Batteries have two electrodes, called an anode and a cathode. The anodes in most of today's lithium-ion batteries are made of graphite. Lithium ions are contained in a liquid called an electrolyte, and these ions are stored in the anode during recharging. 

The researchers tested bee pollen- and  -derived carbons as anodes. "Both are abundantly available," said the author. "The bottom line here is we want to learn something from nature that could be useful in creating better batteries with renewable feedstock." Research findings are detailed in a paper that appeared in Scientific Reports.

Whereas bee pollen is a mixture of different pollen types collected by honey bees, the cattail pollens all have the same shape. The researchers processed the pollen under high temperatures in a chamber containing argon gas using a procedure called pyrolysis, yielding pure carbon in the original shape of the pollen particles. They were further processed, or "activated," by heating at lower temperature - about 300 degrees Celsius - in the presence of oxygen, forming pores in the carbon structures to increase their energy-storage capacity.

The research showed the pollen anodes could be charged at various rates. While charging for 10 hours resulted in a full charge, charging them for only one hour resulted in more than half of a full charge, author said. "The theoretical capacity of graphite is 372 milliamp hours per gram, and we achieved 200 milliamp hours after one hour of charging," he said.

The researchers tested the carbon at 25 degrees Celsius and 50 degrees Celsius to simulate a range of climates. "This is because the weather-based degradation of batteries is totally different in New Mexico compared to Indiana," author said. Findings showed the cattail pollens performed better than bee pollen.

The work is ongoing. Whereas the current work studied the pollen in only anodes, future research will include work to study them in a full-cell battery with a commercial cathode.

http://www.purdue.edu/newsroom/releases/2016/Q1/from-allergens-to-anodes-pollen-derived-battery-electrodes.html