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- Energy; Chemistry; Engineering; Multi-scale porosity; Ge anode; Co-precipitation; Selective reduction; Lithium-ion batteries
Dual-porous Ge nanostructures are synthesized via two straightforward steps. Compared with conventional approaches related to porous Ge materials, different types of pores can be readily generated by adjusting the relative ratio of the precursor amounts for GeO 2 and SiO 2. Unlike using hard templates with different sizes for introducing secondary pores, this system makes a uniformly blended structure of porogen and active sites in the nanoscale range. When GeO 2 is subjected to zincothermic reduction, it is selectively converted to pure Ge still connected to unreacted SiO 2. During the reduction process, primary pores (larger than 50 nm) are formed by eliminating zinc oxide by-products, while inactive SiO 2 with respect to zinc metal could contribute to retaining the overall structure. Finally, the HF treatment completely leaches remaining SiO 2 and formed secondary pores (micro/mesopores) to complete the dual-porous Ge structure. The resulting Ge structure is tested as an anode material for lithium-ion batteries. The Ge electrode exhibits an outstanding reversibility and an exceptional cycling stability corresponding to a capacity retention of 100% after 100 cycles at C/5 and of 94.4% after 300 cycles at C/2. Furthermore, multi-scale pores facilitate a facile Li-ion accessibility, resulting in an excellent rate capability delivering ∼740 mAh g −1 at 5C.