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CN-117645316-B - N-TiO2Diatomite/C composite diaphragm modified material, preparation thereof and application thereof in modification of lithium-sulfur battery diaphragm

CN117645316BCN 117645316 BCN117645316 BCN 117645316BCN-117645316-B

Abstract

The invention belongs to the field of battery materials, and particularly discloses a preparation method of an N-TiO 2 /diatomite/C composite diaphragm modified material, which comprises the steps of carrying out electrostatic spinning treatment on spinning solution containing N-TiO 2 , diatomite and a polymer, and then carrying out heat treatment at a temperature of 550-850 ℃ to obtain the N-TiO 2 which is N-doped TiO 2 . The invention also comprises the material prepared by the preparation method and the modified diaphragm thereof. The material prepared by the method can obviously improve the performance of the modified diaphragm material.

Inventors

  • LIU SAINAN
  • XIAO WENJIE

Assignees

  • 中南大学

Dates

Publication Date
20260505
Application Date
20231130

Claims (20)

  1. 1. The preparation method of the N-TiO 2 /diatomite/C composite diaphragm modified material is characterized by comprising the steps of carrying out electrostatic spinning treatment on spinning solution containing N-TiO 2 , diatomite and a polymer, and then carrying out heat treatment at 550-850 ℃ to obtain the N-TiO 2 /diatomite/C composite diaphragm modified material; The N-TiO 2 is N-doped TiO 2 ; The polymer is at least one of PVP, PVA, PEO.
  2. 2. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 1, wherein the N-TiO 2 is prepared by hydrolyzing a titanium source and a nitrogen source under acid; the titanium source is one or more of titanium alkoxide, titanium salt and titanyl ammonium oxalate.
  3. 3. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 2, wherein the titanium alkoxide comprises at least one of tetraethyl titanate, tetraisopropyl titanate and tetrabutyl titanate; the titanium salt comprises at least one of titanium tetrachloride, titanium trichloride, titanium sulfate and titanyl sulfate; The nitrogen source is at least one of ammonium salt, ammonia water, urea, ethylenediamine, thiourea and hydrazine hydrate; The weight ratio of the titanium source to the nitrogen source is 5-50:1; The temperature of the hydrolysis process is above 35 ℃.
  4. 4. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 3, wherein the weight ratio of the titanium source to the nitrogen source is 15-30:1; The temperature in the hydrolysis process is 40-90 ℃.
  5. 5. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 1, wherein the diatomite is pretreated diatomite subjected to heat pretreatment and/or acid pretreatment.
  6. 6. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 5, wherein the temperature of the heat pretreatment process is 400-800 ℃.
  7. 7. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 6, wherein the temperature of the heat pretreatment process is 500-600 ℃.
  8. 8. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 5, wherein the solute concentration of the acid liquor in the acid pretreatment stage is 10% -50% by weight, and the acid pretreatment time is more than 10 hours.
  9. 9. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 1, wherein the weight ratio of the N-TiO 2 , the diatomite and the polymer in the spinning solution is 1-10:1-5:1-10.
  10. 10. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 1, wherein the solvent in the spinning solution comprises at least one of N-N dimethylformamide, N-N dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, ethanol and acetic acid; The concentration of diatomite in the spinning solution is 1-50 mg/mL.
  11. 11. The preparation method of the N-TiO 2 /diatomite/C composite membrane modified material according to any one of claims 1-10, which is characterized in that the spinning temperature is 20-35 ℃, the humidity is 20% -55%, the voltage is 16 kV-24 kV, and the receiving distance is 10-20 cm; the spinning time is 8-12 hours.
  12. 12. The method for preparing the N-TiO 2 /diatomite/C composite membrane modified material according to claim 11, wherein the spinning is completed and then dried, and then the heat treatment is performed; the heat treatment process is carried out in a protective atmosphere; The heat treatment time is 1-3 h.
  13. 13. An N-TiO 2 /diatomaceous earth/C composite separator modified material prepared by the preparation method according to any one of claims 1 to 12.
  14. 14. The application of the N-TiO 2 /diatomite/C composite diaphragm modified material prepared by the preparation method according to any one of claims 1-12, which is characterized in that the modified material is used as a modified material for preparing a modified diaphragm for a lithium-sulfur battery.
  15. 15. The use according to claim 14, wherein said modified membrane is prepared by coating it on a membrane base film.
  16. 16. The modified diaphragm for the lithium-sulfur battery is characterized by comprising a base film and a modified material compounded on the surface of the base film, and the modified material is characterized by comprising the N-TiO 2 /diatomite/C composite diaphragm modified material prepared by the preparation method according to any one of claims 1-12.
  17. 17. The modified separator for lithium-sulfur batteries of claim 16 wherein said base film is at least one of PP and PE.
  18. 18. The modified separator for a lithium sulfur battery as in claim 16 wherein said modified material further comprises a binder.
  19. 19. The modified separator for a lithium sulfur battery of claim 18 wherein said binder comprises at least one of PVDF, CMC, SBR, PAA, PTFE, PVA.
  20. 20. The modified separator for a lithium-sulfur battery as in claim 18, wherein said modified material further comprises a conductive agent.

