Electrolyte-Driven Suppression of Oxygen Dimerization and Oxygen Evolution in High-Voltage Li-Ion Batteries

Abstract

High-voltage operation of Ni-rich layered cathodes in lithium-ion batteries (LIBs) induces oxygen redox reactions, leading to singlet oxygen evolution, interfacial degradation, and electrolyte decomposition. While cathode engineering has been extensively explored to mitigate these challenges, electrolyte-based strategies for directly regulating oxygen redox remain limited. To address this limitation, an anthracene-functionalized cyanoethyl polyvinyl alcohol (An-PVA-CN) gel polymer electrolyte (GPE) is developed, offering dual functionalities: anchoring oxidized surface oxygen and scavenging singlet oxygen. The anthracene moiety binds to oxidized lattice oxygen prior to O-O dimer formation, forming a stable Ni & horbar;O & horbar;C bridging structure that suppresses singlet oxygen release. It also acts as an effective scavenger for any singlet oxygen generated. Simultaneously, the electron-rich nitrile groups coordinate with transition metals, suppressing over-oxidation of Ni during charging. Spectroscopic and computational analyses confirm the suppression of oxygen redox and stabilization of surface oxygen species. By regulating charge compensation via transition metal redox while inhibiting oxygen redox, oxygen gas evolution and transition metal dissolution are effectively mitigated. As a result, An-PVA-CN GPE enables 81% capacity retention over 500 cycles at 4.55 V in full-cell configurations. This work demonstrates a rare electrolyte-centered approach to oxygen redox regulation and offers a promising design strategy for stabilizing high-voltage LIBs.