The number of electric vehicles and mobile devices is expected to surge over the coming decade, which would place considerable strain on our environment and resources as far as battery technology currently stands. In an effort to find more sustainable alternatives for battery materials, researchers from the University of California, Riverside have created a battery incorporating the skins of portabella mushrooms. The move not only has the potential to reduce the economic and environmental cost of battery production, but may also result in batteries whose capacity increases over time.

Batteries consist of three main elements: a negative terminal (cathode), a positive terminal (anode) and a solid or liquid separating them (electrolyte). Synthetic graphite is commonly used for the anode in lithium-ion batteries, but this material requires the use of chemicals such as hydrofluoric and sulfuric acids for purification and preparation. These processes are not only expensive, but also produce hazardous waste that is harmful to the environment.

Scientists at the UC Riverside were keen to explore the potential of portabella mushrooms as a more natural substitute for graphite for two reasons. Firstly, earlier research had shown that the mushrooms were highly porous, which is a desirable attribute when it comes to batteries as the tiny holes allow extra room for both the storage and transfer of energy, which improves performance. Secondly, they contain high amounts of potassium salt, which causes more of these pores to be activated over time, something that would increase the level of electrolyte-active material as it is used, and in effect boost the battery's capacity.

The team found that taking skin from the cap of the portabella mushrooms and heating it to 500° C (932° F) saw it transform into a naturally derived carbon nanoribbon-like architecture. Further heating the material to 1,100° C (2,012° F) saw it then turn into an interconnected porous network-like carbon nanoribbon, a material that could nicely lend itself to battery design as it offers a relatively large surface area for storing energy. The researchers say the results indicate that, if optimized, the mushroom-derived carbon anodes could come to replace conventional graphite anodes.

"With battery materials like this, future cell phones may see an increase in run time after many uses, rather than a decrease, due to apparent activation of blind pores within the carbon architectures as the cell charges and discharges over time," says Brennan Campbell, a graduate student at UC Riverside.

The research was published in the journal Nature Scientific Reports.