Hexagonal BC${_3}$ as a Robust Electrode Material for Li, Na, and K Ion Batteries*

We propose hexagonal BC${_3}$ as a robust electrode material for Li, Na, and K ion batteries based on first-principles density functional theory calculations. We show that, by intercalating Li, Na, and K in BC${_3}$, it is possible to form Li$_{1.5}$BC${_3}$, Na$_{1}$BC${_3}$, and K$_{1.5}$BC${_3}$ which correspond to a high theoretical capacity of 858 mA h/g, 572 mA h/g, 858 mA h/g, respectively. In addition, this material presents small open circuit voltage variations of 0.49, 0.12, and 0.16 V when used as electrode for Li, Na, and K ion batteries, respectively.