Germanium-Based High-Performance Dual-Ion Batteries

Recently, dual-ion batteries (DIBs) have received immense attention owing to their high operating voltage and low cost, and further enhancement of their energy densities and cyclabilities is being intensively pursued. Herein, a novel Ge-based DIB is developed by using a rationally designed nanocomposite of Ge particles embedded in one-dimensional carbon nanofibers (Ge/CNFs) as anode for the first time. The resultant battery delivers a high discharge capacity of 281 mAh g-1 at the discharge current of 0.25 A g-1 and superb rate capability of 94 mAh g-1 at the discharge current of 2.5 A g-1, which greatly surpasses those of most reported DIBs. These remarkable properties can be ascribed to that the uniform one-dimensional nanostructure facilitates the improvement of lithium-ion diffusion within the hybrids, and the carbon matrix effectively alleviates the volume expansion of Ge during the cycling process and simultaneously enhances electrical conductivity of the hybrids. The charge storage mechanism of the Ge/CNFs is revealed to be Ge alloying with Li accompanied by a phase transformation process from crystalline Ge to amorphous LixGe alloys. This work paves the way for the rational utilization of Ge-based materials in new-generation high-performance DIBs.