On August 13, Hainan University (HNU) announced a breakthrough by a research team led by professors Shi Xiaodong and Tian Xinlong from the School of Marine Sciences and Engineering. The team developed a mullite-based solid-state electrolyte for aqueous zinc-iodine batteries on the basis of high-throughput theoretical calculations and a zinc-ion exchange strategy. The findings were published in the international academic journal Advanced Materials.

Iodine, a halogen element with abundant reserves in the ocean, is present in seawater at an average concentration of about 0.06 milligrams per liter. The marine iodine reserves are estimated to reach 93 billion tons in total. Developing high-performance, long-lasting aqueous zinc-iodine batteries holds significant potential for the high-value utilization of marine halogen resources.

According to the researchers, zinc dendrites, iodine dissolution, and the shuttle effect of polyiodides are the primary factors that cause capacity degradation and shortened lifespan in zinc-iodine batteries. Professors Shi and Tian both agree that developing new solid-state electrolytes suitable for aqueous batteries is the breakthrough solution as it can enhance the capacity retention and extend the lifespan of zinc-iodine batteries.

To this end, the research team has discovered, through theoretical calculations and electrochemical testing, that mullite-based solid-state electrolytes possess excellent properties, including intrinsic electronic insulation, a low zinc-ion diffusion barrier, and strong adsorption of polyiodides. These characteristics allow the electrolyte to serve dual functions as both a separator and an electrolyte, effectively isolating the redox reactions between the zinc metal anode and the iodine-loaded cathode. During battery cycling, the mullite-based solid-state electrolyte guides the uniform deposition and stripping of zinc ions at the anode, suppressing the growth of zinc dendrites and by-products. Simultaneously, at the cathode, it inhibits iodine dissolution and the polyiodide shuttle effect, thereby reducing the rate of capacity decline.

Tian notes that this research is the first to utilize abundant, inexpensive and easily accessible natural minerals as the solid-state electrolyte in aqueous batteries. It has taken into account the need for both the low-cost and high-performance batteries. This innovation not only provides a new avenue for the development of long-lasting aqueous energy storage devices but also inspires the optimization of the mineral-based solid-state electrolyte, thus promoting its wider application in zinc-based secondary batteries.

Source from HNU News

Translated by Han Yunsheng

Proofread by Kuang Xiaowen, Yang Jie