Electrochemically Induced Phase Transition in V₃O₇ · H₂O Nanobelts/Reduced Graphene Oxide Composites for Aqueous Zinc‐Ion Batteries

Abstract

V3O7·H2O nanobelts/reduced graphene oxide (rGO) composites (weight ratio: 86%/14%) are synthesized by a microwave approach with a high yield (85%) through controlling pH with acids. The growth mechanisms of the highly crystalline nanobelts (average diameter: 25 nm; length: ≈20 µm; oriented along the [101] direction) have been thoroughly investigated, with the governing role of the acid upon the morphology and oxidation state of vanadium disclosed. When used as the ZIB cathode, the composite can deliver a high specific capacity of 410.7 and 385.7 mAh g−1 at the current density of 0.5 and 4 A g−1, respectively, with a high retention of the capacity of 93%. The capacity of the composite is greater than those of V3O7 · H2O, V2O5 nanobelts, and V5O12 · 6H2O film. Zinc ion storage in V3O7·H2O/rGO is mainly a pseudocapacitive behavior rather than ion diffusion. The presence of rGO enables outstanding cycling stability of up to 1000 cycles with a capacity retention of 99.6%. Extended cycling shows a gradual phase transition, that is, from the original orthorhombic V3O7 · H2O to a stable hexagonal Zn3(VO4)2(H2O)2.93 phase, which is a new electrochemical route found in V3O7 materials. This phase transition process provides new insight into the reactions of aqueous ZIBs.

Constructing Advanced Aqueous Zinc‐Ion Batteries with 2D Carbon‐Rich Materials

“…Mossin et al added GO solution into microwave reactor with VOSO 4 · x H 2 O to synthesize V 3 O 7 ·1.5H 2 O nanobelts/rGO composites (Figure 5d), whose electron transfer kinetics and cycling stability were significantly promoted in the presence of rGO. [ 60 ] Fan et al synthesized a 2D hierarchical Mn 2 O 3 @graphene cathode by molten salt method. The vertical growth of numerous Mn 2 O 3 nanosheets on 2D hierarchical graphene possessed large surface area and high exposure of open edges for Zn 2+ storage.…”

“…Reproduced with permission. [60] Copyright 2021, John Wiley and Sons. cathode delivered a high rate capacity of 174.4 mAh g À1 at 100 A g À1 (Figure 5c).…”

Rapid Electrochemical Activation of V2O3@C Cathode for High‐Performance Zinc‐Ion Batteries in Water‐in‐Salt Electrolyte

“…The extra peaks indicate that the oxidation of vanadium ion in the water‐in‐salt electrolyte is more sufficient than in the Zn(CF 3 SO 3 ) 2 electrolyte, as it may facilitate multistep V 3+ /V 4+ /V 5+ conversion and promote additional active sites for Zn 2+ storage. The material is thus allowed to undergo V 5+ to V 3+ redox reaction to contribute a higher specific capacity [37,46,47] . Moreover, the lower electrochemical polarization in water‐in‐salt electrolyte can also be seen from the position of the highest redox peaks that is referred to V 4+ →V 5+ .…”

“…The material is thus allowed to undergo V 5 + to V 3 + redox reaction to contribute a higher specific capacity. [37,46,47] Moreover, the lower electrochemical polarization in water-in-salt electrolyte can also be seen from the position of the highest redox peaks that is referred to V 4 + !V 5 + . For example, the redox peak position in Zn(CF 3 SO 3 ) 2 electrolyte is 1.05 V/1.29 V, while the peak position in Zn(CF 3 SO 3 ) 2 + LiTFSI electrolyte is 1.10 V/1.22 V. The positions of the redox peaks are closer for the Zn(CF 3 SO 3 ) 2 + LiTFSI electrolyte, indicating an alleviated polarization in the high concentration water-in-salt electrolyte.…”

Low‐Power Photodetectors Based on PVA‐Modified Reduced Graphene Oxide Hybrid Solutions

“…To address this problem, simple and economical reduced graphene oxide (rGO) flakes are considered promising candidates to meet the requirements. [12][13][14] As a result, devices based on rGO or rGO composites that possess properties of high performance, large area, simple process, and low cost have been widely developed for green energy, [15,16] sensing, [17][18][19][20][21] and energy storage fields. [22][23][24] In addition, rGO with different reduction levels can be easily achieved by varying the annealing temperature.…”