Improvement of current Li-ion batteries and development of next-generation batteries have been a most important issue for future renewable energy society. Besides, the microscopic phenomena inside the batteries are full of interesting electronics, ionics and redox chemistry from a fundamental viewpoint. However, the in-situ or operando measurement is still difficult to capture what’s going on the atomic scale under the operation.

To elucidate such microscopic processes in batteries, we have investigated several selected issues on battery electrolytes, electrodes and interfaces, with first-principles density-functional theory calculations. We have theoretically proposed novel mechanisms of reductive decomposition of electrolyte molecules and formation mechanism of interfacial film (so called SEI film) on the anode, peculiar chemistry of superconcentrated electrolyte and Na-excess cathode materials, and possible origin of interfacial resistance to the ion transport in all-solid-state Li-ion batteries, all of which are long-standing issues or current hot topics in the battery field. In this talk, I’ll introduce these computational explorations in our group.