Ions move between two electrodes—a cathode and an anode—during a lithium-ion battery’s charge and discharge cycles. However, as these lithium ions transfer back and forth, they leave behind a buildup of microscopic fibers called dendrites. This residue can accumulate on the electrodes, and eventually cause the electrical current passing through them to short-circuit, and the battery to overheat or catch fire. A recent discovery—the addition of nanodiamonds to the battery’s electrolyte—may prevent that.
Dendrite formation is a major concern for the energy storage industry. By blending lithium with graphene for electrode production, battery makers have successfully inhibited the formation of dendrites. However, the blend also significantly reduces the energy storage capacity of the batteries.
Inside the ion exchange
In order to better understand the dynamics taking place, a team of researchers at the University of Michigan recently cut open a next-generation lithium battery and created a window so that they were able to view the growth of the microscopic lithium strands.
The University of Michigan team found that dendrites grew as lithium accumulated on the surface of the electrode and would shrink when the cycle reversed. They also discovered that the small pits that formed on the electrode when the lithium was removed became the site of dendrites during the next cycle.
“As researchers try to cram more and more energy in the same amount of space, morphology problems like dendrites become major challenges,” explained Kevin Wood, a postdoctoral researcher and part of the University of Michigan team. “If we want high energy density batteries in the future and don’t want them to explode, we need to solve the dendrite problem.”
In a paper published recently in Nature Communications, collaborating research teams from Drexel University, Tsinghua University in Beijing, and Hauzhong University of Science and Technology in Wuhan, China, explain that they have discovered a way to inhibit the formation of dendrites with cathodes made with a higher percentage of lithium. By adding nano-sized diamond particles—10,000 times smaller than the diameter of a human hair—to the electrolyte inside the battery, they were able to inhibit the electrochemical deposits that form dendrites.
The team reported that, “…nanodiamonds work as an electrolyte additive to co-deposit with lithium ions and produce dendrite-free lithium deposits.”
Though the research is likely years away from any real-world application, the team’s findings may enable pivotal technological advancements that enhance both energy storage capacity and battery safety.