CN112331916A - Electrolyte and application thereof - Google Patents
Electrolyte and application thereof Download PDFInfo
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- CN112331916A CN112331916A CN202011192193.7A CN202011192193A CN112331916A CN 112331916 A CN112331916 A CN 112331916A CN 202011192193 A CN202011192193 A CN 202011192193A CN 112331916 A CN112331916 A CN 112331916A
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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
- 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
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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
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Abstract
The invention provides an electrolyte and application thereof, wherein the electrolyte comprises a combination of lithium salt, a solvent, a flame retardant additive and a film forming additive; the film-forming additive comprises a compound A with a structure shown in a formula I and a compound B with a structure shown in a formula II; the film forming additive can form a stable, compact and low-impedance SEI film on the anode and cathode materials of the battery, effectively solves the problems of low conductivity of the electrolyte, poor compatibility with the electrode materials and the like caused by the addition of the flame retardant additive, and improves the structural stability of the anode and cathode electrode materials; the flame retardant is applied to the lithium ion battery, so that the lithium ion battery has excellent flame retardant property and cycle performance, and is suitable for large-scale industrial production.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to an electrolyte and application thereof.
Background
The large-capacity lithium ion battery has the characteristics of large capacity, high specific energy, long cycle life, no environmental pollution and the like, and has a huge application prospect in the fields of civil power supplies such as mobile phones and notebook computers and the like to vehicle-mounted power supplies for driving automobiles and the like, so that the large-capacity lithium ion battery attracts the attention of a plurality of scientific workers. At present, the main obstacle in developing the high-capacity lithium ion power battery is the safety problem, especially, the potential safety hazards such as ignition, explosion and the like often exist when the high-capacity lithium ion battery is used in the states such as thermal shock, overshoot, overdischarge, short circuit and the like, and the safety problems also always restrict the development and application of the high-capacity lithium ion battery.
At present, the most common method for solving the above problems is to add a flame retardant additive into the battery electrolyte to improve the high-temperature stability of the electrolyte, thereby improving the safety performance of the battery. CN108346821A discloses an electrolyte containing a flame retardant additive and a preparation method thereof, wherein the flame retardant additive is added into the existing lithium ion battery electrolyte; the flame retardant additive is 2-fluoro-2-triethyl phosphorylacetate, and the flame retardant additive in the electrolyte can obviously play a flame retardant role when the weight percentage of the flame retardant additive in the electrolyte is 1-20%, so that the flame retardant electrolyte meets the actual production requirements, improves the stability of the electrolyte and further ensures the safety of the battery. However, the flame retardant additive has low viscosity, low conductivity, poor compatibility with electrode materials and high addition amount, and can seriously affect the stability of a Solid Electrolyte Interface (SEI) in an Electrolyte, so that the electrochemical performance of the battery is seriously affected.
In order to construct a more stable anode/cathode/electrolyte interface and improve the stability of the SEI film, it is necessary to add a film-forming additive while adding a flame-retardant additive to the electrolyte. CN107293788A discloses a flame-retardant electrolyte for a lithium ion battery and a preparation method thereof, wherein the electrolyte consists of a solvent, a cosolvent, a film-forming agent, a cosolvent, a flame retardant and a lithium salt, has a good flame-retardant effect, can effectively improve the safety and reliability of the lithium ion battery, and has good compatibility with a graphite carbon cathode, and the lithium ion battery assembled by using the electrolyte has good electrochemical performance. CN107293790A discloses a flame-retardant lithium ion battery electrolyte, which comprises lithium salt, an organic solvent, a fluoroalkoxy silicon-based polyphosphazene flame retardant and a film-forming additive, wherein the fluoroalkoxy silicon-based polyphosphazene flame retardant is low in viscosity and high in conductivity, and the flame-retardant efficiency is high due to the fact that the fluoroalkoxy silicon-based polyphosphazene flame retardant contains various flame-retardant elements such as P, N, Si and F, a stable SEI film can be formed on the surface of an electrode material by adding the ethylene carbonate film-forming additive, the structural stability of the anode and cathode electrode materials is improved, the electrolyte is prevented from being oxidized and decomposed, and the. However, the film-forming additives added to the two electrolytes are not sufficient to improve the structural stability of the electrode material, and the cycle performance of the prepared lithium ion battery is still to be improved under the low-temperature condition.
