Spontaneous knitting behavior of 6.7-nm thin (NH4)0.38V2O5 nano- ribbons for binder-free zinc-ion batteries

Rechargeable, aqueous Zn-ion batteries in a neutral or mildly acidic electrolyte have attracted great attention. The fabrication of binder-free electrodes to boost the Zn 2+ transport is extremely desirable for the development of aqueous zinc-ion batteries but remains a big challenge. Herein, we revealed a spontaneous knitting behaviour in 6.7 nm thin, flexible (NH 4 ) 0.38 V 2 O 5 nanoribbons by a hydrothermal route to form binder-free paper cathode for aqueous zinc-ion batteries. Conductive multi-walled carbon nanotubes (CNTs) was also successfully imbedded into this paper to enhance the electronic conductivity and produce abundant meshes (pore size: 1-3 µm) inside the paper. Taking advantage of the binder-free design and the porous architecture of the paper cathode, it delivered a reversible capacities of 465 mAh·g −1 at 100 mA·g −1 . A capacity retention of above 89.3 % after 500 cycles at 100 mA·g −1 has been achieved. Importantly, the resulting paper electrode exhibited a specific energy as high as 343 Wh·kg −1 , which remarkably outperforms most of the zinc-ion batteries based on powder form cathode with the presence of polymer binder. Our work reveals a novel self-grown strategy for the binder-free, freestanding electrodes on Zn 2+ ion storage from the ultrathin, flexible ammonium vanadates nanostructures, and it might be applicable to the storage of other metal/non-metallic ions (Na + , Mg 2+ , Ca 2+ , Al 3+ , NH 4 + etc.) in next-generation electrochemical energy storage devices.