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CN-122000435-A - Preparation method of sulfide solid electrolyte slurry, preparation method of positive plate, all-solid-state battery and preparation method of all-solid-state battery

CN122000435ACN 122000435 ACN122000435 ACN 122000435ACN-122000435-A

Abstract

The invention discloses a preparation method of sulfide solid electrolyte slurry, a preparation method of positive plate, an all-solid-state battery and a preparation method thereof, wherein the method comprises the following steps: the modified perfluoropolyether oil is prepared by taking perfluoropolyether carboxylic acid as a raw material, and the modified perfluoropolyether oil is mixed with lithium salt, a suspension stabilizing additive and sulfide electrolyte to prepare slurry. The modified perfluoropolyether oil adopts asymmetric end group design, one end is a glycidyl ether group, and the other end is a cyano group. According to the invention, the modified perfluoropolyether oil is introduced as a protective medium and an ion conduction enhancer of the sulfide electrolyte, so that the problems of air stability, space charge layer and high-voltage operation of the sulfide electrolyte are solved, the process is simple, the cost is low, and the industrial application prospect is good. A gel state ion conducting layer is formed between the positive plate and the electrolyte layer of the all-solid-state battery, and has high viscoelasticity, so that good solid-solid interface contact can be kept under a lower external pressure condition.

Inventors

  • CAI XIAOLAN
  • QIN JIAN
  • LI QIAO
  • XU YANHUI
  • LIANG WEI

Assignees

  • 孝感楚能新能源创新科技有限公司

Dates

Publication Date
20260508
Application Date
20260130

Claims (10)

