Study On Preparation And Application Of The Sulfide Inorganic Solid Electrolyte

Compared with traditional electrolytes,inorganic solid electrolytes have many advantages:non-flammable,non-explosive,good mechanical properties,good stability,no reaction with metallic lithium,wide electrochemical window,and high lithium ion migration（close to 1）.Therefore,the inorganic solid electrolyte will become an inevitable trend for the application of the new generation lithium batteries.The most notable type of the inorganic solid electrolyte is the sulfide inorganic solid electrolyte.Although the sulfide solid electrolyte has excellent electrochemical performance,it still remains some problems such as the sensitivity to water and oxygen,bad stability of lithium metal,and the low conductivity of the solid electrolyte.To solve these problems,this dissertation studies how to improve the conductivity and electrochemical stability of sulfide solid-state electrolytes by means of modification of the same group elements.The research content is as follows:（1）Li₁₀GeP₂S₁₂ powder material was prepared via solid-state sintering method.The effect of sintering temperature on the electrochemical performance of Li₁₀GeP₂S₁₂powder was studied by changing the sintering temperature.The best sintering temperature is 570°C under the conditions of planetary ball mill spinning at 300 rpm for 3 h.Subsequently,Li₁₀GeP₂S₁₂ powders at 570°C were prepared by ball milling at600 rpm for 3 h using a high-energy ball mill.The prepared samples were powders with a particle size of several micrometers.The highest ionic conductivity of the sample was2.83×10^-3 S/cm at room temperature.（2）The solid-state sintering method was used to dope the S-site of the inorganic solid electrolyte Li₁₀GeP₂S₁₂ with O element to prepare Li₁₀GeP₂S_12-xO_x（x=0,0.2,0.4,0.6,0.8,1.0）prepared at different doping ratios.After doping the O element,the electrical conductivity of the doped sample decreases as the proportion of O element increases.The electrochemical window of the doped sample of Li₁₀GePS_11.4O_0.6 was studied and found to be more stable to metallic lithium.（3）The solid state sintering method was used to dope the S element in the inorganic solid electrolyte Li₁₀GeP₂S₁₂ to prepare Li₁₀GeP₂S_12-2xSe_x（x=0,0.2,0.4,0.6,0.8,1.0）.The electrical conductivity of the electrolyte material doped with 1 mol%GeSe2 at room temperature was 3.41×10^-3 S/cm at maximum.Since the ion radius of Se is larger than the ion radius of S,the transmission path of Li⁺is widened,which is favorable for the transmission of Li⁺.The electrochemical stability between Li₁₀GeP₂S_11.8Se_0.2 and metallic lithium can also be stabilized from 0 to 6 V.