An economical method for producing cathode materials will enhance lithium-ion batteries.
Lithium-ion batteries continue to be the primary sources of energy storage, particularly in electric transportation. They are categorized by the type of cathode material. Of course, the anode and other components of the battery also play a significant role, but it is the composition and structure of the cathode material that primarily determine the battery's final characteristics: energy density, power, cost, safety, and lifespan. Different cathode materials are selected based on the application. For instance, batteries using lithium-nickel-manganese-cobalt oxide (NMC) cathodes have high energy density, making them favorites for electric vehicles designed for long ranges.
“We are enhancing the technology for producing lithium iron phosphate (LFP) cathode materials for lithium-ion batteries. They are less expensive than NMC and have a longer lifespan. Despite having lower energy density, LFP is used for batteries in urban electric vehicles optimized for short to medium-distance trips, as well as for electric buses and forklifts,” explains one of the patent authors, junior researcher at the Skoltech Energy Technologies Center, Elvira Styuf.
“Moreover, safety is a crucial factor, not only in electric transportation,” adds co-author of the patent and distinguished professor at the Skoltech Energy Technologies Center, Artem Abakumov, co-recipient of the “Challenge” award. “Batteries based on lithium iron phosphate are more resistant to overheating and less prone to explosions and fires, even when damaged. Enhanced safety, combined with good capacity and power characteristics, makes this type of battery suitable for backup power needs during outages and for storing solar and wind energy.”
The patented method developed by Skoltech for producing LFP allows for the creation of material in the form of spherical micro-particles, which enables denser packing, resulting in a lithium-ion battery with increased energy density: it can store more energy within the same volume.
LFP is synthesized through high-temperature processing of a precursor material, which appears as an orange powder and is obtained by spraying an aqueous suspension of reagents into a stream of hot air. The tiny droplets of the suspension dry instantly, leaving behind spherical powder particles. It turns out that if the droplets are dried not with hot air but using microwave radiation, all the starting substances in each spherical particle will be distributed more evenly.
This allows for the creation of a uniform carbon conductive coating that envelops the particles of the material during subsequent thermal treatment, achieving high electrochemical capacity and more stable operation of the cathode. Additionally, the method described in the patent is faster and saves about a quarter of the electricity typically consumed by installations for spray drying with hot air.
“This effect is explained by the fact that the heating of the sprayed droplets occurs from their center to the periphery due to the direct impact of microwaves, rather than the other way around as in the case of hot air drying,” explains co-inventor and senior researcher at the Skoltech Energy Technologies Center, Alexandra Savina. “The rapid removal of water from the droplets of the suspension using microwave radiation allows for an even distribution of all components throughout the volume of the spherical—or nearly spherical—conglomerates of the precursor. As a result, a more branched conductive carbon network forms in the cathode material. In the traditional approach, this network is not as pervasive, and larger non-conductive areas can be found. The electrical conductivity of the cathode is critically important for high energy density and its stable operation over a long period.”
The invention has been registered with Rospatent.