(592i) Operando Energy-Dispersive X-Ray Diffraction of Sulfur-Based All Solid-State Lithium Batteries

Lithium-ion batteries have dominated the market for portable electronics and electric vehicles due to their high energy density and high cycle life. However, safety concerns have arisen due to their use of highly flammable organic liquid electrolytes. All solid-state lithium-ion batteries (ASSBs) offer a safer option due to their nonflammable solid-state electrolytes (SSEs) and could potentially offer higher power and energy density than traditional lithium-ion batteries.¹

Sulfide-based argyrodite electrolytes, Li₆PS₅X (where X = Cl, Br, I), are interesting due to their high ionic conductivity at room temperature. This work discusses the characterization of cells using the electrolyte Li₆PS₅Cl as the SSE, NMC111 as the cathode material, and a layered indium lithium (In-Li) foil anode material.

This SSE faces two main challenges for commercialization: the narrow voltage window where the electrolyte is electrochemically stable, and its reactivity with NMC and Li metal active materials. In this ASSB system, it is proposed that the SSE decomposes where it contacts the cathode particles, causing ionically insulating interfaces to form and hindering the transport of lithium ions. This decomposition of active materials causes a large capacity loss in the first cycle, and the reactivity of NMC and the SSE has prevented this battery from achieving high energy density.^1–3 Herein we report operando evolution of the cathode material during initial cycling. Given the air and moisture sensitivity of the SSE, deconstruction of the cell to perform ex situ characterization would be problematic. Operando energy-dispersive x-ray diffraction (EDXRD) allows data to be collected from buried locations in the bulk of intact and sealed ASSBs during cycling. The time-dependent lithiation gradient in the cathode reveals information about the current distribution and its time evolution.