Sodium-ion batteries

Global lithium resources are rapidly declining and mining operations create a large carbon footprint. Sodium-ion batteries could offer a sustainable alternative which, if optimized, could be used in electric vehicles. The key to improving energy capacity in batteries lies in the material and design of anodes, which provide the energy storage function. Despite their ultra-high theoretical capacity, further research has been needed to unlock the potential of batteries made with metallic sodium anodes and address the risks posed by this material's highly reactive nature.

A team at Imperial College London have created a technology which could enable the transition from lithium-ion to sodium-ion batteries. By preparing carbons from lignin, a waste by-product of the paper industry, researchers improved the energy density, sustainability and safety of sodium-ion batteries.

In this study, lignin mats were produced using a process known as 'electrospinning' where lignin fibers are spun in a similar manner to how spiders spin their webs in nature. The fibers were then carbonized to produce numerous defects in the material structure. These defects support an even and stable deposition of metallic sodium, the element responsible for energy storage, resulting in an increased energy capacity. By combining metallic sodium with specially tailored lignin-based carbon, the energy capacity benefits are retained and utilized while the safety risks associated with a build-up of dendrite—which causes batteries to short-circuit—are reduced. The process also requires less heat to carbonize the lignin than other methods, which further reduces the carbon footprint of the manufacturing process.

Sodium-ion batteries have shown immense promise in the energy field, but their limited energy capacity has so far restricted their widespread uptake. This new technology could enable them to replace lithium-ion batteries on a much wider scale than is currently possible and be used in products as large as electric vehicles. The results, published in Energy and Environmental Science. The team will now continue to fine-tune the technology, experimenting with different types of cells and carrying out further experiments.

https://techxplore.com/news/2021-08-scientists-technology-sustainable-next-generation-batteries.html