Design Strategy of High Stability Vertically Aligned RGO@V2O5 Heterostructure Cathodes for Flexible Quasi-Solid-State Aqueous Zinc-Ion Batteries

Advances of Vanadium-based Cathodes forAqueous Zinc Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are promising for energy storage due to their high safety, low cost, and environmental friendliness. Vanadium-based materials, including vanadium oxides, vanadium sulfides, vanadate, and vanadium carbon composites, have gained attention for their diverse crystal structures, multiple oxidation states, and high theoretical capacities. This review summarizes recent advances in vanadium-based cathodes, focusing on structural design and modification strategies, such as amorphous structures, defect engineering, conductive carbon matrices, and cation pre-intercalation to enhance Zn2+ storage. Vanadium oxides and vanadium sulfides offer unique ion diffusion advantages, while vanadate and vanadium carbon composites improve conductivity and stability. Vanadate is highlighted as a critical approach to reduce electrostatic repulsion and facilitate Zn2+ storage. Vanadium carbon composites (V-MOF derivations, vanadium oxides @ carbon, combined with graphene and conductive polymer) have unique advantages in terms of conductivity, ion diffusion, and structural stability. Emerging materials like VN, VOPO₄ and V2CTx are also discussed. Future directions include multi-guest doping, anion pre-intercalation, and advanced carbon integration. This review aims to guide the development of high-performance AZIBs and inspire future research in this field.

Sulphur-decorated Ti3C2 MXene structures as high-capacity electrode for Zn-ion batteries: a DFT study

MXene-based structures have gained tremendous attention in energy storage applications, especially in ion batteries due to their promising electrical conductivity and high energy storage properties. Herein, we studied sulphur-decorated Ti3C2 MXene structures for Zn-ion batteries with augmented storage capacity (462.5 mAh g-1). Moreover, we systematically investigated the adsorption energy, structural stability, electronic band structure, open-circuit voltage and diffusion barrier of the sulphur-decorated Ti3C2 MXene using first-principles calculations. Our findings reveal that the studied MXene structures retain metallic characteristics with high open-circuit voltage (1.13 V) and charge transfer of 1.30 |q|. Hence, the designed sulphur-modified Ti3C2 MXene structures could be considered as promising cathode materials in Zn-ion batteries.

Exploring the Electrochemical Superiority of V2O5/TiO2@Ti3C2-MXene Hybrid Nanostructures for Enhanced Lithium-Ion Battery Performance

The use of vanadium(V)-based materials as electrode materials in electrochemical energy storage (EES) devices is promising due to their structural and chemical variety, abundance, and low cost. V-based materials with a layered structure and high multielectron transfer in the redox reaction have been actively explored for energy storage. Our current work presents the structural and electrochemical properties of a vanadium-based composite with TiO2@Ti3C2 MXene, referred to as VM. This composite is obtained through the in situ thermal decomposition of the VO2(OH)/Ti3C2mixture, which is achieved by solution mixing and drying. The material structure is confirmed using various characterization tools, which establish an orthorhombic V2O5 nanostructure compositing with nanocrystalline TiO2@Ti3C2. VM with 5 wt % MXene, referred to as VM5, can achieve 460 mAhg-1 at a current density of 0.1 Ag1- and 290 mAhg-1 at 1 Ag1-, with an average coulombic efficiency of 98.5%. The presence of the V2O5/TiO2 (nanocrystals) heterojunction attached with Ti3C2 sheets contributed to reduced charge transfer resistance. The cyclic stability shows a capacity retention of 62% over 500 cycles at 1 Ag1- (4C rate, where 1C equals 0.25 Ag1-) with a 0.22 capacity drop with each cycle. Dunn's approach to examining the charge storage mechanism demonstrates 72% contribution of the surface-dominant capacitive process and 28% of the diffusion-controlled intercalation process at 0.4 mVs-1, suggesting a potential high-performance pseudocapacitive hybrid electrode material for lithium-ion batteries.

Unveiling Intercalation Chemistry via Interference-Free Characterization Toward Advanced Aqueous Zinc/Vanadium Pentoxide Batteries

Aqueous Zn/V2O5 batteries are featured for high safety, low cost, and environmental compatibility. However, complex electrode components in real batteries impede the fundamental understanding of phase transition processes and intercalation chemistry. Here, model batteries based on V2O5 film electrodes which show similar electrochemical behaviors as the real ones are built. Advanced surface science characterizations of the film electrodes allow to identify intercalation trajectories of Zn2+, H2O, and H+ during V2O5 phase transition processes. Protons serve as the vanguard of intercalated species, facilitating the subsequent intercalation of Zn2+ and H2O. The increase of capacity in the activation process is mainly due to the transition from V2O5 to more active V2O5·nH2O structure caused by the partial irreversible deintercalation of H2O rather than the increase of active sites induced by the grain refinement of electrode materials. Eventually, accumulation of Zn species within the oxide electrode results in the formation of inactive (Zn3(OH)2V2O7·2H2O) structure. The established intercalation chemistry helps to design high-performance electrode materials.