Therefore, the development of an electrolyte with high safety, high stability, non-flammability and excellent electrochemical performance, which is applied to a lithium ion battery to improve the cycle performance of the battery, is an urgent problem to be solved in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide an electrolyte and application thereof, wherein a compound A and a compound B with specific structures are used as film forming additives to be added into the electrolyte containing a flame retardant additive to obtain the electrolyte with high safety, high stability, non-flammability and excellent electrochemical performance, and the electrolyte is applied to a lithium ion battery, so that the cycle performance of the battery is improved, and the electrolyte has wide application prospect.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an electrolyte comprising a combination of a lithium salt, a solvent, a flame retardant additive, and a film forming additive.
The film forming additive comprises compound a and compound B.
The compound A has a structure shown in a formula I:
the compound B has a structure shown in a formula II:
wherein R is1Selected from substituted or unsubstituted C2-C8 (e.g., C3, C4, C5, C6, C7, etc.) linear or branched alkylene groups, substituted or unsubstituted C2-C5 (e.g., C3, C4, C5, etc.) linear or branched alkylene groups;
the substituted substituents are respectively and independently selected from any one of F, Cl and Br;
the electrolyte provided by the invention comprises a combination of lithium salt, a solvent, a flame retardant additive and a film forming additive, wherein the film forming additive is added while the flame retardant additive is added, the film forming additive comprises a compound A and a compound B with specific structures, the compound A can form SEI films on the positive electrode and the negative electrode of a battery, the SEI film formed by the single compound A is not stable enough and is easy to damage in the charging and discharging overcharge of the battery, the addition of the compound B can promote the A to form the SEI film with compact structure, stable chemical property and small impedance, and the cycle life of the battery can be obviously prolonged. The problems of low viscosity, low conductivity, poor compatibility with electrode materials and serious influence on a solid electrolyte interfacial film in the electrolyte caused by the addition of the flame retardant additive are solved, the structural stability of the anode and cathode electrode materials is improved, the electrolyte is prevented from being oxidized and decomposed, and the electrolyte with high safety, high stability, incombustibility and excellent electrochemical performance is developed.
Preferably, the compound a is a five-membered ring or a six-membered ring.
Preferably, said R is1Is selected from any one of substituted or unsubstituted C2-C6 straight chain or branched chain alkylene, and substituted or unsubstituted C2-C4 straight chain or branched chain alkylene.
Each of the substituted substituents is independently selected from F, Cl or Br.
Preferably, the compound a is selected from any one of the following compounds:
preferably, the mass ratio of the compound A to the compound B is (5-35): 1, such as 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, 19:1, 21:1, 23:1, 25:1, 27:1, 29:1, 31:1 or 33: 1.
As a preferred technical scheme of the invention, when the mass ratio of the compound A to the compound B in the film-forming additive is (5-35): 1, the film-forming additive is more favorable for forming a stable, compact and low-impedance SEI film on a positive electrode material and a negative electrode material when added into an electrolyte, and is more favorable for improving the stability of the electrolyte; if the content of the compound A is too high, the compound B cannot fully play a role, the formed SEI film is unstable in property, and the charge-discharge process is easily damaged; if the content of the compound B is too high, the resistance of the formed SEI film increases, the internal resistance of the battery increases, and lithium ion migration is not facilitated.
Preferably, the film-forming additive comprises
Combinations of (a) and (b).
Preferably, the film-forming additive comprises
Combinations of (a) and (b).
Preferably, the film-forming additive comprises
Combinations of (a) and (b).
Preferably, the film-forming additive comprises
Combinations of (a) and (b).
PreferablySaid film-forming additive comprising
Combinations of (a) and (b).
Preferably, the film-forming additive comprises
Combinations of (a) and (b).
Preferably, the electrolyte solution contains 0.05 to 5% by mass of the film-forming additive, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6% or 4.8%, and specific values therebetween are not exhaustive, and for brevity and conciseness, and the invention does not include the range including the specific values.
As a preferred technical scheme, when the mass percentage of the film-forming additive in the electrolyte is 0.05-5%, the electrolyte has excellent flame retardant property and cycle performance, if the addition amount of the film-forming additive is too small, when the film-forming additive is applied to a lithium ion battery, an SEI film with sufficient stability cannot be formed on the surface of an electrode material, and the structural stability of positive and negative electrode materials is insufficient, so that the final cycle performance of the battery is poor; if the addition amount of the film-forming additive is too high, the SEI film formed on the surface of the electrode material is thick, so that lithium ion transmission is influenced on one hand, and excessive lithium ions are consumed on the other hand, so that the cycle performance and the capacity of the lithium ion battery are influenced.
Preferably, the solvent is an organic solvent.
