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CN-121983646-A - Polyether-based lithium battery electrolyte and preparation method thereof

CN121983646ACN 121983646 ACN121983646 ACN 121983646ACN-121983646-A

Abstract

The invention relates to the field of lithium electric polyether-based electrolytes; the invention provides a polyether-based lithium battery electrolyte and a preparation method thereof, wherein polyethylene oxide and bis (fluorosulfonyl) lithium imine are used as main bodies, dynamic polyether prepolymer and polyether shell-layer alumina nano powder are matched, the imine bond conversion rate, the median particle diameter D50, the organic shell layer content and the molar ratio of lithium salt to ethylene oxide units are controlled, and the electrolyte is prepared by pulping, casting, sectional drying and post curing of an anhydrous acetonitrile system to obtain a membranous or coated electrolyte, so that the water content is not higher than 500mg/kg, the total residual organic solvent content is not higher than 1000mg/kg, the viscosity and the thickness are controllable, the residual epoxy value is reduced, the problem that the viscosity and the purity are difficult to be compatible for casting film formation is solved, and the electrolyte is suitable for large-scale preparation of lithium battery electrolyte membranes.

Inventors

  • ZHANG WENXUAN
  • ZHAO BINGBING
  • Zhou Kangqian

Assignees

  • 江苏利宏科技发展有限公司

Dates

Publication Date
20260505
Application Date
20260409

Claims (10)

