Freestanding 3D nanoporous Cu@1D Cu₂O nanowire heterostructures: from a facile one-step protocol to robust application in Li storage

Structural deterioration and low conductivity are key factors that give rise to severe capacity fading of transition metal oxides as anodes for lithium-ion batteries (LIBs). An effective way to overcome this challenge is to construct nanosized metal oxide heterostructures integrated with a 3D nanoarchitectured metal matrix to buffer volume variation, reinforce structural stability and improve electronic conductivity. Herein, a facile and effective underpotential oxidation (UPO) assisted dealloying protocol has been developed successfully to synthesize freestanding monolithic 3D nanoporous copper@1D cuprous oxide nanowire network (3D NPC@1D Cu₂O NWN) heterostructures. Based on their dealloying behavior, the evolution law can be well established, sequentially described as "dealloying of (Mn, Cu) accompanying Cu₂O NW germination", "growth of Cu₂O NWs accompanying (Mn, Cu) re-dealloying" and "Cu₂O NWN coarsening". Compared to other Cu_xO-based electrode materials with different structural designs reported in the literature, the unique nanocomposites as an anode for LIBs exhibit far superior Li storage performance including an ultrahigh initial reversible capacity of 2.71 mA h cm^-2, good cycling stability with 60.2% capacity retention after 150 cycles (just 0.007 mA h per cm² per cycle for capacity fading), and excellent rate capability with reversible capacity as high as 1.64 mA h cm^-2 after 55 high-rate cycles. This mainly originates from effectively accommodating huge volume changes during charge/discharge processes, providing abundant reaction active sites, shortening electron/ion transport paths, and building a reliable 3D/1D composite nano-configuration without additional binders and conductive agents, indicative of a considerably promising anode candidate for high-performance LIBs.