Rate performance enhancement of lithium-ion battery using precise thickness-controllable-carbon-coated titanium dioxide nanowire array electrode via atomic layer deposition

An atomic layer deposition (ALD) of ultra-thin and conformal carbon shell is demonstrated as a powerful technique for enhancing the rate performance of a nanostructured Li-ion battery (LIB) electrode. Structuring conformal-carbon-shell-coated TiO₂ nanowire (NW) arrays with precise thickness control can be realized via the ALD process using a CBr₄ precursor and a hydrogen plasma reactant. The vertically-aligned TiO₂ NWs grown via hydrothermal and annealing method are used as a complex nanostructure anode. Ultrathin carbon-shell-coated (thickness 1–2 nm) TiO₂ NW anodes show long-term cyclability and excellent rate-performance (capacity retention of 96.5% after 500 charge/discharge cycles and 105 mAh g⁻¹ at 30 C, 1 C = 230 mA g⁻¹) whereas thick carbon-shell-coated (thickness 6–7 nm) TiO₂ NW anodes exhibit lower rate capability than the bare TiO₂ NW anode, which is attributed to fast charge and mass transport of conformal and ultrathin carbon shell. This carbon coating method by ALD can be potentially applied to various nano-sized electrodes with complicated structures with uniform and precise thickness control coating.