Scientists from Stanford University and the SLAC National Accelerator Laboratory have broken the previous record of energy storage by using the “yolk-shell” design in lithium-ion battery with sulfur cathode.
This research has been published online in the January 8th issue of the journal Nature Communications.
With this design, scientists stored five times more energy in the sulfur cathode of a rechargeable lithium-ion battery than usually is stored in the conventional batteries. Not only this but the cathode efficiency was also much improved with high level of performance, i.e. Coulombic efficiency of 98.4%, even after 1,000 charge/discharge cycles while today’s lithium ion batteries retain only 80% of the starting capacity after 500 charge/discharge cycles.
For those who are not well aware about the working of lithium-ion batteries; it works by the movement of lithium ions between the anodes (negative terminal of battery) and cathodes (positive terminal of the battery). While charging the battery, ions and electrons move towards the anode developing an electrical potential to give power to the devices while electrons and ions move towards the cathode while discharging the battery.
In the research, scientists developed cathode composed of nanoparticles made up of minute amount of sulfur with a hard shell of porous titanium dioxide like an egg yolk in an eggshell. Scientists leave a tiny space between the yolk and the shell, where egg-white would be present, so that the sulfur would be able to expand. During discharging of the battery, the lithium ions move through the shell and bind to the sulfur that expands to fill the space and the shell protects the sulfur-lithium intermediate compound from electrolyte solvent that would dissolve it.
The embedded cathode particles are just 800 nanometers in diameter i.e. one hundredth of the diameter of the human hair.
“It basically worked the first time we tried it,” Cui said in a statement. “The sulfur cathode stored up to five times more energy per sulfur weight than today’s commercial materials.
“After 1,000 charge/discharge cycles, our yolk-shell sulfur cathode had retained about 70 percent of its energy-storage capacity. This is the highest performing sulfur cathode in the world, as far as we know,” he said. “Even without optimizing the design, this cathode cycle life is already on par with commercial performance. This is a very important achievement for the future of rechargeable batteries.”
Researchers have planned to work on the combination of yolk-shell sulfur cathode with a yolk-shell silicon anode to check for the efficiency of the battery.
This research has been funded by DOE Office of Basic Energy Sciences through SLAC’s Laboratory Directed Research and Development Program.
Wei Seh, Z., Li, W., Cha, J., Zheng, G., Yang, Y., McDowell, M., Hsu, P., & Cui, Y. (2013). Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries Nature Communications, 4 DOI: 10.1038/ncomms2327