Three dimensional metallic porous SiC4 allotropes: Stability and battery applications

Three metallic three-dimensional (3D) microporous SiC4 crystals are identified for the first time by using an unbiased structure search based on the particle-swarm optimization (PSO) algorithm combined with density functional theory (DFT) calculations, which are found to be thermally, dynamically and mechanically stable. The unusual metallicity of these three microporous SiC4 allotropes stems from the delocalized p electrons along carbon ribbons or chains. Moreover, empowered by the appropriate channel size and metallic feature, SiC4-I manifests as a promising anode material for Na-ion batteries with theoretical capacity of 176.3 mAhg(-1), diffusion energy barrier of 0.25-0.41 eV for Na ions, appropriate average open circuit voltage of 0.55 V and negligible volume change of 0.57% during charging/discharging process.