High air-stability and superior lithium ion conduction of Li3+3xP1-xZnxS4-xOx by aliovalent substitution of ZnO for all-solid-state lithium batteries

Abstract

A series of new solid electrolytes of Li3+3xP1-xZnxS4-xOx (x = 0.01, 0.02, 0.03, 0.04, 0.05, 0.06) are synthesized successfully via Zn, O co-doping the Li3PS4 glass-ceramic for the first time. The result shows that Li3PS4 aliovalent substitution of 2 mol% ZnO (Li3.06P0.98Zn0.02S3.98O0.02) presents the highest conductivity of 1.12×10−3 S cm−1 at room temperature, which is twice that of the pristine Li3PS4. Besides, Li3.06P0.98Zn0.02S3.98O0.02 exhibits excellent stability against humid air, lithium metal and chlorobenzene solvent. The mechanisms of the enhancement of conductivity and air-stability are well understood by conducting first-principles density functional theory (DFT) calculation and Bond-Valence (BV) analysis, and the results well demonstrate that the conductivity and air-stability of Li3PS4 could be improved via Zn, O dual-doping, in which partial P5+ could be substituted by Zn2+, and a part of S2- could be replaced by O2-. Finally, the all-solid-state lithium battery (ASSLB) with bi-layer electrolytes of LiCoO2/Li10GeP2S12/Li3.06P0.98Zn0.02S3.98O0.02/Li is assembled, and it delivers an initial discharge capacity of 139.1 mAh g−1 at 0.1 C and a capacity retention of 81.0% after 100 cycles at room temperature. This work combines systematical experimental characterizations and sufficient theoretical calculations to develop a new promising sulfide electrolyte with superior lithium ion conductivity and high air-stability for ASSLBs application.