CN-121983664-A - Electrolyte for improving infiltration efficiency of lithium ion battery and infiltration method

CN121983664ACN 121983664 ACN121983664 ACN 121983664ACN-121983664-A

Abstract

The invention discloses electrolyte for improving the infiltration efficiency of a lithium ion battery and an infiltration method, and relates to the technical field of lithium ion batteries, wherein the electrolyte comprises lithium salt, an organic solvent and an additive, the concentration of the lithium salt in the electrolyte is 0.5-3mol/L, the additive comprises a fluorine-containing interface modifier accounting for 0.05-5wt% of the total mass of the electrolyte, a viscosity regulator accounting for 0.5-10wt% of the total mass of the electrolyte and an electrocapillary effect promoter accounting for 0.01-3wt% of the total mass of the electrolyte, the surface tension of the electrolyte at 25 ℃ is less than or equal to 15mN/m, the viscosity is less than or equal to 10cP, and the surface tension can be reversibly increased to be more than or equal to 25mN/m after the voltage is more than or equal to 2.5V. The electrolyte provided by the invention realizes rapid and uniform permeation of the lithium ion battery through a transient super-infiltration-dynamic regulation mechanism, is especially suitable for high-energy density lithium ion batteries with high-compaction and thick pole pieces, and can greatly improve the production efficiency and the battery performance.

Inventors

DONG JIAO
CAO YONG
WANG YAJUN
MA RENLIANG
LI JIAN

Assignees

合肥国轩高科动力能源有限公司

Dates

Publication Date: 20260505
Application Date: 20260123

Claims (10)

1. The electrolyte for improving the infiltration efficiency of the lithium ion battery is characterized by comprising lithium salt, an organic solvent and an additive; Wherein the concentration of the lithium salt in the electrolyte is 0.5-3mol/L; The additive comprises: 1) The fluorine-containing interface modifier accounts for 0.05-5wt% of the total mass of the electrolyte, can reduce the initial surface tension of the electrolyte, and can be electrochemically decomposed to generate inert fluorinated products when the battery is charged to 2.5-3.5V (relative to Li + /Li) for the first time; 2) A viscosity modifier accounting for 0.5-10wt% of the total mass of the electrolyte, wherein the viscosity modifier is a heat-responsive polymer which can reduce the initial viscosity of the electrolyte and the viscosity rises after the temperature rises; 3) An electrocapillary effect promoter accounting for 0.01-3wt% of the total mass of the electrolyte, wherein the electrocapillary effect promoter can be oriented and generate additional capillary pressure under an external electric field; The surface tension of the electrolyte is less than or equal to 15mN/m at 25 ℃, the viscosity is less than or equal to 10cP, and the surface tension is reversibly increased to be more than or equal to 25mN/m after the voltage is more than or equal to 2.5V.
2. The electrolyte of claim 1, wherein the fluorine-containing interface modifier is selected from at least one of a fluorine-containing tertiary amine, a fluorine-containing phosphate, and a fluorine-containing siloxane; Preferably, the structural formula of the fluorine-containing tertiary amine is Rf- (CH 2 ) n -N(R) 2 ), wherein Rf is C4-C12 perfluoroalkyl, R is C1-C6 alkyl or hydroxyalkyl, n is more than or equal to 0 and less than or equal to 3 and is an integer; The structural formula of the fluorine-containing phosphate is Rf-O-PO (OR) 2 , wherein Rf is C4-C12 perfluoroalkyl, R is H OR C1-C4 alkyl; The structural formula of the fluorine-containing siloxane is Rf- (CH 2 ) n -Si(OR) 4-n ), wherein Rf is C4-C12 perfluoroalkyl, n is more than or equal to 1 and less than or equal to 3 and is an integer.
3. The electrolyte of claim 2, wherein the fluorine-containing interfacial stabilizer is selected from C 8 F 17 -N(CH 3 ) 2 or/and C 6 F 13 -CH 2 -N(C 2 H 5 ) 2 ; preferably, the fluorine-containing interfacial stabilizer accounts for 0.1-2wt% of the total mass of the electrolyte.
4. The electrolyte of claim 1, wherein the viscosity modifier is selected from at least one of a block copolymer, a hyperbranched polymer, a silicone modified polymer; preferably, the block polymer comprises at least one of polyether, polyester and polyolefin chain segments, and has a molecular weight of 2000-50000g/mol; The hyperbranched polymer comprises at least one of hyperbranched polyglycerol, hyperbranched polyamide-amine or hyperbranched polyacrylate; The silicone modified polymer is a polymer comprising a polydimethylsiloxane segment.
5. The electrolyte of claim 4, wherein the viscosity modifier is PTMEGx-b-PEOy, wherein x = 1000-3000 and y = 400-1000; preferably, the viscosity modifier comprises 1-5wt% of the total mass of the electrolyte.
6. The electrolyte of claim 1, wherein the electrocapillary effect promoter is selected from at least one of ionic liquids, organometallic complexes, polar aromatic compounds; Preferably, the ionic liquid is at least one of imidazole, pyridine or quaternary ammonium salt ionic liquid containing [ BF 4 ] - 、[PF 6 ] - 、[B(CN) 4 ] - or [ FSI ] - anions; the organic metal complex is cyclopentadienyl, carbonyl or cyano complex containing Fe, co, ni or Cu metal ions; The polar aromatic compound is an aromatic compound containing cyano, nitro or sulfonic groups.
7. The electrolyte according to claim 6, wherein the electrocapillary effect promoter is at least one selected from [ EMIM ] [ B (CN) 4 ]、[BMIM][BF 4 ], [ PP13] [ FSI ]; preferably, the electrocapillary effect promoter accounts for 0.05-1wt% of the total mass of the electrolyte.
8. The electrolyte according to any one of claims 1 to 7, wherein the electrolyte has a surface tension of 10 to 15mN/m, a viscosity of 5 to 10cP, a contact angle of 15 ° or less, an electrochemical window of 4.8V (vs.li+/Li) or more, and an ionic conductivity of 8mS/C or more at 25 ℃.
9. The method for producing an electrolytic solution according to any one of claims 1 to 8, comprising the steps of: 1) Dissolving lithium salt in an organic solvent under inert atmosphere, and stirring and dispersing; 2) Adding a viscosity regulator and an electrocapillary effect promoter into the mixture 1), and performing ultrasonic dispersion; 3) Adding the fluorine-containing interface modifier into the step 2), stirring, dispersing and filtering to obtain the fluorine-containing interface modifier.
10. The method for impregnating an electrolyte according to any one of claims 1 to 8 or an electrolyte prepared by the method according to claim 9, characterized by the steps of: 1) Impregnating, namely injecting electrolyte into a battery at 20-30 ℃, standing for 10-30min at normal pressure or micro negative pressure, and 2) performing thermo-electric coupling treatment, namely performing thermo-electric coupling treatment under staged control: the first stage is to charge the battery to 2.8-3.3V at 20-30 ℃ under the current of 0.01-0.1 ℃; the second stage is to charge the battery to 3.5-4.0V at 40-60 ℃ under 0.1-0.5C; And in the third stage, the mixture is placed at 20-30 ℃ for 0.5-5h.

