Researchers Demonstrate a Safe, Cheap, Flexible Water-Based Battery for Better Wearables
Able to self-heal if cut, resistant to fire, and bendable back to 180 degrees, these batteries show real promise for future wearables.
A team of researchers from the Guilin University of Technology, the Huazhong University of Science and Technology, Anhui University, and the Hubei University of Automotive Technology have developed a new type of battery for wearable devices — which, they claim, is safer, cheaper, and more flexible than current solutions: a self-healing aqueous micro battery (AMB).
"Up till now, sadly, AMBs have not lived up to their potential," claims co-lead researcher Ke Niu of the team's work. "To be able to be used in a wearable device, they need to withstand a certain degree of real-world bending and twisting. But most of those explored so far fail in the face of such stress."
The problem that has stopped aqueous batteries, which use a water-based electrolytic solution, from being commonplace in wearables before is that metallic compounds in the electrolyte react strongly with the metal in the electrodes and limit their performance. "So we started investigating the possibility of non-metallic charge carriers," co-lead Junjie Shi explains, "as these would not suffer from the same difficulties from interaction with the electrodes."
The result is a battery that incorporates ammonium salts into a polyvinyl alcohol (PVA) hydrogel, with a titanium carbide anode and a carbon nanotube matrix with manganese dioxide serving as the cathode. All together, the battery delivers the advantages of AMBs — including being self-healing if cut and resistant to fire if punctured — while being flexible enough for use in wearables.
The team's prototypes delivered a 82.48µWh/cm⁻² energy and 3.09mw/cm⁻² power density, claimed by the researchers to be "excellent" with respect to competing designs, with with an 81.67 per cent capacity retention after 3,000 charge-discharge cycles. In flex testing, the batteries retained 95.68 per cent of their capacity through 180-degree bending, and 94.16 per cent after ten self-healing cycles.
The team's work has been published in the journal Nano Research Energy under open-access terms; the researchers have said they are currently working on refining the prototype as part of preparations into commercial production.