Rutile TiO2 Inverse Opal Anodes for Li‐Ion Batteries with Long Cycle Life, High‐Rate Capability, and High Structural Stability

Rutile TiO2 inverse opals provide long cycle life and impressive structural stability when tested as anode materials for Li‐ion batteries. The capacity retention of TiO2 inverse opals (IOs) is greater than previously reported values for other rutile TiO2 nanomaterials, and the cycled crystalline phase and material interconnectivity is maintained over thousands of cycles. Consequently, this paper offers insight into the importance of optimizing the relationship between the structure and morphology on improving electrochemical performance of this abundant and low environmental impact material. TiO2 IOs show gradual capacity fading over 1000 and 5000 cycles, when cycled at specific currents of 75 and 450 mA g−1, respectively, while maintaining a high capacity and a stable overall cell voltage. TiO2 IOs achieve a reversible capacity of ≈170 and 140 mA h g−1 after the 100th and 1000th cycles, respectively, at a specific current of 75 mA g−1, corresponding to a capacity retention of ≈82.4%. The structural stability of the 3D IO phase from pristine rutile TiO2 to the conductive orthorhombic Li0.5TiO2 is remarkable and maintains its structural integrity. Image analysis conclusively shows that volumetric swelling is accommodated into the predefined pore space, and the IO periodicity remains constant and does not degrade over 5000 cycles. Rutile TiO2 inverse opal Li‐ion battery anodes demonstrate long cycle life (tested to 5000 cycles in this work) and enhanced structural stability in the absence of polymeric binders and conductive additives. Image analysis confirms that volumetric swelling of the walls of the inverse opal is accommodated into the predefined pore space, and the overall inverse opal morphology is retained after 5000 cycles.