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CN-122025756-A - Sulfide solid electrolyte, positive plate, lithium-sulfur battery and preparation method of lithium-sulfur battery

CN122025756ACN 122025756 ACN122025756 ACN 122025756ACN-122025756-A

Abstract

The embodiment of the application discloses a sulfide solid electrolyte, a positive plate, a lithium-sulfur battery and a preparation method thereof, wherein the general formula of the sulfide solid electrolyte is Li (7‑x+y) P (3‑x) M x S (11‑y) X y , M is a doping element and is selected from at least one of Sn, ge, si, al, zr and Ta, X is a doping element and is selected from at least one of O, F, cl, br and I, X is more than 0 and less than or equal to 0.5, and y is more than or equal to 0 and less than or equal to 1.0. By doping the doping element M into the material, the M part replaces P 5+ , extra lithium ions are introduced, the concentration of the lithium ions is increased, meanwhile, the covalent nature of the P-S bond is reduced, the stability of the [ PS 4 ] 3‑ tetrahedral unit is enhanced, the [ PS 4 ] 3‑ tetrahedral unit is more difficult to reduce by lithium metal, and the generation of gases such as H 2 S、P 2 S 6 is further reduced.

Inventors

  • NI WENXIAO
  • LI YANG
  • TAN MINGSHENG
  • WEI HAITAO
  • YUAN DINGDING

Assignees

  • 湖北亿纬动力有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (10)

  1. 1. A sulfide solid electrolyte is characterized by having a general formula of Li (7-x+y) P (3-x) M x S (11-y) X y , wherein M is a doping element and is selected from at least one of Sn, ge, si, al, zr and Ta, X is a doping element and is selected from at least one of O, F, cl, br and I, X is more than 0 and less than or equal to 0.5, and y is more than or equal to 0 and less than or equal to 1.0.
  2. 2. The sulfide solid state electrolyte of claim 1, wherein M is Sn or Ge and X is Cl or O.
  3. 3. The sulfide solid state electrolyte according to claim 1 or 2, characterized in that the sulfide solid state electrolyte includes Li 7 P 2.9 Sn 0.1 S 10.9 Cl 0.1 .
  4. 4. A positive electrode sheet comprising an active material layer comprising elemental sulfur, a conductive agent, a binder, and the sulfide solid state electrolyte as claimed in any one of claims 1 to 3.
  5. 5. The positive electrode sheet according to claim 4, wherein the mass ratio of the elemental sulfur, the conductive agent, the binder, and the sulfide solid electrolyte in the active material layer is (50 to 70): (15 to 25): (5 to 10): (10 to 20).
  6. 6. The positive electrode sheet according to claim 4 or 5, further comprising a current collector, wherein the active material layer is disposed on the current collector.
  7. 7. A lithium-sulfur battery, comprising a positive electrode sheet, a solid electrolyte membrane and a negative electrode sheet which are sequentially laminated, wherein the positive electrode sheet is the positive electrode sheet according to any one of claims 4 to 6, the solid electrolyte membrane comprises the sulfide solid electrolyte according to any one of claims 1 to 3, and the negative electrode sheet is a lithium metal negative electrode.
  8. 8. A method for preparing a lithium sulfur battery, comprising: mixing elemental sulfur, a conductive agent, a binder and the sulfide solid state electrolyte according to any one of claims 1 to 3 to prepare a positive electrode sheet; preparing the sulfide solid electrolyte as claimed in any one of claims 1 to 3 into a solid electrolyte membrane; providing a negative plate, wherein the negative plate is a lithium metal negative electrode; And sequentially stacking the positive plate, the solid electrolyte membrane and the negative plate, and applying external pressure to package the lithium-sulfur battery.
  9. 9. The method for preparing a lithium sulfur battery according to claim 8, wherein the external pressure is 10mpa to 50mpa.
  10. 10. The method for producing a lithium-sulfur battery according to claim 8, wherein the sulfide solid electrolyte is dry-pressed at 200 to 300MPa to obtain the solid electrolyte membrane, or And mixing the sulfide solid electrolyte with a solvent to obtain slurry, and carrying out tape casting molding and drying treatment on the slurry to obtain the solid electrolyte membrane.

