<p>The physicochemical properties of cathode‒electrolyte interfaces (CEIs) play a key role in determining long-term cycling and reliable electrochemical behaviors, which are critically important in high-voltage batteries. Increasing the operating voltage improves the energy density of a battery but accelerates cathode degradation and destabilizes the CEI. Currently, the interface dynamics and working mechanism of CEIs are still under evaluation and debated. In this review, we first summarize the key CEI-related challenges and the principal structural and chemical degradation mechanisms of high-voltage cathode materials, underscoring their intrinsic inconsistencies, stochasticity, and failure modes. We then explore the intrinsic correlation between CEI degradation and electrochemical deterioration and propose targeted strategies for regulating CEIs. Furthermore, we highlight the recent advances in characterization techniques for tracking dynamic structural and compositional changes. Through this comprehensive review, we aim to deepen the understanding of CEI behavior and offer valuable insights for guiding the design and development of more reliable and sustainable next-generation high-energy batteries.</p> Graphical Abstract <p></p>