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CN-120497427-B - Selenium-doped sulfide solid electrolyte and preparation method thereof

CN120497427BCN 120497427 BCN120497427 BCN 120497427BCN-120497427-B

Abstract

The invention discloses a Se-doped sulfide solid electrolyte and a preparation method thereof, and relates to the technical field of battery materials; mixing a lithium source, a non-metal source and a second nonpolar organic solvent, heating the obtained second mixed solution to a first preset temperature, adding the first mixed solution, stirring for a first preset time, continuously heating to a second preset temperature, stirring for a second preset time, drying the obtained coprecipitate, and annealing at 300-400 ℃ to obtain the Se-doped sulfide solid electrolyte, wherein the boiling point of the first organic solvent is less than or equal to the first preset temperature and less than or equal to the second preset temperature. The invention adopts the double-solvent gradient evaporation technology and combines low-temperature annealing to realize the uniform doping of Se elements, and the prepared Se doped sulfide solid electrolyte has higher ionic conductivity and air stability compared with undoped electrolyte.

Inventors

  • CHEN JIE
  • ZHAO SILIANG
  • CHEN ZIHONG
  • ZOU YU

Assignees

  • 深圳固研新材料科技有限公司

Dates

Publication Date
20260508
Application Date
20250526

Claims (10)

  1. 1. The preparation method of the selenium-doped sulfide solid electrolyte is characterized by comprising the following steps of: Mixing a selenium source, a complexing agent and a first organic solvent to obtain a first mixed solution; mixing a lithium source, a non-metal source and a second nonpolar organic solvent to obtain a second mixed solution, wherein the non-metal source comprises a sulfur source; Heating the second mixed solution to a first preset temperature, adding the first mixed solution, stirring for a first preset time at the first preset temperature, then continuously heating to a second preset temperature, and stirring for a second preset time at the second preset temperature to obtain a coprecipitate; Drying the coprecipitate, and then annealing at the temperature of 300-400 ℃ to obtain the selenium doped sulfide solid electrolyte; wherein the boiling point of the first organic solvent is less than or equal to a first preset temperature and less than or equal to a second preset temperature of the second nonpolar organic solvent; the complexing agent comprises at least one of citric acid and polyethylene glycol; The selenium-doped sulfide solid electrolyte has a core-shell structure, the core material is sulfide solid electrolyte doped with Se in a crystal lattice, and the shell layer is a passivation layer containing Se elements; the first organic solvent comprises at least one of acetone and tetrahydrofuran; the second nonpolar organic solvent includes at least one of n-hexane and cyclohexane.
  2. 2. The method of preparing according to claim 1, wherein the selenium source comprises at least one of lithium selenate and lithium selenide; the mole number of selenium in the selenium source is 5% -20% of that of sulfide solid electrolyte.
  3. 3. The method according to claim 1, wherein the concentration of the complexing agent in the first mixed solution is 0.1 to 0.5 mol/L, and the concentration of the selenium source is 1 to 5 mol/L.
  4. 4. The method of claim 1, wherein the lithium source comprises Li 2 S, and/or, The nonmetallic source further includes at least one of a phosphorus source and a chlorine source.
  5. 5. The method according to claim 1, wherein, In the second mixed solution, the total concentration of the lithium source and the non-metal source is 0.5-2 mol/L.
  6. 6. The preparation method of claim 1, wherein the first mixed liquid is added dropwise, and the dropping speed is 1-5 mL/min.
  7. 7. The method according to claim 1, wherein the stirring is carried out at a first preset temperature at a speed of 200 to 500 rpm for 5 to 15 minutes, and/or, Stirring at the second preset temperature at a rotating speed of 200-500 rpm for 5-15 min.
  8. 8. The method according to claim 1, wherein the drying is carried out in an inert atmosphere or in vacuum at a temperature of 100 to 150 ℃ for a time of 2 to 5 hours, and/or, And the annealing time is 1-2 h.
  9. 9. A selenium-doped sulfide solid state electrolyte, characterized in that the selenium-doped sulfide solid state electrolyte is prepared by the preparation method of any one of claims 1 to 8.
  10. 10. The selenium-doped sulfide solid state electrolyte of claim 9, wherein the selenium-doped sulfide solid state electrolyte comprises Se-doped Li 6 PS 5 Cl or Se-doped Li 5.5 PS 4.5 Cl 1.5 .

