Battery performance tends to degrade over time due to the natural wear that occurs when, for example, cathode active materials (CAMs) expand and contract while shuttling ions for the reversible storage and release of electrical energy. CAMs also degrade due to interactions with the electrolytes. New technology from the startup Volexion (Chicago, Ill.; www.volexion-inc.com) aims to prevent that degradation by encapsulating solid particles of CAMs with a nanoscale layer of graphene.
“For battery performance, careful engineering of the interfaces between components is very important,” explains Volexion CEO Joe Adiletta. “Volexion has focused on the cathode interface, which we think has been somewhat neglected over time.”
The company has developed a low-cost mechanical exfoliation method for generating unfunctionalized graphene from graphite. “In the past, most processes to generate graphene have either been low-cost, but with low-performance, or high-performance, but very expensive,” Adiletta says. “Our focus has been to generate pristine graphene at low costs.”
For the encapsulation step, Volexion has also focused on low-cost solutions. The company uses a dry-processing approach that capitalizes on existing technology, allowing a drop-in solution that is compatible with existing lithium-ion-battery manufacturing processes, Adiletta says.
The company’s conformal encapsulation technique results in an even and thin coating of graphene that accounts for a tiny fraction of the CAMs’ weight, he adds. In addition, Adiletta points out that his company’s process is a platform technology, applicable to many known lithium-ion battery chemistries, including lithium-nickel-manganese-cobalt (NMC), lithium-iron-phosphate (LFP) and other variations.
The benefits of the graphene coating for battery longevity and performance are categorized into three areas: chemical benefits, where the passivation of the CAM surface protects the cathode from dissolution by the battery’s electrolyte; electrical benefits, where the conductive graphene coating results in better charge homogeneity; and mechanical benefits, because the graphene acts a lubricant at the nanoscale, allowing better press density of the CAM in dry processing. To date, Volexion has coated CAM samples from almost a dozen potential users for evaluation, and is currently raising series-A funding to build a pilot plant at its Chicago facility next year.