Harvesting energy from clean sources like sun and wind is already possible but storing the energy in a sustainable way requires still efforts. Batteries are one of the main options to store energy. However, as their demand is strongly increasing, the supply chains for raw materials are at risk. European Commission recently launched the Critical Raw Materials Act, which aims at securing supply of raw materials to enable the Green Transition. For batteries, this means putting efforts in European mining and refining activities, and to recycling of the critical raw materials. In addition, substitution of critical raw materials is looked for to reduce the demand of common battery materials, such as lithium.
Our approach in the FinnCERES B2B project is to use bio-based, renewable, and more abundant materials to make batteries. We aim at building a battery, which uses biobased carbon as the anode, nanocellulose-based hydrogel as the electrolyte, and organic materials as the cathode.
The biobased carbon will enable replacing graphite, which is listed as a critical raw material. The organic cathode material will help to replace metals, such as cobalt, nickel and lithium. And the hydrogel electrolyte is aimed to maximise the safety and stabilize the interface with the organic electrode material, increasing the lifetime of the battery. All these materials can be produced from biobased sources, avoiding the need for mining and usage of rare materials.
Reaching the project targets requires focusing on the material synthesis, but also on the processing and characterization methods. Also modelling will be used to help to understand the results and to design the materials.
The research challenges we are tackling are the following. The functionality of the biocarbon is dependent on the microstructure and purity of the material. Our goal is to modify the synthesis process so that we can find an optimal structure for the material while maintaining a sustainable production method, which avoids using extremely high temperatures. For the organic cathode material, our main goal is to demonstrate its functionality in a battery setup with increased lifetime. The main concern with organic electrode materials is the dissolution of the material into the electrolyte, which limits the lifetime. This could be avoided by using a polymeric support in the electrode layer and a solid or gel electrolyte, such as the nanocellulose-based materials.
Thus, by combining all three approaches, we can make a truly sustainable battery. In addition, there are also other benefits, such as the possibility for fast charging and increased safety as we are not using a flammable liquid electrolyte. And even though the volumetric energy density will not be as high as with the batteries using metallic electrode materials, the biobased batteries can be used in such applications where energy density is not critical.
The research is currently in early stage, but the potential impact for future green energy solutions is significant. If we can produce batteries that do not use any critical raw materials, do not require mining, and are able to use sustainable and local raw material sources or even waste streams, we will help to secure sufficiency and sustainability of batteries. The developed bio-based battery solutions are not meant to replace all batteries. The conventional Li-ion batteries and high energy density Li-metal batteries will be needed still in the future. Instead, they will help to cope with the increasing energy storage need, in parallel with other technologies, and find their own specific applications areas where their properties can be exploited in the best way.
Marja Vilkman Principal Scientist, Flexible sensors and devices VTT Technical Research Centre of Finland Ltd
Virpi Siipola Senior Scientist, Thermal liquefaction and upgrading VTT Technical Research Centre of Finland Ltd
Professor, Electrochemical Energy Conversion
Professor, Multifunctional Materials Design