Search

CN-122000625-A - Composite diaphragm, preparation method thereof and sodium metal battery

CN122000625ACN 122000625 ACN122000625 ACN 122000625ACN-122000625-A

Abstract

The invention relates to the technical field of battery materials, and provides a composite diaphragm, a preparation method thereof and a sodium metal battery. The composite diaphragm comprises a base film and a composite coating coated on the surface of the base film, wherein the composite coating comprises a first coating and a second coating which are sequentially arranged close to the base film, the first coating is arranged close to the base film, the components of the first coating comprise 80-98% by weight of molecular sieve and 2-20% by weight of first adhesive, the components of the second coating comprise 30-79% by weight of ion conductor, 20-69% by weight of polymer solid electrolyte and 1-10% by weight of second adhesive, and the ion conductor is at least one of lithium aluminum titanium phosphate, sodium fluoride, sodium hexafluoroaluminate, sodium zirconium silicon phosphorus oxide, beta-Al 2 O 3 , sodium borohydride and sodium titanium phosphate. After the composite diaphragm is applied to a sodium metal battery, the charging and discharging efficiency of negative sodium metal can be improved, the growth of sodium metal dendrites is reduced, and the gas production is reduced, so that the electrochemical performance of the sodium metal battery is improved.

Inventors

  • LI XIANG
  • ZHOU SHIHAO
  • ZHANG WEIQING
  • YANG QINGHENG
  • Yang Yishuang

Assignees

  • 江苏中兴派能电池有限公司

Dates

Publication Date
20260508
Application Date
20241101

Claims (10)

  1. 1. A composite diaphragm, which is characterized by comprising a base film and a composite coating coated on the surface of the base film; the composite coating comprises a first coating and a second coating which are sequentially arranged close to a base film, and the first coating is arranged close to the base film; the first coating comprises 80-98% by weight of molecular sieve and 2-20% by weight of first adhesive; the second coating comprises 30-79% by weight of ionic conductor, 20-69% by weight of polymer solid electrolyte and 1-10% by weight of second adhesive; The ion conductor is at least one selected from titanium aluminum lithium phosphate, sodium fluoride, sodium hexafluoroaluminate, sodium zirconium silicon phosphorus oxide, beta-Al 2 O 3 , sodium borohydride and titanium sodium phosphate.
  2. 2. The composite membrane of claim 1, wherein the molecular sieve is selected from at least one of a 3A molecular sieve, a 4A molecular sieve, a 5A molecular sieve, a 10Z molecular sieve, a 13Z molecular sieve, and a Y-type molecular sieve.
  3. 3. The composite separator of claim 1, wherein the first binder is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, styrene butadiene rubber, and polyvinylidene fluoride.
  4. 4. The composite separator of claim 1, wherein the second binder is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, styrene butadiene rubber, and polyvinylidene fluoride.
  5. 5. The composite separator of claim 1, wherein the polymer solid electrolyte is selected from at least one of polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate.
  6. 6. The composite membrane of claim 1, wherein the base film is a PE film or a PP film.
  7. 7. The composite membrane of claim 1, wherein the first coating thickness is 0.5-5 μm; And/or the thickness of the second coating is 0.5-5 mu m.
  8. 8. The method for preparing a composite membrane according to any one of claims 1 to 7, comprising: applying a first slurry comprising the molecular sieve and the first binder to the base film, followed by a first drying to form the first coating; And (3) coating a second slurry containing the ionic conductor, the polymer solid electrolyte and the second adhesive on the first coating, and then drying for the second time to obtain the second coating.
  9. 9. The method according to claim 8, wherein the temperature at the time of the first drying and/or the second drying is 60 to 150 ℃ and the drying time is 5 to 12 hours.
  10. 10. A sodium metal battery comprising a composite separator according to any one of claims 1 to 7, wherein the second coating of the composite separator is bonded to a sodium negative electrode.