  1. 1. A polyether-based lithium battery electrolyte is characterized by comprising 40-75 parts by mass of polyethylene oxide, 16-28 parts by mass of bis (fluorosulfonyl) imide lithium and 5-25 parts by mass of dynamic polyether prepolymer, wherein the dynamic polyether prepolymer is obtained by condensing polyether amine and terephthalaldehyde, the conversion rate of an imine bond is 65.0-95.0%, and the conversion rate of the imine bond is measured according to 1 HNMR; 1-15 parts by mass of polyether shell alumina nano powder, wherein the polyether shell alumina nano powder is prepared by sequentially reacting alumina nano powder, (3-aminopropyl) triethoxysilane and polyethylene glycol diglycidyl ether, the median particle diameter D50 is 20-120nm, the median particle diameter D50 is measured by a wet laser diffraction method, the content of an organic shell layer is 3.0-20.0wt%, the content of the organic shell layer is measured by thermogravimetric analysis, the molar ratio of lithium bis (fluorosulfonyl) imide to ethylene oxide units in polyethylene oxide is 1:6-1:20, the water content of a polyether-based lithium electrolyte is not higher than 500mg/kg, and the water content is measured by a Karl Fischer titration method.
  2. 2. The polyether-based lithium battery electrolyte of claim 1, wherein the dynamic polyether prepolymer is prepared by: A1. Adding 100 parts by mass of polyetheramine and 18-42 parts by mass of terephthalaldehyde into 100-400 parts by mass of absolute ethyl alcohol, so that the molar ratio of amino groups to aldehyde groups is 1.0:1-1.10:1; A2. Reacting for 2-8h at 45-70 ℃ in nitrogen atmosphere; A3. Removing ethanol and byproduct water for 1-4h at 40-60 ℃ and minus 0.03-0.09 MPa; A4. The dynamic polyether prepolymer is obtained when the conversion of imine bonds is 65.0-95.0% as measured by 1HNMR and the viscosity of the system is 500-10000 mPa.s as measured under the conditions of 25 ℃ and 10s -1 of shearing rate.
  3. 3. The polyether-based lithium battery electrolyte according to claim 1, wherein the amino-silanized alumina nano powder is prepared before the polyether-shelled alumina nano powder is prepared, and the amino-silanized alumina nano powder is prepared by the following steps: B1. Dispersing 100 parts by mass of alumina nano powder in a mixed system of 300-1200 parts by mass of absolute ethyl alcohol and 10-80 parts by mass of deionized water; B2. Adding 5-30 parts by mass of (3-aminopropyl) triethoxysilane and 0.5-5.0 parts by mass of acetic acid to ensure that the pH value of the system is 4.5-6.0, and dispersing for 20-60min; B3. reacting for 2-6h at 50-75 ℃; B4. Washing with absolute ethyl alcohol for 2-4 times, wherein the dosage of the absolute ethyl alcohol is 3-20mL/g of the mass of the amino silanized alumina nano powder each time, and drying to constant weight under the conditions of 60-80 ℃ and minus 0.03-0.09 MPa, and the weighing difference between two adjacent times is not more than 0.1wt% of the total mass; B5. when the aminosilane grafting amount measured by thermogravimetric analysis is 1.0-8.0wt%, the amino silanized alumina nano powder is obtained.
  4. 4. The polyether-based lithium battery electrolyte according to claim 3, wherein the polyether-shelled alumina nano powder is prepared by: C1. 100 parts by mass of amino silanized alumina nano powder with the amino silane grafting amount of 1.0-8.0wt% is dispersed in 100-600 parts by mass of anhydrous acetonitrile; C2. Adding 10-80 parts by mass of polyethylene glycol diglycidyl ether, and reacting for 2-8 hours at 50-70 ℃ in nitrogen atmosphere; C3. Washing with anhydrous acetonitrile and anhydrous ethanol for 1-3 times in sequence, wherein the washing amount of each anhydrous acetonitrile and each anhydrous ethanol is 3-20mL/g of the mass of the polyether-shelled alumina nano powder, and drying to constant weight under the conditions of 50-70 ℃ and minus 0.03-0.09 MPa, and the weighing difference of two adjacent times is not more than 0.1wt% of the total mass; C4. When the content of the shell layer is 3.0-20.0wt% and the median particle diameter D50 is 20-120nm, the polyether-shell alumina nano powder is obtained.
  5. 5. The polyether-based lithium battery electrolyte according to claim 1, wherein in preparing the polyether-based lithium battery electrolyte, a composite electrolyte precursor is prepared first, the composite electrolyte precursor being prepared by: D1. Adding 100 parts by mass of dynamic polyether prepolymer, 5-60 parts by mass of polyether shell alumina nano powder and 20-80 parts by mass of lithium bis (fluorosulfonyl) imide into 100-500 parts by mass of anhydrous acetonitrile; D2. Stirring at 20-45 ℃ for 0.5-4h under nitrogen atmosphere; D3. degassing at 40-60deg.C, -0.03 to-0.09 MPa for 0.5-3 hr; D4. when the water content of the system is not higher than 500mg/kg, the water content is measured by a Karl Fischer titration method, and the viscosity measured under the conditions of 25 ℃ and the shearing rate of 10s -1 is 100-5000 mPa.s, the composite electrolyte precursor is obtained.
  6. 6. The polyether-based lithium battery electrolyte according to claim 1, wherein the polyethylene oxide is 50-65 parts by mass, the lithium bis (fluorosulfonyl) imide is 16-25 parts by mass, the dynamic polyether prepolymer is 8-18 parts by mass, and the polyether-shelled alumina nano-powder is 2-8 parts by mass.
  7. 7. The polyether-based lithium battery electrolyte according to claim 1, wherein the average viscosity average molecular weight of polyethylene oxide is 200000-1000000 and the average molecular weight of polyetheramine is 200-600.
  8. 8. The polyether-based lithium battery electrolyte according to claim 1, wherein the median particle diameter D50 of the polyether-shelled alumina nano-powder is 30-90nm, the organic shell content is 5.0-15.0wt%, and the aminosilane grafting amount of the aminosilane-modified alumina nano-powder is 1.0-5.0wt% when the polyether-shelled alumina nano-powder is prepared, the aminosilane grafting amount being determined by thermogravimetric analysis.
  9. 9. The polyether-based lithium electrolyte according to claim 1, wherein the polyether-based lithium electrolyte is in a film or coating form and has a thickness of 15-80 μm, and the total residual organic solvent, including acetonitrile and ethanol, is not higher than 1000mg/kg, and the total residual organic solvent content is measured by headspace gas chromatography.
  10. 10. A method for preparing the polyether-based lithium battery electrolyte according to any one of claims 1 to 9, comprising the steps of: S1, before preparing polyether-shell alumina nano powder and being used for preparing a composite electrolyte precursor, pre-drying the alumina nano powder at 80-120 ℃ to minus 0.03-0.09 MPa for 4-12 hours, pre-drying polyethylene oxide at 60-80 ℃ to minus 0.03-0.09 MPa for 8-24 hours, and pre-drying lithium bis (fluorosulfonyl) imide at 80-120 ℃ to minus 0.03-0.09 MPa for 8-24 hours; s2, providing a prepared composite electrolyte precursor, wherein the composite electrolyte precursor is a system obtained by mixing and degassing a dynamic polyether prepolymer, polyether-shelled alumina nano powder and lithium bis (fluorosulfonyl) imide in anhydrous acetonitrile; s3, dissolving lithium bis (fluorosulfonyl) imide in anhydrous acetonitrile to obtain a lithium salt solution, wherein the mass fraction of the lithium bis (fluorosulfonyl) imide in the anhydrous acetonitrile is 5-30wt%; S4, controlling the addition amount of lithium bis (fluorosulfonyl) imide and the addition amount of polyethylene oxide in the lithium salt solution obtained in the step S2 and the addition amount of the polyethylene oxide according to a final solid system, wherein the amounts of the polyethylene oxide, the lithium bis (fluorosulfonyl) imide, the dynamic polyether prepolymer and the polyether shell-layer aluminum oxide nano powder are 40-75 parts, 16-28 parts, 5-25 parts and 1-15 parts by mass respectively, the molar ratio of the lithium bis (fluorosulfonyl) imide to ethylene oxide units in the polyethylene oxide is 1:6-1:20, and then adding the composite electrolyte precursor provided in the step S2 and the polyethylene oxide into the lithium salt solution obtained in the step S3, stirring for 6-24 hours at 30-60 ℃ to obtain uniform slurry, and the water content of the uniform slurry is not higher than 200mg/kg and the viscosity of 200-3000 mPa.s; s5, casting the uniform slurry obtained in the step S4 on a release substrate in a controlled environment with the relative humidity not higher than 20% RH, wherein the wet film thickness is 50-300 mu m; S6, drying for 2-8 hours at 30-50 ℃, drying for 8-24 hours at 50-80 ℃ and minus 0.03-0.09 MPa, and continuously preserving heat for 1-6 hours at 50-70 ℃ and minus 0.03-0.09 MPa under the protection of nitrogen atmosphere to obtain the polyether-based lithium battery electrolyte, wherein the mass ratio of the dynamic polyether prepolymer to the polyether-shell alumina nano powder in the prepared polyether-based lithium battery electrolyte is 1:0.1-1:0.6, the dry film thickness is 15-80 mu m, the total residual organic solvent content is not higher than 1000mg/kg, and the water content is not higher than 500mg/kg.