Description

Sulfide solid electrolyte, positive plate, lithium-sulfur battery and preparation method of lithium-sulfur battery Technical Field The application relates to the technical field of batteries, in particular to a sulfide solid electrolyte, a positive plate, a lithium-sulfur battery and a preparation method thereof. Background Lithium-sulfur batteries (Li-S) are considered to be one of the most potential high-energy-density energy storage systems of the next generation because of high theoretical specific capacity (1675 mAh g -1) and high theoretical energy density (2600 Wh kg -1), and the positive active material has rich sulfur reserves, low cost and environmental friendliness. However, conventional liquid lithium sulfur batteries have a number of troublesome problems that severely hamper the commercialization process, mainly including (1) the "shuttle effect" of polysulfide (LiPSs) leading to irreversible loss of active material, rapid capacity decay and low coulombic efficiency, (2) large volume changes (about 80%) during charge and discharge, (3) dendrite growth of lithium metal negative electrodes, which may puncture the separator to cause short circuits, and (4) flammability of organic liquid electrolytes, which brings serious thermal runaway safety risks. The use of nonflammable solid electrolytes, particularly sulfide solid electrolytes (such as Li 10GeP2S12, Li6PS5Cl, Li7P3S11, etc.) having high ion conductivity (up to the order of 10 -2S cm-1), which are physically blocking shuttling of polysulfides and are expected to suppress lithium dendrites while improving the intrinsic safety of the battery, is considered one of the effective solutions to the above problems. However, sulfide solid state electrolytes present serious challenges themselves, mainly poor chemical/electrochemical stability. Thermodynamic instability between sulfide solid state electrolytes and high activity lithium metal cathodes and sulfur anodes (when charged to high potential) results in serious interfacial side reactions. These side reactions, particularly at the lithium negative electrode interface, continue to consume active lithium and electrolyte, producing various gases such as H 2S、P2S6、SO2. The gas production can cause interface contact deterioration and rapid increase of internal resistance, and more serious, the battery bulge can be caused, and huge internal stress is generated under the condition of packaging constraint, so that mechanical failure and short circuit are caused, and the risk of thermal runaway of the battery is greatly increased. Disclosure of Invention The application provides a sulfide solid electrolyte, a positive plate, a lithium-sulfur battery and a preparation method thereof, and aims to solve the technical problem of poor chemical/electrochemical stability of the sulfide solid electrolyte. The application provides a sulfide solid electrolyte which has a general formula of Li (7-x+y)P(3-x)MxS(11-y)Xy, wherein M is a doping element and is selected from at least one of Sn, ge, si, al, zr and Ta, X is a doping element and is selected from at least one of O, F, cl, br and I, X is more than 0 and less than or equal to 0.5, and y is more than or equal to 0 and less than or equal to 1.0. By doping the doping element M into the material, M (e.g., sn 4+) partially replaces P 5+, introducing additional lithium ions, increasing the concentration of lithium ions, simultaneously reducing the covalent nature of P-S bonds, enhancing the stability of the [ PS 4]3- tetrahedral unit, making it more difficult to be reduced by lithium metal, and further reducing the generation of gases such as H 2S、P2S6. Alternatively, in some embodiments of the application, M is Sn or Ge and X is Cl or O. Through the synergistic doping of elements such as Sn or Ge and halogen, the structural stability and the thermal stability of the sulfide solid electrolyte are obviously improved while the high ionic conductivity is maintained, the gas production is inhibited from the source, and the thermal safety threshold of the lithium-sulfur battery is greatly improved. Alternatively, in some embodiments of the application, the sulfide solid state electrolyte includes Li 7P2.9Sn0.1S10.9Cl0.1. Correspondingly, the application also provides a positive plate which comprises an active material layer, wherein the active material layer comprises elemental sulfur, a conductive agent, a binder and the sulfide solid electrolyte. The simple substance sulfur is an active substance of a positive electrode, the binder is used for binding the simple substance sulfur, the conductive agent and the sulfide solid electrolyte together to form an active material layer, the conductive agent is used for constructing a conductive network in the active material layer, and the sulfide solid electrolyte is used for constructing an ion-conducting network in the active material layer. Optionally, in some embodiments of the present application, the mass ratio of the eleme