Scientists tame rogue protons to supercharge water batteries, achieve 500 rapid cycles

A new 2D conductive metal–organic framework (MOF) electrode improves both energy capacity and charging speeds in a safe, low-cost aqueous zinc-ion battery. The new electrode material boosts performance by storing zinc ions and protons sequentially. This study proves that ion storage order can be precisely manipulated through molecular-level engineering. “This study demonstrates that protons, previously regarded as ‘troublemakers’ that could degrade battery performance, can instead be used to store more energy. We expect that applying this principle to various electrode materials will lead to the development of batteries capable of rapidly storing larger amounts of energy,” said Professor Sarah S. Park from KAIST. Sequential ion storage Aqueous zinc-ion batteries use water-based electrolytes that enable ions to flow freely inside the cell. Water-based zinc-ion batteries have long teased engineers. Inexpensive and non-flammable, these water-based batteries offer a safer alternative to lithium-ion systems for large-scale grid storage. But a major challenge has been that these batteries could not hold enough energy or charge fast enough. The culprit was often identified as rogue protons. While nimble, these tiny particles formed performance-choking surface byproducts whenever they rushed into the electrode alongside bulky zinc ions. Battery scientists dubbed them “troublemakers” and spent years trying to shut them out. The KAIST team took the opposite path. Led by Professor Park from the Department of Chemistry, the researchers engineered a novel electrode material, a two-dimensional metal–organic framework known as Cu₃(HHTATP)₂. A metal–organic framework is a porous microscopic architecture formed by connecting metal ions with organic molecules. A voltage-sensitive gatekeeper was created by embedding specific amine functional groups directly inside the material’s tiny pores. Order mattered. At higher voltages, the material lets the heavy, slow-moving zinc ions park inside the electrode structure first. Only as the voltage drops do the amine groups activate, inviting the ultrafast protons to swoop in and pack the remaining spaces. When the zinc ions are already safely in place, the protons cannot cause their usual chaos. The process optimizes electrode space much like filling a bottle with large pebbles first and then trickling fine sand into the remaining gaps. Notably, the electrode achieves maximum storage efficiency without overcrowding by first packing the larger zinc ions and following with the smaller protons. Fast-charging retention In testing, the experimental battery delivered a capacity of 368.7 mAh g⁻¹. Simply put, a tiny amount of this material can hold a massive amount of power. Even when forced to charge and discharge 16 times faster, it retained nearly half its capacity (46.9 percent) and survived over 500 rapid cycles without breaking down. Advanced X-ray analysis confirmed that the electrode reliably repeats this two-step storage process, inserting zinc ions first and then adding protons. The development bridges the long-standing gap between high energy capacity and rapid charging in porous battery materials. “It presents a new direction for developing next-generation aqueous zinc-ion batteries by demonstrating that the storage sequence of different ions can be controlled through molecular-level design,” the researchers noted. Designed specifically for stationary renewable storage rather than electric vehicles, water-based zinc batteries prioritize safety and low cost over weight. The tech offers a vastly safer and more sustainable solution for mass-producing grid-scale energy storage by replacing toxic, scarce metals and flammable solvents with non-toxic, eco-friendly materials. This design strategy paves the way for safe, economical water-based batteries that charge rapidly without sacrificing storage capacity. The research was officially published in the international chemistry journal Chem. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.