The uses of lithium-ion batteries have grown to include smartphones, laptops, and even electric vehicles in recent years, and now the world could not work without them. However, the energy density of lithium-ion batteries has almost reached its theoretical limit. This is a major barrier as electric vehicles are about to enter a period of mass adoption. This is because the cruising range on a single charge is not growing. Moreover, since lithium-ion batteries are made from expensive metals such as cobalt and nickel, there is a limit on how far costs can be reduced.
Accordingly, battery manufacturers and automakers around the globe are working to develop next-generation batteries. Solid state batteries, which use solids rather than liquids as electrolytes, are one such example. Yuto Katsuyama, who is pursuing a doctorate researching next-generation batteries in the Kaner group at UCLA (https://kaner.chem.ucla.edu/), focuses on reducing cost as well as improving performance, and has chosen new battery materials. They are made from basic elements like carbon, nitrogen, oxygen, and sodium. Katsyama has created next-generation high-performance batteries using earth abundant substances instead of using expensive minerals like cobalt and nickel.
Katsuyama and his collaborators succeeded in developing a 3D supercapacitor and 3D sodium ion battery having one of the world's largest capacities. These energy storage devices use protons (hydrogen ions) or sodium ions instead of lithium ions, leading to a significant cost reduction. Furthermore, one method of increasing the energy density as well as lowering the cost of batteries is to thicken the electrode layers. This is because thick electrode layers can reduce the use of inactive battery components such as separators and packaging materials. However, simply increasing their thickness only increases the length of the ion transport pathways, and slows ion transport within the thick electrodes ruining battery function. Katsuyama used an inexpensive 3D printer (<$300) to fabricate bimodal-porous carbon electrodes, successfully making the electrodes thicker, while maintaining the ion diffusion pathways within the electrode. This enabled high-speed ion transport despite an electrode more than 10 times thicker than usual.
In another project, Katsuyama and his collaborators at Tohoku University in Japan are developing "organic batteries" using organic substances. The drawback of organic batteries is that raising the voltage above 2.5 V is difficult. Therefore, Katsuyama and his collaborators turned their attention to a pentagonal organic molecule known as croconic acid (previously considered unsuitable as a battery research material), incorporated it into their organic batteries, and succeeded in improving the voltage output to the 4 V level. As a result, Katsuyama demonstrated that the theoretical energy density can be increased to roughly four times that of conventional lithium-ion batteries. This means that if they can be put to use in electric vehicles, it would quadruple the cruising range on a single charge.
Alongside his activities as a US-based researcher, Katsuyama established a startup “Satoyama Engineering” in Japan as a joint venture in May 2022. He currently serves as Chief Scientific Officer (CSO), working on commercial-scale development of high-performance organic batteries made from biomass-based materials.
