Abstract Although lithium-ion batteries are widely used in mobile devices ranging from mobile phones to notebook computers, and are the longest-lived ones in commercial batteries, lithium-ion batteries have suffered some crashes and fires due to short-circuits in mobile devices. In order to prevent more of these dangerous accidents...
Although lithium-ion batteries are widely used in mobile devices ranging from mobile phones to notebook computers, and are the longest-lived ones in commercial batteries, lithium-ion batteries have recently suffered some collapses and fires due to short-circuits in mobile devices. To prevent more of these dangerous accidents, researchers at Drexel University have developed a method to convert the electrolyte (a key component of most batteries) into a chemical that prevents the battery from causing similar disasters. Yury Gogotsi, a professor at the University of Drexel School of Engineering, and a research team in the Department of Materials Science and Engineering recently published a paper on the work of natural communication. In this paper, they describe the reduction of electrochemical deposition by electroplating through nanodiamonds - tiny diamond particles that are 10,000 times smaller than the hair diameter. This electrochemical deposition may cause a short circuit in the lithium ion battery.
With repeated use and charging of the battery, the electrochemical reaction causes ions to move back and forth between the two electrodes of the battery, which is the essence of current generation. Over time, the repositioning of this ion can produce an accumulation of tendrils like a stalactite formed in a hole. The accumulation of these batteries, called dendrites, is one of the main causes of failure of lithium-ion batteries.
Over time, as the dendritic structure inside the cell is formed, they can reach their point of passage through the separator, and this porous polymer film can effectively prevent the positively charged portion of the battery from contacting the negatively charged portion. When the separator is broken, a short circuit may occur and a fire may occur because the electrolyte solution in most lithium-ion batteries is highly flammable.
In order to avoid the formation of dendritic structures and reduce the probability of fire, the current battery electrode is an electrode made of lithium-filled graphite instead of pure lithium. The use of graphite as the main body of lithium can help prevent the formation of dendrites, but lithium-embedded graphite is about 10 times less energy than pure lithium. The breakthrough of the Gogotsi team means that energy storage can now be greatly increased by eliminating dendrite formation in pure lithium electrodes.
"Battery safety issues are the key to this research," Gogotsi said. “The small primary batteries in the watch use lithium anodes, but they can only be discharged once. When you charge again and again, the dendrites start to grow and there may be several safety cycles, but sooner or later a short circuit will occur, we want to eliminate Or at least minimize this possibility."
Gogotsi and his collaborators at Tsinghua University in Beijing and Hauzhong University of Technology in Wuhan, China, are focusing on making lithium anodes more stable and more uniform in plating, so as not to increase dendrites.
They do this by adding nanodiamonds to the electrolyte solution in the battery. Nanodiamonds have been used in the electroplating industry as a way to make metal coatings more uniform and have been used for some time. Although they are much smaller and cheaper than diamonds in the jeweler's case, nanodiamonds retain the regular structure and shape of expensive progenitor cells. As they deposit, they naturally slide together and form a smooth surface.
The researchers found that this property is very useful for eliminating dendrite formation. They explained in the article that lithium ions can easily attach to the nanodiamonds, so when the ions plate the electrodes, they do the same in the same way as the nanodiamond particles to which they are attached. It is mentioned in the report that nanodiamonds are mixed into the electrolyte of a lithium ion battery, and the dendritic structure is slowed down to zero by 100 charge-discharge cycles.
It's like a Tetris game: a bunch of mismatched blocks is equivalent to a dendrite in a dangerous close to "end of the game". Adding nanodiamonds to the mixture is like using code to slide each new block to the proper position to complete the line and prevent the formation of a threat tower.
Gogotsi pointed out that the discovery of their team was only the beginning of a process, and eventually found suitable electrolyte additives, such as nanodiamonds, which are widely used to produce safe lithium batteries with high energy density. The initial results have shown a stable charge and discharge cycle of up to 200 hours, which is sufficient for use in some industrial or military applications, but not long enough for batteries used in laptops or cell phones. Researchers also need to test large numbers of cells for long enough time under different physical conditions and temperatures to ensure that dendrites never grow.
Gogotsi said: "This may be a random change, but it is not entirely certain that dendrites will not grow." "We expect the first use of the proposed technology will be in less critical applications, not in mobile phones or cars. In batteries, to ensure safety, electrolyte additives such as nanodiamonds need to be combined with other precautions such as flame retardant electrolytes, safer electrode materials and stronger separators.
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