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Researchers smooth out lithium’s dendrite problem

This image shows the temperature driven merging and fusing of lithium dendrites into a uniform (smooth) surface, which eliminates the risk of electrical shorting in lithium-ion batteries. Source: Rensselaer

Researchers at the US’ Rensselaer Polytechnic Institute have made a breakthrough in battery technology, using heat to smooth out dendrite deposits

new technique developed by a team at Rensslaer Polytechnic uses heat to enable lithium-metal to self-heal, eliminating the buildup of dendrites in battery anodes.

Dendrites are a major limiting factor in the size and life-span of lithium batteries. The small strands of lithiated metal grow inside batteries and can eat away at batteries capacity and have even been blamed for causing fires, such as in the case of Samsung’s now-infamous Galaxy Note 7.

Most current batteries have a lithium metal oxide cathode (positive electrode) and a graphite anode (negative electrode). Researchers are now looking at ways to replace the graphite electrode with a lithium metal one, which increases the energy density of the battery. However, repeated use of lithium metal electrodes can spur the growth of dendrites from the surface, which can grow long enough to cause a short circuit.

“We have found that lithium metal dendrites can be healed in situ by the self-heating of the dendritic particles,” said Nikhil Koratkar, the John A. Clark and Edward T. Crossan Professor of Engineering at Rensselaer and author of the paper.

The Rensselaer researchers believe that their new breakthrough will pave the way for more powerful battery technologies.

The technique causes the dendrites to smooth out, preventing them from building up and outwards towards the cell barrier. It takes advantage of resistive heating, where the metal resists current flow and produces heat (the same process found in electric toasters), a natural part of the charge and discharge process.

By ramping up the self-heating effect with an increase in the current density (charge-discharge rate) of the battery, lithium was diffused over the surface of the electrode, spreading the dendrites into an even layer.

They also demonstrated the same in a proof-of-concept demonstration using a lithium-sulphur battery – another possible architecture the battery industry is considering as it looks to improve performance and energy density.

The researchers suggested using software to run cycles of charging and discharging when the battery is not in use to smooth out the dendrites.

“A limited amount of cycles at high current density would occur to heal the dendrites, and then normal operations can be resumed,” Koratkar said. “Self-healing would occur as a maintenance strategy, long before the dendrites become a safety hazard.”

The new technique could increase the efficiency and capacity of next-generation batteries used for EVs and for stationary power storage.

 

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