Description

Composite diaphragm, preparation method thereof and sodium metal battery Technical Field The invention relates to the technical field of battery materials, in particular to a composite diaphragm, a preparation method thereof and a sodium metal battery. Background Development of sustainable energy is an important trend in current energy development due to continuous fermentation of energy crisis and environmental crisis. Sodium ion batteries become one of the important electrochemical energy storage candidates because of the abundant raw material resources and low cost. The cathode-free sodium-ion battery directly takes copper foil or aluminum foil as a cathode, and utilizes reduction electroplating and oxidation stripping of sodium ions as a cathode reaction to construct the cathode-free sodium-ion battery, so that the cathode-free sodium-ion battery has extremely high energy density and potential low cost feasibility. However, the adoption of the traditional battery system generally leads to uneven deposition of sodium metal in the charging process, low coulombic efficiency of the battery and serious gas production. In view of this, the present invention has been made. Disclosure of Invention The present invention aims to provide a composite separator, a preparation method thereof and a sodium metal battery, and aims to improve at least one of the problems mentioned in the background art. The invention is realized in the following way: in a first aspect, the present invention provides a composite separator comprising a base film and a composite coating applied to the surface of the base film; the composite coating comprises a first coating and a second coating which are sequentially arranged close to the base film, and the first coating is arranged close to the base film; the first coating comprises 80-98% by weight of molecular sieve and 2-20% by weight of first adhesive; The second coating comprises 30-79% by weight of ionic conductor, 20-69% by weight of polymer solid electrolyte and 1-10% by weight of second adhesive; The ion conductor is at least one selected from the group consisting of lithium aluminum titanium phosphate, sodium fluoride, sodium hexafluoroaluminate, sodium zirconium silicon phosphorus oxide, beta-Al 2O3, sodium borohydride and sodium titanium phosphate. In alternative embodiments, the molecular sieve is selected from at least one of a 3A molecular sieve, a 4A molecular sieve, a 5A molecular sieve, a 10Z molecular sieve, a 13Z molecular sieve, and a Y-type molecular sieve. In an alternative embodiment, the first binder is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, styrene butadiene rubber, and polyvinylidene fluoride. In an alternative embodiment, the second binder is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, sodium polyacrylate, styrene butadiene rubber, and polyvinylidene fluoride. In an alternative embodiment, the polymer solid electrolyte is selected from at least one of polyethylene oxide, polyacrylonitrile, and polymethyl methacrylate. In an alternative embodiment, the base film is a PE film or a PP film. In an alternative embodiment, the first coating thickness is 0.5-5 μm; And/or the thickness of the second coating is 0.5-5 μm. In a second aspect, the present invention provides a method of preparing a composite separator according to any one of the preceding embodiments, comprising: Coating a first slurry containing a molecular sieve and a first binder on a base film, and then performing first drying to form a first coating; Coating a second slurry containing an ion conductor, a polymer solid electrolyte and a second adhesive on the first coating, and then drying for the second time to obtain a second coating; In an alternative embodiment, the temperature of the first drying and/or the second drying is 60-150 ℃ and the drying time is 5-12 h. In a third aspect, the present invention provides a sodium metal battery comprising a composite separator according to any of the preceding embodiments, the second coating of the composite separator being bonded to a sodium negative electrode. The invention has the following beneficial effects: The composite membrane provided by the embodiment of the invention has the advantages that the first coating contains a large number of molecular sieves, on one hand, the molecular sieves have a large number of apertures smaller than 1nm, so that the solvation structure of sodium ions in the electrolyte can be effectively adjusted, when the solvated sodium ions pass through the molecular sieve layer, part of solvents can be adsorbed inside molecular sieve holes to reduce the decomposition of the solvents on the surface of metal sodium, and on the other hand, the large number of apertures in the molecular sieves can effectively adsorb a large number of gases generated by the reduction of the electrolyte by the metal sodium, so that the phenomenon of uneve