Program Results

Introduction to the event

Transition metal oxides are key electrode materials in electrochemical technologies, where charge transport mechanisms critically determine device performance. Perovskite oxides, in particular, exhibit ultrafast energy storage and are widely employed in pseudocapacitors. However, the conventional view that charge storage originates from oxygen vacancy intercalation has long been debated, as oxygen ions diffuse extremely slowly at room temperature. The theoretical diffusion coefficient is nearly ten orders of magnitude lower than experimental observations, leaving a long-standing mechanistic inconsistency. Here, through electrochemical analysis, synchrotron-based X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy, we demonstrate that perovskite oxides achieve rapid charge–discharge via a proton–electron ambipolar diffusion mechanism, in which hydrogen insertion governs charge storage. This revised framework resolves the discrepancy between theory and experiment, explains the fast pseudocapacitive behavior of perovskite oxides, and provides new insights into the electrochemical properties of transition metal oxides.

Moreover, we identify hydrogen insertion as the key origin of self-discharge in layered oxide cathodes for lithium batteries. By establishing a mixed conduction model involving lithium ions, protons, and electrons, we elucidate the thermodynamic and kinetic pathways of self-discharge and outline strategies to mitigate capacity loss and extend battery lifetime. Collectively, these findings highlight the long-overlooked significance of hydrogen insertion in transition metal oxides and underscore its profound implications for enhancing the energy density, stability, and durability of both lithium batteries and electrochemical capacitors, thereby opening new directions for the rational design of advanced energy storage technologies.