Upcycling of phosphogypsum waste for efficient zinc-ion batteries

Zinc metal is a promising anode material for next-generation aqueous batteries, but its practical application is limited by the formation of zinc dendrite. To prevent zinc dendrite growth, various Zn2+-conducting but water-isolating solid-electrolyte interphase (SEI) films have been developed, however, the required high-purity chemical materials are extremely expensive. In this work, phosphogypsum (PG), an industrial byproduct produced from the phosphoric acid industry, is employed as a multifunctional protective layer to navigate uniform zinc deposition. Theoretical and experimental results demonstrate that PG-derived CaSO4·2H2O can act as an artificial SEI layer to provide fast channels for Zn2+ transport. Moreover, CaSO4·2H2O could release calcium ions (Ca2+) due to its relatively high Ksp value, which have a higher binding energy than that of Zn2+ on the Zn surface, thus preferentially adsorbing to the tips of the protuberances to force zinc ions to nucleate at inert region. As a result, the [email protected] anode achieves a high Coulombic efficiency of 99.5% during 500 cycles and long-time stability over 1000 hours at 1 mA cm−2. Our findings will not only construct a low-cost artificial SEI film for practical metal batteries, but also achieve a high-value utilization of phosphogypsum waste.