New research from SLAC National Accelerator Laboratory, Menlo Park, CA, could help remove a major barrier to developing lithium-sulfur and lithium-air batteries. The SLAC engineering team discovered that adding two chemicals to a lithium metal battery's electrolyte prevents the formation of dendrites, “fingers” of lithium that pierce the barrier between the battery’s halves and cause electrical shorts, overheating, and fires. The engineers discovered that adding both chemicals, in specific amounts, stopped lithium dendrite formation and the lithium metal electrode acquired a stable protective coating that improved the battery’s performance.
Coin cell batteries, similar to the ones that power calculators, were developed. The researchers added various concentrations of two chemicals – lithium polysulfide and lithium nitrate – to the ether-based electrolyte. The team then ran the batteries through many charge/discharge cycles, took them apart, and examined the electrodes. An electron microscope and an X-ray technique revealed their morphology and chemical composition.
In tests, batteries with both of the added chemicals operated at 99 percent efficiency after more than 300 charge-discharge cycles, compared to significantly decreased efficiency after 150 cycles for batteries treated with lithium nitrate alone, said Fiona (Weiyang) Li, a postdoctoral researcher in the lab and first author of the paper.
