Aqueous zinc-ion batteries have the advantages of good safety and low cost, and have important application potential in the field of energy storage. However, water in the electrolyte is like a double-edged sword in zinc-ion batteries. Thanks to the use of aqueous solvents, zinc-ion batteries are not only safe, but also have a high ionic conductivity, which ensures that the batteries have an excellent fast charging and discharging capability. In addition, the presence of water in the electrolyte helps to provide protons for insertion into the cathode material, thereby increasing capacity. However, excess water can lead to corrosion of the negative electrode, zinc dendrite formation, and dissolution problems of the positive electrode material, thereby affecting the long-term cycling performance of zinc ion batteries. Therefore, in order to achieve both high capacity and long life of zinc ion batteries, the water content must be precisely controlled.
A research team at CAS DICP chose acetonitrile as organic solvent to investigate the effects of different water contents in the electrolyte on the kinetics and stability of the anode and cathode reactions, and to find out the influence on the capacity and life of the full battery. It was found that even with only a small amount of water in the electrolyte, the highest capacity of zinc ion batteries could be realized and excellent long-term cycling stability was demonstrated. The capacity retention was as high as 80% after 9,000 cycles at 6A/g current.
In addition, the team systematically and thoroughly investigated the effect of water content on the microreaction mechanism at the interface of vanadium-based anode and zinc anode, steps towards using the excellent performance of zinc ion batteries through the design of electrolyte.