Description

Polyether-based lithium battery electrolyte and preparation method thereof Technical Field The invention relates to the field of lithium battery electrolyte materials, in particular to a polyether-based lithium battery electrolyte and a preparation method thereof. Background The lithium electric device evolves to the direction of high safety and high energy density, so that the electrolyte needs to maintain a stable ion transmission channel in long-term operation and also needs to maintain the continuity and the dimensional stability of the membrane under the action of volume change and stress induced by charge and discharge. Polyether systems have potential advantages due to segment polarity and flexibility, wherein polyethylene oxide is easily processed into films and is suitable for forming film-like or coating-like electrolytes, but the microstructure is sensitive to salt complexation, segment movement and phase distribution, and fluctuations in formulation and process can lead to interface contact degradation or local defects. Practical applications also require that the electrolyte has low water content and low residual organic solvent to reduce side reaction and interface instability risks, and to combine viscosity controllability in the slurry casting process and complete film forming property in the subsequent drying and curing process, so that comprehensive requirements of purity, processability and structural stability are required to be met on component design and process paths. The existing polyether-based electrolyte schemes improve comprehensive properties by increasing lithium salt proportion, introducing inorganic filler or adopting a cross-linked network, but are still easy to cause structural contradiction between processability and final-state purity. For example, chinese patent publication No. CN114976231a discloses a method for improving ionic conductivity of solid electrolyte of lithium ion battery, solid electrolyte prepared by the method, and battery, but the control problem of phase distribution and film uniformity may still be brought to the high-salt system in the solvent casting and drying process. For another example, chinese patent publication No. CN113471522a discloses a composite solid electrolyte, and a preparation method and application thereof, but the interfacial interaction and dispersion stability of the inorganic phase and the polyether chain segment are significantly affected by surface chemistry, if a targeted interfacial structure is lacking, the problems of agglomeration, interfacial voids or difficulty in thoroughly removing residual small molecules in the post-treatment process easily occur, thereby limiting further improvement of the membranous or coated electrolyte in terms of process window and long-term stability. Disclosure of Invention The invention aims to provide a polyether-based lithium battery electrolyte and a preparation method thereof, which solve the problems that the viscosity requirement, the final water content and the total residual organic solvent content are difficult to control in the pulp casting process of the existing polyether system, and the interface crosslinking construction is insufficient in the post-curing stage. The invention combines the imine bond dynamic characteristic of the dynamic polyether prepolymer with the polyether shell layer of the polyether shell layer alumina nano powder and the residual epoxy group, so that the system keeps controllable viscosity and uniform dispersion in the pulping and casting stages, covalent crosslinking points are formed at interfaces by utilizing the ring-opening addition reaction of the residual primary amino end group and the residual epoxy group in the drying and post-curing stages, and the structural integrity and purity of the membranous or coating electrolyte are improved cooperatively by matching with the control of the water content and the total residual organic solvent content. In order to achieve the above object, the present invention provides the following technical solutions: A polyether-based lithium battery electrolyte comprises 40-75 parts by mass of polyethylene oxide, 16-28 parts by mass of bis (fluorosulfonyl) imide lithium and 5-25 parts by mass of dynamic polyether prepolymer, wherein the dynamic polyether prepolymer is obtained by condensing polyether amine and terephthalaldehyde, the conversion rate of an imine bond is 65.0-95.0%, and the conversion rate of the imine bond is measured according to 1 HNMR; 1-15 parts by mass of polyether shell alumina nano powder, wherein the polyether shell alumina nano powder is prepared by sequentially reacting alumina nano powder, (3-aminopropyl) triethoxysilane and polyethylene glycol diglycidyl ether, the median particle diameter D50 is 20-120nm, the median particle diameter D50 is measured by a wet laser diffraction method, the content of an organic shell layer is 3.0-20.0wt%, the content of the organic shell layer is measured by