A Comprehensive Review of the Mechanism and Modification Strategies of V2O5 Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have attracted wide attention due to their affordability, inherent safety, and environmental friendliness, recognized as one of the most ideal next generation energy storage systems. Vanadium-based cathodes have garnered significant interest in the field of AZIBs, presenting vast application prospects in stationary energy storage. Among them, layered vanadium pentoxide (V2O5) stands out a promising material due to its high theoretical capacity, drawing extensive research efforts. However, the research on V2O5 is greatly hindered by issues such as cathode material dissolution, low conductivity, and byproduct formation. Therefore, this review starts from the characteristics of V2O5 materials, summarizes the energy storage mechanism of Zn2+, and elucidates the main challenges faced by V2O5. Subsequently, current modification strategies are summarized based on these challenges, along with the relationships between the issues and strategies. Finally, further challenges and directions faced by each modification strategy are proposed. It is expected to provide researchers with information to quickly familiarize themselves with the current applications and inspiring prospects of V2O5 in AZIBs.

Oxygen defects engineering and structural strengthening of hydrated vanadium oxide cathode by coating glucose hydrothermal carbon and pre-embedding Mn (II) ion for high-capacity aqueous zinc ion batteries

Vanadium oxide-based cathode with unique layered structure is considered as a candidate for aqueous zinc ion batteries (AZIBs). Unfortunately, considering poor electronic conductivity, sluggish diffusion kinetics, and the destruction of layered structures in the cycling process, the actual capacity and rate capability are constrained. Herein, the glucose hydrothermal carbon (GHC) and transition metal Mn2+ ion have been utilized to incorporate hydrated vanadium oxide (Mn-VOH@GHC). The oxygen vacancies defects of VOH, induced by GHC anchored on surface and Mn2+ inserted between interlayers, provides more active sites, higher electronic conductivity, and faster ion diffusion. In addition, GHC reinforces the integrity of external structure, while Mn2+ ion acts as structural pillars to support the interlayer structure. The Mn-VOH@GHC electrode can produce a high capacity of 530 mAh/g at the current density of 0.2 A/g thanks to these crucial properties, and after 2000 cycles at a high current density of 2 A/g, it can also produce a reversible capacity of 344 mAh/g. The results suggest that the synergistic effect of defect engineering and metal ion pre-insertion provides a new idea in enhancement of the electrochemical performance of AZIBs cathode materials.

Boosting Material Utilization via Direct Growth of Zn2 (V3 O8 )2 on the Carbon Cloth as a Cathode to Achieve a High-Capacity Aqueous Zinc-Ion Battery

Aqueous zinc-ion batteries (AZIBs) have attracted the attention of researchers because of their high theoretical capacity and safety. Among the many vanadium-based AZIB cathode materials, zinc vanadate is of great interest as a typical phase in the dis-/charge process. Here, a remarkable method to improve the utilization rate of zinc vanadate cathode materials is reported. In situ growth of Zn2 (V3 O8 )2 on carbon cloth (CC) as the cathode material (ZVO@CC) of AZIBs. Compared with the Zn2 (V3 O8 )2 cathode material bonded on titanium foil (ZVO@Ti), the specific capacity increases from 300 to 420 mAh g-1 , and the utilization rate of the material increases from 69.60% to 99.2%. After the flexible device is prepared, it shows the appropriate specific capacity (268.4 mAh g-1 at 0.1 A g-1 ) and high safety. The method proposed in this work improves the material utilization rate and enhances the energy density of AZIB and also has a certain reference for the other electrochemical energy storage devices.

Dual-Ion Co-intercalation Mechanism on a Na2V6O16·3H2O Cathode with a Commercial-Level Mass Loading for Aqueous Zinc-Ion Batteries with High Areal Capacity

A proton (H⁺) and zinc ion (Zn²⁺) co-insertion model is put forward in this study to elucidate the capacity origin of an aqueous zinc ion battery (ZIB) based on a heavily loaded (∼15 mg cm^-2) cathode, which consists of Na₂V₆O₁₆·3H₂O (NVO) embedded particularly in the macropores of activated carbon cloth (ACC), coupled with a highly stable Zn/In anode. The confinement effect of these porous channels not only prevents the detachment of NVO from ACC but also well mitigates its volume change resulting from H⁺ and Zn²⁺ co-intercalation, which collectively render the stability of NVO/ACC markedly enhanced. Moreover, the bicontinuous structure of NVO/ACC, as a result of the self-interlacing of intrapore NVO, which is first engineered into the nanobelts, and their interlocking with the carbon fibers of ACC, simultaneously giving rise to a solid and a holey framework, is favorable to the electron and ion transport throughout the entire electrode. The synergistic effect of such facile charge transfer kinetics and the high packing density of NVO in the cathode endows ZIBs with not only a good rate performance but also an exceptional areal capacity amounting to 4.6 mAh cm^-2, far surpassing those reported for additional vanadium-based counterparts reported in the literature.