Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a technology to turn waste paper, from single-use packages and bags, and cardboard boxes, into a core component of lithium-ion batteries.
Through a process called carbonization that turns paper into pure carbon, the NTU researchers have turned paper fibers into electrodes, which can be made into rechargeable batteries that power mobile phones, medical equipment and electric vehicles.
To carbon paper, the team exposed the paper to high temperatures, which reduced it to pure carbon, water vapor, and oils that can be used for biofuels. Because carbonization occurs in the absence of oxygen, this emits trace amounts of carbon dioxide, and the process is a greener alternative to disposing of kraft paper through incineration, which produces significant amounts of greenhouse gases.
The carbon anodes produced by the research team also demonstrated superior durability, flexibility, and electrochemical properties. Laboratory tests have shown that the anodes can be charged and discharged up to 1,200 times, which is at least twice as durable as the anodes in current phone batteries. Batteries using NTU-made anodes can also withstand greater physical stress than their counterparts, absorbing breaking energy up to five times better.
The method developed by NTU also uses less energy and heavy metal intensive processes than current industrial methods for manufacturing battery anodes. The anode value accounts for 10 percent to 15 percent of the total cost of a lithium-ion batteryThis last method, which uses low-cost waste materials, is expected to lower its manufacturing cost as well.
The results have been published in a peer-reviewed scientific journal additive manufacturing in October.
Using waste paper as a raw material to produce battery anodes would also reduce our dependence on traditional sources of carbon, such as carbon fillers and carbon-producing binders, which are then mined and subsequently treated with harsh chemicals and machinery.
Paper waste, which consists of discarded paper bags, cardboard, newspapers and other paper packaging materials, accounted for nearly a fifth of the waste generated in Singapore in 2020..
Kraft paper bags, which make up the bulk of Singapore’s waste paper, have also been found to have significant environmental impacts compared to their cotton and plastic counterparts, due to their greater contribution to global warming when burned and the potential for environmental toxicity in production. Them, a separate 2020 NTU study have found.
The current innovation that presents an opportunity to recycle waste products and reduce our dependence on fossil fuels, accelerating our transition towards a circular economy, green materials, and clean energy, reflects NTU’s commitment to mitigating our impact on the environment, which is one of the four major human challenges that the university seeks to address through Its NTU 2025 strategic plan.
Associate Professor Lai Changquan, from NTU’s School of Mechanical and Aerospace Engineering, who led the project, said: “Paper is used in many aspects in our daily lives, from gift packaging and arts and crafts, to countless industrial uses, such as heavy-duty packaging, packaging Protective film, and filling voids in construction.However, little has been done to manage them when disposed of, besides incineration, which generates high levels of carbon emissions due to their composition.Our way of giving Kraft paper another chance of life, and channeling it into the growing need for devices such as cars Electricity and smartphones, will not only help reduce carbon emissions, but also reduce dependence on mining methods and heavy industry.”
The research team has filed a patent application with NTUitive, NTU’s innovation and enterprise company. They are also working on commercializing their invention.
A recipe for greener battery parts
To produce the carbon anodes, NTU researchers joined forces and laser-cut several thin sheets of kraft paper to form various lattice geometries, some of which resemble a spiky pinata. The paper was then heated to 1,200 degrees Celsius in an oven without the presence of oxygen, to convert it into carbon, and to form the anodes.
The NTU team attributes the superior toughness, flexibility, and electrochemical properties of the anode to the arrangement of the paper’s fibers. They said the combination of strength and mechanical toughness exhibited by NTU-made anodes would allow phone, laptop and car batteries to better resist shock from drops and accidents.
Current lithium battery technology relies on internal carbon electrodes that gradually crack and collapse after physical shock falls, which is one of the main reasons why battery life is getting shorter over time.
The researchers say their anodes, which are stronger than the current electrodes used in batteries, will help address this problem and extend the life of batteries in a wide range of uses, from electronics to electric vehicles.
Study co-author Mr Lim Guo Yao, a research engineer from NTU College of Mechanical and Aerospace Engineering, said: “Our anodes displayed a range of strengths, such as toughness, shock absorption, and electrical conductivity, which are not found in current materials. These demonstrate structural properties. And functional paper anodes made from kraft paper are a sustainable and scalable alternative to existing carbon materials, and will find economic value in cutting-edge, multifunctional applications, such as the emerging field of structural batteries.”
Professor Lai added: “Our method transforms a common and ubiquitous material – paper – into another extremely durable and much-needed material. We hope our anodes will serve the world’s rapidly growing need for a greener and sustainable material for batteries, whose improper manufacture and management have shown to have a negative impact on our environment.”
Highlighting the importance of the work done by the research team at Cornell University, Professor Juan Hinestroza of the Department of Human-Centered Design at Cornell University in the US, who was not involved in the research, said: “Because kraft paper is produced in very large quantities and discarded I think the creative approach pioneered by the researchers at NTU Singapore has great potential to impact on a global scale.Any discovery that will allow waste to be used as raw material for high-value products such as electrodes and foams is indeed a major contribution.I think this work has It opens a new avenue and motivates other researchers to find pathways to transform other cellulose-based substrates, such as textiles and packaging materials, which are discarded in large quantities around the world.”
The NTU team will conduct further research to improve the energy storage capacity of their materials and reduce the heat energy needed to convert paper into carbon.
 Lux Research. Lithium-ion battery innovation roadmap (2019).
 Singapore National Environment Agency. Reducing overall waste generation in 2020, with less waste being sent to the Simacau landfill (2021).
 Nanyang Technological University. NTU scientists in Singapore reported that plastic bags can be more environmentally friendly than paper and cotton bags in cities like Singapore (2020).
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