Abstract
Long-term durability and safety are required to develop Li-ion batteries that can operate at high voltages. However, side reactions, including the release of O(2) from the electrode and CO(2) from the organic electrolyte, occur at the positive-electrode/electrolyte interface during charging at high voltages. In this study, universal neural network potential (UNNP)-driven molecular dynamics (MD) calculations are used to investigate the mechanism of the reaction between Li(x)CoO(2) (0 ≤ x ≤ 1) or Li(x)NiO(2) (0 ≤ x ≤ 1), as the positive-electrode material, and an ethylene-carbonate-based electrolyte, with a solid-liquid interface composed of ∼1700 atoms. Molecular CO(2) and O(2) evolve from the partially or fully Li-deintercalated Li(x)NiO(2), while no gas-evolution reactions are observed for Li(x)CoO(2). Hence, compared Li(x)NiO(2), the LiCoO(2) electrode is more stable toward the decomposition of ethylene carbonate in the charged state. The decomposition reactions at the solid-liquid interface during charging are also analyzed using a NN force field. This study provides a robust approach involving MD simulations using UNNP to better understand the side reactions in electrochemical devices, which can guide manufacturers in selecting appropriate materials.