First principles derived potential barriers to Li-ion transport through Solid Electrolyte Interphases in batteries

Charging a Li-ion battery is dependent on the ability of Li ions to transport between the cathode and the anode. Li-ion transport is dependent upon (among other factors) the electrostatic environment the ion encounters on the Solid-Electrolyte-Interphase (SEI) which separates an anode from the surrounding electrolyte. Previous first principles work has had difficulty accurately reflecting the electrostatic potential barrier for ions moving through the SEI due to the large length scale necessary to simulate. In this work, we develop and apply the Quantum Continuum Approximation (QCA), a methodology for coupling explicit Density Functional Theory (DFT) calculations of interfaces with Poisson-Boltzmann distributions of charge in bulk insulating systems to provide an equilibrium electronic potentiostat for first-principles interface calculations. Using QCA, we calculate the electrostatic potential barrier for Li-ion transport through various SEIs on Li metal anodes. We demonstrate that the SEI potential barriers are dependent on the electronic voltage in each system, although the degree of dependency varies based on the specific SEI interface. This work suggests modifying the voltage and anode-SEI interface structure as a strategy for improved charging rates in Li-ion battery systems.