Suppressing structural degradation of single crystal nickel-rich cathodes in PEO-based all-solid-state batteries: Mechanistic insight and performance

All-solid-state batteries (ASSBs) with poly(ethylene oxide) (PEO)-based electrolytes are believed to be pragmatic and economical. However, the oxidation of PEO-based electrolytes on high-voltage cathode hinders its application in high-energy-density ASSBs. Single crystal LiNi x Co y Mn z O 2 ( x + y + z = 1) (SC NCM) cathode is one of the most promising cathode due to its ability to relieve the formation of cracks to remain structural integrity. However, the poor compatibility between SC NCM cathode and PEO remains a challenge. Besides, the mechanism of single crystal Ni-rich cathode structure degradation induced by PEO is still unclear. In this work, the interaction mechanism between PEO-based electrolyte and SC NCM is firstly revealed: 1) the strong oxidizability of SC NCM at high voltage accelerates the oxidization of PEO, leading to the self-oxygen loss and the consequent formation of rock-salt phase of SC NCM; 2) free H + formed in the oxidation/dehydration reaction of PEO reacts with TFSI − to form HTFSI, resulting in the dissolution of transition metal ions on the surface of SC NCM83 particles. Based on this, a Li + conductor Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP) surface coating layer on single crystal LiNi 0.83 Co 0.12 Mn 0.05 O 2 (SC NCM83) is introduced to stabilize the cathode/electrolyte interface and ensure lithium-ion transport simultaneously. The LATP coated SC NCM83 (LATP@SC NCM83) shows excellent cycling performance with retention of 90.5% after 100 cycles, while SC NCM83 shows inferior cycling performance with retention of 63.4% after 100 cycles. In brief, this work reveals the interaction mechanism at the cathode/electrolyte interface and provides an effective interfacial stabilization strategy by LATP coating to enable high-voltage operation with PEO-based electrolytes.