Microscopic Study of Solid–Solid Interfacial Reactions in All-Solid-State Batteries

Abstract

The sulfide-based solid-state electrolyte has garnered attention as a potential material for next-generation all-solidstate batteries. However, during cycling, interfacial reactions between the sulfide solid-state electrolytes and the cathode can occur, which is a serious issue that needs to be addressed. Therefore, resolving interfacial reactions has become a crucial issue in the development of solid-state batteries. A sulfide-based allsolid-state battery paired with LiFePO 4 has shown poor first-cycle discharge capacity and efficiency, which have been attributed to LiFePO 4 /Li 6 PS 5 Cl interfacial reactions. Thus, in this study, the microscopic LiFePO 4 /Li 6 PS 5 Cl interface reactions were visualized using nano-beam X-ray fluorescence (nano-XRF) mapping and nano-beam X-ray absorption spectroscopy (nano-XAS). The mapping evolution of the Fe valence state of LFP in a different state of charge was observed. The nano-XRF and nano-XAS tools at the nanoscale allowed for the decoupling of the interfacial reactions on the cathode/sulfide, which can shed light on new directions for an in-depth understanding of the interfacial phenomena of solid-state batteries. This study paves the way for the development of all-solid-state batteries with improved performance and stability.

Detection of a Cobalt-Containing Interphase at the Li6PS5Cl-NMC111 Interface by In Situ μXANES and EIS

“…A similar study was recently reported using Fe K-edge nXANES at the surface of LiFePO 4 in contact with a sulfide. 18 We also performed in situ piecewise EIS on (Li/In|Li 6 PS 5 Cl|NMC111/Li 6 PS 5 Cl) cells with 10 mg composite cathodes to study the evolution of impedances during cycling. This piecewise EIS allowed an estimation of the active surface area in a cell with uncoated NMC, which was 7.5× lower than the theoretical value.…”