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CN-122000447-A - Preparation method and application of air-stable sulfide composite electrolyte

CN122000447ACN 122000447 ACN122000447 ACN 122000447ACN-122000447-A

Abstract

The invention provides a preparation method and application of an air-stable sulfide composite electrolyte, the method comprises the steps of S1, weighing M sources (M=Cd, mn and Zn), P 2 S 5 and S powder according to a ratio of 1:1:3, adding iodine for catalysis, carrying out heat preservation for 6-7 days at 700-720 ℃, K+ insertion, li+ exchange and ultrasonic centrifugation to obtain LiMyPS 3 nano-sheet dispersion liquid, S2, dissolving PEO and LiTFSI in acetonitrile for film formation and drying to obtain a pure PEO film, immersing the pure PEO film in 2mg/ml of dopamine Tris buffer solution with pH=8.5, carrying out oscillation for 12-24 hours in an oxygen environment, washing and drying to obtain a PDA@PEO film, S3, carrying out suction filtration on the LiMyPS 3 dispersion liquid to obtain a self-supporting film, stacking according to the conditions of 'PDA@PEO film-sulfide film- & PDA@PEO film', carrying out isostatic pressing, and then carrying out vertical cutting at 0 ℃ to obtain a 20-30 mu M composite film. The membrane has good air stability, almost no loss of conductivity after 30 days, 9.2-10.2ms/cm of room temperature conductivity, excellent interfacial binding force and mechanical strength, 4.3-4.5V of stability window and adaptation to a high-voltage positive electrode, and can be used for a high-energy density solid-state lithium battery.

Inventors

  • YIN HAIBIN
  • LIU HUAIPING
  • YAO XIN

Assignees

  • 江苏昆仑互联新能源集团有限公司

Dates

Publication Date
20260508
Application Date
20260407

Claims (8)

  1. 1. The preparation method of the air-stable sulfide composite electrolyte is characterized by comprising the following steps of: S1, preparing LiMyPS 3 nano-sheet dispersion liquid: Weighing a manganese source, a Mn powder, a phosphorus source, P 2 S 5 , a sulfur source and S powder according to a stoichiometric ratio of 1:1:3, adding a small amount of iodine as a catalyst, mixing the weighed raw materials, vacuum-sealing, placing in a quartz tube, preserving heat for 6-7 days at 700-720 ℃ in the middle of the tube furnace, cooling to room temperature, collecting a product at a cold end, washing by using ethanol to remove residual iodine to obtain MPS 3 crystals, soaking the MPS 3 crystals in a mixed solution, and performing K + insertion, li + exchange and ultrasonic stripping to obtain LiMyPS 3 nano-sheet dispersion; S2, preparing PEO electrolyte membrane: Dissolving PEO powder and lithium salt in acetonitrile to prepare a solution with the solid content of 10wt%, coating the solution on a PTFE plate to form a film, and then vacuum-drying at 40-60 ℃ for 12 hours to obtain a pure PEO film, dissolving dopamine in Tris buffer solution with the pH value of 8.5 to obtain a dopamine derivative solution with the concentration of 2mg/ml, immersing the pure PEO film in the dopamine derivative solution, oscillating for 12-24 hours in an oxygen environment, washing with deionized water, vacuum-drying at 40-60 ℃ for 12 hours, and drying to obtain a PDA@PEO film; s3, assembling and cutting: Carrying out suction filtration on the LiMyPS 3 nano-sheet dispersion liquid obtained in the step S1, peeling from a filter membrane after solvent evaporation to obtain a self-supporting LiMyPS 3 sulfide membrane, repeatedly stacking according to the sequence of PDA@PEO membrane, self-supporting LiMyPS 3 sulfide membrane and PDA@PEO membrane until the required size is reached, and then carrying out isostatic pressing treatment, and then cutting along the direction perpendicular to the surface of the membrane at the temperature of 0 ℃ to obtain the composite electrolyte membrane with the thickness of 20-30 mu m, namely the final solid electrolyte membrane with a vertical transmission path.
  2. 2. The method for preparing an air-stable sulfide composite electrolyte according to claim 1, wherein in the step S1, the purity of the manganese source is not less than 99%, the purity of the phosphorus source is not less than 98%, and the purity of the sulfur source is not less than 99%; The K+ intercalation process uses a mixed solution of 0.5M KCl+ M K 2 CO 3 +1M EDTA, and is stirred at 50 ℃ for 2 hours, and the Li + exchange process uses a 2M LiCl solution and is stirred at room temperature for 4 hours.
  3. 3. The method for preparing an air-stable sulfide composite electrolyte according to claim 1, wherein in the step S2, the molecular weight of the PEO powder is 100000 g/mol, the lithium salt is lithium bistrifluoromethane sulfonyl imide, and the thickness of the PDA coating layer in the PDA@PEO film is 50-100 nm.
  4. 4. The method of preparing an air-stable sulfide composite electrolyte according to claim 1, wherein in step S2, PEO powder and PDA nanoparticles are mixed, lithium salt and acetonitrile solvent are added, and the PEO@PDA film containing PDA particles is obtained after coating and drying, and then surface PDA coating treatment is performed.
  5. 5. The method for preparing an air-stable sulfide composite electrolyte according to claim 1, wherein in the step S3, the isostatic pressure is 10-20 MPa, the dwell time is 30 minutes, and the cutting direction is perpendicular to the surface of the membrane to construct a longitudinal lithium ion transport channel.
  6. 6. The composite electrolyte membrane according to any one of claims 1 to 5, wherein the composite electrolyte membrane has a room temperature ionic conductivity of 9.2 to 10.2 mS/cm, an electrochemical stability window of 4.3 to 4.5V, a tensile strength MD of 2.4 to 2.7 MPa, a tensile strength TD of 3.0 to 3.3MPa, and an ionic conductivity retention of 96% or more after 30 days of standing in air.
  7. 7. The application of the composite electrolyte membrane in the solid lithium battery, which is characterized in that the composite electrolyte membrane can be used for assembling a soft-packed battery or a button battery without applying external pressure, and is suitable for high-voltage positive electrode materials such as LiNi0.8, co0.1, mn0.1O2 and the like.
  8. 8. A PEO-based solid electrolyte modified by PDA is characterized by comprising a PEO polymer matrix, lithium salt and PDA serving as a functional additive, wherein the PDA is introduced into the PEO polymer matrix in an in-situ polymerization or physical blending mode and is used for improving the peel strength between the solid electrolyte and an electrode as well as between the solid electrolyte and a sulfide electrolyte, and improving the oxidation resistance and high-voltage stability of the solid electrolyte, the molar ratio of EO units to Li + in the PEO polymer matrix is 15:1, and the addition amount of the PDA is 5: 5wt% of the weight of the PEO polymer matrix.