Preferably, the organic solvent is a carbonate-based organic solvent.
Preferably, the carbonate-based organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate or methylethyl carbonate or a combination of at least two thereof.
Preferably, the lithium salt comprises any one of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis- (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonato) imide, lithium difluorophosphate, lithium tetrafluoroborate or lithium difluoro (oxalato) phosphate, or a combination of at least two thereof.
Preferably, the lithium salt is present in an amount of 0.5 to 1.5mol, for example, 0.6mol, 0.7mol, 0.8mol, 0.9mol, 1mol, 1.1mol, 1.2mol, 1.3mol or 1.4mol, based on 1L of the solvent, and specific values therebetween are not exhaustive, and for the sake of brevity, the invention is not limited to the specific values included in the ranges.
Preferably, the flame retardant additive comprises a phosphate based flame retardant additive.
Preferably, the phosphate-based flame retardant additive comprises trimethyl phosphate.
Preferably, the electrolyte contains 1 to 50% by mass of the flame retardant additive, such as 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46% or 48%, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the range.
Preferably, the electrolyte comprises a lithium salt, a solvent, a flame retardant additive, and a film forming additive; the film forming additive comprises (5-35): 1 mass ratio
A combination of (1); the mass percentage of the film forming additive in the electrolyte is 0.05-5%, and the mass percentage of the flame retardant additive is 1-50%; and the content of the lithium salt is 0.5-1.5 mol based on 1L of the solvent.
In a second aspect, the present invention provides a lithium ion battery, including the electrolyte according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the electrolyte provided by the invention, the flame retardant additive is added, and the compound A and the compound B are added as film forming additives, so that the problems of low conductivity of the electrolyte, poor compatibility with electrode materials and the like caused by the addition of the flame retardant additive are solved, the film forming additive can form a stable, compact and low-impedance SEI film on the anode and cathode materials of the battery, and the structural stability of the anode and cathode materials is improved; compared with the electrolyte in the prior art, the electrolyte added with the film-forming additive provided by the invention has the advantages that the capacity retention rate is improved by 0.6-5% and the DCIR is reduced by 2-33% under the condition that the self-extinguishing time is unchanged; the lithium ion battery with excellent flame retardant property and cycle performance is obtained, and is suitable for large-scale industrial production and application.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The invention provides a composition comprising
The compounds of the structure are commercially available or can be synthesized by known synthetic methods.
Example 1
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is lithium hexafluorophosphate (LiPF)6) The solvent is a mixture of Ethylene Carbonate (EC), Propylene Carbonate (PC) and dimethyl carbonate (DMC) in a mass ratio of 2:1:7, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 5 percent,
quality of (1)The content of the components in percentage by weight is 0.5 percent,
the mass percentage of (B) is 0.05%.
The preparation method comprises the following steps: adding LiPF to the solvent6Obtaining LiPF6The molar concentration of the mixed solution is 1 mol/L; then adding trimethyl phosphate into the mixture,
And obtaining the electrolyte.
Example 2
An electrolyte which differs from example 1 only in that the film-forming additive in the electrolyte is
In the combination of (a) and (b),
the mass percentage content of the components is 0.5 percent,
the mass percentage of (A) is 0.1%, and other components, the use amount and the preparation method are the same as those of the example 1.
Example 3
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is lithium hexafluorophosphate (LiPF)6) The solvent is a mixture of Ethylene Carbonate (EC), Propylene Carbonate (PC) and dimethyl carbonate (DMC) in a mass ratio of 2:1:7, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
And
a combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 5 percent,
the mass percentage content of the components is 1 percent,
the mass percentage of (B) is 0.05%.
The preparation method is the same as that of example 1.
Example 4
An electrolyte which differs from example 3 only in that
The mass percentage of the components is 5 percent,
the mass percentage of (A) is 0.25%, and other components, the use amount and the preparation method are the same as those of the embodiment 3.
Example 5
An electrolyte which differs from example 3 only in that
The mass percentage of the components is 5 percent,
the mass percentage of (A) is 0.25%, and other components, the use amount and the preparation method are the same as those of the embodiment 3.
Example 6
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC, PC and methyl ethyl carbonate (EMC) in a mass ratio of 2:2:6, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
And
a combination of (1); wherein trimethyl phosphate is contained in the electrolyteThe mass percentage content is 10 percent,
the mass percentage content of the components is 1 percent,
the mass percentage of (B) is 0.1%.
The preparation method is the same as that of example 1.
