TiO₂-Nanocoated Black Phosphorus Electrodes with Improved Electrochemical Performance

Black phosphorus (BP) is a promising electrode material with high energy density for lithium-ion batteries. However, volumetric expansion of BP upon lithiation leads to rapid capacity fading of the electrode. Herein, BP composite electrodes are prepared by mixing microsized BP particles with carbon nanotubes and KetjenBlack as dual conducting agents, which facilitate the construction of stable and conductive networks in the electrodes. An ultrathin TiO2 nanocoating is deposited on the surface of the BP composite electrode by electron-beam evaporation. The TiO2 nanocoating acts as a protective layer to prevent the BP particles from directly contacting the electrolyte by forming a LixTiyOz passivation coating on the electrode surface. The LixTiyOz passivation layer suppresses propagation of the formed irreversible solid electrolyte interlayer on the BP particles, resulting in an improved Coulombic efficiency of the BP electrode. Moreover, the LixTiyOz passivation layer facilitates lithium-ion diffusion and electron transfer and thus superior cycling and rate performance of the BP electrode are achieved.