Water-based gel electrolyte
In the final step, the scientists stacked the two current collectors with the applied electrodes on top of each other, separated by a barrier layer similar to a picture frame, while the gap in the frame was filled with the electrolyte gel.
N
iederberger emphasises that this gel is environmentally more friendly than the commercial electrolytes: “Liquid electrolyte in today’s batteries are flammable and toxic.” In contrast, the gel electrolyte that his doctoral student Chen developed contains water with a high concentration of a lithium salt, which not only facilitates the flow of lithium ions between cathode and anode while the battery is charging or discharging, but also keeps the water from electrochemical decomposition.
The scientists joined the various parts of their prototype together with adhesive. “If we want to market the battery commercially, we’ll have to find another process that will keep it sealed tight for a longer period of time,” Niederberger says.
Numerous potential applications
More and more applications for a battery like this are emerging every day. Well-known manufacturers of mobile phones are vying with each other to produce devices with foldable screens. Other possibilities include rollable displays for computers, smartwatches and tablets, or functional textiles that contain bendable electronics – and all of these require a flexible power supply. “For instance, you could sew our battery right into the clothing,” Niederberger says. What’s important is, in the event of battery leakage, to ensure that the liquids that come out cause no damage. This is where the team’s electrolyte offers a considerable advantage.
However, Niederberger stresses that more research is necessary to optimise the flexible battery before they consider commercialising it. Above all, the team has to increase the amount of electrode material it can hold. A new doctoral student has recently begun refining the stretchable power supply. The inventor of the initial prototype, Xi Chen, returned to his homeland of China after completing his doctoral thesis to take up a new job – as a consultant for the battery industry.