Example 7
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC, PC and methyl ethyl carbonate (EMC) in a mass ratio of 2:2:6, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 10 percent,
the mass percentage content of the components is 2 percent,
the mass percentage of (B) is 0.1%.
Example 8
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of PC, diethyl carbonate (DEC) and EMC in a mass ratio of 1:3:6, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 15 percent,
the mass percentage content of the components is 1 percent,
the mass percentage of (B) is 0.1%.
The preparation method is the same as that of example 1.
Example 9
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC, PC and methyl ethyl carbonate (EMC) in a mass ratio of 2:2:6, the flame retardant additive is trimethyl phosphate, and the film forming additive is trimethyl phosphate
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 10 percent,
the mass percentage content of the components is 2 percent,
the mass percentage of (B) is 0.1%.
Example 10
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC, DEC and DMC in a mass ratio of 2:3:5, the flame retardant additive is trimethyl phosphate, and the film forming additive is
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 20 percent,
the mass percentage content of the components is 1.5 percent,
the mass percentage of (B) is 0.1%.
The preparation method is the same as that of example 1.
Example 11
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC, DEC and DMC in a mass ratio of 2:3:5, the flame retardant additive is trimethyl phosphate, and the film forming additive is
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 20 percent,
the mass percentage content of the components is 1.5 percent,
the mass percentage of (B) is 0.1%.
The preparation method is the same as that of example 1.
Example 12
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC and EMC with the mass ratio of 3:7, the flame retardant additive is trimethyl phosphate, and the film forming additive is
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 25 percent,
the mass percentage content of the components is 2 percent,
the mass percentage of the component (A) is 0.15%.
The preparation method is the same as that of example 1.
Example 13
An electrolyte comprising a lithium salt, a solvent, a flame retardant additive, and a film forming additive; wherein the lithium salt is LiPF6The solvent is a mixture of EC and EMC in a mass ratio of 3:7, and the flame retardant additive is trimethyl phosphateEster, film-forming additive of
A combination of (1); wherein the mass percentage of trimethyl phosphate in the electrolyte is 25 percent,
the mass percentage content of the components is 2.5 percent,
the mass percentage of the component (A) is 0.15%.
The preparation method is the same as that of example 1.
Comparative example 1
An electrolyte solution, which is different from example 1 only in that a film-forming additive is not included, and other components, amounts and preparation methods are the same as those of example 1, was obtained.
Comparative example 2
An electrolyte solution which is different from example 6 only in that a film-forming additive is not included, and other components, amounts and a preparation method are the same as those of example 6, was obtained.
Comparative example 3
An electrolyte solution which is different from example 8 only in that a film-forming additive is not included, and other components, amounts and a preparation method are the same as those of example 8, was obtained.
Comparative example 4
An electrolyte solution, which is different from example 10 only in that a film-forming additive is not included, and other components, amounts and preparation methods are the same as those of example 10, was obtained.
Comparative example 5
An electrolyte solution which was different from example 12 only in that a film-forming additive was not included, and other components, amounts and a preparation method were the same as those of example 12, was obtained.
Comparative example 6
An electrolyte comprising a lithium salt and a solvent; wherein the lithium salt is LiPF6The solvent is EC. Mixture of DEC and EMC in a mass ratio of 3:2: 5.
The preparation method comprises the following steps: adding LiPF to the solvent6Obtaining LiPF6The molar concentration of (3) is 1mol/L, namely the electrolyte.
Comparative example 7
An electrolyte is different from the electrolyte in example 12 only in that vinyl sulfate (DTD) is used as a film forming additive, the mass percentage of the DTD in the electrolyte is 2.15%, and other components, the using amount and the preparation method are the same as those in example 14.
Comparative example 8
An electrolyte is different from the electrolyte in example 12 only in that 1, 4-Butyl Sultone (BS) is used as a film forming additive, the mass percentage of the BS in the electrolyte is 2.15%, and other components, the using amount and the preparation method are the same as those in example 14.
Comparative example 9
An electrolyte is different from the electrolyte in example 12 only in that PS (1, 3-propane sultone) is used as a film forming additive, the mass percentage of BS in the electrolyte is 2.15%, and other components, the using amount and the preparation method are the same as those in example 14.
Comparative example 10
An electrolyte solution differs from the electrolyte solution in example 12 only in that 1, 3-Propylene Sultone (PST) is used as a film forming additive, the mass percentage of BS in the electrolyte solution is 2.15%, and other components, the use amounts and the preparation method are the same as those in example 14.
