Lithium-ion batteries are used in so many of our electronics these days from computers to smartphones to bigger things like electric vehicles. The technology has become the gold-standard for batteries because it can hold a lot of energy while also remaining relatively small and lightweight.
One of the downsides to the technology is that the battery can sometimes short out or catch on fire, a major concern when the battery packs are used in electric cars. Within the battery, dendrites -- little fingers of lithium -- may form and pierce the barrier between the battery's halves, which causes malfunctions and, sometimes -- though rarely -- the battery to burst into flame.
Researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have figured out a way to prevent these dendrites from forming, making the batteries far safer and paving the way for even better performing next-generation batteries like lithium-sulfur and lithium-air batteries that could store up to 10 times more energy per weight.
The researchers built coin cell batteries like the ones in calculators, remote controls and watches and added two chemicals -- lithium nitrate and lithium polysulfide -- to the electrolyte in various concentrations. They charged and discharged the batteries several times and then studied them with an electron microscope. After many different trials, they found the right amounts of each chemical that stopped the formation of dendrites, while harmless pancake-like deposits grew instead.
The SLAC said, "The lithium metal electrode acquired a stable coating that helped protect it from further degradation and actually improved the battery’s performance. 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."
“This is a really exciting observation,” said Fiona (Weiyang) Li, one of the Stanford University researchers. “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. This does not completely solve all the problems associated with lithium metal batteries, but it’s an important step.”
The next step is to build even larger-scale batteries, like those that would power an electric vehicle, with these chemical additives and see if they observe the same increase in safety and performance. A breakthrough like that could remove many of the fears that surround EV adoption.
The combination of chemicals may also work for electrodes made from metals like magnesium, calcium or aluminum that could lead to batteries that store much more energy without an increase in size or weight, leading to the extended-range vehicles of the future.