Lithium batteries only rarely burst into flames. However, considering the fact that they are ubiquitous in phones, laptops and a host of other consumer electronics, it's certainly an issue worth addressing.
Scientists have already made significant advances in improving the safety of current lithium batteries, and now, a group of researchers at Stanford University are turning their attention to making the next generation of lighter, more efficient lithium batteries as safe as possible before they reach the market. The lithium in these next-generation batteries tends to form spikes — known as dendrites — that pierce through parts of the battery, causing it to overheat and sometimes even catch fire. However, the researchers found that a way to make the lithium in these next-generation batteries form harmless pancake-like structures instead of spikes.
"Because these batteries would be much lighter than today's rechargeable batteries, they have a lot of potential for extended-range electric vehicles," Yi Cui, an associate professor at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, said in a statement. "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."
Next-generation lithium-sulfur or lithium-air batteries can store as much as 10 times more energy for their weight compared with those currently used in consumer electronics and electric vehicles. Adding just two chemicals to the mix within the batteries flattened the finger-like dendrites that tend to spark fires, researchers report in a study published in the journal Nature Communications.
One of the chemicals is lithium-nitrate, a compound that researchers have already explored extensively as a way to improve battery performance. Lithium-polysulfide, the second chemical, has gotten attention from scientists in the past for the opposite reason — it forms as a by-product of reactions in the battery and can destroy it as it builds up.
"We had been doing experiments all along with these two chemicals in there, but this was the first time we looked at the synergistic effect," lead study author Fiona (Weiyang) Li said in a statement. "This is a really exciting observation."
The two halves of a battery, the anode and the cathode, must remain separate for the battery to function properly. However, when the lithium in the anode forms spiky dendrites, they can pierce through the separator and cause the battery to short circuit. With the addition of the right amounts of these two chemicals, the lithium in the anode instead forms a bunch of flat, pancake-like structures that serve as a protective layer instead of the damaging dendrites.
"This does not completely solve all the problems associated with lithium metal batteries, but it's an important step," Li said in a statement.
Next, the researchers plan to scale up this design to see if their approach works in more practically-sized batteries.
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