Highly reversible lithium storage in a 3D macroporous Ge@C composite

A porous Ge@C composite was synthesized by magnesiothermic reduction reaction of GeO2, Mg powder and glucose followed by an etching process with HCl solution. Compared to a porous Ge electrode, the porous Ge@C composite electrode delivers better cycling stability (similar to 100% capacity retention after 100 cycles at the 0.2 C rate) and higher rate capability (440 mA h g(-1) at 1800 mA g(-1)). The improved electrochemical performance results from the synergistic effect of the 3D interconnected porous structure and the carbon shells. The local pores could buffer the volume change and the conductive carbon shell could prevent the aggregation of Ge as well as enhance the electronic conductivity of the whole electrode.