Preparation And Properities Of Dual-doped Argyrodite Sulfide Solid Electrolytes

The safety and durability of traditional lithium-ion batteries are increasingly prominent.The replacement of organic liquid electrolytes with inorganic solid electrolytes not only provides a wide electrochemical stability window,but also make the batteries safer,more durable and a higher energy density.Among the various potential candidates of inorganic solid electrolytes,Li argyrodite Li₆PS₅X（X=Cl,Br,I）has been considered as the most promising because of its high ionic conductivity,good mechanical properties and wide electrochemical window.However,it still remains some problems,such as ion conductivity still needs to be improved,the sensitivity to water and oxygen,poor stability of metal lithium,incompatible interface between electrolyte and electrode.In view of these problems,this paper studies how to improve the ionic conductivity and electrochemical stability of the Li argyrodite solid electrolyte Li₆PS₅X（X=Cl,Br,I）by using the method of dual-doped and modification.The research contents are as follows:（1）The solid phase sintering method was used to dope the Li-site and S-site of Li argyrodite Li₆PS₅Br with Zn and O element to prepare Li_6-2xZn_xPS_5-xO_xBr（0≤x≤0.15）prepared at different doping ratios.Through the study of crystal structure and Raman test,the success of ZnO doping was confirmed.Among them,Li_5.7Zn_0.15PS_4.85O_0.15Br novel solid electrolyte shows high stability in humid air and good compatibility with electrode material.NCM811/Li_5.7Zn_0.15PS_4.85O_0.15Br/Li-In battery shows higher initial coulombic efficiency and rate capability.（2）Inspired by the former work,the P-sit cation and S-sit anion were doped,that is,Si²⁺and O^2-were used to replace P⁵⁺and S^2-in Li₆PS₅Br.The chemical stability and electrochemical properties of Li_6+x+x P_1-xSi_xS_5-2xO_2xBr（0≤x≤0.2）samples were studied.Among them,Li_6.1P_0.9Si_0.1S_4.8O_0.2Br electrolyte ion conductivity is up to 2.36×10^-3 S/cm and good interface stability of the electrode material.Assembly solid-state batteries NCM811/Li_6.1P_0.9Si_0.1S_4.8O_0.2Br/Li-In showed lower interfacial impedance and excellent rate performance.（3）The solid phase sintering method was used to dope the P-site and S-site of Li argyrodite Li₆PS₅I with Sn and O element to prepare Li_6+xP_1-x-x Sn_xS5-_2xO_2xI（0≤x≤0.5）prepared at different doping ratios.The ionic conductivity of Li_6.3P_0.7Sn_0.3S_4.4O_0.6I electrolyte room temperature was 2.03×10^-4 S/cm at maximum,which is an order of magnitude higher than Li₆PS₅I.Meanwhile,it shows good interface stability with metallic lithium and excellent resistance to lithium dendrites.The assembled all-solid battery LiNbO₃@LiCoO₂/Li_6.3P_0.7Sn_0.3S_4.4O_0.6I/Li has higher initial discharge specific capacity and capacity retention.