One-step synthesis of novel mesoporous three-dimensional GeO2 and its lithium storage properties

Abstract

Novel mesoporous three-dimensional GeO₂ was successfully synthesized by a facile one-step synthesis method followed by mixing with graphene using a spray drying process. The well-dispersed mesoporous GeO₂ demonstrates a bean-like morphology (b-GeO₂) with a particle size of 400 to 500 nm in length and 200 to 300 nm in diameter, in which mesopores with an average size of 3.6 nm are distributed. The b-GeO₂ without any additional conductive surface layer shows a high reversible capacity for lithium storage of 845 mAh g⁻¹ after 100 cycles, with nearly no capacity fading. When graphene was employed to be mixed with GeO₂via a spray drying method, the electrochemical performance is further significantly improved. The b-GeO₂/graphene composite electrode gives a higher de-lithiation capacity of 1021 mAh g⁻¹, and the capacity retention is measured to be as high as 94.3% after 200 charge–discharge cycles for constant current cycling at 0.2 C, as well as an excellent rate performance, even displaying a reversible capacity of 730 mAh g⁻¹ at a rate of 5 C.