Skoltech researchers have patented a novel technology for producing high-quality lithium iron phosphate — a key component in lithium-ion batteries for electric cars, buses, backup power systems, and residential renewable energy solutions. The new manufacturing process employs microwave radiation instead of conventional hot-air drying to prepare the raw material for making lithium iron phosphate, which then exhibits higher capacity and longevity. Used in cathodes, the improved material will increase the lifespan of lithium-ion batteries and the amount of energy stored, while also saving time and cutting the energy costs in manufacture. The patent was issued by the Russian Federal Service for Intellectual Property.

Lithium-ion batteries dominate the energy storage market, including electric mobility. There are multiple types of widely used lithium-ion batteries, distinguished by the cathode materials used. With the materials of the anode and the other components playing a somewhat secondary role, the composition of the cathode is what largely determines the battery’s performance: its power, cost, safety, and lifespan.

The cathode materials invariably contain lithium, with a sometimes long string of other elements thrown in the mix. To give just two examples, the lithium nickel manganese cobalt oxide (aka NMC) cathode excels at energy density and makes for batteries that are good for long-range vehicles. Some high-end performance cars have batteries based on the lithium nickel cobalt aluminum oxide (NCA) chemistry, which are more expensive and somewhat less safe.

“We work on cathode materials for lithium iron phosphate batteries. These are cheaper than their nickel-based counterparts and needn’t be replaced as often — the tradeoff is less energy density. Such a profile of characteristics makes these the batteries of choice for mass-market city cars geared toward short- and midrange trips, as well as electric buses and forklifts,” one of the patented technique’s inventors, Junior Research Scientist Elvira Styuf from Skoltech Energy, says.

“Also, let’s not forget the safety, both in electric vehicles and beyond,” adds patent co-author, the director of Skoltech Energy, Distinguished Professor Artem Abakumov, who is a co-laureate of the 2024 Vyzov Prize. “Lithium iron phosphate batteries are highly resistant to overheating and not prone to explode or burn even when damaged. The safety factor, combined with operation in a fairly broad temperature range, are also advantageous for residential solutions that store solar and wind energy and manage power outages.”

A battery’s capacity is its key performance characteristic. Capacity is primarily limited by the energy density of the cathode material, which is why scientists and engineers keep tinkering with the makeup and the manufacture of lithium iron phosphate — aka LFP — and other cathode materials.

The new Skoltech patent describes a way to modify the manufacture of LFP for battery cathodes, such that the resulting material has a higher energy density, ultimately improving battery performance. The developed manufacturing process is also somewhat faster and conserves about a quarter of the electricity normally expended by the hot-air dryer.

LFP is produced by baking feedstock in a furnace. The feedstock, in turn, is a powder, initially orange in color, made by spraying a water suspension of raw materials in a stream of hot air. The droplets instantaneously dry up, leaving behind the spherical particles that make up the powder. If, however, the droplets are exposed to microwave radiation instead of hot air, they will dry up faster and with less electricity expended. Even more importantly, the distribution of the components in each spherical powder particle will be more homogeneous. This improves the material’s energy density and extends its lifespan.

“The reason for this effect is that hot air dries the particles from the outside in, and microwaves dry them from the center out,” patent co-author Senior Research Scientist Aleksandra Savina of Skoltech Energy explained. “Rapid water removal from suspension droplets via microwave radiation ensures an even distribution of all components throughout the entire volume of the spherical or spherelike agglomerates of the precursor — the powdered material before baking. This results in many tiny particles, each with a carbon coating, sticking together, forming a fine conductive network of carbon in the final cathode material. Conventionally, you get a more coarse-grained network with bigger nonconductive spans in it, and that means poorer conductivity and, ultimately, less energy density.”