Description

Preparation method and application of air-stable sulfide composite electrolyte Technical Field The invention particularly relates to a preparation method and application of an air-stable sulfide composite electrolyte. Background The current mainstream lithium battery system takes the traditional liquid lithium ion battery as the dominant material, however, the energy density of the current mainstream lithium battery system is close to the theoretical limit (less than or equal to 300 Wh/kg), and the current mainstream lithium battery system is difficult to meet the requirement of continuous improvement of the endurance capacity (more than or equal to 500 Wh/kg) of long-endurance equipment (such as electric automobiles, energy storage power stations and the like). Meanwhile, the organic electrolyte adopted by the liquid lithium ion battery has combustibility and poor thermal stability, and safety accidents such as liquid leakage, fire and even explosion are easy to occur in the charging and discharging process, so that the severe requirements of the power battery on high safety cannot be met. The solid electrolyte has excellent thermal stability and mechanical strength, so that potential safety hazards of liquid electrolyte can be effectively solved, and a key way for realizing high energy density of the power battery is provided, so that the solid electrolyte becomes a core direction of future power battery development. Among the many solid electrolyte materials, sulfide electrolytes are receiving significant attention in both academia and industry due to their high room temperature ionic conductivity (comparable to liquid electrolytes) and thermal decomposition temperatures over three times that of liquid electrolyte systems. The sulfide LixMyPS (M=Cd, mn, zn) based on the novel lithium intercalation two-dimensional conduction mechanism shows super-ionic conductor characteristics, the room-temperature ionic conductivity of the sulfide LixMyPS can reach 120 mS cm-1, which is tens times of that of the traditional sulfide electrolyte, and the sulfide LixMyPS has certain stability in air, and can be used without applying high external pressure of hundreds of MPa. However, the lithium ion conduction of the sulfide electrolyte is mainly limited to the transverse direction (parallel to the surface of the film), and the specific conduction path greatly limits the further application of the sulfide electrolyte in the solid-state battery, and the advantage of high ion conductivity of the sulfide electrolyte cannot be fully utilized. In order to solve the above-mentioned problem of lateral conduction limitation, the prior art has attempted to prepare a high-performance sulfide composite electrolyte membrane by stacking and compositing a polymer membrane and a sulfide electrolyte membrane and then cutting and recombining the polymer membrane and the sulfide electrolyte membrane so that a lithium ion transmission channel is converted into an upper-lower longitudinal direction (perpendicular to the surface of the membrane). In this composite system, polyethylene oxide (PEO) polymer electrolytes are often used as binders to achieve the binding of the sulfide particles to the polymer matrix. However, PEO has obvious defects that on one hand, the interfacial binding force between PEO and an electrode and sulfide particles is insufficient, so that the interfacial impedance is increased in the battery cycle process, and on the other hand, PEO is easy to be oxidized and decomposed under high voltage (generally more than 4.0V), and cannot be adapted to a high-voltage positive electrode material, so that the improvement of the battery energy density is limited. Polydopamine (PDA) is used as a common mussel bionic bonding material, and has unique molecular structure and performance advantages. Catechol/quinone groups in PDA molecules can realize universal super-strong adhesion through covalent bonds, coordination bonds (such as combination with Co 3+/Ni2+), hydrogen bonds and pi-pi stacking effect, and the peel strength can reach 50-100N/m which is far higher than 10-20N/m of PEO, so that the bonding agent is particularly suitable for bonding the surfaces of high-activity electrodes such as silicon cathodes, lithium metals and the like. In addition, the quinone/hydroquinone structure of the PDA has redox reversibility, can dynamically repair interface microcracks generated by volume change in the charge and discharge process of the battery, nitrogen-containing groups (-NH-) in molecules can promote uniform diffusion of Li+ at the interface, reduce ion transmission impedance, and meanwhile, the PDA is rich in reducing groups such as phenolic hydroxyl groups, amino groups and the like, can effectively remove free radicals in an electrolyte system, and improves chemical stability and oxidation resistance of the electrolyte. In the aspect of the process, the PDA can form a film in situ through a room-temperature aqueous solution, has