Highly cross-linked Cu/a-Si core–shell nanowires for ultra-long cycle life and high rate lithium batteries

Abstract

Seeking long cycle lifetime and high rate performance are still challenging aspects to promote the application of silicon-loaded lithium ion batteries (LIBs), where optimal structural and compositional design are critical to maximize a synergistic effect in composite core–shell nanowire anode structures. We here propose and demonstrate a high quality conformal coating of an amorphous Si (a-Si) thin film over a matrix of highly cross-linked CuO nanowires (NWs). The conformal a-Si coating can serve as both a high capacity storage medium and a high quality binder that joins crossing CuO NWs into a continuous network. And the CuO NWs can be reduced into highly conductive Cu cores in low temperature H₂ annealing. In this way, we have demonstrated an excellent cycling stability that lasts more than 700 (or 1000) charge/discharge cycles at a current density of 3.6 A g⁻¹ (or 1 A g⁻¹), with a high capacity retention rate of 80%. Remarkably, these Cu/a-Si core–shell anode structures can survive an extremely high charging current density of 64 A g⁻¹ for 25 runs, and then recover 75% initial capacity when returning to 1 A g⁻¹. We also present the first and straightforward experimental proof that these robust highly-cross-linked core–shell networks can preserve the structural integrity even after 1000 runs of cycling. All these results indicate a new and convenient strategy towards a high performance Si-loaded battery application.