Flexible Three-Dimensional Heterostructured ZnO-Co3O4 on Carbon Cloth as Free-Standing Anode with Outstanding Li/Na Storage Performance

Herein, a facile and binder-free method was developed to prepare a flexible electrode for dual battery applications, which was achieved by fabricating nanosheets of ZnO-Co3O4 heterostructures attached on the surface of highly conductive carbon cloth (CC). Remarkably, for Li-ion batteries, the combined effects of two dimensional (2D) heterostructural and three dimensional (3D) carbon fiber substrate offered an excellent reversible capacity rate of approximately 1785 mAh g−1 at a current density of 200 mA g−1. Even at a charge-discharge rate of 2000 mA g−1, the ZnO-Co3O4@CC composite exhibited a reversible capacity of 491 mAh g−1 after 400 cycles. For sodium-ion batteries, the composite exhibited a reversible specific capacity of 684 mAh g−1 at a current density of 200 mA g−1 and a capacity of 265 mAh g−1 after 500 cycles at a current density of 1000 mA g−1. Flexible half-cells were also constructed, which exhibited high flexibility and excellent electrochemical performance. The excellent performance is mainly due to the in situ growth of ZnO-Co3O4 nanosheets on the CC, which provided a large contact area between the active material and the flexible and conductive substrate, ultimately facilitating rapid electron transport and preventing the aggregation of large surface area nanosheets.