Lignin is an essential component of wood and gives it its stability. Up to now, it has been burned as a by-product of the paper industry to generate energy.
However, researchers from the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) and Friedrich-Schiller-University Jena are now developing, within the framework of the project “ThüNaBsE” (Thuringian Sodium-Ion Battery for Scalable Energy Storage), a novel sodium-ion battery with lignin.
The aim is to contribute to reducing dependence on critical raw materials and to the transition toward cheaper, more sustainable, and safer batteries.
Project participants
The project is accompanied by an industry advisory board comprising companies such as Mercer Rosenthal GmbH, Glatt Ingenieurtechnik GmbH, IBU-tec advanced materials AG and EAS Batteries GmbH, as well as Petrochemical Holding GmbH from Vienna.
In addition, the project aims to promote early-career researchers in Thuringia. Therefore, scientists who
are pursuing doctoral studies in the fields of energy and battery research are involved in the project.
From by-product to value-added material
Lignin consists, according to IKTS, mainly of hydrocarbon building blocks that can be used in chemistry, for example, as electrode materials for batteries. In the project, the bio-based raw material will be used for the negative electrode.
„We want to avoid critical metals such as lithium, cobalt and nickel in batteries along the value chain. In addition, we would like to keep the fluorine content in electrodes and electrolyte as low as possible and test to what extent it can be completely avoided,“ explains Dr. Lukas Medenbach, a scientist at Fraunhofer IKTS in Arnstadt, and adds: „The core of the project is, however, the processing of locally available, high-quality lignin into high-performance electrodes in our sodium-ion batteries.“
The lignin
is supplied by Mercer Rosenthal GmbH. It is thermally converted under exclusion of air into carbon, which is then processed into the electrode.
„Our project partners from the Institute of Technical Chemistry and Environmental Chemistry at Friedrich-Schiller-University Jena led by Prof. Martin Oschatz process the lignin further through thermal processes into so-called hard carbon,“ says Dr. Cornelius Dirksen.
Hard Carbon
The structure of this hard carbon, according to Dirksen, is well suited to reversibly store sodium ions. Hard carbon offers high electrochemical performance, good cycling stability, and low acquisition costs—especially when derived from sustainable raw materials.
For the positive electrode, Prussian Blue analogs, non-toxic iron compounds, are to be used. This substance was used as a pigment about 200 years ago and is characterized by good material availability, environmental compatibility, and sodium-ion storage properties.
Test phase
In the Fraunhofer IKTS battery
test center in Arnstadt, at the Fraunhofer IKTS in Hermsdorf, and at Friedrich-Schiller University Jena, the first small demonstration cells are currently being built and tested. Realistic simulations are also being conducted.
„The lab cell has not degraded significantly after 100 charging and discharging cycles. The aim is to demonstrate 200 charging and discharging cycles for the 1 Ah full cell by project completion,“ explains Medenbach.
Application possibilities
The finished battery could be used as a stationary or mobile storage system—and exactly where fast charging times are not required.
The lignin-based sodium-ion batteries would be suitable, for example, for mobile applications with lower power requirements – including microcars (45 km/h cars) or warehouse vehicles such as forklifts.
After the project is completed, the technology should be scaled further. Plans include advancing to the next technology readiness levels with a larger consortium.
