Sulfide electrolytes for all-solid-state lithium-sulfur batteries 

Xiayin Yao

Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences

Abstract: Traditional lithium-sulfur batteries with organic liquid electrolyte are always facing two major challenges, i.e. safety problems and the polysulfide shuttle reaction, which seriously hampered their practical applications. Using inorganic solid electrolytes instead of combustible liquid electrolytes is considered as the ultimate solution to address the above issues. Compared with oxide electrolytes, sulfide electrolytes are considered to be promising ion conductors due to their high ioinc conductivities and favorable interface compatibility with sulfide or sufur-based electrodes.

A series of sulfide solid electrolytes with room temperature ionic conductivity of 10-3 ~ 10-2 S/cm are successfully synthesized. Meanwhile, a new battery construction containning a solid electrolyte bilayer, i.e. Li10GeP2S12 and 70%Li2S-29%P2S5-1%P2O5, have been designed, well addressing the compatibility between electrolyte and metallic lithium. Besides, the intimate contact interface can be realized by coating sulfide electrolytes evenly on the surface of active materials, which enables the battery to withstand the large stresses/strains during repeated charging/discharging, leading to significant improvements in energy density and cycle life.

Furthermore, a reduced graphene oxide coated with ~2 nm sulfur composites were employed in all-solid-sate lithium-sulfur battery, which significantly reduced the interface resistance and stress/strain of sulfur cathodes. At 60 °C, the all-solid-state lithium-sulfur cell can maintain a high reversible capacity of 830 mA h g-1 at 1.0 C for 750 cycles. Minimization of the stress/strain of solid cells is crucial for long cycle life of all-solid-state lithium-sulfur batteries.

Biography: Dr. Xiayin Yao is a professor at Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences. He received Ph.D in materials physics and chemistry from Institute of Solid State Physics and Ningbo Institute of Materials Technology & Engineering (NIMTE), Chinese Academy of Sciences, P. R. China in 2009. After that, he joined NIMTE and worked there until now. During 2012-2014, he was a research fellow in Hanyang University, S. Korea and Nanyang Technological University, Singapore. Up to now, he has published over 60 peer-reviewed papers in the journals such as Nano Letters, Advanced Energy Materials, Energy Storage Materias and so on. His major interests include developing solid state electrolytes with high ionic conductivities and solid state lithium-sulfur batteries as well as solid state sodium batteries.