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 Zn2+ 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 (NH4)(0.38)V2O5 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 mu m) 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 Zn2+ ion storage from the ultrathin, flexible ammonium vanadates nanostructures, and it might be applicable to the storage of other metal/non-metallic ions (Na+, Mg2+, Ca2+, Al3+, NH4+ etc.) in next-generation electrochemical energy storage devices.

Automated summary

The study demonstrates a novel self-grown strategy for binder-free, freestanding electrodes on Zn2+ ion storage using thin, flexible ammonium vanadates nanostructures. The resulting paper cathode exhibits high reversible capacity and specific energy, outperforming most zinc-ion batteries based on powder form cathodes. The design of the paper electrode with binder-free and porous architecture shows great potential in Zn2+ ion storage.