The effects of structural properties on the lithium storage behavior of mesoporous TiO₂

Understanding the effects of structural properties on the lithium storage behavior of mesoporous TiO₂ is crucial for further optimizing its performance through rational structure design. To achieve this, herein, the surface area and the grain size of the prepared mesoporous TiO₂ are intentionally adjusted by controlling the calcination temperatures. It is found that the capacities of the mesoporous TiO₂ contain both the lithium-ion insertion into the bulk phase (Q _in) and the additional surface lithium storage (Q _as). The Q _in gradually increases with grain sizes to a steady level and then slightly drops. By contrast, the Q _as is directly proportional to the specific surface area of the mesoporous TiO₂ and is ascribed to the capacity originated from the lithium-ion insertion into the surface layer. The experimental comparison and analysis demonstrate that the fast kinetics of the Q _as ensure both the better rate performance and capacity retention of mesoporous TiO₂ than bulk ones. Specially, the mesoporous TiO₂ calcinated at 350 °C shows the highest reversible specific capacity of 250.2 mA h g^-1, the best rate capability (132.5 mA h g^-1 at 2C) and good cycling stability. Our findings shed great light on the design of high-performance nanostructured TiO₂ with surface lithium storage.