US scientists have found a way to convert harmful algal blooms into cheap and efficient electrodes for sodium-ion batteries.
Algal blooms are the biggest threat to natural and artificial aquifers. Formed as a result of warm temperatures, and consequently the development of large populations of cyanobacteria, algal blooms are often toxic, very strong, and deadly to the water inhabitants. As temperatures are about to raise under the influence of the inevitable climate change, scientists predict that the problem of algal blooms in lakes might accelerate drastically in the near future.
A team of enthusiastic scientists from Wayne State University, Detroit, found a way to make use of the harmful algal blooms (HABs), and turn them into high-performance, cheap electrodes for sodium-ion (Na-ion) batteries.
The team experimented with HABs collected from the water system in Toledo, Ohio, where the toxic cyanobacteria caused such incredible pollution, that half a million people were left without drinking water.
The samples of HABs were brought to the lab, where the scientists heated them up to temperatures of 1000 degrees C using argon gas. The team observed that the HABs turn into the so-called “hard carbon” material. This process they called ‘trash-to-treasure approach’, and the name was given because it turned out that hard carbon can be used as part of an excellent green electrode for Na-ion batteries.
These new eco-friendly and very cheap electrodes consist of 80% hard carbon, 10% black carbon and 10% binder. This mix is fully dry and shaped into coin-shape cells, where sodium foil acts as the counter electrode. Now, in terms of performance, the electrode did not do so great, but it showed incredible potential. After the first cycle, the initially high capacity of 440 mAh/g drops down to 230 mAh/g. Nevertheless, there is a good capacity retention as from the second cycle.
The team behind the technology is highly motivated to boost these numbers. The guys are convinced that this is more than feasible, especially since they already identified temperature at which the algae is heated to be crucial for the performance of the electrode. Their main priority now is to take care of the drop in capacity during the first cycle, but they also want to optimize the process of harvesting the algae on a larger scale. In this way, they will tackle two major problems at once- algal pollution and cheap energy storage.
The study with a lead author Dr. Da Deng, appears in the latest issue of the journal Environmental Science and Technology, where the method is described in full detail.
Image (c) Da Deng, Wayne State University
