CN111106388B - Electrolyte and lithium ion battery - Google Patents
Electrolyte and lithium ion battery Download PDFInfo
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- CN111106388B CN111106388B CN202010055270.8A CN202010055270A CN111106388B CN 111106388 B CN111106388 B CN 111106388B CN 202010055270 A CN202010055270 A CN 202010055270A CN 111106388 B CN111106388 B CN 111106388B
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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
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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
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- 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 and a lithium ion battery, wherein the electrolyte comprises: solvents, lithium salts and additives; the additive comprises a fluorosulfonyl silane carbonate compound and an isonitrile acid ester compound, wherein the fluorosulfonyl silane carbonate compound accounts for 0.5-25% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2-20% of the total mass of the electrolyte. Compared with the prior art, the electrolyte provided by the invention has good thermal stability and film forming effect, can maintain the structural integrity of a negative electrode material in the charge and discharge process, has good circulation and storage performances at higher voltage and higher temperature, and has good storage stability.
Description
Technical Field
The invention belongs to the field of electrochemistry, and particularly relates to an electrolyte and a lithium ion battery.
Background
Because of higher energy density, lower production cost and pollution-free charging and discharging processes, the lithium ion battery becomes the most widely used electrochemical energy storage device and is widely applied to the fields of electronic consumer products, electric automobiles, power grid energy storage and the like.
However, the cycle life of the lithium ion battery is short, and one of the main reasons is that the electrolyte continuously generates side reactions on the surface of the negative electrode, consumes lithium elements in the electrolyte, reduces the cycle performance of the lithium ion battery, increases the impedance of the lithium ion battery, and is not beneficial to the transmission of lithium ions. In order to improve the cycle performance and the storage performance of the lithium ion battery, the development of novel additives and the optimization of the electrolyte formula are not easy.
Disclosure of Invention
The invention provides an electrolyte and a lithium ion battery, aiming at solving the technical problem that the cycle performance and the storage performance of the lithium ion battery are poor due to the side reaction of the conventional electrolyte on a negative electrode.
The specific technical scheme is as follows:
an electrolyte, characterized in that it comprises:
solvents, lithium salts and additives;
the additive comprises a fluorosulfonyl silane carbonate compound and an isonitrile acid ester compound;
the fluorosulfonyl silane carbonate compound comprises at least one of compounds shown in a formula I;
wherein R is1、R2、R3、R4And R5Independently selected from alkyl with 1-10 carbon atoms or alkoxy with 1-10 carbon atoms, m is an integer from 0 to 10, and n is an integer from 0 to 10;
the isonitrile acid ester compound comprises at least one of compounds shown in a formula II-a and/or at least one of compounds shown in a formula II-b;
wherein R is6、R7、R8、R9And R10Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, alkoxy with 1-10 carbon atoms or phenyl;
the fluorosulfonyl silane carbonate compound accounts for 0.5-25% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2-20% of the total mass of the electrolyte.
Further, m is 0 or 1.
Further, n is 0 or 1.
Further, R6、R7、R8And R9Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkoxy with 1-10 carbon atoms; r10Is phenyl.
Further, the fluorosulfonyl silane carbonate compound includes one or more of the following compounds:
further, the isonitrile acid ester compound comprises one or more of the following compounds:
further, the fluorosulfonyl silane carbonate compound accounts for 5% -10% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2% -5% of the total mass of the electrolyte.
A lithium ion battery, characterized in that the lithium ion battery comprises: a positive electrode, a negative electrode, a separator, and the electrolyte solution.
Further, the anode includes an anode active material including one or more of graphite, hard carbon, or silicon.
Compared with the prior art, the electrolyte provided by the invention has good thermal stability and film forming effect, can maintain the structural integrity of a negative electrode material in the charge and discharge process, has good circulation and storage performances at higher voltage and higher temperature, and has good storage stability.
Detailed Description
The principles and features of this invention are described below in conjunction with embodiments, which are included to explain the invention and not to limit the scope of the invention.
