Energy storage is a tricky problem. Renewable power sources like solar and wind are amazing, but they don't always produce energy when we need it. That's where batteries come in - to store the energy and make it available later. Yet, even the best options today have flaws.

Lithium-ion batteries are everywhere, from phones to massive grid systems. But they aren't perfect; there are safety concerns with risks like fires, in addition to limitations for large-scale, sustainable applications.

So, what else can we use? Well, that's where bromide-based aqueous flow batteries enter the picture. They're safer, cheaper, and easier to source. But, they're also a bit messy, well, until now, that is.

Scientists at the University of Wisconsin-Madison have devised a smart fix for the problems holding bromide batteries back. And it's all thanks to something they call "soft-hard zwitterionic trappers," or SH-ZITs. These tiny chemical additives address issues that have plagued bromide flow batteries for years.

Think of bromide as the underdog. It's cheap, abundant, and has serious potential for grid energy storage. But it's also trouble-prone. Bromide ions can pass through the membranes inside the battery, causing leaks and lowering efficiency. Sometimes, they clump together, forming an oily residue that ruins the solution. Worst of all, they can create toxic gas - a huge safety hazard.

Fixing these problems isn't easy. But Patrick Sullivan, Gyohun Choi, and Dawei Feng found a way. Working together, the team developed SH-ZITs. These additives stabilize bromide ions, keeping them dissolved in water and out of trouble. As a result, the batteries stay efficient and safe to use.

Here's what's exciting: Batteries with these additives don't break down. They keep working without a problem for months, where before they'd fail in a day. That's a massive improvement. The additives even prevent toxic gas formation, so the batteries are safer for everyone.

The team proved SH-ZITs can be produced at an industrial scale. That means this isn't just a science experiment; it's something we might see in real-world use soon.

Why should we care? Because we need better ways to store renewable energy. As the world shifts toward greener energy sources, storage will be key. Bromide batteries, supercharged with SH-ZITs, could fill that gap. They're safer than lithium-ion, and now, more reliable than ever before.

Sullivan, now CEO of a renewable energy company called Flux XII, is pushing this breakthrough closer to commercial use. Meanwhile, Choi and Feng continue their research, looking for even more ways to make these batteries better. Together, they're turning an idea into something that could reshape how we store and use energy.

This isn't the end of the story - far from it. But it's a big step forward. Safer, longer-lasting batteries could help renewable energy go further than we ever thought possible. More research is needed to ensure the technology is viable for real-world use with larger-grid scale system tests.

Reference: Choi, G., Sullivan, P., Lv, XL. et al. Soft-hard zwitterionic additives for aqueous halide flow batteries. Nature 635, 89-95 (2024). https://doi.org/10.1038/s41586-024-08079-4