Breaking the voltage-dependent degradation paradigm: high cut-off voltage enables stable cycling of single-crystal lithium-rich cathodes

Single-crystal lithium-rich manganese-based oxides (SC-LRM) are promising cathodes for high-energy lithium-ion batteries owing to their structural robustness and suitability for high-voltage operation. However, their stability under elevated cut-off voltages remains insufficiently understood. In this study, SC-LRM was cycled at 4.6 V and 4.8 V using a commercial multi-component electrolyte designed for high-voltage applications. Pre-cycling characterization confirmed that both samples shared similar morphologies and slightly different crystal structures. Unexpectedly, SC-LRM exhibited improved capacity retention, reduced polarization, and enhanced structural stability at 4.8 V. Through a multi-scale analysis combined with a differential capacity-based coupling strategy, it was revealed that this behavior originated from voltage-dependent interfacial reconstruction. At 4.8 V, selective decomposition of fluorinated and boron-based electrolyte components promoted the formation of a uniform, inorganic-rich CEI. This interphase effectively suppressed oxygen release, transition metal dissolution, and harmful phase transitions during cycling. In contrast, the CEI formed at 4.6 V was less uniform and less protective. These findings challenge the conventional view that higher cut-off voltages necessarily worsen stability in lithium-rich systems and underscore the importance of electrolyte-voltage synergy in enabling favorable interfacial evolution. This work provides broadly applicable insights for the interfacial engineering and voltage protocol design of SC-LRM and other high-voltage cathode systems.