Revolutionizing Lithium Storage Capabilities in TiO2 by Expanding the Redox Range

TiO2 is a widely recognized intercalation anode material for lithium-ion batteries (LIBs), yet its practical capacity is kinetically constrained due to sluggish lithium-ion diffusion, leading to a lithiation number of less than 1.0 Li+ (336 mAh g–1). Here, the growth of TiO2 crystallites is restrained by integrating Si into the TiO2 framework, thereby enhancing the charge transfer and creating additional active sites potentially residing at grain boundaries for Li+ storage. This strategy is corroborated by the expanded redox range of Ti, as thoroughly demonstrated via synchrotron radiation-based X-ray spectroscopy and Cs-corrected electron microscopy. Consequently, when deployed for lithium storage, the tailored material achieves an extraordinarily high reversible capacity of 559 mAh g–1, 116% of the theoretical maximum of 483 mAh g–1 calculated based on all active species, while simultaneously retaining superior rate capability and robust cycling stability. This work offers fresh perspectives on the revitalization of traditional electrode materials to achieve enhanced capacities.