Description

Electrolyte for improving infiltration efficiency of lithium ion battery and infiltration method Technical Field The invention relates to the technical field of lithium ion batteries, in particular to electrolyte for improving the infiltration efficiency of a lithium ion battery and an infiltration method. Background Under the background of continuous expansion of application fields such as large-scale energy storage, the market has put higher demands on the energy density of lithium ion batteries. Increasing the electrode thickness (i.e., increasing the areal density of the battery electrode) and increasing the pole piece compaction density (i.e., decreasing the porosity) are effective technological paths for increasing the energy density. However, the above densified electrode structure may affect the wetting effect of the electrolyte, thereby affecting the rate capability and cycle life of the battery. Currently, in order to solve the problem of poor infiltration effect of large-size battery cells or high-compaction-density battery pole pieces, methods such as increasing infiltration time, increasing infiltration temperature, vacuum infiltration and the like are generally adopted. The high-temperature long-time infiltration not only severely restricts the productivity, but also aggravates the side reaction of the electrolyte in the long-time high-temperature environment, thereby further deteriorating the battery performance, and in addition, the vacuum infiltration equipment has high cost and has the potential risk of damaging the microstructure of the electrode. On the other hand, in the prior art, it has been reported that the surface tension can be reduced by adding a surfactant to the electrolyte, and the infiltration effect can be directly improved, but there is also a risk of increasing gas production, deteriorating the stability of the electrode-electrolyte interface, and the like. Therefore, developing a new lithium ion battery electrolyte with excellent wetting effect and good interface compatibility for high-compaction and thick electrode plates has become a necessary and urgent technical task. Disclosure of Invention Based on the technical problems in the background art, the invention provides an electrolyte based on gas-liquid interface regulation and capillary effect reinforcement and an infiltration method using the electrolyte, which are particularly suitable for rapid infiltration of high-energy density lithium ion batteries with high compaction and thick pole pieces. In a first aspect, the electrolyte for improving the infiltration efficiency of a lithium ion battery provided by the invention comprises lithium salt, an organic solvent and an additive; Wherein the concentration of the lithium salt in the electrolyte is 0.5-3mol/L; The additive comprises: 1) The fluorine-containing interface modifier accounts for 0.05-5wt% of the total mass of the electrolyte, can reduce the initial surface tension of the electrolyte, and can be electrochemically decomposed to generate inert fluorinated products when the battery is charged to 2.5-3.5V (relative to Li +/Li) for the first time; 2) A viscosity modifier accounting for 0.5-10wt% of the total mass of the electrolyte, wherein the viscosity modifier is a heat-responsive polymer which can reduce the initial viscosity of the electrolyte and the viscosity rises after the temperature rises; 3) An electrocapillary effect promoter accounting for 0.01-3wt% of the total mass of the electrolyte, wherein the electrocapillary effect promoter can be oriented and generate additional capillary pressure under an external electric field; The surface tension of the electrolyte is less than or equal to 15mN/m at 25 ℃, the viscosity is less than or equal to 10cP, and the surface tension is reversibly increased to be more than or equal to 25mN/m after the voltage is more than or equal to 2.5V. In the invention, the electrolyte has the effect of rapid infiltration for lithium ion batteries, especially batteries with high energy density, which benefits from the synergistic effect of the components in the electrolyte, and based on the synergistic mechanism of transient super infiltration-dynamic regulation, rapid and uniform electrode infiltration is realized through the following triple effects: 1. transient super-wetting interface engineering Fluorine-containing interface modifier-dynamic regulation of fluorine-containing amphiphilic molecules: Compared with the prior electrolyte, the surface tension is reduced by adding the surfactant, the surface tension is reduced by static state, and the defect of residual gas production exists, the fluorine-containing interface modifier added by the invention can reduce the surface tension of the electrolyte in the initial stage of liquid injection, so that the electrolyte can be quickly spread to micropores of an electrode, and the compound is electrochemically decomposed into inert fluorinated products when the electrolyte is c