Researchers at the University of Eastern Finland have developed a hybrid anode with a sustainable silicon material and carbon nanotubes that can improve the performance of solid state lithium ion battery (LIB) technology. The team is looking to include this in the recently announced European Battery 2030+ roadmap.
The hybrid of mesoporous silicon microparticles and carbon nanotubes can be used as the anode in a silicon battery. At 3579 mAh/g the capacity of silicon is ten times higher than the capacity of the graphite currently used in LIBs and has sparked a number of startups. Using silicon in the anode makes it possible to double the capacity of the total battery cell, but there is a challenge in producing anodes made solely from silicon. Research teams across the world are also working on combining carbon and silicon for a battery anode.
To minimise the reducing effect of high charging rates on the capacity of silicon anodes, researchers from the University of Eastern Finland used mesoporous silicon (PSi) microparticles and carbon nanotubes (CNTs). These have to be combined chemically to ensure the right diffusion of lithium ions into the silicon with the right levels of electrical conductivity and mechanical durability.
“The progress of the LIB research is very exciting, and we want to contribute to the field with our know-how related to mesoporous structures of silicon. Hopefully, the EU will invest more in the basic research of batteries to pave the wave for high performance batteries and to support the competitiveness of Europe in this field. The Battery 2030+ roadmap would be essential in supporting this progress,” said Prof Vesa-Pekka Lehto from the University of Eastern Finland.
Rather than using traditional sources of silcon, the PSi microparticles were produced from barley husk ash to minimise the carbon footprint of the anode material and to support its sustainability.
The silicon PSi was produced through a simple magnesiothermic reduction process applied to the amorphous porous silica structures called phytoliths that are found in abundance in husk ash.
The team built a coin cell with a lithium cathode to test the material, with long-term cycling showing promising results with a stable capacity of approximately 1150 mAh/g up to 110 cycles. Next, the researchers are aiming to produce a full silicon anode with a solid electrolyte to address the challenges related to the safety of LIBs and to the unstable solid electrolyte interface (SEI).
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