One-Step Synthesis of Novel Mesoporous Three-Dimensional GeO 2 and Its Lithium Storage Properties

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 after 100 cycles, with nearly no capacity fading. When graphene was employed to be mixed with GeO2 via a spray drying method, the electrochemical performance is further significantly improved. The b-GeO2/graphene composite electrode gives a higher de-lithiation capacity of 1,021 mAh g, and the capacity retention is measured to be as high as 94.3% after 200 charge/discharge cycles for constant current cycling at 0.2C, as well as an excellent rate performance, even displaying a reversible capacity of 730 mAh g at a rate of 5C.