Comparative example 11
An electrolyte is different from the electrolyte in example 12 only in that Biphenyl (BP) is used as a film forming additive, the mass percentage of BS in the electrolyte is 2.15%, and other components, the using amount and the preparation method are the same as those in example 14.
Comparative example 12
An electrolyte solution which differs from the electrolyte solution of example 3 only in that the electrolyte solution contains 1.05% by mass of the electrolyte solution and does not contain the electrolyte solution
The other components, amounts and preparation methods were the same as in example 3.
Comparative example 13
An electrolyte solution which differs from the electrolyte solution of example 3 only in that the electrolyte solution contains 1.05% by mass of the electrolyte solution and does not contain the electrolyte solution
The other components, amounts and preparation methods were the same as in example 3.
Application examples 1 to 13
A lithium ion battery is prepared by respectively using the electrolytes obtained in embodiments 1-13, and the process conditions are as follows:
mixing nickel cobalt lithium manganate (NCM622), a positive pole binder (PVDF), carbon (C) and conductive carbon black (Super-P) according to a mass ratio of 95.5:2:1:1.5 to prepare positive pole slurry; mixing t carbon (C), conductive carbon black (Super-P), carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR) and a mixture in a mass ratio of 95.9:0.5:1.5:2.1 to prepare negative pole slurry;
coating the positive electrode slurry on an aluminum foil current collector, coating the negative electrode slurry on a copper foil current collector, drying to prepare a positive electrode plate and a negative electrode plate, packaging the positive electrode plate and the negative electrode plate with a polyethylene diaphragm, drying, injecting 6.5g of the electrolyte prepared in the embodiments 1-13, forming to obtain the lithium ion battery, and testing the electrical properties of the lithium ion battery.
Comparative application examples 1 to 13
The lithium ion battery is characterized in that the electrolyte is obtained in comparative examples 1-13, and the preparation process conditions of the lithium ion battery are the same as those of application example 1.
And (3) performance testing:
(1) self-extinguishing time test: 5g of the electrolyte obtained in the examples 1-13 and the comparative examples 1-13 is put in a crucible, an ignition device is quickly removed after the electrolyte is ignited, and the time from the beginning of the electrolyte combustion to the automatic extinguishing is recorded; the electrolyte obtained from each example was tested 5 times and averaged.
(2) Capacity retention ratio: after the lithium ion batteries obtained in the application examples 1-13 and the comparative application examples 1-13 are charged to 4.2V at 1C (the charge cut-off current is 0.05C) in a battery test system (Xinwei test system CT-ZWJ-4' S-T-1U), the 1C is discharged to 2.75V, and the capacity of the lithium ion battery is tested in a cyclic charge-discharge process for 100 weeks.
The electrolytes obtained in examples 1 to 13 and comparative examples 1 to 13 were subjected to a self-extinguishing time test according to the test method (1), and the lithium ion batteries provided in application examples 1 to 13 and comparative application examples 1 to 13 were subjected to an electrical performance test according to the test method (2), and the test results are shown in table 1.
(3) DCIR test: after the battery was charged to 4.2V at 1C in the nova battery test system (charge cutoff current of 0.05C), the battery was discharged to 50% SOC (50% capacity state), and the battery was discharged for 10s at 3C while the steady voltage was maintained for 1h, and the DCIR of the battery at this time was calculated.
TABLE 1
From the data in table 1, it can be seen that: the electrolyte provided by the embodiments 1-13 of the invention has excellent flame retardant property and cycle performance; specifically, the method comprises the following steps: the electrolyte provided by the embodiments 1 to 5 has a self-extinguishing time of 29s, a capacity retention rate of 96.43 to 99.68%, and a DCIR of 61.2 to 67.1m omega, and compared with the electrolyte provided by the comparative examples 1, 12, and 13, the capacity retention rate is improved by 0.6 to 5%, and the DCIR is reduced by 2 to 33% under the condition of ensuring the same self-extinguishing time; examples 6 and 7 provided electrolytes with a self-extinguishing time of 18s, capacity retention rates of 96.82% and 97.16%, respectively, and DCIR of 70.7m Ω and 80.2m Ω, respectively, which were improved by 6% and 6.5%, and reduced by 27% and 12%, respectively, compared to the electrolyte provided in comparative example 2, while ensuring the same self-extinguishing time; the self-extinguishing time of the electrolytes provided in examples 8 and 9 is 9s, the capacity retention rates are 93.55% and 92.74% respectively, and the DCIR are 93.1m omega and 92.4m omega respectively, compared with the electrolyte provided in comparative example 3, under the condition that the self-extinguishing time is the same, the capacity retention rates are improved by 7% and 6%, and the DCIR is reduced by 7% and 6% respectively; the self-extinguishing time of the electrolytes provided in examples 10 and 11 is 4s, the capacity retention rates are 92.74% and 88.26%, respectively, and the DCIR are 102.6m Ω and 101.5m Ω, respectively, compared with the electrolyte provided in comparative example 4, under the same self-extinguishing time condition, the capacity retention rates are respectively increased by 11% and 5%, the DCIR are respectively decreased by 5% and 6%, the electrolytes provided in examples 12 and 13 cannot be ignited, the self-extinguishing time is 0, the capacity retention rates are respectively 84.85% and 84.68%, and the DCIR are respectively 112.4m Ω and 113.8m Ω, compared with the electrolytes provided in comparative examples 5 and 7-11, the capacity retention rates are increased by 4-5% and the DCIR are decreased by 2-5%, which shows that the electrolyte provided by the invention has higher capacity retention rate and lower DCIR while ensuring good flame retardant performance.
