阅读说明：本技术 一种锂离子电池电解液及锂离子电池 (Lithium ion battery electrolyte and lithium ion battery ) 是由 李枫 杜冬冬 路晨昊 于立娟 廖兴群 于 2018-08-03 设计创作，主要内容包括：为克服现有锂离子电池存在抗过充性能和低温放电性能不足的问题,本发明提供了一种锂离子电池电解液,包括溶剂、锂盐、2-二氰基乙烯基-4-乙烯基-1,3-二氧戊环和3,4-乙烯二氧噻吩。同时,本发明还公开了包括上述电解液的锂离子电池。通过本发明提供的锂离子电池电解液可以很好地改善电池的抗过充性能以及低温放电性能。(In order to overcome the problems of insufficient overcharge resistance and low-temperature discharge performance of the conventional lithium ion battery, the invention provides a lithium ion battery electrolyte, which comprises a solvent, a lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylenedioxythiophene. Meanwhile, the invention also discloses a lithium ion battery comprising the electrolyte. The lithium ion battery electrolyte provided by the invention can well improve the overcharge resistance and low-temperature discharge performance of the battery.)

1. The lithium ion battery electrolyte is characterized by comprising a solvent, lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylenedioxythiophene.

2. The lithium ion battery electrolyte of claim 1, wherein the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane is present in the electrolyte in an amount of 0.1-5% by weight.

3. The lithium ion battery electrolyte of claim 1, wherein the 3, 4-ethylenedioxythiophene is present in the electrolyte in an amount of 0.1-5% by weight.

4. The lithium ion battery electrolyte of claim 1, wherein the concentration of the lithium salt in the electrolyte is between 0.5M and 2M.

5. The lithium ion battery electrolyte of claim 1, wherein the lithium salt comprises one or more of an organic lithium salt and an inorganic lithium salt.

6. The lithium ion battery electrolyte of claim 1, wherein the lithium salt comprises one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, and lithium tris (trifluoromethylsulfonyl) methide.

7. The lithium ion battery electrolyte of claim 1, wherein the solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, and tetrahydrofuran.

8. The lithium ion battery electrolyte of claim 1, wherein the electrolyte consists of a solvent, a lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane, and ethoxy (pentafluoro) cyclotriphosphazene.

9. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte according to any one of claims 1 to 8.

10. The lithium ion battery of claim 9, wherein the positive plate comprises a positive active material comprising one or more of lithium cobaltate, nickel cobalt manganese lithium ternary material, lithium iron phosphate and lithium manganese.

Technical Field

The invention belongs to the technical field of secondary batteries, and particularly relates to a lithium ion battery electrolyte and a lithium ion battery.

Background

The lithium ion battery has the remarkable advantages of high specific energy, large specific power, long cycle life, small self-discharge and the like, is popular with consumers, and is widely applied to 3C electronic products and power batteries such as mobile communication, digital cameras, video cameras and the like. With the daily wide application of lithium ion batteries, various electronic devices have higher requirements on the safety performance of the lithium ion batteries.

Safety is the most basic requirement of the lithium ion battery, in a safety test, overcharge resistance is one of safety performance, and at present, overcharge and ignition are one of the main problems encountered by the lithium ion battery.

Secondly, the performance of low-temperature discharge is very important to the application range of the lithium ion battery, and good low-temperature discharge performance is used for solving the daily use problem of users in alpine regions.

Disclosure of Invention

The invention provides a lithium ion battery electrolyte and a lithium ion battery, aiming at the problem that the existing lithium ion battery has insufficient overcharge resistance and low-temperature discharge performance.

The technical scheme adopted by the invention for solving the technical problems is as follows:

in one aspect, an embodiment of the present invention provides an electrolyte for a lithium ion battery, including a solvent, a lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane, and 3, 4-ethylenedioxythiophene.

