Fibrous-Root-Inspired Design and Lithium Storage Applications of a Co–Zn Binary Synergistic Nanoarray System

Developing lithium ion batteries (LIBs) with fast charging/discharging capability and high capacity is a significant issue for future technical requirements. Transition-metal oxide (TMO) materials are widely studied as the next-generation LIB anode to satisfy this requirement due to their specific capacity, nearly three times than that of conventional graphite anode, and low cost. Meanwhile, they also suffer from slow lithium diffusion and limited electrochemical and structural stability, especially at high charging/discharging rate. The structure design of TMO is an effective strategy to obtain desirable LIB performance. Herein, inspired by natural fibrous roots consisting of functional and supporting units that can enhance substances and energy exchange efficiently, fibrous-root-like Zn(x)Co(3-x)O4@Zn(1-y)Co(y)O binary TMO nanoarrays are designed and synthesized on Cu substrates through a facile one-pot, successive-deposition process for use as an integrated LIB anode. In a multilevel array ordered by orientation, ultrafine Zn(x)Co(3-x)O4 nanowire functional units and stable Zn(1-y)Co(y)O nanorod supporting units synergize, resulting in superior rate performance. At a high current density of 500 mAg(-1), they could maintain a discharge capacity as high as 804 mAh g(-1) after 100 cycles, working much higher than unary cobalt-based and zinc-based nanoarrays. This binary synergistic nanoarray system identifies an optimized electrode design strategy for advanced battery materials.