Three‐Dimensional Manganese Oxide@Carbon Networks as Free‐Standing, High‐Loading Cathodes for High‐Performance Zinc‐Ion Batteries

Zinc‐ion batteries (ZIBs), which are inexpensive and environmentally friendly, have a lot of potential for use in grid‐scale energy storage systems, but their use is constrained by the availability of suitable cathode materials. MnO 2 ‐based cathodes are emerging as a promising contenders, due to the great availability and safety, as well as the device's stable output voltage platform (1.5 V). Improving the slow kinetics of MnO 2 ‐based cathodes caused by low electrical conductivity and mass diffusion rate is a challenge for their future use in next‐generation rapid charging devices. Herein, the aforementioned challenges are overcome by proposing a sodium‐intercalated manganese oxide (NMO) with 3D varying thinness carbon nanotubes (VTCNTs) networks as appropriate free‐standing, binder‐free cathodes (NMO/VTCNTs) without any heat treatment. A network construction strategy based on CNTs of different diameters is proposed for the first time to provide high specific capacity while achieving high mass loading. The specific capacity of as‐prepared cathodes is significantly increased. The resulting free‐standing binder‐free cathodes achieve excellent capacity (329 mAh g −1 after 120 cycles at 0.2 A g −1 and 225 mAh g −1 after 200 cycles at 1 A g −1 ) and long‐term cycling stability (158 mAh g −1 at 2 A g −1 after 1000 cycles).