A team at Imperial College London have created a battery material they believe could enable the transition from lithium-ion to sodium-ion batteries.
The scientists prepared lignin (a waste by-product of the paper industry)-derived carbon nanofibre to produce mats that serve as a protective “skeleton” to protect the cell’s metallic sodium anode.
The team from the Titirici Group in the Department of Chemical Engineering used coin cells in the tests with an energy density of around 384Wk/kg-1, which was based on the total active mass of the cathode and anode.
The plan is to next test the technique at pouch level with the goal of producing sodium batteries that can be used in EV or grid energy storage stations as flexible or structural energy storage devices.
The results were published in journal Energy and Environmental Science.
Lignin mats were produced using ‘electrospinning’, with the fibres then carbonised to produce numerous defects in the material structure that support an “even and stable” deposition of metallic sodium.
By combining metallic sodium with specially tailored lignin-based carbon, the team was able to retain and utilise the energy capacity benefits while the safety risks associated with a build-up of dendrite— which causes batteries to short-circuit— were reduced.
Normally, a sodium metal anode can directly store sodium ions, but the dendrite formation would cause a short circuit of the batteries, said Zhen Xu, a research postgraduate at the Faculty of Engineering, Department of Chemical Engineering.
Co-author of the paper Xu (pictured) told BEST: “Therefore, we need a skeleton to protect the sodium metal anode. Bulk sodium metals are pieces of normal sodium metal without any skeleton.
“In this study, the lignin-derived carbon nanofibre mats serve as a skeleton to protect the metallic sodium anode from the dendrite formation, so the metallic sodium is the active anode material to store sodium ions in fact.
“To the best of my knowledge, this is the first time to use the lignin-derived carbon nanofibre mats to protect the sodium metal anode.”
Xu added: “Our research shows the great potential for sodium-ion batteries to play a significant role in a sustainable energy future. Now we hope to work with industry to develop this technology on an industrial scale and explore new applications for sodium-ion batteries.”
Corresponding author of the paper, professor Magda Titirici, said: “It is exciting to see new opportunities for lignin utilisation in the battery sector and its potential to develop new sodium-based technologies, which could revolutionise the electric vehicle sector by creating high performance, safe and more sustainable batteries.”