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 Li _xTi _yO _z passivation coating on the electrode surface. The Li _xTi _yO _z 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 Li _xTi _yO _z passivation layer facilitates lithium-ion diffusion and electron transfer and thus superior cycling and rate performance of the BP electrode are achieved.