Capacity Fade in Solid-State Batteries: Interphase Formation and Chemomechanical Processes in Nickel-Rich Layered Oxide Cathodes and Lithium Thiophosphate Solid Electrolytes

TLDR

All‑solid‑state lithium‑ion batteries promise long‑term, high‑performance energy storage, but their success depends on compatible electrode materials, with nickel‑rich layered oxides currently the benchmark cathodes for conventional batteries and the next step for solid‑state systems. This study implements high‑nickel LiNi₀.₈Co₀.₁Mn₀.₁O₂ in a bulk‑type solid‑state battery with β‑Li₃PS₄ and investigates how the cathode–electrolyte interface governs performance. In situ electrochemical impedance spectroscopy and X‑ray photoemission spectroscopy were employed to monitor interphase formation during cycling. Charging the NCM‑811/β‑Li₃PS₄ cell forms a passivating interphase that decomposes the sulfide electrolyte, causing irreversible first‑cycle capacity loss, overvoltage, and contact loss due to chemomechanical contraction, underscoring the critical impact of electro‑chemo‑mechanical effects on solid‑state battery performance.

Abstract

All-solid-state lithium ion batteries may become long-term, stable, high-performance energy storage systems for the next generation of electric vehicles and consumer electronics, depending on the compatibility of electrode materials and suitable solid electrolytes. Nickel-rich layered oxides are nowadays the benchmark cathode materials for conventional lithium ion batteries because of their high storage capacity and the resulting high energy density, and their use in solid-state systems is the next necessary step. In this study, we present the successful implementation of a Li[Ni,Co,Mn]O2 material with high nickel content (LiNi0.8Co0.1Mn0.1O2, NCM-811) in a bulk-type solid-state battery with β-Li3PS4 as a sulfide-based solid electrolyte. We investigate the interface behavior at the cathode and demonstrate the important role of the interface between the active materials and the solid electrolyte for the battery performance. A passivating cathode/electrolyte interphase layer forms upon charging and leads to an irreversible first cycle capacity loss, corresponding to a decomposition of the sulfide electrolyte. In situ electrochemical impedance spectroscopy and X-ray photoemission spectroscopy are used to monitor this formation. We demonstrate that most of the interphase formation takes place in the first cycle, when charging to potentials above 3.8 V vs Li+/Li. The resulting overvoltage of the passivating layer is a detrimental factor for capacity retention. In addition to the interfacial decomposition, the chemomechanical contraction of the active material upon delithiation causes contact loss between the solid electrolyte and active material particles, further increasing the interfacial resistance and capacity loss. These results highlight the critical role of (electro-)chemo-mechanical effects in solid-state batteries.