Long Cycle Life, Highly Ordered SnO<sub>2</sub>/GeO<sub>2</sub> Nanocomposite Inverse Opal Anode Materials for Li‐Ion Batteries
David McNulty, Hugh Geaney, Quentin M. Ramasse, Colm O’Dwyer
Abstract
Abstract Nanocomposite SnO 2 /GeO 2 inverse opals (IOs) provide long cycle life with excellent capacity retention when tested as anode materials for Li‐ion batteries. It is demonstrated that the electrochemical performance of SnO 2 is significantly improved via the engineering of a nanocomposite of nanoparticles of tetragonal SnO 2 and hexagonal GeO 2 into a highly ordered, porous inverse opal architecture. By introducing a GeO 2 component, the SnO 2 /GeO 2 IOs demonstrate stepwise lithium storage processes to improve cycling stability by mitigating capacity fade from material volume variations in a material that already improves cycling repose by its architecture. This results in higher capacity and better capacity retention. SnO 2 /GeO 2 IOs achieve a reversible capacity of ≈ 880 and 690 mAh g −1 after the 50th and 250th cycles, respectively, at a specific current of 150 mA g −1 . SnO 2 /GeO 2 IOs are capable of delivering high specific capacities (average value of ≈ 570 mAh g −1 ) with stable capacity retention over 750 cycles at a specific current of 450 mA g −1 . Tailoring the composition of nanocomposite metal‐oxide anodes to exploit the combination of conversion and alloying mechanisms enables stable binder‐free Li‐ion anodes. Nanoscaling the walls of the ordered macroporous structure provides efficient reversible redox lithiation mechanisms involving the oxides of Sn and Ge, which are simpler to prepare.