TECHNOLOGY/ENVIRONMENT
A team of scientists from Singapore’s Nanyang Technological University (NTU) have developed a way to convert waste paper from single-use packaging, bags and cardboard boxes into a crucial component of lithium-ion batteries. Through a process called carbonisation, which converts paper into pure carbon, the team turned the paper’s fibres into electrodes, which can be made into rechargeable batteries that power mobile phones, medical equipment and electric vehicles.
The paper was exposed to high temperatures, reducing it to pure carbon anodes, water vapour and oils that can be used for biofuel. These anodes also demonstrated superior durability, flexibility, and electrochemical properties. Lab tests have shown the anodes can be charged and discharged up to 1,200 times, making them at least twice as durable as anodes in current phone batteries. The batteries that use the NTU anodes could also withstand more physical stress than their counterparts, absorbing crushing energy up to five times better.
Carbonisation also uses less energy-intensive processes and heavy metals compared to current industrial methods of manufacturing battery anodes. As the anode is worth 10–15% of the total cost of a lithium-ion battery, the cost of manufacturing them is expected to drop.
The findings were published in the peer-reviewed journal Additive Manufacturing in October.
Using waste paper as the raw material to produce battery anodes would also ease our reliance on conventional sources for carbon, such as carbonaceous fillers and carbon-yielding binders, which are mined and then processed using harsh chemicals and machinery.
Assistant Professor Lai Changquan, from NTU’s School of Mechanical and Aerospace Engineering, who led the project, says, “Paper is used in many facets in our daily lives, from gift wrapping and arts and crafts, to a myriad of industrial uses, such as heavy-duty packaging, protective wrapping, and the filling of voids in construction. Our method to give kraft paper another lease of life, funnelling it into the growing need for devices such as electric vehicles and smartphones . . . would also ease the reliance on mining and heavy industrial methods.”
The NTU team, which has filed for a patent and is working to commercialise the invention, says the combination of strength and mechanical toughness would allow batteries in phones, laptops and vehicles to better withstand shocks from falls and crashes. Current lithium battery technology relies on internal carbon electrodes that gradually crack and crumble after physical shocks from being dropped, which is one of the main reasons battery life gets shorter with time.
“Our method converts a common and ubiquitous material — paper — into another that is extremely durable and in high demand,” notes Lai. “We hope our anodes will serve the world’s quickly growing need for a sustainable and greener material for batteries, whose manufacturing and improper waste management have shown to have a negative impact on our environment.”
Highlighting the significance of the work done by the NTU research team, Professor Juan Hinestroza from the Department of Human Centred Design at Cornell University in the US, who wasn’t involved in the research, says, “As kraft paper is produced in very large quantities and disposed likewise all over the world, I believe the creative approach pioneered by the researchers at NTU Singapore has a great potential for impact at a global scale. Any discovery that will allow the use of waste as a raw material for high-value products like electrodes and foams is indeed a great contribution. I think this work may open a new avenue and motivate other researchers to find pathways for the transformation of other cellulose-based substrates, such as textiles and packaging materials, which are being discarded in large quantities all over the globe.”
The NTU team will conduct further research to both improve the energy storage capacity of the material and minimise the heat energy required to convert the paper into carbon.
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