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Page 2 of 12 Cui et al. Energy Mater 2023;3:300023 https://dx.doi.org/10.20517/energymater.2022.90

Keywords: Aqueous zinc-ion batteries, cathode material, Zn (OH) V O ·2H O, carbon cloth, zinc storage
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mechanism
INTRODUCTION
Nowadays, there are two determining factors in the development of lithium-ion batteries (LIBs): safety and
cost price. The rechargeable aqueous Zn-ion batteries (AZIBs) are considered as a preferred solution due to
their high level of safety, low cost, and environmental friendliness . However, the wide application of
[1-4]
AZIBs has been seriously hampered by the lack of high-performance cathode materials. Layered vanadium-
based compounds with an open framework structure can facilitate the fast Zn-ion intercalation/de-
intercalation and enhance the specific capacities. Besides, the multiple oxidation states of vanadium can
[5-9]
further contribute to increasing the specific capacity .

Zn (OH) V O ·2H O (ZVO) materials became a powerful competitor among all vanadium-based
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compounds. This was because the structural water located between the V-O layers, which was attached by
hydrogen bonds to hydroxyl groups, enlarged the interlayer spacing, leading to high capacity and high-rate
capability [10,11] . While they were commonly used as cathode electrodes in LIBs, only a few studies reported
their usage in AZIBs. For example, Li et al. developed hexagonal ZVO nanoplates by a hydrothermal route
[12]
and applied them as a cathode material for AZIBs . The ZVO electrode displayed a discharge capacity of
117.69 mAh g at a current density of 50 mA g . Xia et al. reported ultra-long ZVO nanowires (ZVNW) by
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a microwave method . The ZVNW were utilized as a cathode for AZIBs and showed a high capacity of
[13]
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[13]
213 mAh g at 50 mA g due to the short Zn diffusion channel . However, their inherent low
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conductivity caused sluggish charge transfer kinetics. Recently, the N-doping carbon as an effective
conductive support was doped into ZVNW, which exhibited a large capacity of 295 mAh g at 0.1 A g -1[14] .
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However, multiple interfaces formed among the active materials, additives (such as ancillary binders) and
collectors could impede the mass transfer, leading to the unsatisfied performances.
To address these issues, the carbon cloth (CC) with high conductivity, light weight, and excellent structural
stability has been used as the growth template to ensure the orientation of active materials and as
collectors [15-18] to fasten the electron transport due to the strong attachment between the active materials and
CC. In this study, we first prepared the ultra-long ZVO nanowires on CC (ZVNW-CC) through a
hydrothermal route. ZVNW-CC was directly utilized as a cathode for AZIBs and exhibited a high specific
capacity of 361.8 mAh g (at 50 A g ). ZVNW-CC electrodes displayed higher rate performance and more
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favorable cycle retention than pristine ZVNW, indicating that the construction of an efficient electron/ion
transport path of ZVNW-CC cathode for AZIBs was beneficial to the improvement of electrochemical
performance.

EXPERIMENT
Preparation of Zn (OH) V O ·2H O nanowires grown on carbon cloth
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All the chemicals used in this study were analytical grade without any further purification. They were
purchased from Sinopharm Group Chemical Reagent Co. CC (3 × 3 cm) was pretreated by immersing it in a
mixture solution of 20% nitric acid and sulfuric acid (v% 1:1) for 12 h. Then NH VO (2 mmol) and
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ZnSO ·6H O (3 mmol) were dissolved into 60 mL deionized water at 80 °C to form a clear, light yellow
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solution. Later, 7 mL H O was added to the solution. Subsequently, they were transferred to a 100 mL
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polytetrafluoroethylene-lined container along with the pretreated CC. The mixture was heated at 180 °C for
14 h and cooled naturally. Finally, the prepared CC was moved out and washed with deionized water and
ethanol several times, then dried at 60 °C for 12 h to obtain the sample (ZVNW-CC). A synthesis diagram