An electrolyte, characterized in that it comprises:
solvents, lithium salts and additives;
the additive comprises a fluorosulfonyl silane carbonate compound and an isonitrile acid ester compound;
the fluorosulfonyl silane carbonate compound comprises at least one of compounds shown in a formula I;
wherein R is1、R2、R3、R4And R5Independently selected from alkyl with 1-10 carbon atoms or alkoxy with 1-10 carbon atoms, m is an integer from 0 to 10, and n is an integer from 0 to 10;
the isonitrile acid ester compound comprises at least one of compounds shown in a formula II-a and/or at least one of compounds shown in a formula II-b;
wherein R is6、R7、R8、R9And R10Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, alkoxy with 1-10 carbon atoms or phenyl;
the fluorosulfonyl silane carbonate compound accounts for 0.5-25% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2-20% of the total mass of the electrolyte.
Further, m is 0 or 1.
Further, n is 0 or 1.
Further, the fluorosulfonyl silane carbonate compound includes one or more of trimethylsilylfluorosulfonyl methyl carbonate, triethylsilylfluorosulfonyl methyl carbonate, trimethylsilylfluorosulfonyl ethyl carbonate, triethylsilylfluorosulfonyl ethyl carbonate, trimethylsilylfluorosulfonyl methoxy carbonate, trimethylsilylfluorosulfonyl ethoxy carbonate, trimethylsilylfluorosulfonyl methyl carbonate, triethylsiloxane fluorosulfonyl methyl carbonate, trimethylsilylfluorosulfonyl ethyl carbonate, triethylsiloxane fluorosulfonyl ethyl carbonate, trimethylsilylfluorosulfonyl methoxy carbonate, triethylsiloxane fluorosulfonyl methoxy carbonate, trimethylsilylfluorosulfonyl ethoxy carbonate, triethylsiloxane fluorosulfonyl ethoxy carbonate, trimethoxysilane fluorosulfonyl methyl carbonate, or triethoxysilane fluorosulfonyl ethyl carbonate .
Further, R6、R7、R8And R9Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkoxy with 1-10 carbon atomsA group; r10Is phenyl.
Further, the isocyanate compound includes methyl trimethylsilane isocyanate, methyl triethylsilane isocyanate, ethyl trimethylsilane isocyanate, ethyl triethylsilane isocyanate, propyl trimethylsilane isocyanate, propyl triethylsilane isocyanate, butyl trimethylsilane isocyanate, butyl triethylsilane isocyanate, methoxy trimethylsilane isocyanate, methoxy triethylsilane isocyanate, ethoxy trimethylsilane isocyanate, ethoxy triethylsilane isocyanate, propoxy trimethylsilane isocyanate, propoxy triethylsilane isocyanate, butoxy trimethylsilane isocyanate, butoxy triethylisocyanate, methyl trimethoxysilane isocyanate, methyl triethoxysilane isocyanate, ethyl trimethoxysilane isocyanate, ethyl triethoxysilane isocyanate, propyl trimethoxysilane isocyanate, butyl trimethylsilane, one or more of isocyanatopropyl triethoxysilane, isocyanatobutyl trimethoxysilane, isocyanatobutyl triethoxysilane, isocyanatovinyl trimethoxysilane, isocyanatopropylene trimethoxysilane, isocyanatobutylene trimethoxysilane or p-phenylene diisocyanate.
Further, the lithium salt includes lithium hexafluorophosphate (LiPF)6) Lithium tetrafluoroborate (LiBF)4) Lithium methanesulfonate (LiCH)3SO3) Lithium trifluoromethanesulfonate (LiCF)3SO3) Lithium hexafluoroarsenate (LiAsF)6) Lithium hexafluoroantimonate (LiSbF)6) Lithium perchlorate (LiClO)4)、Li[BF2(C2O4)]、Li[PF2(C2O4)2]、Li[N(CF3SO2)2]、Li[C(CF3SO2)3]Lithium difluorooxalato borate (LiODFB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO)2F2) Lithium bis (fluorosulfonyl) imide (LiFSI) and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI).
Further, the lithium salt includes lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI) and lithium tetrafluoroborate (LiBF)4) One or more ofAnd (4) seed preparation.
Further, the concentration of the lithium salt is 0.8 mol/L-2 mol/L.