  1. 1. A method for preparing sulfide solid electrolyte slurry, comprising the steps of: S1, preparing modified perfluoropolyether oil by taking perfluoropolyether carboxylic acid as a raw material, and performing acyl chlorination reaction, cyano end group introduction, epoxy end group introduction and hydrogenation reduction treatment, wherein the modified perfluoropolyether oil takes the perfluoropolyether oil as a skeleton structure, adopts an asymmetric end group design, has one end being a glycidyl ether group and the other end being a cyano group; S2, mixing the modified perfluoropolyether oil and lithium salt in vacuum or inert gas protection, and stirring at a rotating speed of 150-250rpm for 150-210min to completely dissolve the lithium salt; S3, adding a suspension stabilizing additive into the mixture obtained in the step S2, and continuously stirring for 10-20min to uniformly disperse the suspension stabilizing additive; S4, adding sulfide electrolyte powder into the mixture obtained in the step S3 in batches, wherein the interval between each batch is 3-7min; S5, after all the sulfide electrolyte powder is added, raising the stirring rotation speed to 400-600rpm, and continuously stirring for 3-5 hours to obtain sulfide solid electrolyte slurry; The sulfide solid electrolyte slurry comprises, by mass, 70% -80% of sulfide electrolyte, 15% -30% of modified perfluoropolyether oil, 1% -2% of lithium salt and 0.05% -0.15% of suspension stabilizing additive, wherein the sulfide electrolyte is selected from one or two of Li 6 PS 5 Cl or Li 3 PS 4 , and the particle size D50 is 0.5-2 mu m.
  2. 2. The preparation method according to claim 1, wherein the preparation method of the modified perfluoropolyether oil in step S1 specifically comprises the following steps: S101, reacting perfluoropolyether carboxylic acid with the number average molecular weight of 1500-2500 with thionyl chloride for 3-5h at 50-70 ℃, and distilling under reduced pressure to remove excessive thionyl chloride to obtain perfluoropolyether acyl chloride; s102, under the protection of inert atmosphere, adding 4-aminobenzyl cyanide and a catalyst triethylamine into the perfluoropolyether acyl chloride, reacting for 5-7 hours at 70-90 ℃, and introducing cyano end groups at one end of a perfluoropolyether molecular chain through amidation reaction, wherein the molar ratio of the 4-aminobenzyl cyanide to the perfluoropolyether acyl chloride is 1.0-1.2:1; S103, adding epichlorohydrin into the product obtained in the step S102, reacting for 5-7 hours at 50-70 ℃ under the catalysis of potassium hydroxide, and introducing an glycidyl ether group into the other end of the perfluoropolyether molecular chain through etherification reaction, wherein the molar ratio of the epichlorohydrin to the perfluoropolyether acyl chloride is 1.0-1.5:1; S104, carrying out hydrogenation reduction treatment under the condition of hydrogen pressure of 0.3-0.7MPa by adopting a Pd/C catalyst, and controlling the functionality to obtain the modified perfluoropolyether oil, wherein the molar ratio of epoxy groups to cyano groups is 1.0-1.5:1, the volatilization temperature of the modified perfluoropolyether oil is above 250 ℃, and the structural formula of the glycidyl ether groups is-O-CH 2 -CH(-O-)-CH 2 .
  3. 3. The preparation method of the suspension stabilizer according to claim 1, wherein the lithium salt is one or more of lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium tetrafluoroborate and lithium difluoro (oxalato) borate, and the suspension stabilizer additive is one or more of trimethyl silicon mercaptan, perfluorooctyl mercaptan, dodecyl mercaptan and mercaptopropyl trimethoxy silane.
  4. 4. The preparation method according to claim 1, further comprising a step S6 of heating the slurry obtained in the step S5 to 90-110 ℃ and maintaining the temperature for 2-4 hours to polymerize the modified perfluoropolyether oil in situ to form a gel state particle structure, wherein after the heated and polymerized slurry is exposed to an air atmosphere at 35 ℃ for 4-6 hours, the release amount of H 2 S is less than 0.5ppm, the H 2 S inhibition rate is more than 99.9%, and the ionic conductivity is 9.0X10 -4 to 1.0X10 -3 S/cm.
  5. 5. The preparation method of the positive plate adopts a dry process and is characterized by comprising the following steps: s1, performing fibrosis treatment on polytetrafluoroethylene adhesive to form a fibrous structure; s2, mixing the positive electrode active material, the conductive agent and the fibrillated adhesive with the sulfide solid electrolyte slurry prepared by the method of claim 1, and performing ball milling treatment to obtain a mixture, wherein the modified perfluoropolyether oil in the slurry plays a role of a lubricant at the stage; S3, paving the mixture on a current collector, repeatedly rolling the mixture by adopting a hot roll squeezer with the temperature of 80-90 ℃, and thinning the mixture to a target thickness to form a pole piece; And S4, placing the rolled pole piece in a vacuum environment, drying for 2-4 hours at the temperature of 100-120 ℃ to enable the modified perfluoropolyether oil in the slurry to be subjected to thermal polymerization and solidification, and forming a crosslinked gel state ion conduction network between the positive electrode active material and the sulfide electrolyte to obtain the dry-method positive electrode piece.
  6. 6. The preparation method of claim 5, wherein the positive electrode active material is one or more of nickel cobalt manganese ternary positive electrode material, lithium iron phosphate and nickel cobalt aluminum ternary positive electrode material, the conductive agent is one or more of conductive carbon black, carbon nano tube, graphene and ketjen black, and the current collector is one or more of carbon-coated aluminum foil, graphite-coated aluminum foil, graphene-coated aluminum foil and carbon nano tube-coated aluminum foil; The positive electrode comprises, by mass, 200-220 parts of positive electrode active material, 2-4 parts of polytetrafluoroethylene adhesive, 2-3 parts of conductive agent, 40-60 parts of sulfide solid electrolyte slurry, and 80-90 ℃ of hot rolling temperature in step S3, wherein the thickness of a rolled pole piece is 80-120 mu m.
  7. 7. The preparation method of the positive plate adopts a wet process and is characterized by comprising the following steps: S1, dissolving a polyvinylidene fluoride adhesive in an N-methyl pyrrolidone solvent to form a glue solution, then adding an anode active material, a conductive agent and the sulfide solid electrolyte slurry prepared by the method of claim 4, and stirring and dispersing uniformly to obtain an anode slurry; S2, coating the positive electrode slurry on a current collector to form a wet film; S3, placing the coated current collector in a vacuum environment, drying for 6-8 hours at 100-120 ℃ to sufficiently remove the N-methylpyrrolidone solvent, and then carrying out rolling treatment to reach a target thickness to obtain the wet positive plate.
  8. 8. The preparation method of claim 7, wherein the positive electrode active material is one or more of nickel-cobalt-manganese ternary positive electrode material, lithium iron phosphate and nickel-cobalt-aluminum ternary positive electrode material, and the current collector is one or more of carbon-coated aluminum foil, graphite-coated aluminum foil, graphene-coated aluminum foil and carbon nanotube-coated aluminum foil; The positive electrode comprises, by mass, 200-220 parts of positive electrode active material, 2-4 parts of polyvinylidene fluoride adhesive, 2-3 parts of conductive agent, 40-60 parts of sulfide solid electrolyte slurry, 120-160 parts of N-methylpyrrolidone solvent and 80-120 mu m of rolled pole piece.
  9. 9. A method of making an all-solid-state battery comprising the steps of: s1, coating sulfide solid electrolyte slurry prepared by the method of claim 1 on the surface of a dry positive plate prepared by the method of claim 5 or 6 or the surface of a wet positive plate prepared by the method of claim 7 or 8 by adopting a tape casting method, and controlling the height of a doctor blade to be 40-60 mu m by adopting a doctor blade coating mode; S2, placing the coated positive plate in a vacuum environment, and heating for 2-4 hours at 90-110 ℃ to enable modified perfluoropolyether oil in the slurry to undergo in-situ thermal polymerization to form a positive electrode-electrolyte layer integrated structure; S3, rolling the anode-electrolyte layer integrated structure obtained in the step S2, and controlling the total thickness to be 120-150 mu m; s4, laminating the integrated positive plate and the negative plate according to the number of design layers, and then welding and packaging the lugs to obtain the soft-packaged battery, wherein the negative plate is a lithium-copper composite belt and comprises a copper foil substrate with the thickness of 6-10 mu m and a metal lithium layer with the thickness of 8-12 mu m which is composited on one side of the copper foil substrate; S5, placing the soft package battery in a warm isostatic pressing device, performing isostatic pressing treatment at the temperature of 40-60 ℃ and the pressure of 40-60MPa, wherein the pressurizing time is 3-7min, the pressurizing gradient is 8-12MPa/min, the pressure maintaining time is 3-7min, and the pressure releasing gradient is 8-12MPa/min, so that the all-solid-state battery is obtained.
  10. 10. An all-solid-state battery prepared by the preparation method of claim 9, wherein the all-solid-state battery comprises a positive electrode plate, an electrolyte layer and a negative electrode plate, a gel-state ion conducting layer is formed between the positive electrode plate and the electrolyte layer, the gel-state ion conducting layer is formed by a crosslinked network structure formed by thermal polymerization of modified perfluoropolyether oil and lithium salt together, and the crosslinked network structure comprises a polyether network formed by ring-opening polymerization of a glycidyl ether group and a triazine ring structure formed by cyano trimerization; Under the condition of 50kg of clamp force, the initial coulomb efficiency of the all-solid-state battery is more than or equal to 88%, the 0.2C discharge capacity is more than or equal to 0.95Ah, the 2C discharge capacity is more than or equal to 0.89Ah, the cycle test is carried out under the condition of 0.5C charge/1C discharge, and the cycle times when the capacity is attenuated to 70% are more than or equal to 220 times.

