Multifunctional Carbon Modification Enhancement for Vanadium-Based Phosphates as an Advanced Cathode of Zinc-Ion Batteries

Abstract

In recent years, rechargeable aqueous zinc-ion batteries (ZIBs) have shown extraordinary potential due to their safety, nontoxicity, sustainable zinc resources, and low price. However, the lack of suitable cathode materials hinders the development of ZIBs. Recently, layered phosphates have been widely used as cathode materials. As one typical phosphate cathode, vanadium oxyphosphate (VOPO4) has inherently low electronic conductivity and structural dissolution in electrochemical reactions, limiting its development. To solve these problems, VOPO4/C is prepared by combining multifunctional carbon material with a VOPO4 interlayer and an external surface, which not only improves the electronic conductivity of the composite material but also effectively inhibits the dissolution of VOPO4 in the electrolyte. As a result, the prepared VOPO4/C could deliver a reversible capacity of 140 mA h g–1 at a current density of 100 mA g–1. Furthermore, the rate performance of the VOPO4/C composite has also been improved significantly. In the process of charging and discharging, zinc ions in the composite show perfect intercalate and deintercalate performance.

A B-doped layered VOPO4·2H2O cathode for high-performance zinc-ion batteries with an H+/Zn2+ co-insertion mechanism

“…14 In addition, many studies have been carried out on their layered structure, and the focus was on increasing the interlayer spacing, through pre-intercalation of organic compounds ( polyaniline and polypyrrole) and metal ions (Na + , K + and Zn 2+ ). 15 For instance, Srinivasan et al demonstrated that pre-intercalating polypyrrole and water amounts between the crystallographic layers of the VOPO 4 cathode is essential for easy and reversible Zn 2+ intercalation/deintercalation. 16 Hu et al inserted lamellar vanadium phosphate with various interlayer spacings (14.8 Å, 15.6 Å, and 16.5 Å) using extended interlayer distances using a controlled aniline intercalation strategy and the solvothermal process.…”

Regulating Crystal Orientation in VO2 for Aqueous Zinc Batteries with Enhanced Pseudocapacitance

“…To further improve the electrochemical performance of cathode materials, various methods such as doping, 25 synthesis of ordered nanostructures, 26 compositing with high conductivity materials, 27 surface modification, 28 engineering 29 have been applied. Among them, the crystal facet engineering has a main purpose of promoting crystal anisotropic growth, forming a specific crystal orientation, and exposing the desired facets.…”

“…To further improve the electrochemical performance of cathode materials, various methods such as doping, synthesis of ordered nanostructures, compositing with high conductivity materials, surface modification, and crystal facet engineering have been applied. Among them, the crystal facet engineering has a main purpose of promoting crystal anisotropic growth, forming a specific crystal orientation, and exposing the desired facets. , For example, by using V 2 O 5 as a vanadium source and oxalic acid as a reducing agent, VO 2 with various phases and morphologies can be synthesized through the hydrothermal method at different temperatures .…”

In Situ Induced Core–Shell Carbon‐Encapsulated Amorphous Vanadium Oxide for Ultra‐Long Cycle Life Aqueous Zinc‐Ion Batteries

“…This often results in a limited capacity and rapid performance fading. [18] Until now, some pioneering strategies have been demonstrated to inhibit the dissolution of vanadium-based cathode materials in aqueous electrolytes, including intercalating organic polymers/metal ions into the vanadium-based cathodes to enhance structural robustness and relieve the intercalation stress, [19][20][21][22][23] coating the surface of vanadium-based cathodes with a protective layer (e.g., polymers, [24][25][26] metal oxides, [27,28] sulfate, [29] and MXene [30] ) to prevent the structural collapse during cycling, employing "water-in-salt" electrolytes with high salt concentration to decrease the water content, [31][32][33] and tuning the electrolyte solvation structure to reduce water activity and improve the electrode-electrolyte interfacial chemistry. [34][35][36][37] While these strategies can solve the vanadium dissolution problem and improve the cathode stability to some extent, there are still considerable challenges.…”