Further, the fluorosulfonyl silane carbonate compound includes one or more of the following compounds:
further, the isonitrile acid ester compound comprises one or more of the following compounds:
further, the fluorosulfonyl silane carbonate compound accounts for 5% -10% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2% -5% of the total mass of the electrolyte.
A lithium ion battery, characterized in that the lithium ion battery comprises: a positive electrode, a negative electrode, a separator, and the electrolyte solution.
Further, the anode includes an anode active material including one or more of graphite, hard carbon, or silicon.
The invention has the main effect of reducing the influence of the side reaction of the electrolyte on the cathode.
Wherein the synthetic route of the formula I-a is as follows:
the compound shown as the formula A is dropwise added into NaHCO containing the compound shown as the formula B3Stirring and cooling the mixture in the aqueous solution for 3 hours, heating the mixture to room temperature, carrying out reflux reaction for 12 hours, and carrying out reduced pressure distillation to obtain a target product;
wherein the synthetic route of the formula I-b is as follows:
the compound shown as the formula C is dropwise added into NaHCO containing the compound shown as the formula B3Stirring and cooling the mixture in the aqueous solution for 3 hours, heating the mixture to room temperature, carrying out reflux reaction for 16 hours, and carrying out reduced pressure distillation to obtain a target product;
wherein the synthetic route of the formula I-c is as follows:
the compound shown as the formula D is dropwise added into NaHCO containing the compound shown as the formula B3Stirring and cooling the aqueous solution for 3 hours, then heating the aqueous solution to room temperature, then refluxing and reacting the aqueous solution for 20 hours, and distilling the aqueous solution under reduced pressure to obtain the target product.
Example one
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-a and formula II-b-1; wherein, the contents of the formula I-a and the formula II-b-1 in the electrolyte are shown in the following table 1.
TABLE 1 content of formula I-a and formula II-b-1 in electrolyte
Example two
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-a and formula II-a-1; wherein, the contents of the formula I-a and the formula II-a-1 in the electrolyte are shown in the following table 2.
TABLE 2 contents of formulae I-a and II-a-1 in the electrolyte
EXAMPLE III
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-b and formula II-b-1; wherein, the contents of the formula I-b and the formula II-b-1 in the electrolyte are shown in the following table 3.
TABLE 3 contents of formulae I-b and II-b-1 in the electrolyte
Example four
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-b and formula II-a-1; wherein, the contents of the formula I-b and the formula II-a-1 in the electrolyte are shown in the following table 4.
TABLE 4 contents of formulae I-b and II-a-1 in the electrolyte
EXAMPLE five
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-c and formula II-b-1; wherein, the contents of the formula I-c and the formula II-b-1 in the electrolyte are shown in the following Table 5.
TABLE 5 content of formula I-c and formula II-b-1 in electrolyte
EXAMPLE six
In a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-c and formula II-a-1; wherein, the contents of the formula I-c and the formula II-a-1 in the electrolyte are shown in the following Table 6.
TABLE 6 content of formula I-c and formula II-a-1 in electrolyte
Comparative example 1
Preparation of electrolyte D1:
in a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-a; wherein, the content of the formula I-a in the electrolyte is 10 percent.
Comparative example No. two
Preparation of electrolyte D2:
in a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula II-b-1; wherein the content of the formula II-b-1 in the electrolyte is 5 percent.
Comparative example No. three
Preparation of electrolyte D3:
in a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L.
Comparative example No. four
Preparation of electrolyte D4:
in a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: formula I-a; wherein, the content of the formula I-a in the electrolyte is 5 percent.
Comparative example five
Preparation of electrolyte D5:
in a dry argon atmosphere, firstly, uniformly mixing different solvents according to a certain mass ratio, adding lithium salt and additives with different types and concentrations on the basis, and uniformly dissolving to obtain the electrolyte.
The types and the proportions of the solvents in the electrolyte are as follows: EC. PC and DEC (mass ratio is 1: 2: 6);
the lithium salt being LiPF6The concentration is 1 mol/L;
the specific types of additives used in the electrolyte are: II-b-1; wherein the content of the formula II-b-1 in the electrolyte is 10 percent.
