[Image above] Drexel researchers added nanodiamonds to a lithium battery, preventing dendrite formation. Credit: Drexel University and Tsinghhua University
Scientists have been working to improve lithium-ion battery technology for years. And with the recent spate of fires from smartphones, hoverboards, and laptops, I’m fairly certain that research in this area has ramped up significantly. A quick search of Ceramic Tech Today yields dozens of articles, all describing some of the latest achievements in lithium battery research.
Now, a new development has emerged from a research team at Drexel University that would significantly reduce the chances of a battery malfunction. Yury Gogotsi, Distinguished University and Bach professor at the College of Engineering, and his team of researchers from the Department of Materials Science and Engineering developed a process using nanodiamonds to curb the growth of dendrites in lithium batteries.
Dendrites are those pesky growths—like unwanted vines growing in your garden—that form inside a battery due to the constant flow of ions when the battery is in use or being charged. Over a period of time, dendrites can grow enough to break through the battery’s separator, joining positive and negative into one large short-circuited fire.
Nanodiamonds, carbon-based particles 10,000 times narrower than a human hair, have found their calling in a number of applications, including automotive lubricants, polishing compounds, and even skincare products. In fact, Gogotsi has already been experimenting with nanodiamonds for drug delivery applications.
According to Drexel’s news release, one way to minimize dendrite formation is to use a lithium-filled graphite electrode, as opposed to a pure lithium electrode. Graphite prevents dendrite formation but doesn’t hold as much energy as pure lithium. So your choice is either no dendrite formation and a battery with less energy storage, or a battery with higher energy storage and the chance of dendrite formation.
Gogotsi and team solved this dilemma by adding nanodiamonds to the battery’s electrolyte. Because lithium ions like nanodiamonds, they join together in an orderly manner as they’re plating the electrode. According to the paper, “lithium prefers to adsorb onto nanodiamond surfaces with a low diffusion energy barrier, leading to uniformly deposited lithium arrays.”
Dendrite formation (left column) can result in lithium battery malfunctions. Adding nanodiamonds to the electrolyte creates order and prevents dendrite formation. Credit: Drexel University.
After 100 cycles of charging and discharging, the researchers found that nanodiamonds contributed to the formation of uniform lithium ion deposits and suppression of dendrite formation. This is a huge breakthrough for lithium-ion batteries—however, Gogotsi believes this is only the beginning of exploring electrolyte additives.
“It’s potentially game-changing, but it is difficult to be 100% certain that dendrites will never grow,” Gogotsi says in the release. “To ensure safety, additives to electrolytes, such as nanodiamonds, need to be combined with other precautions, such as using non-flammable electrolytes, safer electrode materials, and stronger separators.
“It’s important to remember that additives suppressing dendrite growth should be combined with more sturdy separators and other safety features to exclude the chance of a short-circuit,” he writes in an email.
Besides the obvious—smartphones and laptops—Gogotsi suggests the process can initially be used in less critical applications. “New materials and technologies are usually introduced in applications that have smaller volumes and more tolerance to risk,” he adds. “We envision that this approach can be used in small coin cell batteries, in applications that require a shorter cyclic lifetime (home tools), or military applications where much better performance justifies some risks. When proven safe and scaled-up during use in niche applications, the technology may spread out to large-volume applications as well.”
The paper, published in Nature Communications, is “Nanodiamonds suppress the growth of lithium dendrites” (DOI: 10.1038/s41467-017-00519-2).