Lewis Acid Probe for Basicity of Sulfide Electrolytes Investigated by B-11 Solid-State NMR

Sulfide-based solid-state lithium-ion batteries (SSLIB)have attracteda lot of interest globally in the past few years for their high safetyand high energy density over the traditional lithium-ion batteries.However, sulfide electrolytes (SEs) are moisture-sensitive which posesignificant challenges in the material preparation and cell manufacturing.To the best of our knowledge, there is no tool available to probethe types and the strength of the basic sites in sulfide electrolytes,which is crucial for understanding the moisture stability of sulfideelectrolytes. Herein, we propose a new spectral probe with the Lewisbase indicator BBr3 to probe the strength of Lewis basicsites on various sulfide electrolytes by B-11 solid-stateNMR spectroscopy (B-11-NMR). The active sulfur sites andthe corresponding strength of the sulfide electrolytes are successfullyevaluated by the proposed Lewis base probe. The probed strength ofthe active sulfur sites of a sulfide electrolyte is consistent withthe results of DFT (density functional theory) calculation and correlatedwith the H2S generation rate when the electrolyte was exposedin moisture atmosphere. This work paves a new way to investigate thebasicity and moisture stability of the sulfide electrolytes.