News piece for Materials Today from back in April – Vol. 16, No. 4. You can also see it in the shiny online issue of the magazine: http://digital.materialstoday.com/launch.aspx?referral=other&refresh=q02P1Na7Kr30&PBID=28728065-41ee-4ac6-90c0-c37a05ad0fa0&skip=
Suppressing Dendrite Growth Can Reduce Failure of Lithium Batteries
Scientists at Purdue University have demonstrated that it is possible to control dendritic growth in lithium, the main failure mechanism in lithium-ion batteries
The reliability of lithium-ion batteries came into sharp focus last year, when they were linked to fires on-board two Boeing aircraft. It has been suggested that battery failure, caused by an internal short circuit may have led to these fires. When lithium batteries are recharged, ions move through the electrolyte separating the battery’s two electrodes. This charge flow also draws material from the electrolyte and results in the formation of lithium dendrites on the positive electrode (anode) of the battery. These dendrites can grow so large that they span the distance between the electrodes; the moment the dendrite reaches the cathode, the battery fails. Prof R. Edwin García, a materials engineer at Purdue, describes a more worrying outcome: “If you have too much current going through the dendrites while the battery is being charged, the battery can catch fire.”
This had been thought to be an unavoidable characteristic of lithium batteries, the main limiting factor in their performance, and an obvious safety concern. But García’s team from Purdue have shown that, at least on paper, it is possible to control dendrite growth, leading to Li-ion batteries with improved performance and reliability. Their analytical theory may allow researchers to actively predict the early stages of dendrite formation.
The work, which appeared in the Journal of the Electrochemical Society, identified the various ways that lithium-ion batteries can fail during recharge, and suggested possible solutions to limit dendrite formation. For example, dendrites grow on very specific locations on the anode; one option may be to engineer the anode’s surface, so that instead of nucleating into beads (and then dendrites) the lithium wets the electrode surface evenly.
A potential outcome to this particular solution is a lithium battery that could charge in minutes rather than hours. Dendrites grow faster when exposed to the high voltages needed for fast recharging, which has limited the recharging speed of Li-ion batteries. Uniformly distributed lithium deposits may be less susceptible to these high voltages, so may finally make fast charging a reality.
This paper represents the first analytical approach to the issue of dendritic growth in lithium batteries, and if the suggestions are adapted by other research groups, may lead to a new generation of more reliable, safer Li-ion batteries.
Reference: Journal of the Electrochemical Society (2013) DOI: 0013-4651/2013/160(4)/A662/7/