Future oriented: Batteries are typically rigid blocks, making it difficult to design small, flexible, and wearable electronics around them. Researchers are beginning to tackle the problem by rethinking the elements used to make batteries, resulting in thin, flexible materials that can reliably retain electricity after repeated stretching or compression.
Two groups of researchers recently published studies on the possibility of designing flexible batteries almost simultaneously. Although they are unrelated, the papers describe similar prototypes.
The American Chemical Society reports A team from Nanjing University has designed a lithium-ion battery whose components can stretch up to 5,000% of their original length. In addition, the battery remains in good condition for about 70 full charge cycles.
According to researchersOther batteries have attempted to achieve flexibility by folding strong materials like paper or weaving them into conductive fabric. However, these batteries can be difficult to manufacture or lose their charge due to components that weaken from repeated stretching and bending.
The researchers solved the problem by going further and making each part of the battery elastic. The electrodes essential to the technology include a stack of conductive paste, silver nanowires, carbon black, polydimethylsiloxane, lithium salt, electrode film and protective coating. A solid, rubber-like layer forms when activated by light.
Although there is still room for improvement, this material could allow connected objects and implants to better adapt to users’ movements. A team from the University of Cambridge published another approach to the problem on the same day as the Nanjing researchers.
This study accomplished It is a gelatinous material that can retain a charge and return to its original shape after being crushed or stretched up to 10 times its original length. The central component – hydrogels – is mostly water but has properties that allow researchers to manipulate their mechanical attributes.
By changing the salt content of the hydrogels, they become more adhesive and stronger, increasing their charge and allowing them to stretch without losing their charge. The researchers could potentially modify the material’s properties to match those of human tissue, making it ideal for powering electrical implants. Tests on living organisms are planned.
The design of the Cambridge study draws heavily on the biological structure of electric eels, which use special organs to shock and stun their prey. Early studies of electric eels in the 18th century also contributed to inspire the invention of the first electric battery in 1800.
Photo credit: American Chemical Society