Dodecahedral ZnO/C framework on reduced graphene oxide sheets for high-performance Li-ion battery anodes

Abstract

To prepare high-performance ZnO/C nanocomposite anode materials, dodecahedral ZIF-8 was first deposited on exfoliated reduced graphene oxide (rGO) by precipitation from methanol. The ZIF-8 was carbonized by annealing in argon to produce ZnO/C that retained the structure of the ZIF-8 template. ZIF-8-derived ZnO/C and ZnO/C/rGO were deposited over Cu substrates using low-cost, scalable supersonic cold spraying to facilitate the rapid production of Li-ion battery anodes. The synergy of the ZIF-8-derived dodecahedral nano-ZnO/C framework with rGO significantly enhanced conductivity, reduced aggregation, and shortened Li-ion transfer pathways. Electrochemical impedance spectroscopy showed enhanced Li-ion diffusion. The rGO/ZnO/C framework demonstrated a specific capacity of 1325 mAh·g−1 at a specific current of 100 mA·g−1. At a higher current of 2.5 A·g−1, the anode delivered a capacity of 525 mAh·g−1. The composite also showed a highly stable reversible capacity of 1063 mAh·g−1 after 300 cycles. The outstanding electrochemical performance of the rGO/ZnO/C sample was facilitated by the three-dimensional morphology of the exfoliated rGO and ZIF-8-derived dodecahedral porous ZnO/C structure. A quantitative comparison of specific capacity and capacity retention shows that the electrochemical performance of these rGO/ZnO/C composites exceeds that of previously-reported anodes based on ZnO, carbon, and/or rGO.