Waste to storage? Cigarette butts for storing energy

Those cigarette butts you see on the ground could soon be a vessel for storing energy. Scientists from South Korea's Seoul National University successfully converted used cigarette filters into a high-performing material for use in computers, handheld devices, electrical vehicles and wind turbines.

According to the team, the material's superior performance can be compared to commercially available carbon, graphene and carbon nanotubes.

The researchers hope the material can be used to coat the electrodes of supercapacitors – electrochemical components that can store extremely large amounts of electrical energy – while also offering a solution to the growing environmental problem caused by used cigarette filters.

It is estimated that as many as 5.6 trillion or about 766,571 metric tons of cigarette butts are deposited into the environment worldwide every year.

Carbon is the most popular material that supercapacitors are composed of, due to its low cost, high surface area, high electrical conductivity and long-term stability.

Scientists around the world are currently working towards improving the characteristics of supercapacitors – such as energy density, power density and cycle stability – while also trying to reduce production costs.

In their study, the researchers demonstrated that the cellulose acetate fibres that cigarette filters are mostly composed of could be transformed into a carbon-based material using a simple, one-step burning technique called pyrolysis.

As a result of this burning process, the resulting carbon-based material contained a number of tiny pores, increasing its performance as a supercapacitive material.

"A high-performing supercapacitor material should have a large surface area, which can be achieved by incorporating a large number of small pores into the material," said Professor Jongheop Yi, from Seoul National University. "A combination of different pore sizes ensures that the material has high power densities, which is an essential property in a supercapacitor for the fast charging and discharging."

Once fabricated, the carbon-based material was attached to an electrode and tested in a three-electrode system to see how well the material could absorb electrolyte ions and then release them.

The material stored a higher amount of electrical energy than commercially available carbon and also had a higher amount of storage compared to graphene and carbon nanotubes, as reported in previous studies.