Dendrites are the enemy of lithium-ion batteries. As ions transfer back and forth between the anode and the cathode in those batteries, they can leave behind tendril-like buildups called dendrites. Similar to stalactites that form inside a cave, these battery buildups (dendrites) are one of the main causes of lithium battery malfunction.
Lithium is the ideal material for cathodes in terms of energy storage potential, but pure lithium cathodes suffer from significant dendrite formations. To solve that issue, battery makers have started blending the lithium with graphene. The resulting compound inhibits the formation of dendrites but also significantly reduces the energy storage capacity of the cathode. A pure lithium cathode is capable of storing 10 times as much electrical energy as a cathode made of lithium and graphene.
Researchers at Drexel University, working closely with colleagues at Tsinghua University in Beijing and Hauzhong University of Science and Technology in Wuhan, China, may have found a way to inhibit the formation of dendrites and allow cathodes to be made with a higher percentage of lithium. Their discovery involves adding nanosized diamonds to the electrolyte inside the battery.
On August 25, Professor Yury Gogotsi and his research team from the Department of Materials Science and Engineering at Drexel published their research in the journal Nature Communications. Entitled “Nanodiamonds Suppress Growth of Lithium Dendrites,” it describes how diamond particles 10,000 times smaller than the diameter of a human hair curtail the electrochemical deposits that form dendrites.
“Battery safety is a key issue for this research,” Gogotsi said. “Small primary batteries in watches use lithium anodes, but they are only discharged once. When you start charging them again and again, dendrites start growing. There may be several safe cycles, but sooner or later a short-circuit will happen. We want to eliminate or, at least, minimize that possibility.”
Nanodiamonds are used in the electroplating industry to make metal coatings more uniform. The researchers found this property to be exceedingly useful for eliminating dendrite formation. In the paper, they explain that mixing nanodiamonds into the electrolyte solution of a lithium-ion battery virtually eliminates dendrite during the first 100 charge/discharge cycles.
Like all breakthroughs in the laboratory, the new technology may be years away from finding its way into commercial applications. The researchers will need to test a large number of battery cells over a long enough period of time under various physical conditions and temperatures to ensure that dendrite creation is actually eliminated.
“It’s potentially game-changing, but it is difficult to be 100 percent certain that dendrites will never grow,” Gogotsi said. “We anticipate the first use of our proposed technology will be in less critical applications — not in cell phones or car batteries. 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.”