Scientists at Nanyang Technological University in Singapore (NTU Singapore) have created a method to transform waste paper from cardboard boxes and single-use packaging into a vital component of lithium-ion batteries.
The NTU researchers used a process called carbonization, which turns paper into pure carbon, to transform the paper’s fibers into electrodes that can be used to create rechargeable batteries for electric cars, medical equipment, and mobile devices.
The team heated the paper to high temperatures to carbonize it, which turns it into pure carbon, water vapor, and oils that may be utilized to make biofuel. Although carbonization occurs in the absence of oxygen and produces very little carbon dioxide, it is a more environmentally friendly method of disposal for kraft paper than incineration, which releases a lot of greenhouse gases.
The research team’s carbon anodes also showed improved toughness, adaptability, and electrochemical qualities. According to laboratory studies, the anodes are at least twice as robust as the anodes in today’s phone batteries and may withstand 1,200 charges and discharges. The NTU-produced anode-based batteries could tolerate physical stress better than their rivals, absorbing crushing energy up to five times better.
In comparison to current industrial techniques for producing battery anodes, the NTU-developed technology also employs less energy-intensive procedures and heavy metals. This newest technique, which uses a cheap waste material, is anticipated to lower the cost of making lithium-ion batteries because the anode accounts for 10% to 15% of their overall cost.
The findings were published in the scientific peer-reviewed journal Additive Manufacturing in October.
Our dependence on conventional sources of carbon, such as carbonaceous fillers and carbon-yielding binders, which are mined and subsequently processed with harsh chemicals and machinery, would be reduced if we used waste paper as the starting material to create battery anodes.
As kraft paper is produced in very large quantities and disposed likewise all over the world, I believe that 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 that 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.
Professor Juan Hinestroza
Paper waste, which comprises disposed paper bags cardboard, newspaper, and other paper packaging, accounted for nearly a fifth of the waste generated in Singapore in 2020.
Kraft paper bags, which make up the bulk of Singapore’s paper waste, were also found to have large environmental footprints compared to their counterparts made of cotton and plastic, due to their greater contribution to global warming when incinerated and the eco-toxicity potential in producing them, a separate 2020 NTU study found.
The current innovation, which offers a chance to recycle waste products and lessen our reliance on fossil fuels while speeding up our transition to a circular economy, green materials, and clean energy, reflects NTU’s dedication to minimizing our impact on the environment, one of four grand challenges facing humanity that the University seeks to address through its NTU 2025 strategic plan.
Assistant Professor Lai Changquan, from NTU’s School of Mechanical & Aerospace Engineering, who led the project, said: “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. However, little is done to manage it when it is disposed of, besides incineration, which generates high levels of carbon emissions due to their composition. 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 not only help cut down on carbon emissions but would also ease the reliance on mining and heavy industrial methods.”
The research team has filed for a patent with NTUitive, NTU’s innovation and enterprise company. They are also working towards commercialising their invention.
The recipe for greener battery parts
To produce the carbon anodes, the NTU researchers joined and laser cut several thin sheets of kraft paper to form different lattice geometries, some resembling a spikey piñata. The paper was then heated to 1200°C in a furnace without the presence of oxygen, to convert it into carbon, forming the anodes.
The NTU team believes that the arrangement of the paper fibers is responsible for the anode’s exceptional strength, flexibility, and electrochemical characteristics. They said that the NTU-made anodes’ combination of strength and mechanical toughness would improve the ability of phone, laptop, and automotive batteries to absorb shocks from falls and collisions.
One of the main reasons why battery life decreases over time is that current lithium batteries rely on internal carbon electrodes that progressively crack and collapse following physical shocks from being dropped.
The researchers claim that their anodes, which are more durable than the current battery electrodes, will help address this issue and increase the lifespan of batteries in a variety of applications, from electronics to electric vehicles.
Co-author of the study Mr. Lim Guo Yao, a research engineer from NTU’s School of Mechanical & Aerospace Engineering, said: “Our anodes displayed a combination of strengths, such as durability, shock absorption, electrical conductivity, which are 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-end, multifunctional applications, such as the nascent field of structural batteries.”
Asst Prof Lai added: “Our method converts a common and ubiquitous material paper into another that is extremely durable and in high demand. We hope that 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 Centered Design of Cornell University, US, who was not involved in the research, said:
“As kraft paper is produced in very large quantities and disposed likewise all over the world, I believe that 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 that 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 carry out additional research to increase the material’s potential for storing energy and lower the amount of heat energy needed to turn paper into carbon.
