New Sensor Technology Makes Charging of Lithium-ion Batteries Five Times Faster

Researchers at WMG at the University of Warwick have developed a new technology that can be used to charge Lithium-ion batteries five times faster. They used sensor technology to keep tabs on the internal temperature and electrode potentials of Lithium-ion batteries and this technology works in-situ during the normal working of a battery without compromising its performance in any manner. The research team has already tested their innovative technology on commercially available batteries.

It is expected that this new technology will further advance the development of battery technology and it also offers potential for the development of high performance applications like motor racing and grid balancing.

In that event that a battery becomes overheated, it becomes dangerous as there will be severe damage to its electrolyte and the electrolyte can break down to form gases that not only are flammable but can also cause pressure buildup. When the anode of a battery is overcharged, it can lead to the formation of metallic dendrites which can pierce through the separators and thus cause an internal short circuit.

It is to avoid such situations that manufacturers clearly stipulate a maximum charging rate or intensity for the batteries based on the temperature and potential levels they think should be avoided. It was previously not possible to test the internal temperature of a battery and gauge its potential without in any way affecting the performance of the battery. The only option was the use of limited, external instrumentation which provided readings that were not very precise, thus forcing manufacturers to err on the conservative side to minimize chances for damage to the battery.

The researchers in WMG at the University of Warwick have been able to develop methods to make direct, and highly precise measurements of the internal temperature and “per-electrode” status monitoring of Lithium-ion batteries of different types. The data obtained through the use of such methods is a lot more precise than external sensing. The group was able to determine that use of the technology can make it possible to charge commercially available lithium batteries at least five times faster than the current recommended maximum rates of charge.
The researchers at WMG have published their findings in the form of an article titled “Understanding the limits of rapid charging using instrumented commercial 18650 high-energy Li-ion cells” in the renowned journal Electrochimica Acta

Dr Tazdin Amietszajew, the WMG researcher who led on this research, said that the new techniques by increasing performance could bring huge benefits to areas like motor racing and will also offer immense benefits to consumers and energy storage providers. Consumers would like to have the option to charge faster even though to some extent, it would affect battery life. This option offers greater flexibility when it comes to charging strategies. Power companies can also balance grid supplies using vehicles connected to the grid.
Before this technology can be used for commercial batteries, it would be necessary to ensure that battery management systems on vehicles, and the infrastructure being used for electric vehicles is able to accommodate variable charging rates.

The technology the WMG researchers have developed for this new direct in-situ battery sensing employs miniature reference electrodes and Fibre Bragg Gratings (FBG) threaded through bespoke strain protection layer. An outer skin of fluorinated ethylene propylene (FEP) was applied over the fiber, adding chemical protection from the corrosive electrolyte. This resulted in the creation of a device that has direct contact with all the main parts of the battery and which can tolerate electrical, chemical and mechanical stress created during the operation of the battery while still permitting precise temperature and potential readings.

WMG Associate Professor Dr Rohit Bhagat who was a part of the research team said that the new method resulted in a novel instrumentation design that minimizes the need for alterations to cell geometry in commercial 18650 cells. The device essentially comprised an in-situ reference electrode paired with an optical fiber temperature sensor. He went on to express his confidence that similar techniques can also be used for pouch cells.

Dr. Bhagar said that this is just one of the technological solutions that the group has come up with and it will be looking at other innovative approaches also.