Sensors allow lithium batteries to charge five times faster

Sensors allow lithium batteries to charge five times faster

Technology News |
By Nick Flaherty

The technology developed by the Warwick Manufacturig Group (WMG) works as part a battery’s normal operation and has been tested on standard commercially available automotive battery cells. If a battery becomes over heated it risks severe damage to the electrolyte, breaking down to form gases than are both flammable and cause significant pressure build up. Overcharging of the anode can lead to lithium electroplating that forms metallic dendrites that can cause internal short circuits and fires.

The WMG researchers developed miniature reference electrodes and Fibre Bragg Gratings (FBG) threaded through a bespoke strain protection layer. An outer skin of fluorinated ethylene propylene (FEP) was applied over the fibre, adding chemical protection from the corrosive electrolyte. The result is a sensor with direct contact with all the key parts of the battery and withstand electrical, chemical and mechanical stress inflicted during the batteries operation while still enabling precise temperature and potential readings.

“This method gave us a novel instrumentation design for use on commercial 18650 cells that minimises the adverse and previously unavoidable alterations to the cell geometry,” said WMG Associate Professor Dr Rohit Bhagat. “The device included an in-situ reference electrode coupled with an optical fibre temperature sensor. We are confident that similar techniques can also be developed for use in pouch cells.”

The data from the sensor is much more precise than external sensing and this has been used to show that commercially available lithium batteries available today could be charged at least five times faster than the current recommended maximum rates of charge.

“This could bring huge benefits to areas such as motor racing which would gain obvious benefits from being able to push the performance limits, but it also creates massive opportunities for consumers and energy storage providers,” said Dr Tazdin Amietszajew, who led the research. “Faster charging as always comes at the expense of overall battery life but many consumers would welcome the ability to charge a vehicle battery quickly when short journey times are required and then to switch to standard charge periods at other times. Having that flexibility in charging strategies might even/further down the line help consumers benefit from financial incentives from power companies seeking to balance grid supplies using vehicles connected to the grid.

“This technology is ready to apply now to commercial batteries but we would need to ensure that battery management systems on vehicles, and that the infrastructure being put in for electric vehicles, are able to accommodate variable charging rates that would include these new more precisely tuned profiles and limits,” he said.

The work was part of AMPLIFII, a collaborative research project with the University of Warwick coordinating a team with Alexander Dennis, Ariel Motor, Augean, Axion Consulting, Delta Motorsport, HORIBA MIRA, Jaguar Land Rover, JCB, Potenza Technology, Trackwise Designs and the University of Oxford.

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