Aqueous zinc ion batteries (ZIBs), a new type of aqueous secondary batteries proposed in recent years, show great practical value and developmental prospects in the field of scale energy storage including electric vehicle and energy storage grid owing to their high energy density and high power density, safe and efficient discharge processes, cheap and nontoxic electrode materials and simple manufacturing process. At present, one of the main factors hindering the further development of ZIBs is the lack of suitable cathode materials. Due to the large ion radius of Zn2 + and its hydrated ions, it will cause irreversible deformation or structural collapse of the cathode electrode material during insertion/desorption process, resulting in a rapid decline in battery capacitance. The poor conductivity of the cathode electrode material and serious electrode polarization during charging and discharging cause the charging voltage of cathode partially overlaps with the oxygen evolution voltage. As a result, the cathode electrode material will catalyze the water to produce oxygen, causing the battery flatulence to invalid during the charging process. Moreover, the strong electrostatic interaction between the divalent Zn2 + and the crystal structure of the cathode electrode material leads to unsatisfactory Zn2 + insertion capacitance. Therefore, it is crucial to develop a cathode material that can provide high capacity and maintain good structural stability during Zn2 + insertion/desorption process. In view of the shortcomings of the cathode material of the ZIBs, a variety of modification methods are used to improve their performance: (I) guest particles, such as metal ions, organic molecules and water molecules, are introduce in to the host so a more stable frame can be obtained through its structural changes; (II) intrinsic mixed valence materials are prepared because of their better adaptability to the volume changes and valence changes of the cathode electrode material during charging and discharging; (III) introduce oxygen vacancies to increase active sites to promote Zn2 + diffusion kinetics and increase material capacity; (IV) conductive materials are composed to improve the overall conductivity of the material and enhance structural stability; (V) the nanostructure modification is carried out to enlarge specific surface area of cathode material, shorten the Zn2 + diffusion distance and increase the contact area of electrochemical reaction. This article gives a brief introduction to ZIBs, its advantages and its energy storage mechanisms. Based on the key role of cathode materials in ZIBs, several common cathode materials such as manganese-based oxides, vanadium-based oxides, and prussian blue analogs are emphatically reviewed. Moreover, the structures, properties and defects of all above cathode materials are expounded, and the modification methods including doping guest particles, compositing with conductive materials, preparing intrinsic mixed valence states and constructing nanostructures are primarily discussed. At the end of this view, we pointed out several promising directions of the development of cathode materials for ZIBs. © 2022 Cailiao Daobaoshe/ Materials Review. All rights reserved.
