Long Cycle Life, Highly Ordered SnO₂/GeO₂ Nanocomposite Inverse Opal Anode Materials for Li‐Ion Batteries

Nanocomposite SnO2/GeO2 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 SnO2 is significantly improved via the engineering of a nanocomposite of nanoparticles of tetragonal SnO2 and hexagonal GeO2 into a highly ordered, porous inverse opal architecture. By introducing a GeO2 component, the SnO2/GeO2 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. SnO2/GeO2 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. SnO2/GeO2 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.