A Caffeine Boost for Battery Performance

­For most people, there’s nothing that gives you a kick in the morning like a strong cup of coffee or tea. However, it might not be only humans that caffeine can invigorate, batteries could get a performance boost out of those drinks too. Researchers looking for new battery materials have found both tea and coffee to offer properties that can help batteries perform better. In a story that was initially covered in a PSD blog two years ago, we reported on scientists at University of Indonesia’s Faculty of Engineering, Metallurgy and Materials Engineering Department (DTMM FTUI) who had turned coffee grounds into graphene to increase the conductivity of lithium titanate oxide. Additionally, they also turned coconut shell waste into active carbon for use in the anode. Together, these materials helped improve Li-ion battery charging times and made the batteries safer by reducing the possibility of short circuits during charging. These benefits were achieved because the nanoparticles of graphene produced using coffee grounds have a larger surface area, which allows more ions to pass through the material than in conventional batteries, and therefore provide better energy flow.

It was an interesting story, and I thought that was the last time I’d read about coffees and batteries in the same article. However, recently another story popped up on my newsfeed about a research team from Kazakhstan and South Korea taking advantage of the elements left in the coffee grounds after the coffee has been brewed to improve the performance of sodium-ion batteries. The researchers synthesized pyrolytic hard carbon from the grounds and then used the material to enhance the electrochemical performance of the anode in sodium-ion batteries. The synthesis of P-doped hard carbon used coffee grounds as a precursor and phosphoric acid as the doping agent. They then performed tests using different concentrations of the acid to determine the optimal doping level that would maximize the incorporation of phosphorus ions into the carbon framework.

Closely following that article, a further story popped about how another team of researchers had been using tea leaves for a similar purpose. Using a technique that sounded similar to the one in the previous paragraph, the scientists from Harvard had used tea leaves to create an affordable and sustainable sodium-ion battery anode. High temperatures converted raw tea leaf stems into hard carbon. It was then treated with acid to lower capacity loss. The porous material that they created, named TS-1400-Hcl, allows for better electrolyte penetration and absorption of sodium ions. It provided a 70% increase in initial capacity, along with 91% higher efficiency in the first charge-discharge cycle. It also offered between seven to nine times greater longevity. The new anode lasted over 1,000 cycles with an energy density comparable to commercial Li-ion batteries.

It is amazing that scientists can help the drive to sustainability by using waste material to improve battery performance. Millions of tons of coffee grounds and tea leaf stems are dumped every year, so there would be no shortage of raw material to use. Tomorrow, I’ll drink a toast to those scientists with my morning coffee.