High Reversible Pseudocapacity in Mesoporous Yolk-Shell Anatase TiO2/TiO2(B) Microspheres Used as Anodes for Li-Ion Batteries

As an anode material for lithium-ion batteries, titanium dioxide (TiO 2 ) shows good gravimetric performance (336 mAh g -1 for LiTiO 2 ) and excellent cyclability. To address the poor rate behavior, slow lithium-ion (Li + ) diffusion, and high irreversible capacity decay, TiO 2 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 TiO 2 and the shell is TiO 2 (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 TiO 2 (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.