- Scientists always knew that lithium metal could revolutionize batteries, but they have one fatal flaw: they often short circuit.
- No one knew why this happened – until now.
- Now scientists can build better lithium metal batteries to ultimately produce more electric vehicles.
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If you’re looking for an anode material for your next-generation battery, you can’t do much better than lithium metal. Due to its high capacity, low density and non-flammability, lithium metal batteries could represent an absolute breakthrough for electric vehicles and the green technology revolution in general.
There’s just one problem: lithium metal batteries have a tendency to short circuit due to tiny cracks in the ceramic electrolyte called dendrites.
The quest to find out Why this happening (and designing a battery that bypasses this unfavorable outcome) is something of a holy grail for materials scientists – and the scientific world may have found its Galahad.
This week, researchers from Stanford University and the SLAC National Accelerator Laboratory revealed evidence of why these dendrites form in lithium metal batteries.
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Previous theories suggested that an accidental flow of electrons or some other chemical mishap could be the cause of the battery’s failure. But after conducting more than 60 experiments, the researchers found that tiny “nanoscopic” cracks in the ceramic solid electrolyte, some as wide as just 20 nanometers (a human hair is 80,000 nanometers, by the way), occur when they’re under pressure during fast charging.
These cracks allowed a lithium-metal “bridge” to form between the anode and cathode, causing a short circuit. The results have been published in the journal Nature Energy.
“Just a slight nick, bending, or twisting of the batteries can cause nanoscopic cracks in the materials to open and allow lithium to enter the solid electrolyte, causing it to short circuit,” study co-author William Chueh said in a statement. “Even dust or other impurities introduced during production can create enough stress to cause failure.”
The researchers combined an electrical probe and an electrolyte to create a miniature battery in an attempt to understand why lithium settled in certain areas and caused short circuits. At rest, the lithium anode performed as designed, but any nick, bend, or twist (along with dust particles collected during the manufacturing process) increased the likelihood of failure.
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Lead co-author Xin Xu compared the process to pits. Just as car tires stomp rain and snow into tiny imperfections that create an ever-growing structural defect, the same thing happens in lithium metal batteries (albeit in a a lot of smaller scale).
Thankfully, this isn’t a death knell for the future of lithium metal – in fact, it’s great news.
Now engineers already hard at work designing lithium-metal batteries can consider these findings to work around these shortcomings. The authors of the paper also mention that they are now investigating ways to strengthen the electrolyte during production, as well as developing ways to coat the ceramic barrier so that it repairs itself when it occurs.
In 2019, the same Stanford lab developed a method to make lithium metal batteries retain 85 percent charge after 160 cycles — a big improvement over the previously reported 30 percent.
“These improvements all start with a single question: why?” says co-author Teng Cui. “Once we know that, we can improve things.”
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Now researchers ask the question of Why, the general question about the future of lithium metal is less like “if” and more like “when.”
