Development of an efficient CVD technique to prepare TiO2/porous–carbon nanocomposites for high rate lithium-ion capacitors

Abstract

Titanium dioxide is a promising electrode material for lithium-ion capacitors. When using TiO₂ as an electrode material, it is necessary to combine it with carbon at the nanometer level to improve its low electrical conductivity and low reactivity with Li⁺. However, preparation methods of reported TiO₂/porous–carbon nanocomposites are generally not cost-effective, and their productivities are low. In this study, the vacuum liquid-pulse chemical vapor deposition (VLP-CVD) technique was developed to easily prepare TiO₂/porous–carbon nanocomposites, where TiO₂ nanoparticles with a diameter of ∼4 nm could be homogeneously deposited inside the pores of meso- or macroporous carbons. Because the deposited TiO₂ nanoparticles had access to effective electrically conductive paths formed by the porous–carbon substrate, they showed a high discharge capacity of ∼200 mA h g⁻¹-TiO₂ (based on TiO₂ weight). In particular, the composite prepared from macroporous carbon showed an extremely high rate performance, where 50% of the discharge capacity was retained at a current density of 15 000 mA g⁻¹ when compared to that measured at 50 mA g⁻¹. In addition, the composite also showed very high cyclability, where 80% of the discharge capacity was retained at the 10 000^th cycle. Because the VLP-CVD technique can be performed using simple apparatus and commercially available starting materials, it can be expected to boost industrial production of TiO₂/porous–carbon for lithium-ion capacitors.