Vanadium oxides represent a promising cathode material for aqueous zinc ion batteries (ZIBs) owing to their abundant valences and versatile cation-storage capacities. However, the sluggish Zn2+ diffusion kinetics in the...

The reversible storage of Zn ions in aqueous electrolyte typically follows the intercalation mechanism. [22][23][24][25][26][27][28][29][30][31][32] Though the radius of Zn 2+ is only 0.074 nm, its bivalency and large solvation sheath generally cause sluggish insertion kinetics. [33][34][35][36][37][38][39] Therefore, materials with tunnel structure or 2D channels could facilitate the Zn ion insertion/extraction, and thus serving as suitable cathode materials for zinc-ion batteries (ZIBs).Vanadium-based materials (e.g., V 2 O 5 •nH 2 O, [40] LiV 3 O 8 , [41] Na 2 V 6 O 16 •n-H 2 O [42] ) are attractive cathode materials for ZIBs since the multiple chemical valence of vanadium from +5 to +3 can result in a high specific capacity of ≈400 mA h g −1 . [43,44] Especially, hydrated vanadium pentoxide (V 2 O 5 •nH 2 O) has a layered structure with a large interlayer spacing of 1.2 nm that allows facile accessibility of Zn ions. ZIBs are advantageous to conventional Li-ion batteries not only in the safety and cost, but also in their significantly higher power densities since the aqueous electrolytes own a several orders of magnitude higher ion diffusion rate than the organic counterparts. [45] However, the intrinsically low electrical conductivity and unstable structure of V 2 O 5 •nH 2 O usually cause a fast decline in capacity under high rates or charge/discharge cycling. To address these challenges, constructing free-standing films incorporating V 2 O 5 •nH 2 O and conductive materials such as graphene or CNTs with improved ionic and electronic transport could be an effective way. [46,47] At present, electrochemical deposition, [48] vacuum filtration, [34] and atomic layer deposition [49] are usually used to prepare V 2 O 5 /carbon films. However, these tedious and discontinuous processes make them difficult to scale up. Blading coating is a solution-processable technology to construct large-area film that requires well-dispersed ink and suitable mechanical properties of the functional materials. Typically, neutral surfactants are introduced for the preparation of V 2 O 5 /carbon hybrid inks since V 2 O 5 is dissolvable in both acidic and alkaline solutions. [50][51][52][53] However, these surfactants are difficult to remove and increase the electrode resistance, resulting in decreased rate performance. Until now, it is still challenging to fabricate a surfactant-free V 2 O 5 /carbon ink with excellent stability and ultrahigh concentration.Aqueous zinc-ion batteries (ZIBs) based on near-neutral electrolytes represent a promising large-scale energy storage solution for a deeper and broader penetration of clean renewable energy. The preparation of electrode paste is vital for the normal performance and stability of ZIBs. Herein, the authors report an additive-free V 2 O 5 •1.6H 2 O (h-V 2 O 5 )/carbon nanotube (CNT) hybrid ink to prepare large-scale free-standing h-V 2 O 5 /CNT film for high-rate and durable ZIBs. The as-prepared h-V 2 O 5 /CNT film exhibits a high specific capacity of 446.4 mA h g −1 (volumetric capaci...

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