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 DLi+ 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.