Description

Selenium-doped sulfide solid electrolyte and preparation method thereof Technical Field The invention relates to the technical field of battery materials, in particular to a selenium-doped sulfide solid electrolyte and a preparation method thereof. Background All-solid-state batteries are regarded as the core direction of the next-generation energy storage technology, the research hot-blast comes from the three major bottleneck breakthrough requirements of the traditional liquid lithium ion batteries, namely 1, the safety problem that liquid electrolyte is easy to leak and inflammable, and the thermal runaway risk is caused, and the thermal runaway risk of the all-solid-state batteries is reduced by more than 90% by using solid-state electrolyte to replace the liquid electrolyte. 2. The energy density is limited by the liquid battery being limited by a graphite negative electrode (the theoretical capacity is 372 mAh/g), while the all-solid battery can be matched with a lithium metal negative electrode (the theoretical capacity is 3860 mAh/g), and the energy density is expected to break through 500Wh/kg (the traditional battery is only 200-300 Wh/kg). 3. The fast charge requirement is that the ion transmission path of the solid electrolyte is shorter, and the full solid battery can realize 10 minutes fast charge, while the liquid battery needs more than 30 minutes. In the technical route of four solid-state electrolytes of oxide, sulfide, polymer and halide, sulfide solid-state electrolytes are the preferred scheme of all solid-state batteries because of the unique performance, and sulfide electrolytes have the following performance that 1 and ultra-high ion conductivity, namely, the ion conductivity of sulfide solid-state electrolytes (such as Li 9.54Si1.74P1.44S11.7Cl0.3) can reach 25mS/cm, and far super oxide (1-10 mS/cm) and polymer (10 -3～10-2 mS/cm) solid-state electrolytes are close to the level of liquid electrolyte (10 -2～10-1 mS/cm). 2. Mechanical flexibility, namely the sulfide solid electrolyte can be cold-pressed to form a film, does not need additional adhesive, is tightly contacted with the positive and negative electrode interfaces, and reduces interface impedance. 3. The sulfide solid state electrolyte density (about 2.5g/cm 3) is significantly lower than the oxide solid state electrolyte (> 5g/cm 3), and has excellent compatibility with lithium metal, silicon negative electrode and high-nickel positive electrode, and is suitable for high-energy density electrode materials. 4. Cost optimization potential lithium phosphorus oxysulfide (Li 7P3S7.5O3.5) developed by the Ma Cheng team of China university of Kokoku reduces the cost to $14.42/kg through cheap raw materials (lithium hydroxide hydrate and phosphorus sulfide), and is reduced by 92% compared with the traditional sulfide. Despite the remarkable advantages of sulfide solid state electrolytes, industrialization is still faced with the key challenges of 1 and poor air stability that sulfide solid state electrolytes are easy to hydrolyze to generate H 2 S and Li 3PO4 when exposed to humid air, resulting in a decrease in ionic conductivity, such as 50% in conductivity after LPSC (lithium phosphorus sulfur chloride) is exposed to air for 24 hours. 2. The interface resistance is high, and unstable Solid Electrolyte Interface (SEI) is easy to form when sulfide solid electrolyte contacts with a lithium metal anode, dendrite growth and capacity decay are initiated (for example, the charging time is prolonged to 45 minutes after 50 times of circulation). 3. The synthesis process is complex, the traditional doping (such as O, F) needs high-temperature annealing, the energy consumption is high, and the lattice structure is easy to damage. 4. The cost and the scale contradiction are that raw materials such as lithium sulfide (Li 2 S) and the like are expensive (more than or equal to 650 dollars/kg), and the traditional synthetic path is difficult to meet the demand of kiloton-level productivity. In recent years, researchers have improved the performance of sulfide solid state electrolytes by constructing nano-coatings or by elemental doping. For example, sulfide solid electrolyte performance is improved by constructing a nano-coating layer (e.g., lif@li 2 O shell layer), but the preparation process of the nano-shell layer is complicated (e.g., high temperature annealing or chemical vapor deposition), and uniform coating is difficult to achieve, increasing cost. Specifically, the preparation of the nano Li 2 O/LiF shell layer depends on a high-temperature annealing or solution blending method, and the coating layer is easy to be uneven or the internal structure is easy to be damaged. The slow cooling heat treatment process can form LiF@Li 2 O nanoshells, but has high energy consumption and is difficult to scale. In addition, the addition of LiF suppresses lithium dendrites, but its wide bandgap (14.2 eV) and high electronic insulation may exacerbate