MXene current collectors could reduce size, improve recyclability of Li-ion batteries

(Press-News.org) The vast majority of consumer electronics use lithium-ion batteries, and with each generation, these devices are designed smaller, lighter and with longer battery life to meet the growing demands of consumers. Each new iteration also brings the batteries that power the devices closer to the limits of their size, weight and performance. Researchers are constantly testing new approaches and materials for making lightweight, high-performance components. The latest contender is MXene, a type of metallically conductive two-dimensional nanomaterial discovered by Drexel University researchers that has recently demonstrated potential as a current collector, the part of the battery that directs electrical current to its electrodes. A recent paper from Drexel researchers reports that a current collector made of MXene film could reduce the battery’s weight and thickness while improving its available capacity.

Published in the journal Cell Reports Physical Science, the paper reports that MXene current collectors perform as well as the copper foils being used in current lithium-ion batteries, but they are 3-4 times thinner and about 10 times lighter. Using them to make the battery components would reduce the overall weight contribution from inactive materials, allowing for more energy-storing material to be used without increasing the battery’s weight, thus improving the battery’s capacity.

The researchers also demonstrated that the MXene current collectors can be readily recycled for use in other batteries, an important step toward reducing battery waste and conserving limited material resources.

Current collectors are key to battery performance because they direct the flow of electrons within the battery, directing them to and from the electrode, which translates the chemical energy into the electrical current that powers electronic devices. They are also prime contributors to a battery’s weight – comprising nearly 15% of its total weight.

“Recent progress in battery technology is centered on improving capacity while reducing their weight,” said Yury Gogotsi, PhD, Distinguished University and Bach professor in Drexel’s College of Engineering, who was a leader of the research. “But the field has also widely acknowledged the importance of finding recyclable alternatives to current battery components in order to ensure their sustainable manufacturing. Our findings suggest that MXene materials could be a strong candidate for use in the batteries of the future.”

MXenes have been tested in dozens of applications – including several in energy storage – since their discovery at Drexel more than a decade ago. Their aptitude for use as a current collector is tied to their exceptional electrical conductivity, excellent flexibility and high mechanical strength. MXenes also remain electrochemically stable in acidic and corrosive electrolytes, and are dispersible in water, which allows for easy processing.

“This is an exciting finding because MXenes are compatible with a variety of electrode materials, so they have the potential to improve next-generation batteries without requiring significant structural design changes,” said Professor Patrice Simon, PhD, a co-author of the research from Université de Toulouse in France.

The final test of the components examined the cycling stability and recyclability of the MXene current collector. After eight weeks of continuous charging and discharging, the MXene–graphite electrode maintained good adhesion, the graphite active material remained evenly distributed, and did not detach from the MXene film. The MXene current collector also preserved its layered structure, showing no degradation. Using a simple and environmentally friendly recycling process developed by the team, the electrode was disassembled and reconstituted using reclaimed materials for the current collector. Electrochemical testing confirmed that its performance remained unchanged.

“As battery materials become increasingly scarce, and sustainability and circular economy become increasing important, it will be essential to design components that can be reused,” said Yuan Zhang, PhD, who is a post-doctoral researcher in Gogotsi’s lab and co-author of the research. “Thanks to their outstanding electrochemical durability, MXenes can be recycled without losing much of their exceptional properties.”

The investigation was led by Sokhna Dieng, Schlumberger Future Fellow in Gogotsi’s lab, who contributed to the work as part of her doctoral research. She plans to continue exploring MXenes as conductive additives and other passive components in batteries that can improve performance and also enhance safety by preventing dendrite growth.

“We envision batteries with MXene components being used one day in wearable and portable microelectronics, where size and weight are absolutely critical and the amount of material required is minimal,” Gogotsi said. “Another potential use is in systems where low weight is essential, such as drones or other flying vehicles.”

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