EXAMPLE seven
Preparing a lithium ion battery with silicon as a negative active material:
preparing a positive pole piece:
mixing lithium cobaltate (LiCoO)2) The positive electrode slurry is prepared from a conductive agent (SuperP) and a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP). The solid content in the positive electrode slurry is 77%, wherein the mass ratio of the lithium cobaltate to the conductive agent SuperP to the PVDF is 97: 1.4: 1.6. and uniformly coating the slurry on an aluminum foil of a positive current collector, drying at 85 ℃, cold-pressing, trimming, cutting and slitting, drying at 85 ℃ for 4 hours in vacuum, and welding tabs to prepare the positive plate of the lithium ion battery.
Preparing a negative pole piece:
silicon used as a negative electrode active material, conductive carbon black (SuperP), thickener carboxymethyl cellulose sodium (CMC) and binder Styrene Butadiene Rubber (SBR) are mixed according to the weight ratio of 93: 1: 1: 5, mixing, adding deionized water, and uniformly stirring to obtain the cathode slurry. And uniformly coating the slurry on a copper foil of a negative current collector, drying at 80 ℃, then cutting edges, cutting pieces and dividing strips, drying for 12 hours at 120 ℃ under a vacuum condition, and welding tabs to prepare the negative plate of the lithium ion battery.
Preparing a lithium ion battery:
stacking the positive electrode, the isolating film and the negative electrode in sequence to enable the isolating film to be positioned between the positive electrode sheet and the negative electrode sheet, and then winding the stacked electrode sheets and the isolating film to obtain a bare cell; and placing the bare cell in an outer package, injecting the prepared electrolyte into the dried battery, packaging, standing, forming (charging to 3.4V at a constant current of 0.02C and then charging to 3.85V at a constant current of 0.1C), shaping, and testing capacity to finish the preparation of the lithium ion battery.
By adopting the above steps, lithium ion batteries as shown in table 7 were prepared using different types of electrolytes.
Table 7 raw materials and proportions for manufacturing lithium ion battery with silicon as negative electrode active material
Example eight
Preparing a lithium ion battery with graphite as a negative active material:
preparing a positive pole piece:
mixing lithium cobaltate (LiCoO)2) The positive electrode slurry is prepared from a conductive agent (SuperP) and a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP). The solid content in the positive electrode slurry is 77%, wherein the mass ratio of the lithium cobaltate to the conductive agent SuperP to the PVDF is 97: 1.4: 1.6. and uniformly coating the slurry on an aluminum foil of a positive current collector, drying at 85 ℃, cold-pressing, trimming, cutting and slitting, drying at 85 ℃ for 4 hours in vacuum, and welding tabs to prepare the positive plate of the lithium ion battery.
Preparing a negative pole piece:
graphite serving as a negative electrode active material, conductive carbon black (SuperP), a thickening agent sodium carboxymethyl cellulose (CMC) and a binder Styrene Butadiene Rubber (SBR) are mixed according to a weight ratio of 93: 1: 1: 5, mixing, adding deionized water, and uniformly stirring to obtain the cathode slurry. And uniformly coating the slurry on a copper foil of a negative current collector, drying at 80 ℃, then cutting edges, cutting pieces and dividing strips, drying for 12 hours at 120 ℃ under a vacuum condition, and welding tabs to prepare the negative plate of the lithium ion battery.
Preparing a lithium ion battery:
stacking the positive electrode, the isolating film and the negative electrode in sequence to enable the isolating film to be positioned between the positive electrode sheet and the negative electrode sheet, and then winding the stacked electrode sheets and the isolating film to obtain a bare cell; and placing the bare cell in an outer package, injecting the prepared electrolyte into the dried battery, packaging, standing, forming (charging to 3.4V at a constant current of 0.02C and then charging to 3.85V at a constant current of 0.1C), shaping, and testing capacity to finish the preparation of the lithium ion battery.
By adopting the above steps, lithium ion batteries shown in table 8 were prepared using different types of electrolytes.
