The liquid electrolytes in most batteries act as a conductive pathway for the movement of ions between the two electrodes of a battery during charge and discharge. However, over the course of battery charge/discharge cycles, dendrites – tendril-like deposits of ions – can build up that can ultimately short-circuit a battery, causing it to overheat or even catch fire.
Current battery designs attempt to avoid this by including one electrode made of graphite filled with lithium instead of pure lithium. However, this impacts energy storage capability to about one tenth that of batteries using pure lithium.
Now, say the researchers, by finding an electrolyte solution “recipe” that prevents the chemical process that causes dendrite formation, “a great increase in energy storage is possible because dendrite formation can be eliminated in pure lithium electrodes.” They found that nanodiamonds – diamond particles 10,000 times smaller than the diameter of a hair – “impose order” on the lithium ion deposition in the electrolyte solution so dendrites don’t form.
Used in the electroplating industry, nanodiamonds have been found to help make metal coatings more uniform due to their tendency to slide together to form a smooth surface when deposited. This same property, say the researchers, helps nanodiamond-attached lithium ions plate the electrode “in the same orderly manner as the nanodiamond particles to which they’re linked.”
The researchers report that mixing nanodiamonds into the electrolyte solution of a lithium ion battery slows dendrite formation to nil through 100 charge/discharge cycles. Initial results also show stable charge/discharge cycling for as long as 200 hours – enough for some industrial or military applications.
“It’s potentially game-changing, but it is difficult to be 100 percent certain that dendrites will never grow,” says Yury Gogotsi, PhD, Distinguished University and Bach professor in the College of Engineering. “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.”
The researchers see this as just the beginning of a process that could eventually see electrolyte additives – like nanodiamonds – widely used to produce safe lithium batteries with a high energy density. For more, see “Nanodiamonds suppress the growth of lithium dendrites.”
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