Stabilizing Li2O-based Cathode/Electrolyte Interfaces through Succinonitrile Addition

Abstract

Li2O-based cathodes utilizing oxide–peroxide conversion are innovative next-generation cathodes that have the potential to surpass the capacity of current commercial cathodes. However, these cathodes are exposed to severe cathode–electrolyte side reactions owing to the formation of highly reactive superoxides (O^x−, 1 ≤ x < 2) from O²⁻ ions in the Li2O structure during charging. Succinonitrile (SN) has been used as a stabilizer at the cathode/electrolyte interface to mitigate cathode–electrolyte side reactions. SN forms a protective layer through decomposition during cycling, potentially reducing unwanted side reactions at the interface. In this study, a composite of Li2O and Ni-embedded reduced graphene oxide (LNGO) was used as the Li2O-based cathode. The addition of SN effectively thinned the interfacial layer formed during cycling. The presence of a N-derived layer resulting from the decomposition of SN was observed after cycling, potentially suppressing the formation of undesirable reaction products and the growth of the interfacial layer. The cell with the SN additive exhibited an enhanced electrochemical performance, including increased usable capacity and improved cyclic performance. The results confirm that incorporating the SN additive effectively stabilizes the cathode–electrolyte interface in Li2O-based cathodes.