Dislocation Effect Boosting the Electrochemical Properties of Prussian Blue Analogues for 2.6 V High-Voltage Aqueous Zinc-Based Batteries

Prussian blue analogues (PBAs) have attracted increasing attention in aqueous zinc-based batteries (AZBs) with the advantages of an open framework, adjustable redox potential, and easy synthesis. However, they exhibited a low specific capacity and a poor cycle performance. In this work, crystalline potassium iron hexacyanoferrate (FeHCF) with dislocation was designed and prepared by a poly(vinylpyrrolidone) (PVP) additive. The metastable state provided by PVP would cause an electrostatic interaction between cyanogen and water molecules. The reduced force increases the steric resistance of the water molecules entering the crystal. The low content of crystal water in FeHCF is associated with the formation of dislocation. The dislocation effect effectively improves the electrochemical reactivity and reaction kinetics of FeHCF. Thus, it presents a high reversible capacity of 131 mAh g-1 with a superior capacity retention of 85% after 550 cycles at 0.5 A g-1. When used as a cathode, the AZBs display a high voltage of 2.6 V, a fast charging capability (<5 min), and a satisfactory cycle stability with a capacity retention of 82% after 400 cycles at 0.2 A g-1 in decoupling electrolytes. This work provides an effective strategy for the design of high-performance PBA-based cathodes for 2.6 V AZBs.

Multifunctionalized Supramolecular Cyclodextrin Additives Boosting the Durability of Aqueous Zinc-Ion Batteries

The poor cycling stability of aqueous zinc-ion batteries hinders their application in large-scale energy storage due to uncontrollable dendrite growth and harmful hydrogen evolution reactions. Here, we designed and synthesized an electrolyte additive, N-methylimidazolium-β-cyclodextrin p-toluenesulfonate (NMI-CDOTS). The cations of NMI-CD+ are more easily adsorbed on the abrupt Zn surface to regulate the deposition of Zn2+ and reduce dendrite generation under the combined action of the unique cavity structure with abundant hydroxyl groups and the electrostatic force. Meanwhile, p-toluenesulfonate (OTS-) is able to change the Zn2+ solvation structure and suppress the hydrogen evolution reaction by the strong interaction of Zn2+ and OTS-. Benefiting from the synergistic role of NMI-CD+ and OTS-, the Zn||Zn symmetric cell exhibits superior cycling performance as high as 3800 h under 1 mA cm-2 and 1 mA h cm-2. The Zn||V2O5 full battery also shows a high specific capacity (198.3 mA h g-1) under 2.0 A g-1 even after 1500 cycles, and its Coulomb efficiency is nearly 100% during the charging and discharging procedure. These multifunctional composite strategies open up possibilities for the commercial application of aqueous zinc-ion batteries.

Vanadium Oxide Cathode Coinserted by Ni2+ and NH4+ for High-Performance Aqueous Zinc-Ion Batteries

Vanadium-based oxides have garnered significant attention as cathode materials for aqueous zinc-ion batteries (AZIBs) because of their high theoretical capacity and low cost. However, the limited reaction kinetics and poor long-term cycle stability hinder their widespread application. In this paper, we propose a novel approach by coinserting Ni2+ and NH4+ ions into V2O5·3H2O, i.e., NNVO. Structural characterization shows that the coinsertion of Ni2+ and NH4+ not only extends the interlayer spacing of V2O5·3H2O but also significantly promotes the transport kinetics of Zn2+ because of the synergistic "pillar" effect of Ni2+ and NH4+, as well as the increased oxygen vacancies that effectively lower the energy barrier for Zn2+ insertion. As a result, the AZIBs with an NNVO electrode exhibit a high capacity of 398.1 mAh g-1 (at 1.0 A g-1) and good cycle stability with 89.1% capacity retention even after 2000 cycles at 5.0 A g-1. At the same time, a highly competitive energy density of 262.9 Wh kg-1 is delivered at 382.9 W kg-1. Considering the simple scheme and the resultant high performance, this study may provide a positive attempt to develop high-performance AZIBs.