Exploring the Electrochemical Stability Window of an All-Solid-State Composite Cathode via a Novel <i>Operando</i> Tender XPS Setup
Rebecca Wilhelm, Robin Schuster, Tobias Kutsch, Simon Qian, Johannes Mahl, Tim Kratky, Johannes Wandt, Ethan J. Crumlin, Hubert A. Gasteiger
Abstract
High Resolution Image Download MS PowerPoint Slide All-solid-state batteries (ASSBs) have the potential to provide greater energy density than conventional batteries based on liquid electrolytes. Here, an operando ASSB cell setup for tender X-ray photoelectron spectroscopy (XPS) was developed, and the interface of a Ni-rich layered transition metal oxide cathode active material (CAM) and an Li 6 PS 5 Cl (LPSCl) solid electrolyte (SE) was evaluated during initial charge/discharge cycles. After validating the cell performance against a conventional pouch cell operated at high compression, intermittent galvanostatic cycling was performed, and XPS data were recorded as a function of state of charge (SOC). Upon the initial charge of the cell to ≈3.3 V Li, the LPSCl appears to decompose into LiCl, Li 3 PS 4, and polysulfides, whose amount gradually increases with potential. Upon further charge, at a potential higher than ≈ 3.8 V Li, initially, present sulfate and sulfite impurities decompose, and at ≈74% SOC (corresponding to a cathode potential of ≈4.10 V Li ), surface reconstruction of the CAM particles due to lattice oxygen release is detected. In addition, at potentials beyond ≈ 4.6 V Li, a decrease of the S 1s counts of the sum of the LPSCl, the thiophosphate, and polysulfide species suggests the formation of elemental sulfur that is lost via sublimation into the vacuum chamber.