Atomic‐Scale Direct Identification of Surface Variations in Cathode Oxides for Aqueous and Nonaqueous Lithium‐Ion Batteries

The electrochemical (de)intercalation reactions of lithium ions are initiated at the electrode surface in contact with an electrolyte solution. Therefore, substantial structural degradation, which shortens the cycle life of cells, is frequently observed at the surface of cathode particles, including lithium-metal intermixing, phase transitions, and dissolution of lithium and transition metals into the electrolyte. Furthermore, in contrast to the strict restriction of moisture in lithium-ion cells with nonaqueous organic electrolytes, electrode materials in aqueous-electrolyte cells are under much more reactive environments with water and oxygen, thereby leading to serious surface chemical reactions on the cathode particles. The present article presents key results regarding structural and composition variations at the surface of oxide-based cathodes in both high-performance nonaqueous an…