Balaji Sambandam

Owing to their safety and low cost, aqueous rechargeable Zn-ion batteries (ARZIBs) are currently more feasible for grid-scale applications, as compared to their alkali counterparts such as lithium- and sodium-ion batteries (LIBs and SIBs), for both aqueous and nonaqueous systems. However, the materials used in ARZIBs have a poor rate capability and inadequate cycle lifespan, serving as a major handicap for long-term storage applications. Here, we report vanadium-based Na2V6O16·3H2O nanorods employed as a positive electrode for ARZIBs, which display superior electrochemical Zn storage properties. A reversible Zn2+-ion (de)intercalation reaction describing the storage mechanism is revealed using the in situ synchrotron X-ray diffraction technique. This cathode material delivers a very high rate capability and high capacity retention of more than 80% over 1000 cycles, at a current rate of 40C (1C = 361 mA g–1). The battery offers a specific energy of 90 W h kg–1 at a specific power of 15.8 KW kg–1, enlightening the material advantages for an eco-friendly atmosphere.

The development of new battery technologies requires them to be well-established given the competition from lithium ion batteries (LIBs), a well-commercialized technology, and the merits should surpass other available technologies’ characteristics for battery applications. Aqueous rechargeable zinc ion batteries (ARZIBs) represent a budding technology that can challenge LIBs with respect to electrochemical features because of the safety, low cost, high energy density, long cycle life, high-volume density, and stable water-compatible features of the metal zinc anode. Research on ARZIBs utilizing mild acidic electrolytes is focused on developing cathode materials with complete utilization of their electro-active materials. This progress is, however, hindered by persistent issues and consequences of divergent electrochemical mechanisms, unwanted side reactions, and unresolved proton insertion phenomena, thereby challenging ARZIB commercialization for large-scale energy storage applications. Herein, we broadly review two important cathodes, manganese and vanadium oxides, that are witnessing rapid progress toward developing state-of-the-art ARZIB cathodes.

α-Zn₂V₂O₇ nanowire is utilized as cathode for aqueous Zn-ions energy storage application. This cathode is sustained a high reversible capacity of 138 mA h g⁻¹ after 1000 cycles and displays a high specific energy, added advantage for aqueous battery system.

Layered K₂V₆O₁₆·2.7H₂O nanorod cathode, utilized for aqueous rechargeable Zn-ion batteries, displays high reversible capacities, exceptional rate capabilities and long cycle-span of 700 (altering three different current densities) and 500 (~82% capacity retention at 6 A g⁻¹) cycles.