PNNL researchers have discovered that dissolving a simple sugar into the electrolyte in a flow battery boosts peak power output by a remarkable 60%. What's more, after being constantly cycled for a year, the battery lost almost none of its capacity.

Flow batteries – well, most flow batteries, anyway – aren't the kinds of things you'd expect to find in a car or laptop. They're typically best suited to large, long-duration energy storage jobs, so there's been a lot of interest in them in recent years, as cities struggle to work out how to smooth out the daily, seasonal and weather-related intermittency of renewable energy sources.

Typically, they consist of two liquids, an anolyte and a catholyte, that are stored separately, then pumped through on either side of an ion-selective membrane to create a current when energy is needed. This confers certain advantages; you can "refuel" your system by swapping out depleted electrolyte for charged electrolyte, for example – or you can charge it back up using grid power to reverse the discharge cycle.

Pacific Northwest National Laboratory researchers were the first to try dissolving a sugar called β-cyclodextrin into the anolyte of the cell, hoping it would help with a completely different problem. They weren't expecting it to supercharge the battery: “We were looking for a simple way to dissolve more fluorenol in our water-based electrolyte,” said Ruozhu Feng, first author on a new study. “The β-cyclodextrin helped do that, modestly, but it’s real benefit was this surprising catalytic ability.”