Three-in-one organic-inorganic heterostructures: From scalable ball-milling synthesis to freestanding cathodes with high areal capacity for aqueous zinc-ion batteries

Aqueous Zn-ion batteries (AZIBs) have great potential in large-scale energy storage, however, developing suit-able cathodes with high energy/power densities remains highly challenging. Herein, a unique organic-inorganic heterostructures (denoted as Ov-PVO/G) of poly(3,4-ethylenedioxythiophene) intercalated V2O5 nanocrystals anchored on few-layer graphene by a simple and scalable ball-milling approach are demonstrated for high areal -capacity AZIBs cathodes, in which, adjusted interlayer spacing, abundant oxygen vacancies and robust hetero-interfaces can be simultaneously constructed. Moreover, the feature of being well dispersed in different polar solvents (H2O, NMP, etc.) enable facile incorporation of the Ov-PVO/G heterostructures into conductive net-works of single-walled carbon nanotubes to fabricate freestanding composite cathodes. Electrochemical mea-surement and first-principles calculations indicate that such "Three-in-One" heterostructure can significantly enhance Zn2+ adsorption/desorption, electrical conductivity and charge transfer due to strong synergy, thereby exhibiting high-capacity and accelerated reaction kinetics during cycling. Specifically, at a practical mass loading of 12.0 mg/cm2, the freestanding Ov-PVO/G cathodes show a high areal-capacity of 6.1 mAh/cm2 at 2.4 mA/cm2 and works stable with an area-capacity of 1.63 mAh/cm2 at 120 mA/cm2 after 500 cycles. More importantly, flexible soft-packaged AZIBs based on 3x3 cm2 high mass-loading Ov-PVO/G cathodes deliver record-high and stable electric energy beyond 21.5 mAh at different bending states. This work paves a more promising way to practical application of high-performance AZIBs.