A High Air-Stability and Li-Metal-Compatible Li3+2xP1-xBixS4-1.5xO1.5x Sulfide Electrolyte for All-Solid-State Li-Metal Batteries

All-solid-state batteries are one of the most promising lithium-ion batteries as they are safe with high energy density and applicable to different occasions. Sulfide solid electrolytes (SSEs) are welcoming due to their good ionic conductivity and processability. However, as the SSE conductor is unstable when exposed to air, its development and application are limited. A series of new Li3+2xP1-xBixS4-1.5xO1.5x (X = 0.02, 0.04, 0.06, 0.08) solid electrolytes are synthesized by co-doping Li3PS4 with Bi and O, and the new electrolytes have better ionic conductivity and air-stability than Li3PS4. The lithium ionic conductivity of Li3.12P0.94Bi0.06S3.91O0.09 solid electrolytes reached up to 2.8 mS cm(-1) at room temperature, the highest and 9 times as high as that of Li3PS4. The doped solid electrolytes are compatible with lithium anode, and the cycling performance is improved. Importantly, the critical current density of Li3.12P0.94Bi0.06S3.91O0.09 electrolytes can reach to 1.2 mA cm(-2). In particular, the Li|Li3.12P0.94Bi0.06S3.91O0.09|Li symmetric cells are stable even after 400 h running at 1 mA cm(-2) and 25 degrees C. Bi2O3 doping SSEs are expected to be the next generation of all-solid-state lithium batteries due to their good ionic conductivity and air-stability.

Automated summary

All-solid-state batteries with sulfide solid electrolytes are promising due to their safety and high energy density, but the instability of the electrolytes when exposed to air limits their development. A series of new solid electrolytes Li3+2xP1-xBixS4-1.5xO1.5x have been synthesized, which exhibit better ionic conductivity and air-stability compared to Li3PS4. These doped solid electrolytes show improved lithium ionic conductivity and cycling performance, making them compatible with lithium anodes. The new Bi2O3-doped SSEs are expected to be the next generation of all-solid-state lithium batteries.