example 1 88 33
Example 2 90 28
Example 3 92 24
Example 4 90 35
Example 5 86 38
Example 6 88 32
Example 7 87 34
Example 8 89 34
Comparative example 1 85 49
Comparative example 2 82 53
Example 9
Preparing a positive plate: lithium iron phosphate LiFePO serving as positive active material4Conductive carbon black, binder (PVDF) in solvent N-methylpyridineThe pyrrolidone (NMP) is uniformly dispersed to prepare the anode slurry. The solid component contains 96 wt% of lithium iron phosphate, 2 wt% of conductive carbon black and 2 wt% of binder. And (3) uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 16 mu m, drying at 90 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the positive plate.
Preparing a negative plate: the negative electrode active material artificial graphite, conductive carbon black, sodium carboxymethyl cellulose thickener (CMC) and binder Styrene Butadiene Rubber (SBR) are uniformly dispersed in deionized water to prepare negative electrode slurry. The solid component comprises 97.2 wt% of artificial graphite, 0.8 wt% of conductive carbon black, 0.8 wt% of CMC and 1.2 wt% of SBR. And uniformly coating the negative electrode slurry on a 12-micron copper foil of a negative electrode current collector, drying at 100 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the negative electrode plate.
Manufacturing a lithium ion battery:
and winding the positive plate, the 12 mu m polypropylene diaphragm and the negative plate to assemble the naked electric core. Filling the bare cell into an aluminum-plastic packaging bag, drying in vacuum for 10h, injecting electrolyte, vacuum packaging, standing for 24h, charging to 3.0V at a constant current of 0.1C, standing for 10min, charging to 3.65V at a constant current of 0.2C, standing for 10min, charging to 3.65V at a constant voltage, discharging to 2.5V at a constant current of 0.2C, repeating the charging and discharging for 2 times, and finally charging to 3.65V at a constant current of 0.1C, thereby completing the manufacture of the lithium ion battery.
The above lithium ion battery is prepared in the same manner as in the previous examples, and the lithium salt and concentration, solvent components and mass ratio are also the same. The additive was formulated at 2% (PI: VC ═ 1.5:0.5), and a blank control group containing no additive was added.
The cycle performance of the lithium ion battery prepared by the electrolyte containing the additive and the electrolyte not containing the additive in example 9 of the present invention was examined.
Testing the cycle performance of the lithium ion battery: discharging at 25 deg.C under constant current of 0.5C to 2.5V, standing for 1min, charging at constant voltage of 0.5C to 3.65V, charging at constant voltage of 3.65V to current of 0.05C, standing for 1min, and repeating the steps.
Referring to fig. 1, fig. 1 is a graph showing cycle life curves of lithium ion batteries prepared from the electrolyte containing the additive and the electrolyte without the additive in example 9 of the present invention.
As can be seen from FIG. 1, when the PI & VC compound additive is added, the battery capacity is reduced to 1.6Ah when the battery is circulated to 1100 circles, and the cycle life is improved by 13.6 percent compared with the 950 circles of a blank sample.
Referring to fig. 2, fig. 2 is a graph comparing the internal direct current resistances of lithium ion batteries prepared from the electrolyte containing the additive and the electrolyte without the additive in example 9 of the present invention.
As shown in FIG. 2, the PI and VC are compounded for use, so that the internal resistance of the battery can be obviously reduced, and the performance of the battery can be improved.
Example 10
Preparing a positive plate: the positive electrode active material NCM523, the conductive carbon black and the binder (PVDF) are uniformly dispersed in a solvent N-methylpyrrolidone (NMP) to prepare positive electrode slurry. The solid component contains 96 wt% of lithium iron phosphate, 2 wt% of conductive carbon black and 2 wt% of binder. And (3) uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 16 mu m, drying at 90 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the positive plate.
Preparing a negative plate: the negative electrode active material artificial graphite, conductive carbon black, sodium carboxymethyl cellulose thickener (CMC) and binder Styrene Butadiene Rubber (SBR) are uniformly dispersed in deionized water to prepare negative electrode slurry. The solid component comprises 97.2 wt% of artificial graphite, 0.8 wt% of conductive carbon black, 0.8 wt% of CMC and 1.2 wt% of SBR. And uniformly coating the negative electrode slurry on a 12-micron copper foil of a negative electrode current collector, drying at 100 ℃, cold pressing, cutting, vacuum drying, and welding a tab to obtain the negative electrode plate.
Manufacturing a lithium ion battery:
and winding the positive plate, the 12 mu m polypropylene diaphragm and the negative plate to assemble the naked electric core. Filling the bare cell into an aluminum-plastic packaging bag, drying in vacuum for 10h, injecting electrolyte, vacuum packaging, standing for 24h, charging to 3.0V at a constant current of 0.1C, standing for 10min, charging to 3.65V at a constant current of 0.2C, standing for 10min, charging to 3.65V at a constant voltage, discharging to 2.5V at a constant current of 0.2C, repeating the charging and discharging for 2 times, and finally charging to 3.65V at a constant current of 0.1C, thereby completing the manufacture of the lithium ion battery.
The above lithium ion battery is prepared in the same manner as in the previous examples, and the lithium salt and concentration, solvent components and mass ratio are also the same. The additive was formulated at 2% (PI: VC ═ 1.5:0.5), and a blank control group containing no additive was added.