Description

N-TiO 2/diatomite/C composite diaphragm modified material, preparation thereof and application thereof in modification of lithium-sulfur battery diaphragm Technical Field The invention belongs to the technical field of battery diaphragms, and particularly relates to the technical field of lithium-sulfur battery diaphragms. Background With the rapid development of the endurance of electric automobiles and electronic devices, the capacity, energy density and cycle performance of electronic energy storage elements are also facing higher requirements. The lithium-sulfur battery has the advantages of high theoretical capacity (1675 mAh/g) and high energy density (2600 wh/kg), has 3-5 times of potential energy density compared with a commercial lithium ion battery, and is hopeful to become a secondary energy storage device of the next generation. However, the active material sulfur in lithium sulfur batteries is non-conductive and polysulfide "shuttling" occurs during use, severely degrading the electrochemical performance of the lithium sulfur battery. The diaphragm is used as an important component of the lithium-sulfur battery, can prevent positive and negative electrodes from contacting, prevent the battery from being short-circuited and transmit ions, and can effectively improve the electrochemical performance of the lithium-sulfur battery theoretically. At present, researchers at home and abroad develop a series of researches on functional diaphragms for lithium-sulfur batteries. By compounding catalytic materials such as metal nitride/metal oxide/metal sulfide on the surface of the diaphragm material, the reaction kinetics inside the lithium sulfur battery is accelerated, and the shuttle effect of polysulfide is inhibited. Titanium dioxide as a metal oxide can form a bond with polysulfide in the battery, and improves the adsorption effect on polysulfide. Some titanium dioxide modified lithium sulfur battery diaphragm schemes are also reported in the prior art, for example, publication No. CN109860476A discloses a titanium dioxide colloid modified diaphragm for a lithium sulfur battery, which comprises a polypropylene diaphragm and a nano-scale compact uniform titanium dioxide colloid layer with the thickness of 1-4 mu m coated on the two surfaces of the polypropylene diaphragm. The conductivity and structural stability of the material are not ideal, and the specific capacity and the cycle performance of the material are required to be improved. In addition, the prior art also reports improved separators based on diatomaceous earth compounding, for example, publication No. CN116315438a discloses a composite separator, a method of preparation, a battery and applications, including a base film and diatomaceous earth dispersed on the surface and ribs of the base film by impregnation. In addition, the prior art reports the scheme of TiO 2 @diatomite materials prepared based on the traditional sol-gel method. Although the prior art reports some schemes of modifying the diaphragm by titanium dioxide and diatomite, the schemes prepared by the prior art have the defects of low conductivity, easy falling of inorganic particles, poor structural stability, non-ideal electrochemical performance of the diaphragm and the like. Disclosure of Invention Aiming at the problems that the existing lithium sulfur battery diaphragm is not ideal in conductivity, the modified material is easy to fall off and is not ideal in electrochemical performance, the first aim of the invention is to provide a preparation method of the N-TiO 2/diatomite/C composite diaphragm modified material, and the aim is to prepare the modified material with excellent modification effect on the lithium sulfur battery diaphragm. The second aim of the invention is to provide the N-TiO 2/diatomite/C composite diaphragm modified material prepared by the preparation method and the application thereof in the modification of lithium-sulfur battery diaphragms. A third object of the present invention is to provide a modified separator comprising the modified material and a lithium-sulfur battery comprising the modified separator. The preparation method of the N-TiO 2/diatomite/C composite diaphragm modified material comprises the steps of carrying out electrostatic spinning treatment on spinning solution containing N-TiO 2, diatomite and a polymer, and then carrying out heat treatment at 550-850 ℃ to obtain the N-TiO 2/diatomite/C composite diaphragm modified material; The N-TiO 2 is N-doped TiO 2. According to the invention, N-TiO 2 and diatomite are subjected to spinning and heat treatment innovatively, so that the coordination and selective regulation of active phases can be realized, the occurrence of structural relationship and morphological characteristics of special components are constructed, the conductivity and structural composite stability of the material are improved synergistically, and the microstructure and active site of the lithium-sulfur battery