In a new study published in Angewandte Chemie, scientists develop a thin, flexible, li-ion battery with self-healing functions that can be safely worn on the body.
Even after completely breaking apart, the battery can grow back together without significant impact on its electrochemical properties.
Currently, li-ion batteries for wearable electronics can be bent and rolled up without any problems, but they can break when they are twisted too far or accidentally stepped on–which can happen often when being worn.
This damage not only causes the battery to fail, but also causes a safety problem: Flammable, toxic, or corrosive gases or liquids may leak out.
Now a team of scientists developed a new family of li-ion batteries that can overcome such accidents due to their amazing self-healing powers.
Fudan University, the Samsung Advanced Institute of Technology, and the Samsung R&D Institute China conducted the study.
In order for a complicated object like a battery to be self-healing, all of its individual components must also be self-healing.
The electrodes in these batteries consist of layers of parallel carbon nanotubes. Between the layers, the scientists embedded the necessary lithium compounds in nanoparticle form.
Different from previous li-ion batteries, the lithium compounds cannot leak out of the electrodes, either while in use or after a break.
The thin layer electrodes are each fixed on a substrate of self-healing polymer. Between the electrodes is a novel, solvent-free electrolyte made from a cellulose-based gel with an aqueous lithium sulfate solution embedded in it.
This gel electrolyte also serves as a separation layer between the electrodes.
After a break, it is only necessary to press the broken ends together for a few seconds for them to grow back together.
Both the self-healing polymer and the carbon nanotubes “stick” back together perfectly. The parallel arrangement of the nanotubes allows them to come together much better than layers of disordered carbon nanotubes.
The electrolyte also poses no problems. Whereas conventional electrolytes decompose immediately upon exposure to air, the new gel is stable.
Free of organic solvents, it is neither flammable nor toxic, making it safe for this application.
The capacity and charging/discharging properties of a battery “armband” placed around a doll’s elbow were maintained, even after repeated break/self-healing cycles.
News source: Wiley.
Figure legend: This Knowridge.com image is credited to Huisheng Peng.