The cycle performance of the lithium ion battery prepared by the electrolyte containing the additive and the electrolyte not containing the additive in example 9 of the present invention was examined.
Testing the cycle performance of the lithium ion battery: discharging at 25 deg.C under constant current of 0.5C to 2.5V, standing for 1min, charging at constant voltage of 0.5C to 3.65V, charging at constant voltage of 3.65V to current of 0.05C, standing for 1min, and repeating the steps.
The PI and VC compound additive is added into the ternary system, the battery capacity is reduced to 1.6Ah when the battery capacity is circulated to 1200 circles, and the cycle life is prolonged by 26.3 percent compared with 950 circles of a blank sample. And PI and VC are compounded for use, so that the internal resistance of the battery can be obviously reduced, and the performance of the battery is improved.
While the present invention has been described in detail with respect to an electrolyte and a lithium ion battery, the principles and embodiments of the present invention are described herein with reference to specific examples, which are provided to facilitate an understanding of the methods and their core concepts, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that approximate the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (10)

1.一种电解液,其特征在于,所述电解液包括邻苯二甲酰亚胺和碳酸亚乙烯酯。1. an electrolytic solution, it is characterized in that, described electrolytic solution comprises phthalimide and vinylene carbonate. 2.根据权利要求1所述的电解液,其特征在于,所述邻苯二甲酰亚胺在所述电解液中的质量含量为0.1%~5%;2. The electrolyte according to claim 1, wherein the mass content of the phthalimide in the electrolyte is 0.1% to 5%; 所述碳酸亚乙烯酯在所述电解液中的质量含量为0.1%~2%。The mass content of the vinylene carbonate in the electrolyte is 0.1% to 2%. 3.根据权利要求1所述的电解液,其特征在于,所述邻苯二甲酰亚胺和所述碳酸亚乙烯酯的质量比为(1~10):1。3 . The electrolyte according to claim 1 , wherein the mass ratio of the phthalimide to the vinylene carbonate is (1-10):1. 4 . 4.根据权利要求1所述的电解液,其特征在于,所述电解液还包括锂盐。4. The electrolyte according to claim 1, wherein the electrolyte further comprises a lithium salt. 5.根据权利要求4所述的电解液,其特征在于,所述锂盐包括六氟磷酸锂、四氟硼酸锂、六氟砷酸锂、高氯酸锂、三氟磺酰锂、二(三氟甲基磺酰)亚胺锂、双(氟磺酰)亚胺锂和三(三氟甲基磺酰)甲基锂中的一种或多种;5. The electrolyte according to claim 4, wherein the lithium salt comprises lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluorosulfonyl, bis(trifluoromethane) one or more of lithium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide and lithium tris(trifluoromethylsulfonyl)methyl; 所述锂盐在所述电解液中的摩尔浓度为0.2mol/L~饱和浓度。The molar concentration of the lithium salt in the electrolyte is 0.2 mol/L~saturated concentration. 6.根据权利要求1所述的电解液,其特征在于,所述电解液还包括溶剂。6. The electrolyte according to claim 1, wherein the electrolyte further comprises a solvent. 7.根据权利要求6所述的电解液,其特征在于,所述溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、γ-丁内酯、甲酸甲酯、甲酸乙酯、甲酸丙酯、乙酸乙酯、丙酸乙酯、丙酸丙酯、甲酸丁酯、乙酸丁酯、丙酸丁酯、丁酸丁酯和四氢呋喃中的一种或多种。7. The electrolyte according to claim 6, wherein the solvent comprises ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, formic acid One or more of methyl ester, ethyl formate, propyl formate, ethyl acetate, ethyl propionate, propyl propionate, butyl formate, butyl acetate, butyl propionate, butyl butyrate and tetrahydrofuran kind. 8.一种锂离子电池,其特征在于,包括权利要求1~7任意一项所述的电解液。8 . A lithium ion battery, characterized in that it comprises the electrolyte according to any one of claims 1 to 7 . 9.根据权利要求8所述的离子电池,其特征在于,所述锂离子电池还包括正极、负极、介于正极和负极之间的隔膜。9 . The ion battery according to claim 8 , wherein the lithium ion battery further comprises a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode. 10 . 10.根据权利要求9所述的锂离子电池,其特征在于,所述正极的活性材料包括磷酸铁锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、聚阴离子正极材料、锂钒氧化物、锂铁氧化物、NCM和NCA中的一种或多种;10. The lithium ion battery according to claim 9, wherein the active material of the positive electrode comprises lithium iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, polyanion positive electrode material, lithium vanadium one or more of oxide, lithium iron oxide, NCM and NCA; 所述负极包括石墨负极、软碳负极、硬碳负极、硅碳负极、氮化物负极和纳米负极材料中的一种或多种;The negative electrode includes one or more of graphite negative electrode, soft carbon negative electrode, hard carbon negative electrode, silicon carbon negative electrode, nitride negative electrode and nano negative electrode material; 所述锂离子电池包括三元正极材料锂离子电池。The lithium ion battery includes a ternary positive electrode material lithium ion battery.
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Application publication date: 20200515