Enhanced Air Stability and High Li-Ion Conductivity of Li_6.988P_2.994Nb_0.2S_10.934O_0.6 Glass–Ceramic Electrolyte for All-Solid-State Lithium–Sulfur Batteries

Abstract

The development of novel sulfide solid-state electrolytes with high Li-ion conductivity, excellent air-stability, and a stable electrode–electrolyte interface is needed for the commercialization of all-solid-state cells. Currently, an ideal solid electrolyte, which can integrate the solid-state batteries, has not been developed. Herein, the Nb and O codoping strategy is excogitated to improve the chemical and electrochemical performance of sulfide electrolytes. The interactive effect of Nb and O in the novel Li6.988P2.994Nb0.2S10.934O0.6 glass–ceramic electrolyte results in a superior Li+ conductivity of 2.82 mS cm–1 and remarkable air-stability and electrochemical stability against the Li metal compared to the Li7P3S11 counterpart at 25 °C. Solid-state 31P MAS-NMR revealed that doping of LiNbO3 (0 ≤ x ≤ 1) not only enhances the degree of crystallization but also produces P2OS64– units with bridging oxygen atoms in the Li6.988P2.994Nb0.2S10.934O0.6 glass–ceramic electrolyte and hence boosts the conductive deportment of glass–ceramics. Impressively, the developed electrolyte exhibits a stable full voltage window of up to 5 V versus Li/Li+. Furthermore, electrochemical impedance spectroscopy analysis shows that the interface resistance of the Li2S/Li6.988P2.994Nb0.2S10.934O0.6/Li–In cell is lower than that of the cell with Li7P3S11 electrolyte. Besides, the battery of the Li6.988P2.994Nb0.2S10.934O0.6 electrolyte delivers initial discharge capacities of 472.7 and 530.9 mAh g–1 after 50 cycles with 98.88% capacity retention from the second cycle. The Coulombic efficiency of the cell remains at ∼100% after 50 cycles. Thus, the proposed codoped strategy produced a sulfide electrolyte, which addressed the challenging issues of chemical/electrochemical stabilities and showed promising industrial prospects for next-generation all-solid-state batteries.