Cu nanowire array with designed interphases enabling high performance Si anode toward flexible lithium-ion battery

To meet the growing demand for wearable smart electronic devices, the development of flexible lithium-ion batteries (LIBs) is essential. Silicon is an ideal candidate for the anode material of flexible lithium-ion batteries due to its high specific capacity, low working potential, and earth abundance. The largest challenge in developing a flexible silicon anode is how to maintain structural integrity and ensure stable electrochemical reactions during external deformation. In this work, we propose a novel design for fabricating core–shell electrodes based on a copper nanowire (CuNW) array core and magnetron sputtered Si/C shell. The nanowire array structure has characteristics of bending under longitudinal stress and twisting under transverse stress, which helps to maintain the mechanical stability of the structure during electrode bending and cycling. The low-temperature annealing generates a small amount of Cu₃Si alloy, which enhances the connection strength between Si and the conductive network and solves the poor conductivity problem of Si, which is known as a semiconductor material. This unique configuration design of CuNW@Si@C-400 °C leads to stable long cycle performance of 1109 mAh∙g⁻¹ after 1000 cycles and excellent rate performance of 500 mAh∙g⁻¹ at a current density of 10 A∙g⁻¹. Furthermore, the CuNW@Si@C-400 °C||LiFePO₄ (LFP) full battery demonstrates excellent flexibility, with a capacity retention of more than 96% after 100 bends. This study provides a promising strategy for the development of flexible lithium-ion batteries.