Description

Preparation method of sulfide solid electrolyte slurry, preparation method of positive plate, all-solid-state battery and preparation method of all-solid-state battery Technical Field The invention relates to the technical field of solid-state batteries, in particular to a preparation method of sulfide solid-state electrolyte slurry, a preparation method of a positive plate, an all-solid-state battery and a preparation method thereof. Background The all-solid-state lithium battery adopts the solid electrolyte to replace the traditional liquid electrolyte, has the advantages of high safety, high energy density and the like, and is an important development direction of the next-generation energy storage technology. Among the many solid electrolyte systems, sulfide solid electrolytes are of interest for their high ionic conductivity (up to 10 -3-10-2 S/cm, approaching liquid electrolyte levels) and good machinability. However, sulfide solid state electrolytes face three technical challenges in practical applications: First, air stability is poor. The P-S chemical bond energy in the sulfide electrolyte is weak, is in a metastable state, and is more prone to react with water or oxygen to form P-O bonds, while releasing toxic H 2 S gas. This not only worsens the ionic conductivity of the electrolyte, but also brings serious potential safety hazards, greatly limiting its industrial application. Second, space charge layer effects. Sulfide is a single ion conductor, and S 2- has extremely weak binding force to Li +. When sulfide electrolyte and oxide positive electrode or graphite, silicon and lithium metal negative electrode form solid-solid contact, lithium ions at the interface can spontaneously migrate from the electrolyte to the interface of the active material due to large chemical potential difference of lithium in different materials, so that a space charge layer is formed. The presence of the space charge layer significantly increases the interface reaction resistance, deteriorating the electrochemical performance of the battery. Third, high pressure operation requirements. Because of the difficulty in forming a tight solid-solid interface contact between the sulfide electrolyte and the electrode material, the conventional sulfide system all-solid-state battery requires an external pressure of up to about 600MPa to maintain a good solid-solid contact during operation to exert high performance, which presents a great challenge for the design and practical application of the battery system. Currently, a common technical means for solving the above problems is to perform cladding doping on the surface of the sulfide electrolyte to form a heterostructure so as to improve stability and slow down the space charge layer effect. Although the method has a certain effect, the homogenization of the material is affected by introducing other phases, new interface impedance is additionally added, the process is complex, the cost is high, and the requirement of large-scale industrialization is difficult to meet. Therefore, developing a technical solution capable of simultaneously solving the problems of air stability, space charge layer and high voltage operation of sulfide solid-state electrolyte has important significance for promoting industrialization of all-solid-state batteries. Disclosure of Invention The invention aims to overcome the defects of the background technology and provide a preparation method of sulfide solid electrolyte slurry, a preparation method of positive plate, an all-solid-state battery and a preparation method thereof, according to the invention, the modified perfluoropolyether oil is introduced as a protective medium and an ion conduction enhancer of the sulfide electrolyte, so that the problems of air stability, space charge layer and high-voltage operation of the sulfide electrolyte are solved, the process is simple, the cost is low, and the industrial application prospect is good. In order to achieve the above purpose, the invention adopts the following technical scheme: In a first aspect, the present invention provides a method for preparing a sulfide solid state electrolyte slurry, comprising the steps of: S1, preparing modified perfluoropolyether oil, namely preparing the modified perfluoropolyether oil by taking perfluoropolyether carboxylic acid as a raw material, and performing acyl chlorination reaction, cyano end group introduction, epoxy end group introduction and hydrogenation reduction treatment, wherein the modified perfluoropolyether oil takes the perfluoropolyether oil as a skeleton structure, adopts an asymmetric end group design, has one end being a glycidyl ether group and the other end being a cyano group; S2, dissolving lithium salt, namely mixing the modified perfluoropolyether oil and the lithium salt in a planetary stirrer protected by vacuum or inert gas, and stirring for 150-210min at a rotating speed of 150-250rpm to completely dissolve the lithium salt; S3, adding