Solid-state electrolytes in Lithium-Sulfur Batteries

Lithium ion conductors based on complex oxide materials are considered to be outstanding from their high safety and reasonable Li-ion conductivity. Compared to others solid Li ionic conductors, oxide materials have additional advantages of easier material handling during synthesis, higher chemical stability and wider electrochemical stability window. The high stiffness and electrochemically stability against metallic Li also make oxide-type Li-ion conductors as a perfect Li anode protector when using in Li-S or Li-air batteries. The use of Tantalum-substituted Li7-xLa3Zr2O12 (LLZ:Ta) as solid electrolyte for solid-state battery has been reported in several papers. The reported solid-state batteries were all constructed with a thin film cathode which was made either by physical vapor or sol-gel deposition [1-2]. In order to realize a Li-ion battery based on an oxide conductor as solid electrolyte, LLZ:Ta powder was synthesized via different synthesis routes including solid-state reaction. LLZ:Ta pellets with optimized sintering parameters exhibit a high Li-ion conductivity of 7.8 x 10-4 S cm-1 at 30 oC with a relative density of ~94%. The material was further implanted as a solid electrolyte by using screen printing to put on thick LiCoO2 (> 50 micrometers) as cathode and subsequently tested versus Li metal.Thin-film solid-state batteries allow – on the one hand – a detailed analysis of the compatibility of active storage material and the electrolyte because of well-defined interfaces. On the other hand, thin-film oxide electrolytes might also have the potential for application as thin Li-ion conductive solid-sate separators on porous substrates in Li-S- batteries.[1] M. Kotobuki et al, Ceramics International 39 (2013) 6481[2] Y. Jin et al, J. Power Sources 239 (2013) 32