Design of ZnO coating on diatomite ceramic separator and construction of stable electrolyte/anode interface for high-performance aqueous zinc-ion battery

In aqueous zinc-ion batteries, Zn dendrite growth, hydrogen evolution reaction and by-product generation upon Zn anode seriously affect the battery performance. To address these issues, in this paper, a diatomite ceramic separator with a porous structure is prepared by sintering diatomite. The diatomite ceramic separator possesses excellent electrolyte affinity, high porosity, and remarkable electrolyte retention ability, and the high mechanical strength of the diatomite ceramic separator has a physical inhibition effect on Zn dendrite growth. When assembled into a Zn NHVO cell, diatomite ceramic separator can effectively inhibit the discharge capacity decay by stabilizing electrolyte/anode interface. To further improve the performance of the diatomite ceramic separator, nanoscale ZnO is coated on the separator surface to construct a more uniform 3D pore structure, which achieves the efficient transport of Zn2+ in the coated separator and improves the ion conductivity of the coated separator (12.0 mS cm- 1). ZnO coating expands the electrochemical window of diatomite ceramic separator (2.10 V), homogenizes the deposition of Zn2+ on the surface of Zn anode, reduces the nucleation overpotential (26.5 mV), and further inhibits the growth of Zn dendrites and the production of by-products. The Zn MnO2 cell assembled with the ZnO coated diatomite ceramic separator exhibits a higher specific discharge capacity of 228.7 mA h g- 1 and a higher capacity retention rate at a current density of 0.5 A g- 1, and the cell still has a specific discharge capacity of 99.5 mA h g- 1 at a current density of 2.0 A g- 1, which is superior to the electrochemical performance of the cell with glass fiber separator. The design of ZnO coating on diatomite ceramic matrix opens up a new idea for the practical application of high-performance aqueous zinc-ion batteries.