Sodium effects on the electronic and structural properties of porous silicon for energy storage

Abstract

Porous silicon is a promising anode material in Na-ion batteries, however, there are still no theoretical studies describing the Na storage mechanism within this material. In this work, we present a density functional theory study on the effects of interstitial and substitutional Na atoms on the electronic and structural properties of hydrogen-passivated porous silicon (pSi H ). The results show that the substitutional Na reduces the band gap, while the interstitial Na induces metallic properties on the pSi H . The diffusion analysis by the nudged elastic band scheme, reveals that the interstitial Na atoms migrate from the silicon lattice to the pore surface, while the pSi H energy barrier decreases by 20.42% relative to the bulk silicon energy barrier value. Finally, the hydrogenated surface proves to be beneficial for both Na adsorption and diffusion. These results could be important for understanding the storage and diffusion mechanism of Na on pSi H .

Tunable electronic properties of silicon nanowires as sodium‐battery anodes

“…40 Nanoporous materials based on Sb present capacities of 506 mAhg À1 and recent studies in porous Si nanomaterials reveal that hydrogen passivation favors the adsorption and diffusion of the Na atoms. 48,49 Silicon nanowires (SiNWs) are potential anodic materials in rechargeable batteries due to their highly tunable electronic properties. 50,51 For instance, they have a semiconducting behavior, with larger band gaps than the bulk Si, when their surface dangling bonds are passivated with hydrogen atoms (H-SiNWs), and the size of the band gap depends on the diameter of the H-SiNW.…”