Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 36, Pages 42670-42681Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c09605
Keywords
XPS; XPEEM; operando; post-mortem; LPS; LCO; interface; all-solid-state battery
Funding
- PSI CROSS initiative
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This study presents real-time measurements of the (electro-)chemical reactivity and local surface potential at the electrified interface in all-solid-state lithium batteries, identifying three main degradation mechanisms.
All-solid-state lithium batteries are a promising alternative for next-generation safe energy storage devices, provided that parasitic side reactions and the resulting hindrances in ionic transport at the electrolyte-electrode interface can be overcome. Motivated by the need for a fundamental understanding of such an interface, we present here real-time measurements of the (electro-)chemical reactivity and local surface potential at the electrified interface (Li2S)(3)-P2S5 (LPS) and LiCoO2 (LCO) using operando X-ray photoelectron spectroscopy (XPS) supplemented by X-ray photoemission electron microscopy (XPEEM). We identify three main degradation mechanisms: (i) reactivity at open circuit potential leading to the formation of reduced Co in the +2 oxidation state at the LCO surface, detected in the Co L-edge, which is further increased upon cycling, (ii) onset of electrochemical oxidation of the LPS at 2.3 V vs InLix detected in the S 2p and P 2p core levels, and (iii) Co-ion diffusion into the LPS forming CoSx species at 3.3 V observed in both S 2p and Co 2p core levels. Concurrently, a local surface overpotential of 0.9 V caused by a negative localized charge layer is detected at the LPS-LCO interface. Furthermore, in agreement with previous theoretical results, the presence of a sharp potential drop at the interface between active materials and solid electrolyte is demonstrated in all-solid-state batteries.
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