Enhanced Air and Electrochemical Stability of Li7P2.9Ge0.05S10.75O0.1 Electrolytes with High Ionic Conductivity for Thiophosphate-Based All-Solid-State Batteries

Sulfide solid electrolytes (SSEs) show tremendous potential to realize highenergy-density secondary batteries and offer distinguishing safety features over the traditional liquid-electrolyte-based system. However, their installation is hindered by the air sensitivity and substandard interfacial compatibility with Li-metal anodes. Herein, an aliovalent P5+/Ge4+ and isovalent S2-/O2- cosubstitution strategy increases the sigma Li+ to 4.77 mS cm-1, which is associated with the lowest activation energy (18.66 kJ mol-1). Impressively, with limited substitution of P/Ge and S/O in Li7P3S11, the derived electrolytes largely suppressed the structural hydrolysis in the air. Furthermore, the Li//Li cell with novel Li(7)P(2.9)Ge(0.05)S1(0)(.75)O(0.1) SSEs realized Li plating/stripping over 100 h at 0.1 mA cm-2/0.1 mAh cm-2 @ RT, with the lowest overpotential at & SIM;5 mV. Next, ex situ X-ray photoelectron spectroscopy (XPS) quantified the electrochemical decomposition of the Li7P3S11/LiNbO3@NCA interface during cell operation. XPS results confirmed better thermodynamic stability between LiNbO3@NCA and L7P3S11 after GeO2 substitution. Accordingly, the LiNbO3@NCA/Li(7)P(2.9)Ge(0.05)S1(0)(.75)O(0.1)/ Li-In cell performed remarkably; first discharge capacity, 158.9 mAh g-1; capacity retention, 89%; and Coulombic efficiency, & SIM;100% after 50 cycles @ 0.064 mA cm-2 and even at 0.3 mA cm-2 versus the first discharge capacity and retention (129.4 mAh g(-1) and 75.73%) after 70 cycles @ RT. These remarkable results could be attributable to the excellent sigma Li+, chemical/electrochemical stability toward LiNbO3@NCA, and meager interfacial resistance, essential for the practical application of sulfide-based batteries.

Automated summary

Sulfide solid electrolytes (SSEs) have great potential for high-energy-density secondary batteries with improved safety features. By using a cosubstitution strategy, the sigma Li+ can be increased and the activation energy can be reduced, leading to the suppression of structural hydrolysis. The novel SSEs show excellent performance in Li plating/stripping over long periods of time and exhibit low overpotential at the interface. The improved stability between the electrolyte and LiNbO3@NCA, achieved through GeO2 substitution, contributes to the remarkable electrochemical performance.