Comparative example 6 is an electrolyte solution to which a flame retardant and a riddling additive were not added, and the self-extinguishing time was 37 seconds, and the flame retardant effect was poor.
The applicant states that the present invention is illustrated by the above embodiments of an electrolyte and the application thereof, but the present invention is not limited to the above embodiments, i.e. it does not mean that the present invention must be implemented by the above embodiments. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. An electrolyte, comprising a combination of a lithium salt, a solvent, a flame retardant additive, and a film forming additive;
the film forming additive comprises compound a and compound B;
the compound A has a structure shown in a formula I:
the compound B has a structure shown in a formula II:
wherein R is1Any one of substituted or unsubstituted C2-C8 straight chain or branched chain alkylene, substituted or unsubstituted C2-C5 straight chain or branched chain alkylene;
the substituted substituents are respectively and independently selected from any one of F, Cl and Br.
2. The electrolyte of claim 1, wherein the compound a is a five-membered ring, a six-membered ring, or a seven-membered ring.
3. The electrolyte of claim 1 or 2, wherein R is1Any one of substituted or unsubstituted C2-C6 straight chain or branched chain alkylene, substituted or unsubstituted C2-C5 straight chain or branched chain alkylene;
each of the substituted substituents is independently selected from F, Cl or Br.
4. The electrolyte of any one of claims 1 to 3, wherein the compound A is selected from any one of the following compounds:
5. the electrolyte according to any one of claims 1 to 4, wherein the mass ratio of the compound A to the compound B is (5-35): 1;
preferably, the film-forming additive comprises
A combination of (1);
preferably, the film-forming additive comprises.
A combination of (1);
preferably, the film-forming additive comprises
A combination of (1);
preferably, the film-forming additive comprises
A combination of (1);
preferably, the film-forming additive comprises
A combination of (1);
preferably, the film-forming additive comprises
Combinations of (a) and (b).
6. The electrolyte according to any one of claims 1 to 5, wherein the electrolyte contains the film-forming additive in an amount of 0.05 to 5% by mass.
7. The electrolyte of any one of claims 1 to 6, wherein the solvent is an organic solvent;
preferably, the organic solvent is a carbonate-based organic solvent;
preferably, the carbonate-based organic solvent includes any one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate or methylethyl carbonate or a combination of at least two thereof.
8. The electrolyte of any one of claims 1 to 7, wherein the lithium salt comprises any one of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium bis- (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonato) imide, lithium difluorophosphate, lithium tetrafluoroborate, or lithium difluoro (oxalato) phosphate, or a combination of at least two thereof;
preferably, the content of the lithium salt is 0.5-1.5 mol based on 1L of the solvent.
9. The electrolyte of any one of claims 1 to 8, wherein the flame retardant additive comprises a phosphate flame retardant additive;
preferably, the phosphate-based flame retardant additive comprises trimethyl phosphate;
preferably, the mass percentage of the flame retardant additive in the electrolyte is 1-50%;
preferably, the electrolyte comprises a lithium salt, a solvent, a flame retardant additive, and a film forming additive; the film forming additive comprises (5-35): 1 mass ratio
A combination of (1); the mass percentage of the film forming additive in the electrolyte is 0.05-5%, and the mass percentage of the flame retardant additive is 1-50%; and the content of the lithium salt is 0.5-1.5 mol based on 1L of the solvent.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the electrolyte according to any one of claims 1 to 9.
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