Table 8 raw materials and proportions for producing lithium ion battery with graphite as negative electrode active material
Example nine
Preparing a lithium ion battery with a negative active material of a silicon and graphite mixture:
preparing a positive pole piece:
mixing lithium cobaltate (LiCoO)2) The positive electrode slurry is prepared from a conductive agent (SuperP) and a binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP). The solid content in the positive electrode slurry is 77%, wherein the mass ratio of the lithium cobaltate to the conductive agent SuperP to the PVDF is 97: 1.4: 1.6. and uniformly coating the slurry on an aluminum foil of a positive current collector, drying at 85 ℃, cold-pressing, trimming, cutting and slitting, drying at 85 ℃ for 4 hours in vacuum, and welding tabs to prepare the positive plate of the lithium ion battery.
Preparing a negative pole piece:
mixing graphite and silicon according to a mass ratio of 1:10 to obtain a negative active material, and mixing the negative active material with conductive carbon black (SuperP), a thickener sodium carboxymethyl cellulose (CMC) and a binder Styrene Butadiene Rubber (SBR) according to a weight ratio of 93: 1: 1: 5, mixing, adding deionized water, and uniformly stirring to obtain the cathode slurry. And uniformly coating the slurry on a copper foil of a negative current collector, drying at 80 ℃, then cutting edges, cutting pieces and dividing strips, drying for 12 hours at 120 ℃ under a vacuum condition, and welding tabs to prepare the negative plate of the lithium ion battery.
Preparing a lithium ion battery:
stacking the positive electrode, the isolating film and the negative electrode in sequence to enable the isolating film to be positioned between the positive electrode sheet and the negative electrode sheet, and then winding the stacked electrode sheets and the isolating film to obtain a bare cell; and placing the bare cell in an outer package, injecting the prepared electrolyte into the dried battery, packaging, standing, forming (charging to 3.4V at a constant current of 0.02C and then charging to 3.85V at a constant current of 0.1C), shaping, and testing capacity to finish the preparation of the lithium ion battery.
By adopting the above steps, lithium ion batteries shown in table 9 were prepared using different types of electrolytes.
TABLE 9 raw materials and proportions for the fabrication of lithium ion batteries with silicon and graphite as the negative active material
Example ten
The lithium ion batteries prepared in the seventh to ninth embodiments were subjected to cycle performance test and storage performance test, and the specific test methods were as follows:
and (3) detecting the cycle performance of the lithium ion battery:
charging the battery at 25 deg.C with 0.5C constant current to 4.45V voltage and constant voltage to 0.05C, standing for 5min, discharging with 0.5C constant current to 3.0V voltage, and standing for 5min, which is a charge-discharge cycle.
And (3) repeatedly carrying out charge-discharge cycles with the capacity of the first discharge as 100% until the discharge capacity is attenuated to 80%, stopping testing, and recording the number of cycles as an index for evaluating the cycle performance of the lithium ion battery.
And meanwhile, the cycle performance of the lithium ion battery at 45 ℃ is tested, and the test method is the same as the test method for the cycle performance of the lithium ion battery at 25 ℃.
Detecting the storage performance of the lithium ion battery:
a 25 ℃ capacity test was first performed: charging to 4.45V at 0.5C constant current, charging to 0.05C at constant voltage, discharging to 3V at 0.5C constant current, recording initial capacity, and fully charging. And (3) charging the battery cell to 4.45V at a constant current of 0.5C and charging the battery cell to 0.05C at a constant voltage, recording the thickness of the battery cell under the full-charge condition, storing the battery cell for 21 days at the temperature of 60 ℃, and recording the thickness of the test battery cell on the 21 st day.
The cycle performance and the storage performance of the lithium ion battery in example seven were measured, and the results are shown in table 10 below.
Table 10 detection results of cycle performance and storage performance of lithium ion battery with silicon as negative electrode active material
The cycle performance and the storage performance of the lithium ion battery in example eight were measured, and the results are shown in table 11 below.
Table 11 results of testing cycle performance and storage performance of lithium ion battery using graphite as negative electrode active material
The cycle performance and the storage performance of the lithium ion battery in example nine were measured, and the results are shown in table 12 below.