The invention provides a lithium ion battery electrolyte, which is added with 2-dicyano vinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylene dioxythiophene as additives, and the inventor finds that compared with the single addition of 2-dicyano vinyl-4-vinyl-1, 3-dioxolane or 3, 4-ethylene dioxythiophene in the electrolyte, the combination of 2-dicyano vinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylene dioxythiophene in the electrolyte improves the stability of the electrolyte, can absorb internal electrons to reduce the reaction heat when a battery core is overcharged, reduces the decomposition of the electrolyte at high temperature and reduces the generation of gas; meanwhile, a stable SEI film is formed on the positive electrode and the negative electrode, so that the low-temperature discharge performance of the lithium ion battery is effectively improved.

Optionally, the mass percentage content of the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane in the electrolyte is 0.1-5%.

Optionally, the 3, 4-ethylenedioxythiophene accounts for 0.1-5% of the electrolyte by mass.

Optionally, the concentration of the lithium salt in the electrolyte is 0.5M to 2M.

Optionally, the lithium salt includes one or more of an organic lithium salt and an inorganic lithium salt.

Optionally, the lithium salt comprises one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide and lithium tris (trifluoromethylsulfonyl) methide.

Optionally, the solvent is two or more selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran.

Optionally, the electrolyte is composed of a solvent, a lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane, and ethoxy (pentafluoro) cyclotriphosphazene.

On the other hand, another embodiment of the invention discloses a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and the electrolyte.

The lithium ion battery provided by the invention has better overcharge resistance and low-temperature discharge performance due to the adoption of the electrolyte.

Optionally, the positive plate includes a positive active material, and the positive active material includes one or more of a lithium cobaltate, a lithium nickel cobalt manganese ternary material, and lithium iron phosphate and lithium manganate.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention discloses a lithium ion battery electrolyte, which comprises a solvent, lithium salt, 2-dicyano vinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylene dioxythiophene.

The chemical structural formula of the 2-dicyano vinyl-4-vinyl-1, 3-dioxolane is shown as follows:

the chemical structural formula of the 3, 4-ethylenedioxythiophene is as follows:

the inventor finds that, compared with the independent addition of 2-dicyanovinyl-4-vinyl-1, 3-dioxolane or 3, 4-ethylenedioxythiophene in the electrolyte, the combination of 2-dicyanovinyl-4-vinyl-1, 3-dioxolane and 3, 4-ethylenedioxythiophene in the electrolyte improves the stability of the electrolyte, can absorb internal electrons to reduce reaction heat when a battery core is overcharged, reduces decomposition of the electrolyte at high temperature, and reduces gas generation; meanwhile, a stable SEI film is formed on the positive electrode and the negative electrode, so that the low-temperature discharge performance of the lithium ion battery is effectively improved.

In some embodiments, the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane is present in the electrolyte in an amount of 0.1 to 5% by weight.

When the mass percentage content of the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane in the electrolyte is less than 0.1 percent, the electrolyte can not play a role of a high-voltage additive; when the mass percentage content is higher than 5%, a compact passive film is easily formed on the positive electrode and the negative electrode to increase the impedance, and the conductivity and the cycle performance of the battery are influenced.

When the mass percentage of the 3, 4-ethylenedioxythiophene in the additive is less than 0.1%, the film forming effect of the electrolyte on the electrode is not ideal, and the improvement effect on the low-temperature discharge performance is not obvious; above 5%, the battery is liable to store swelling and increase in resistance at high temperatures.

In some preferred embodiments, the 3, 4-ethylenedioxythiophene accounts for 0.1-3% of the electrolyte by mass. Further preferably, the upper limit of the content range of the 3, 4-ethylenedioxythiophene in the electrolyte is selected from 5% and 3%, and the lower limit is selected from 0.1%, 0.2% and 0.5%.

In some preferred embodiments, the content of the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane in the electrolyte solution is in a mass percentage range with an upper limit selected from 5% and a lower limit selected from 0.1% and 0.2%.

Still more preferably, the 3, 4-ethylenedioxythiophene accounts for 3 to 5 mass percent of the electrolyte, the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane accounts for 0.2 to 3 mass percent of the electrolyte, and when the content ratio of the 2-dicyanovinyl-4-vinyl-1, 3-dioxolane to the 3, 4-ethylenedioxythiophene is within the above range, the electrolyte has the best high-temperature stability and low-temperature discharge effect.

