Cu₂Nb₃₄O₈₇ nanowires as a superior lithium storage host in advanced rechargeable batteries

In this study, for the first time, Cu₂Nb₃₄O₇₈ nanowires were fabricated via an electrospinning technique and exhibited outstanding electrochemical performance as an anode material. The nanowires presented a charge capacity of 279.8 mA h g⁻¹ with remarkable long-life stability for 300 cycles (0.037% capacity loss per cycle). Significantly, ex situ X-ray diffraction, ex situ high-resolution transmission electron microscopy, and ex situ X-ray photoelectron spectroscopy were performed to unveil the reaction process and change in the microstructure during charge/discharge cycles in detail. The observed evidence demonstrates that the remarkable Li-storage capability is due to the enhanced contact-specific area and reduced transport path of Cu₂Nb₃₄O₇₈ nanowires. In addition, the host mechanism is unraveled, in which the contribution of the reversible capacity is discussed based on the Nb⁵⁺/Nb⁴⁺, Nb⁴⁺/Nb³⁺ and Cu²⁺/Cu⁺ redox couples.