Waste paper, made up of discarded paper bags, cardboard, newsprint and other paper packaging, has a large environmental footprint compared to its cotton and plastic counterparts. They dramatically contribute to global warming when burned and to the ecotoxic potential of their production.

Scientists at Nanyang Technological University, Singapore (NTU Singapore) have developed a technique to convert waste paper from disposable packaging, bags and cardboard boxes into a crucial component of lithium-ion batteries.

Today’s innovation, which presents an opportunity to recycle waste products and reduce our dependence on fossil fuels while accelerating our transition to a circular economy, green materials and clean energy, reflects NTU’s commitment to minimizing our impact on the environment, a of the four major challenges facing humanity that the university is trying to address through its NTU 2025 strategic plan.

Scientists used a process called carbonization to convert paper into pure carbon. Using the process, they turned the fibers of the paper into electrodes, which can be made into rechargeable batteries that power cell phones, medical equipment and electric vehicles.

Scientists then charred the paper by exposing it to high temperatures. This reduces it to pure carbon, water vapor and oils that can be used for biofuel. Since carbonization occurs in the absence of oxygen and produces minimal carbon dioxide, it is a more environmentally friendly method of kraft paper disposal than incineration, which releases many greenhouse gases.

The research team’s carbon anodes also showed improved toughness, adaptability and electrochemical properties. According to lab studies, the anodes are at least twice as robust as those in today’s phone batteries and can withstand 1,200 charge and discharge cycles. The anode-based batteries produced by NTU could tolerate physical stress better than their rivals and absorbed up to five times better crushing energy.

In addition, the newly developed method is less energy intensive. It uses cheap waste material and is also expected to reduce production costs.

Assistant Professor Lai Changquan, from NTU’s School of Mechanical & Aerospace Engineering, who led the project, said: “Paper is used for many facets in our daily lives, from gift wrapping and crafts to a wide range of industrial applications, such as heavy packaging, protective packaging and filling voids in construction. However, little is done to manage it when it is disposed of, apart from incineration, which generates high levels of carbon emissions due to their composition. Our method of giving kraft paper a second life, by connecting it to the growing need for devices such as electric vehicles and smartphones, would help reduce carbon emissions and reduce reliance on mining and heavy industrial methods.

The NTU scientists connected and laser cut several thin sheets of kraft paper to create different lattice topologies, some resembling a spikey piata, to create the carbon anodes. The paper was then burned to 1200 degrees Celsius in an oxygen-free furnace to convert it to carbon, creating the anodes.

Study co-author Mr. Lim Guo Yao, a research engineer from NTU’s School of Mechanical & Aerospace Engineering, said: “Our anodes showed a combination of strengths, such as durability, shock absorption and electrical conductivity, not found in current materials. These structural and functional properties demonstrate that our kraft paper-based anodes are a sustainable and scalable alternative to current carbon materials and would find economic value in demanding, high-performance, multi-purpose applications, such as the burgeoning field of structural batteries.

Assistant Professor Lai Changquan, from NTU’s School of Mechanical & Aerospace Engineering, who led the project, said: “Our method converts a common and ubiquitous material – paper – into another extremely durable material that is in high demand. We hope that our anodes will meet the world’s rapidly growing need for a sustainable and greener material for batteries, the manufacture of which and improper waste management have a negative impact on our environment.”

Professor Juan Hinestroza from the Department of Human Centered Design at Cornell University, USA, who was not involved in the research, emphasized the importance of the work of the NTU research team and said: “Since kraft paper is produced in very large quantities and similarly disposed of all over the world, I believe the creative approach pioneered by the researchers at NTU Singapore has great potential for impact on a global scale. Any discovery that makes it possible to use waste as a raw material for high-value products such as electrodes and foam is indeed a great contribution. I think this work can open a new avenue and motivate other researchers to find ways to transform other cellulose-based substrates, such as textiles and packaging materials, that are discarded in large quantities around the world.”

Magazine reference:

  1. Chang Quan Lai, Guo Yao Lim, Kai Jie Tai, Kang Jueh Dominic Lim, Linghui Yu, Pawan K. Kanaujia, Peiyuan Ian Seetoh. Exceptional energy absorption properties and compressive resilience of functional carbon foams scalable and sustainably derived from additively manufactured kraft paper. Additive manufacturing, 2022; 58: 102992 DOI: 10.1016/j.addma.2022.102992