Thin-shelled hollow mesoporous TiO₂ spheres with less tortuosity as fast-charging anode

TiO₂ is a stable and abundantly available material that is a promising alternative to graphite anodes. However, compact stacking of TiO₆ octahedra induces repulsion between the inserted Li ions, reducing rate performance and achievable capacity. Herein, we propose mesoporous hollow TiO₂ spheres composed of nanosized anatase to mitigate these issues. The hollow structure allows for ion transport both inward and outward. The empty-core material is obtained by depositing sub-20 nm TiO₂ particles synthesized through the sol–gel process onto a carbon nanosphere support, followed by scaffold elimination. Thin TiO₂ shells facilitate ion migration via a reduced tortuosity with minimizing isolated pore formation, allowing D_Li⁺ of 3.22 × 10⁻¹¹ cm² s⁻¹ to be attained, which is 40 times higher than that of bulk-type TiO₂. The facile Li-ion transport enables the insertion of 0.66 mol Li ions per mol of TiO₂ at 0.5C and 67 % rate performance (10C vs. 0.5C). The designed hollow TiO₂ exhibits stable capacity retention of 85.9 % for 1000 cycles at a fast charging rate of 20C. A full cell with a LiFePO₄ cathode exhibits 60 % rate capability (2000 vs. 50 mA g⁻¹). Thin mesoporous hollow TiO₂ facilitates the Li-ion transport and enable fast charging, confirming the potential of this anode for fast-charging applications.