In Situ Conformal Carbon Coating for Constructing Hierarchical Mesoporous Titania/Carbon Spheres as High-Rate Lithium-Ion Battery Anodes

It is of vital importance to improve the transport of electrons and lithium ions at the same time for optimizing the rate capability of lithium-ion battery anode materials. In this work, hierarchical mesoporous titania/carbon (TiO2/C) spheres are fabricated via a soft method and followed by the in situ carbonation of the residual n-hexadecylamine structure-directing agent. This green synthetic method ingeniously makes the waste organic species turn into coaxially conductive carbon layers but does not compromise the high porosity of TiO2. The hierarchical mesoporous TiO2/C spheres not only effectively improve the electrical conductivity of TiO2 electrodes but also accelerate the entry and diffusion of lithium ions. They deliver much superior rate capability compared to mesoporous TiO2, nonporous TiO2/C, and nonporous TiO2 spheres. Furthermore, synthetic conditions of solvothermal time and calcination temperature are systematically investigated. The results demonstrate that the conductive layer, porosity, and nanocrystal size all determine the rate capability of the TiO2 electrode. This work not only represents a green and low-cost method for the synthesis of advanced TiO2 anode materials but also constructs an advanced electrode with high electronic conductivity, high porosity, and small nanocrystals, affording an important and meaningful reference for material synthesis and electrode design.

Automated summary

Improving the transport of electrons and lithium ions simultaneously is crucial for enhancing the rate capability of lithium-ion battery anode materials. In this study, hierarchical mesoporous TiO2/C spheres were synthesized, which exhibited high electrical conductivity and porosity as electrode materials.