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Eliminating dendrite formation

Wed, 04/17/2013 - 18:36 -- Ruth Williams

Researchers at Purdue University in Indiana have suggested a series of experiments designed to study the ways of controlling dendrite growth and to predict them at their early stages of formation. Dendrite formation in lithium batteries could be controlled or even eliminated by the method.

David R. Ely and R. Edwin García, postdoctoral researchers, published the theory in the February edition of the Journal of Electrochemical Society in a paper titled ‘Heterogeneous Nucleation and Growth of Lithium Electro-deposits on Negative Electrodes.’

Dendrites can grow on the anode’s surface formed from the electrolyte, and if it becomes so large that it touches the cathode, the battery will experience an internal short. When exposed to high voltages during rapid charge. the dendrites can form more quickly, thus for safety reasons, charging speed is limited.

The researchers have proposed theories to control the dendrite growth based on behavior associated with their formation. These theories include engineering the chemistry on the surface of the anode to prevent lithium resting at its surface by wetting the surface, rather than nucleating to dendritic growth.

A second approach is to encourage lithium deposits to grow evenly on the surface. The current uneven deposition at various locations on the electrode mean spikes form rather than an even-length all-over layer. This inhibits high-voltage fast-charging but low even lithium deposits would allow for the high voltage charging.

Another method might be to charge the batteries using rapid pulses of electricity instead of a constant current; this could allow vehicle batteries to be re-charged rapidly.

"We have developed an analytical theory that identifies the different ways in which lithium-ion batteries can fail during recharge," Garcia said. "Fundamentally, we proposed a universal roadmap that allows experimentalists and theoreticians to explore the different regimes of behavior during battery recharging. The proposed analytical roadmap enables researchers to identify the charging conditions that will completely suppress or at least minimise the formation of lithium dendrites."

The researchers found that smaller dendrites can transfer mass to larger ones, making the large dendrites grow quicker and more stably. And also, found a way to restrict dendrite from growing beyond its ‘critical kinetic radius’, (the size at which it will either grow more or shrink back depending the current applied.)

"The dendrites don't grow just everywhere, but at very specific locations on the anode," Garcia said. "At the end of the day we want to model that. Such a comprehensive model would lead to advanced battery designs of improved performance and reliability."