Core-shell Ti@Si coaxial nanorod arrays formed directly on current collectors for lithium-ion batteries.

Silicon is a promising candidate to replace the dominantly used carbon as the anode material for lithium ion batteries (LIBs). Si has the highest theoretical capacity (4200 mA·h/g) and is one of the most abundant elements. Unfortunately, Si has the issues of huge volume variation upon dis/charge cycling and low conductivity, leading to poor cycling and rate performances. Designing special nanostructures and improving conductivity and integration of Si electrodes could dramatically enhance their performance. Here, we introduce a novel strategy to integrate the core-shell nanorod arrays of Ti@Si on Ti foil with good conductivity as an additive-free electrode. The Ti core functions as a stable metallic support for the Si shell and dramatically reduces the diffusion length. The as-prepared core-shell nanorod arrays of Ti@Si on Ti foil, without any postsynthesis treatment, as electrodes demonstrated reversible capacity of 1125 mA·h/g over at least 30 cycles with highly improved Coulombic efficiency.