大熊仕良

As an anode material for lithium-ion batteries, titanium dioxide (TiO₂) shows good gravimetric performance (336 mAh g⁻¹ for LiTiO₂) and excellent cyclability. To address the poor rate behavior, slow lithium-ion (Li⁺) diffusion, and high irreversible capacity decay, TiO₂ nanomaterials with tuned phase compositions and morphologies are being investigated. Here, a promising material is prepared that comprises a mesoporous “yolk–shell” spherical morphology in which the core is anatase TiO₂ and the shell is TiO₂(B). The preparation employs a NaCl-assisted solvothermal process and the electrochemical results indicate that the mesoporous yolk–shell microspheres have high specific reversible capacity at moderate current (330.0 mAh g⁻¹ at C/5), excellent rate performance (181.8 mAh g⁻¹ at 40C), and impressive cyclability (98% capacity retention after 500 cycles). The superior properties are attributed to the TiO₂(B) nanosheet shell, which provides additional active area to stabilize the pseudocapacity. In addition, the open mesoporous morphology improves diffusion of electrolyte throughout the electrode, thereby contributing directly to greatly improved rate capacity.

Mesoporous anatase TiO₂ yolk–TiO₂(B) shell microspheres are synthesized via a solvothermal process. Porous shells of thin TiO₂(B) nanosheets are separated by a gap from the anatase TiO₂ cores. These microspheres show a high reversible capacity and long-term cyclability as active anode materials in lithium-ion batteries.