Tiny lithium-free battery leads charge

Researchers at Rice University have managed to build an ultra-slim, ultra-flexible battery that could be the key to powering smartwatches and fitness bands for longer and to creating folding phones.

Building a battery small enough to fit inside a wearable tech device, be it smartglasses or a smartwatch, isn't difficult. However, creating one small and light enough that can actually offer the user more than a few hours' continued use is still a huge challenge.

Likewise, Samsung and LG might have wowed the world with their first flexible-display smartphones this year, but until the battery that powers their screens is equally open to movement, new and exciting phone shapes and designs are still years away from becoming a reality.

What separates the cell created by the team lead by Rice chemist James Tour from other attempts is not its impressive size - it's a hundredth of an inch thick - but that it behaves like a lithium ion battery: it charges quickly, discharges slowly and is tough enough to survive 10 000 charging cycles. Yet, the battery is lithium-free.

The best materials for making batteries tend to be less than flexible and the best materials for making flexible cells tend not to offer a high storage capacity or the power to run something as big as a smartphone, for example.