Free-standing three-dimensional carbon nanotubes/amorphous MnO2 cathodes for aqueous zinc-ion batteries with superior rate performance

Rechargeable aqueous zinc-ion batteries (ZIBs) have gained particular attention in recent years because of their low cost and high safety. However, most of their performances are limited by unsatisfied architecture of cathodes. In addition, the degree of crystallinity of active materials also plays an important role in their electrochemical performance. Herein, we fabricated free-standing composite films with amorphous MnO2 (a-MnO2) and carbon nanotubes (CNTs) by an in situ deposition method. The free-standing a-MnO2@CNTs composite films can directly serve as the cathodes of ZIBs without binder and current collector. The resultant cathode exhibits highly electrical conductivity and fast ion-diffusion because of the corporation of interconnected three-dimensional CNTs architectures and ultra-thin a-MnO2 nanosheets. As a result, the resultant ZIB displays high energy and power density, as well as stable cycling performance. Moreover, based on composite films, flexible ZIBs were constructed, and they could remain stable electrochemical performance under different bending states, which have great potential for the application in flexible and wearable electronics.