The amount of the lithium salt may vary over a wide range, and in some embodiments, the concentration of the lithium salt in the electrolyte is 0.5M to 2M. When the concentration of the lithium salt is too low, the conductivity of the electrolyte is low, and the multiplying power and the cycle performance of the whole battery system can be influenced; when the concentration of the lithium salt is too high, the viscosity of the electrolyte is too high, which is also not beneficial to the improvement of the rate of the whole battery system. In a more preferred embodiment, the lithium salt concentration is 0.9M to 1.3M.

In some embodiments, the lithium salt includes one or more of an organic lithium salt and an inorganic lithium salt.

For example: LiPF₆，LiBF₄，LiSbF₆，LiAsF₆，LiTaF₆，LiAlCl₄，Li₂B₁₀Cl₁₀，Li₂B₁₀F₁₀，LiClO₄，LiCF₃SO₃Salts of lithium chelated orthoborates and chelated orthophosphates, e.g. lithium bis (oxalato) borate [ LiB (C)₂O4)₂]Lithium dimalonate borate [ LiB (O)₂CCH₂CO₂)₂]Lithium bis (difluoromalonate) borate [ LiB (O)₂CCF₂CO₂)₂](malonic acid oxalic acid) lithium borate [ LiB (C)₂O₄)(O₂CCH₂CO₂)]Lithium (difluoromalonic acid oxalic acid) borate [ LiB (C)₂O₄)(O₂CCF₂CO₂)]Lithium tris (oxalato) phosphate [ LiP (C)₂O₄)₃]And three (two)Malonic acid fluoride) lithium phosphate [ LiP (O)₂CCF₂CO₂)₃]And any combination of two or more of the foregoing lithium salts.

In some embodiments, the lithium salt is selected from lithium fluoride salts.

In preferred embodiments, the lithium salt comprises one or more of hexafluorophosphate, hexafluoroarsenate, perchlorate, lithium trifluorosulfonyl, lithium difluoro (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide and lithium tris (trifluoromethylsulfonyl) methide.

In some embodiments, the solvent is selected from non-aqueous organic solvents.

In a preferred embodiment, the solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran.

In some embodiments, the electrolyte solution further includes other additives for promoting the formation of the SEI film, and specifically, the additives include, but are not limited to: vinylene carbonate and its derivatives, ethylene carbonate derivatives having non-conjugated unsaturated bonds in the side chain thereof, cyclic carbonates substituted with halogen, and salts of chelate orthoborates and chelate orthophosphoric esters.

Specifically, the additive comprises one or more of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate and difluoroethylene carbonate.

In one embodiment, the electrolyte is composed of a solvent, a lithium salt, 2-dicyanovinyl-4-vinyl-1, 3-dioxolane, and ethoxy (pentafluoro) cyclotriphosphazene.

Another embodiment of the present invention provides a lithium ion battery, including a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte as described above.

The positive plate comprises a positive active material, wherein the positive active material comprises one or more of lithium cobaltate, manganese nickel cobalt lithium ternary material, lithium iron phosphate and lithium manganate. Preferably, the positive electrode material is lithium cobaltate or nickel cobalt manganese lithium ternary material.

The positive plate also comprises a positive current collector for leading out current, and the positive active material is mixed with the binder, the conductive agent and the solution, then coated on the positive current collector and dried to form the positive plate.

The negative plate comprises a negative current collector and a negative active material coated on the negative current collector, wherein the negative active material is mixed with a binder, a conductive agent and a solution and then coated on the negative current collector and dried to form the negative plate.

The negative active material includes one or more of a carbon material, a metal alloy, a lithium-containing oxide, and a silicon-containing material.

In a preferred embodiment, the negative active material is selected from graphite.

The upper limit charging voltage of the lithium ion battery is 4.5V.

The lithium ion battery provided by the embodiment of the invention can absorb internal electrons to reduce reaction heat when a battery core is overcharged due to the electrolyte, and simultaneously forms a stable SEI film on a positive electrode and a negative electrode, thereby effectively improving low-temperature discharge performance.

The present invention will be further illustrated by the following examples.