Growth of the vertically aligned graphene@ amorphous GeOx sandwich nanoflakes and excellent Li storage properties

Germanium oxide is a promising anode material for lithium ion batteries due to its theoretical capacity (1100   mAh/g) is 3 times higher than the commercial graphite anode (only 372   mAh/g). However, so far only a few studies have reported the application of germanium oxide in LIBs and the cycling performance is unsatisfactory. In this report, we have prepared a unique VAG@ amorphous GeO x sandwich nanostructure by a non-toxic, low temperature CVD method with vertically aligned graphene(VAG) as templates. The graphene sheets form a fast electron transport channel duo to its superior electron conductivity and the vertically aligned sandwich nanoflakes can offer a short pathway for lithium ion thanks to the unified orientation. Additionally, the GeO x sediments that evenly distribute on the surface of graphene flakes have an amorphous structure and their thickness is less than 10   nm, which can mitigate the mechanical stress generating in the lithiation/delithiation process. Owing to these advantages, the as-prepared anode shows a stable capacity of 1008   mAh/g for 100 cycles (with capacity retention of 96%). Rate performance reveals the anode can maintain a capacity of 545   mAh/g even at the rate of 15C. Our results are demonstrated to be so far the most stable performance for germanium oxide anodes.