NiSi(x)/a-Si Nanowires with Interfacial a-Ge as Anodes for High-Rate Lithium-Ion Batteries

Conductive metal nanowire is a promising current collector for the Si-based anode material in high-rate lithium-ion batteries. However, to harness this remarkable potential for high power density energy storage, one has to address the interfacial potential barrier that hinders the electron injection from the metal side. Herein, we present that, solely by inserting ultrathin amorphous germanium (a-Ge) (∼5 nm) at the interface of NiSix/amorphous Si (a-Si), the rate capacity was substantially enhanced, 477 mAh g(-1) even at a high rate of 40 A g(-1). In addition, batteries containing the NiSix/Ge+Si anodes cycled over 1000 times at 10 A g(-1) while the capacity retaining more than 877 mAh g(-1), which is among the highest reported. The excellent electrochemical performance is directly correlated with the significantly improved electrical conductivity and mechanical stability throughout the entire electrode. The potential barrier between the NiSix and a-Si was modulated by a-Ge, which constructs an electron highway. Besides, the a-Ge interlayer enhances the interfacial adhesion by reducing void fraction and the inhomogeneous strain of the Li-Ge and Li-Si stacking structure was accommodated through the bending and twist of relatively thin NiSix, thus ensures a more stable high-rate cycling performance. Our work shows an effective way to fabricate metal/a-Si nanowires for high-rate lithium-ion battery anodes.