Table 12 results of testing cycle performance and storage performance of lithium ion battery having silicon and graphite as negative electrode active material
As can be seen from the test results in tables 10 to 12, when both the fluorosulfonyl silane carbonate compound and the isonitrile acid ester compound are used as additive components in the lithium ion battery electrolyte, the cycle performance and the storage performance of the lithium ion battery are significantly enhanced. The two additives are used simultaneously, so that the improvement on the cycle and storage performance of the lithium ion battery is far higher than the cycle and storage performance of the lithium ion battery prepared by independently using the fluorosulfonyl silane carbonate compound or the isonitrile acid ester compound as the additives.
Moreover, the content of the fluorosulfonyl silane carbonate compound and the isonitrile acid ester compound in the electrolyte is also a key factor influencing the cycle performance and the storage performance of the lithium ion battery. From the test results in table 12, it is known that when the negative active material contains silicon and graphite, the electrolyte contains the fluorosulfonyl silane carbonate compound and the isonitrile acid ester compound, and the content of the fluorosulfonyl silane carbonate compound is 0.5% to 25%, and the content of the isonitrile acid ester compound is 2% to 20%, the cycle performance and the storage performance of the lithium ion battery composed thereof are greatly improved. When the content of the fluorosulfonylsilane carbonate compound and the content of the isonitrile acid ester compound in the electrolyte are not within these ranges without changing the negative electrode active material, the cycle number of the lithium ion battery composed of them falls to 1000 or less.
Further, as can be seen from tables 10 to 12, when the fluorosulfonyl silane carbonate compound accounts for 5% to 10% of the total mass of the electrolyte and the isonitrile acid ester compound accounts for 2% to 5% of the total mass of the electrolyte in the lithium ion battery electrolyte, the cycle performance and the storage performance of the lithium ion battery are greatly improved. If the content of the fluorosulfonyl silane carbonate compound and the content of the isonitrile acid ester compound in the electrolyte are not in the above ranges, the cycle performance and the storage performance of the lithium ion battery comprising the electrolyte are not optimal.
The cycle performance and the storage performance of the lithium ion battery are closely related to those of the negative electrode active material, and it can be seen from tables 10 to 12 that when graphite and silicon are mixed and used as the negative electrode active material and matched with an electrolyte containing a fluorosulfonyl silane carbonate compound and an isonitrile acid ester compound as additives, the cycle performance and the storage performance of the prepared lithium ion battery are excellent, and compared with the lithium ion battery prepared by matching the electrolyte without the additives, the cycle performance and the storage performance of the lithium ion battery are improved most obviously.
The above description is only exemplary of the present invention and should not be construed as limiting the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. An electrolyte, comprising:
solvents, lithium salts and additives;
the additive comprises a fluorosulfonyl silane carbonate compound and an isonitrile acid ester compound;
the fluorosulfonyl silane carbonate compound comprises at least one of compounds shown in a formula I;
wherein R is1、R2、R3、R4And R5Independently selected from alkyl with 1-10 carbon atoms or alkoxy with 1-10 carbon atoms, m is an integer from 0 to 10, and n is an integer from 0 to 10;
the isonitrile acid ester compound comprises at least one of compounds shown in a formula II-a and/or at least one of compounds shown in a formula II-b;
wherein R is6、R7、R8、R9And R10Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, alkoxy with 1-10 carbon atoms or phenyl;
the fluorosulfonyl silane carbonate compound accounts for 0.5-25% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2-20% of the total mass of the electrolyte.
2. The electrolyte of claim 1, wherein m is 1.
3. The electrolyte of claim 1, wherein n is 1.
4. The electrolyte of claim 1, wherein R is6、R7、R8And R9Independently selected from alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms or alkoxy with 1-10 carbon atoms; r10Is phenyl.
5. The electrolyte of claim 1, wherein the fluorosulfonyl silane carbonate compound comprises one or more of the following compounds:
6. the electrolyte of claim 1, wherein the isonitrile acid ester compound comprises one or more of the following compounds:
7. the electrolyte of claim 1, wherein the fluorosulfonyl silane carbonate compound accounts for 5-10% of the total mass of the electrolyte, and the isonitrile acid ester compound accounts for 2-5% of the total mass of the electrolyte.
8. A lithium ion battery, comprising: a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 1 to 7.
9. The lithium ion battery of claim 8, wherein the negative electrode comprises a negative active material comprising one or more of graphite, hard carbon, or silicon.
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