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A kind of electrolytic solution for improving the performance of sei film on the surface of graphite electrode and its preparation method and application

A graphite electrode and electrolyte technology, which is applied in the field of electrolyte and its preparation to improve the performance of the SEI film on the surface of graphite electrodes, can solve problems affecting battery cycle efficiency, increase battery self-discharge rate, etc., and achieve improved cycle performance and good compactness , The effect of improving the capacity retention rate

Active Publication Date: 2022-05-20
SHANGHAI INST OF TECH
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Problems solved by technology

[0003] So far, the addition of film-forming additives such as VC and FEC to the electrolyte of lithium-ion batteries has been widely studied. Due to the presence of polymer components in the reduction product of VC, the formed solid electrolyte film is denser. However, using too much VC will affect the cycle efficiency of the battery and increase the self-discharge rate of the battery

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  • A kind of electrolytic solution for improving the performance of sei film on the surface of graphite electrode and its preparation method and application
  • A kind of electrolytic solution for improving the performance of sei film on the surface of graphite electrode and its preparation method and application

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preparation example Construction

[0029] A kind of preparation method of the electrolytic solution that improves SEI film performance on graphite electrode surface provided by the invention comprises the steps:

[0030] Step 1: Weigh the required lithium salt and ionic liquid according to the molar ratio = 1-5:1, and mix them as the solute;

[0031] Step 2: Dissolve the mixed solute in the PC solvent, fully stir the prepared electrolyte, and let it stand to completely dissolve the solute;

[0032] Step 3: Measure 0.8% of the volume of the carbonate solvent and add fluorocarbonate to the above mixed solution, stir thoroughly, and let stand for 24 hours to obtain the lithium-ion battery electrolyte.

[0033] Since the ionic liquid N-methyl-N-propenylpiperidine bis(trifluoromethylsulfonyl)imide (PP 13 *TFSI) is liquid at room temperature. In step 1, first weigh the ionic liquid, then weigh the lithium salt, and finally add the PC solvent.

[0034] An electrolyte solution for improving the performance of SEI fil...

Embodiment 1

[0036] The electrolytic solution in the present invention is prepared in a glove box, and the main components are: organic solvent, film-forming additive, lithium salt, and ionic liquid. The organic solvent is propylene carbonate (PC), the film-forming additive FEC, the lithium salt is LiTFSI, and the ionic liquid is PP 13 *TFSI, LiTFSI and PP 13 *The molar ratio of TFSI is 2:1, the content of FEC is 0.8% of PC volume, and the total molar concentration of lithium salt and ionic liquid in PC solvent is 3mol / L.

[0037] The preparation method of above-mentioned lithium ion battery electrolyte:

[0038] 1) Weigh the stoichiometric PP according to the molar concentration of the electrolyte and the molar ratio of the lithium salt to the ionic liquid 13 *TFSI, dissolved in a certain volume of PC solvent, shake well;

[0039] 2) Weigh the stoichiometric LiTFSI according to the molar concentration of the electrolyte and the molar ratio of the lithium salt and the ionic liquid, and ...

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Abstract

The invention discloses an electrolytic solution for improving the performance of SEI film on the surface of a graphite electrode and its preparation method and application. The electrolytic solution includes an organic solvent, a film-forming additive and a solute salt, the organic solvent includes a cyclic carbonate solvent, and the film-forming additive includes fluorine Substitute carbonic acid ester, the total molar concentration of solute salt in solvent remains as 3mol / L, and solute salt comprises the mixture of lithium salt and ionic liquid, and the mol ratio of lithium salt and ionic liquid is=2: 1; Lithium salt is lithium di( Trifluoromethylsulfonyl) imide salt, ionic liquid is N-methyl-N-propenyl piperidine bis(trifluoromethylsulfonyl)imide; comprises the following steps: Step 1: according to the molar ratio is 2: 1 Weigh lithium salt and ionic liquid, and mix them as a solute; Step 2: Dissolve the aforementioned solute in a cyclic carbonate solvent, stir fully, and let it stand to dissolve the solute completely. Step 3: Measure the cyclic carbonate Add 0.8% of the ester solvent volume of fluorocarbonate into it, fully stir, and let it stand for 24 hours to obtain the electrolyte; the present invention can form a denser and more stable SEI film on the surface of graphite electrodes when applied to graphite / lithium half cells. Improve the cycle performance of the battery.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to an electrolyte for improving the performance of an SEI film on a graphite electrode surface, a preparation method and an application thereof. Background technique [0002] Graphite is the basis for high-energy lithium-ion batteries because its lithium intercalation potential is close to that of metal lithium. However, due to the interlayer lithium intercalation characteristics of graphite, it encounters many problems in the application process. One of the most important problems is that the layered structure is easily damaged during the process of intercalation and desorption of lithium ions, which affects the cycle life of the battery. Especially in propylene carbonate (PC)-based electrolytes, PC solvated Li ions sneak into the graphite layer during the discharge process, seriously destroying the layered structure of graphite, making the initial efficie...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M10/0567H01M10/0568H01M10/0569H01M10/0525
CPCH01M10/0567H01M10/0568H01M10/0569H01M10/0525H01M2300/0025Y02E60/10
Inventor 高喜梅
Owner SHANGHAI INST OF TECH
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