Sustainable Production of High-Energy Density Flexible Supercapacitors through Direct Laser Writing on Environmentally Friendly Substrates

Supercapacitors (SC) and graphene are two cutting-edge technologies at the forefront of energy storage and materials science. Supercapacitors, often referred to as ultracapacitors or electrochemical capacitors, are energy storage devices that bridge the gap between traditional capacitors and batteries. They are known for their exceptional energy storage and rapid charge-discharge capabilities, making them essential components in a wide range of applications, from consumer electronics to electric vehicles and renewable energy systems^[1]. Graphene, on the other hand, promises to revolutionize the field of supercapacitors, offering significant improvements in terms of energy storage, charge-discharge rates, and overall performance. This effect is mainly due to graphene's high surface area, high electrical conductivity, exceptional capacitance and flexibility, and lightweight. Among a plethora of graphene synthesis and deposition methods, laser-induced graphene (LIG) is one of the most studied^[2]. This innovative technique has attracted considerable attention for its potential to improve energy storage devices and scalability. However, in terms of energy storage, LIG has mostly been fabricated in polyimide, which compromises the sustainability of the fabricated devices. In addition, as an electrical double layer (EDL) material, LIG-based supercapacitors will always have a relatively low energy density^[3].<br/><br/>In this work, we have developed a simple yet elegant sustainable strategy to fabricate LIG SC on paper and cork with improved electrochemical performance. Based on a fire-retardant treatment, the fabricated EDLC exhibited areal-specific capacitances as high as 4.6 mF cm^-2 (0.015 mA cm^-2) for paper and 1.43 mF cm^-2 (0.1 mA cm^-2) for cork. In addition, the devices have excellent cycling stability (&gt; 10,000 cycles at 0.5 mA cm^-2) and good mechanical properties^[4,5]. In order to increase the energy density of the device, two different strategies were explored. In one approach, the substrate was impregnated with a precursor that is converted to manganese oxide, a pseudocapacitor material, upon laser irradiation. The other strategy involved electrodepositing the manganese oxide onto LIG electrodes. Both methods resulted in supercapacitors with relatively high energy densities. The advantages and disadvantages of both techniques will be discussed in detail in this talk.<br/><br/>Despite these promising advantages, it's important to note that graphene-based supercapacitors are still undergoing extensive research and development to optimize their performance and cost-effectiveness. Challenges related to scalability and production costs need to be addressed for widespread commercial adoption. Nevertheless, laser-induced graphene supercapacitors hold great promise for improving energy storage solutions and contributing to a more sustainable and energy-efficient future.<br/><br/>References<br/><br/>[1] J. Coelho, M. P. Kremer, S. Pinilla, V. Nicolosi, <i>Curr Opin Electrochem</i> <b>2020</b>, <i>21</i>, 69.<br/>[2] R. Ye, D. K. James, J. M. Tour, <i>Acc Chem Res</i> <b>2018</b>, <i>51</i>, 1609.<br/>[3] Z. Peng, J. Lin, R. Ye, E. L. G. Samuel, J. M. Tour, <i>ACS Appl Mater Interfaces</i> <b>2015</b>, <i>7</i>, 3414.<br/>[4] J. Coelho, R. F. Correia, S. Silvestre, T. Pinheiro, A. C. Marques, M. R. P. Correia, J. V. Pinto, E. Fortunato, R. Martins, <i>Microchimica Acta</i> <b>2023</b>, <i>190</i>, 1.<br/>[5] S. L. Silvestre, T. Pinheiro, A. C. Marques, J. Deuermeier, J. Coelho, R. Martins, L. Pereira, E. Fortunato, <i>Flexible and Printed Electronics</i> <b>2022</b>, <i>7</i>, 035021.