Solid-state sodium-ion batteries are far safer than conventional lithium-ion batteries, which pose a risk of fire and explosions, but their performance has been too weak to offset the safety advantages. Researchers Friday reported developing an organic cathode that dramatically improves both stability and energy density.
The improved performance, reported in the journal Joule, is related to two key findings:
• The resistive interface between the electrolyte and cathode that commonly forms during cycling can be reversed, extending cycle life, and
• The flexibility of the organic cathode allowed it to maintain intimate contact at the interface with the solid electrolyte, even as the cathode expanded and contracted during cycling.
Yan Yao, associate professor of electrical and computer engineering at the University of Houston and corresponding author of the paper, said the organic cathode -- known as PTO, for pyrene-4,5,9,10-tetraone -- offers unique advantages over previous inorganic cathodes. But he said the underlying principles are equally significant.
"We found for the first time that the resistive interface that forms between the cathode and the electrolyte can be reversed," Yao said. "That can contribute to stabilityandlonger cycle life." Yao also is a principal investigator at the Texas Center for Superconductivity at UH. His research group focuses on green and sustainable organic materials for energy generation and storage.