Scientists from Stanford University developed a nanostructures from crab shells, containing sulfur or silicon, which have the potential to increase energy storage capacity of lithium-ion batteries, by allowing free expansion of the electrodes.
The latest research in the field of material science seems to be heavily focused on finding the cheapest and most environmentally friendly material, which could not only increase the energy storage capacity but also boost the lifespan of conventional lithium-ion batteries.
This was the aim of Yi Cui and team, who published the findings of their latest research in the journal Nano Letters earlier this week. The team explored the possibility of using crab shells consisting of calcium carbonate nanochannels, which have a sufficient size to contain electrode materials.
According to the authors, in theory, if the cobalt oxide cathodes and carbon anodes, typically used in lithium-ion batteries, are replaced by sulfur catodes or silicon anodes, the energy storage capacity of the devices could be increased almost ten times.
To test this, the team made carbon nanofibers by burning off the organic matter on the shells and grinding the calcium carbonate into a fine powder. This powder was then mixed in a solution with dopamine to create a dopamine polymer. Once the powder was heated, it turned the polymer into a layer of carbon.
Removing the calcium carbonate resulted in a hollow carbon nanofibers. These were filled either with sulfur or silicon and tested against each other to assess the performance of the electrodes.
The researchers observed the changes in energy storage capacity of electrochemical devices that used each one of the materials. They observed that after 200 charge-discharge cycles, 60% of the capacity was preserved in the sulfur containing electrode, while the silicon one lost only 5% of the capacity.
Considering that the battery of a typical mobile device preserves around 80% of the capacity after 500 cycles, the team is very positive about their invention. Unfortunately, there is still some work to be done in order to be able to make a proper comparison with full batteries.
Critics of the study claim that although the findings were quite remarkable, a practical use of the new structures, such as their implementation in hybrid cars for example, is not yet feasible.
The team, however, is not giving up. They are now exploring other alternative materials made from rice husks in order to improve even further the storage capacity of the devices.