Based on a lithium-manganese-oxide cathode, the team believe this research could enable smart phones and battery-powered automobiles to last more than twice as long between charges.
"This battery electrode has realised one of the highest-ever reported capacities for all transition-metal-oxide-based electrodes. It's more than double the capacity of materials currently in your cell phone or laptop," explains Professor Christopher Wolverton of Northwestern University, who led the study. "This sort of high capacity would represent a large advancement to the goal of lithium-ion batteries for electric vehicles."
By replacing the traditional cobalt with less expensive manganese, the team says it developed a cheaper electrode with more than double the capacity. But it was not without its challenges: the battery's performance degraded so significantly within the first two cycles that researchers did not consider it commercially viable. They also did not fully understand the chemical origin of the large capacity or the degradation.
After composing a detailed, atom-by-atom picture of the cathode, the team discovered the reason behind the material's high capacity: it forces oxygen to participate in the reaction process. By using oxygen - in addition to the transition metal - to store and release electrical energy, the battery has a higher capacity to store and use more lithium.
The Northwestern team then turned its focus to stabilising the battery in order to prevent its swift degradation.
"Armed with the knowledge of the charging process, we used high-throughput computations to scan through the periodic table to find new ways to alloy this compound with other elements that could enhance the battery's performance," says Zhenpeng Yao, co-first author of the paper.
The computations pinpointed two elements: chromium and vanadium. The team predicts that mixing either element with lithium-manganese-oxide will produce stable compounds that maintain the cathode's unprecedented high capacity.
The team now intends to experimentally test these theoretical compounds in the laboratory.
