For safer batteries just add diamonds, scientists say

Drexel University scientists have suggested that to make lithium-ion batteries safer, nanodiamonds can be added to the battery recipe to curtail the electrochemical deposition, called plating, which is known to cause hazardous short-circuiting of lithium ion batteries.

Scientists at the university have published their work entitled “Nanodiamonds Suppress Growth of Lithium Dendrites” in the journal Nature Communications wherein they have described a process by which nanodiamonds – tiny diamond particles 10,000 times smaller than the diameter of a hair – can prevent plating and thereby hazardous short-circuiting of lithium ion batteries.

The team explains that as batteries are used and charged, the electrochemical reaction results in the movement of ions between the two electrodes of a battery, which is the essence of an electrical current. Over time, this repositioning of ions can create tendril-like buildups — almost like stalactites forming inside a cave. These battery buildups, called dendrites, are one of the main causes of lithium battery malfunction. As dendrites form inside the battery over time, they can reach the point where they push through the separator, a porous polymer film that prevents the positively charged part of a battery from touching the negatively charged part. When the separator is breached, a short-circuit can occur, which can also lead to a fire since the electrolyte solution in most lithium-ion batteries is highly flammable.

To avoid dendrite formation and minimize the probability of fire, current battery designs include one electrode made of graphite filled with lithium instead of pure lithium. The use of graphite as the host for lithium prevents the formation of dendrites. But lithium intercalated graphite also stores about 10 times less energy than pure lithium. The breakthrough made by Gogotsi’s team means that a great increase in energy storage is possible because dendrite formation can be eliminated in pure lithium electrodes.

Scientists focused their work on making lithium anodes more stable and lithium plating more uniform so that dendrites won’t grow. They’re doing this by adding nanodiamonds to the electrolyte solution in a battery. Nanodiamonds have been used in the electroplating industry for some time as a way of making metal coatings more uniform. While they are much, much smaller — and cheaper — than the diamonds you’d find in a jeweler’s case, nanodiamonds still retain the regular structure and shape of their pricey progenitors. When they are deposited, they naturally slide together to form a smooth surface.

The researchers found this property to be exceedingly useful for eliminating dendrite formation. In the paper, they explain that lithium ions can easily attach to nanodiamonds, so when they are plating the electrode they do so in the same orderly manner as the nanodiamond particles to which they’re linked. They report in the paper that mixing nanodiamonds into the electrolyte solution of a lithium ion battery slows dendrite formation to nil through 100 charge-discharge cycles.

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