Instead of creating destructive “fingers” of lithium metal, known as dendrites, when lithium polysulfide is added, harmless pancake-like deposits form instead. (W. Li et al, Nature Communications)
The problem with lithium metal laptop batteries heating up and bursting into flame has been addressed by researchers in the US.
The researchers at the Department of Energy’s SLAC National Accelerator Laboratory have discovered that adding two chemicals to the electrolyte of a lithium metal battery prevents the formation of dendrites – “fingers” of lithium that pierce the barrier between the battery’s halves, which can cause it to short out and overheat.
The findings, published in Nature Communications, could also help remove a major barrier to developing higher capacity lithium-sulphur and lithium-air batteries for use in electric cars.
“Because these batteries would be much lighter than today’s rechargeable batteries, they have a lot of potential for extended-range electric vehicles,” said Yi Cui, an associate professor at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory.
“But one of the things that’s been holding them back is their tendency to form dendrites, which are also the culprit behind overheating and occasional fires in today’s lithium-ion batteries.”
Dendrites form when a battery electrode degrades, and metal ions become deposited on the electrode’s surface. When those finger-like deposits elongate until they penetrate the barrier between the two halves of the battery, they can cause electrical shorts, overheating and fires.
The research has found that by adding chemicals to the electrolyte it can prevent dendrite formation.
There two chemicals were lithium nitrate, known to improve battery performance, and lithium polysulfide, which has been thought to have negative effects. But the research team found that when combined together the chemicals could potentially react with lithium metal to form a stable, solid interface between the electrode and the electrolyte.
In tests, batteries with both chemicals added 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 Cui’s lab and first author of the paper.
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