Disentangling the Li‐Ion transport and Boundary Phase Transition Processes in Li10GeP2S12 Electrolyte by In‐Operando High‐Pressure and High‐Resolution NMR Spectroscopy

Abstract

AbstractLi‐ion transport and phase transition of solid electrolytes are critical and fundamental issues governing the rate and cycling performances of solid‐state batteries. In this work, in‐operando high‐pressure nuclear magnetic resonance (NMR) spectroscopy for the solid‐state battery is developed and applied, in combination with 6Li‐tracer NMR and high‐resolution NMR spectroscopy, to investigate the Li10GeP2S12 electrolyte under true‐to‐life operation conditions. The results reveal that the Li10GeP2S12 phase may become more disordered and a large amount of conductive metastable β‐Li3PS4 as the glassy matrix in the electrolyte transforms into less conductive phases, mainly γ‐Li3PS4, when high current densities (e.g., ≥0.5 mA cm−2) are applied to the electrolyte. The overall Li‐transport also varies and shows a tendency of boundary phases and Li10GeP2S12 synergistic dominant conduction at high currents. Accordingly, a mechanism of structural change induced by stress variation due to the drastic morphological change during Li‐In alloying at high currents, and the local Li+ diffusion coefficient discrepancy is proposed. These new findings of Li‐ion transport and boundary phase transition in Li10GeP2S12 solid electrolyte under high‐pressure and high current density are first reported and will help provide previously lacking insights into the relationship of structure and performance of Li10GeP2S12.