Face to Face at the Cathode Electrolyte Interphase : From Interface Features to Interphase Formation and Dynamics

Development of high-performing lithium-based batteries inevitably calls for a profound understanding and elucidation of the reactivity at the electrode-liquid electrolyte interface and its impact on the overall performance and safety. The formation, composition, properties, and mechanisms of the cathode electrolyte interphase (CEI) formation and function are still to a large extent unknown for most lithium-based battery materials, whereas the same is well considered for the solid electrolyte interphase on negative electrodes in the literature. In particular, in high voltage regions >4.3 V, the oxidative stability limit of most liquid electrolytes is reached and new mechanisms, involving surface reactivity of the active material beside electrolyte decomposition, contribute to the interfacial reactivity and nature of the CEI. Focusing on lithium-based cell chemistries, this review aims to highlight the impact of the still less understood electrolyte decomposition chemistry, dictated by the nature of its components, as well as the in-depth research on the physicochemical and electrochemical properties of CEI formation and evolution at positive electrode material surface and sub-surfaces