A Water-Based Battery Survived 60,000 Fast-Charge Cycles

A water-based battery chemistry has passed an unusually long laboratory endurance test. Researchers led by Flinders University report that a zinc-iodine cell retained useful performance through more than 60,000 rapid charge-discharge cycles by trapping troublesome iodine compounds inside a polymer made from cyclodextrin.

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More than 60,000 laboratory cycles were recorded at a capacity of 150 mAh per gram and a three-minute charge rate.

A molecular cage keeps iodine where it belongs

Zinc-iodine batteries use water in their electrolyte, reducing the flammability concern associated with common organic electrolytes. Their persistent weakness is the polyiodide shuttle: reactive iodine species dissolve, travel away from the cathode and trigger capacity loss or corrosion.

The team built the cathode around a cross-linked polycyclodextrin network. Cyclodextrins are ring-shaped sugar molecules whose cavities can temporarily hold polyhalide ions. The binding is strong enough to restrain them, but not so strong that the battery reaction stops.

Experiments and computer modelling indicated that the cavity size and water-repelling interior produced the required balance. The chemistry supported two-electron storage at roughly 205 mAh per gram and four-electron storage reaching 365 mAh per gram under the reported test conditions.

Fast charging came with a capacity trade-off

The endurance headline describes one particular operating mode. At a three-minute charge and 150 mAh per gram, cells exceeded 60,000 cycles. A slower seven-minute charge delivered about 200 mAh per gram for 8,000 cycles at 1.3 to 1.4 volts.

That distinction matters because cycle records obtained at high current and modest material loading do not automatically predict the lifetime of a large battery. NewTqnia previously covered how a promising sodium cell still required laboratory validation after computational screening, and why fast charging is only one part of proving a practical battery.

What happens next

Flinders University says the group is working with industry to build a prototyping platform. The next persuasive evidence would come from larger pouch or stacked cells with realistic iodine loading, limited excess electrolyte and repeated testing under changing temperatures and charge rates.

If the polymer keeps working at that scale, zinc-iodine batteries could become useful for stationary storage where weight matters less than cost, fire resistance and long service life. For now, the 60,000-cycle figure describes a carefully controlled cell, not a battery ready to sit beside a solar farm.