Automation and Optimized Fabrication of Mxene-Based Textile-Based Supercapacitors

Power management for mobile devices is a research challenge to address global energy concerns. The development of textile-based supercapacitors (TSCs) and the incorporation of TSCs into clothing presents a promising solution. TSCs function as electrochemical double-layer capacitors, storing energy through the accumulation of electrostatic charge at the electrode-electrolyte interface. Here we explore the use of wool and casein yarns for the development of TSCs by coating them with MXene conductive material. The general formula for MXene is M_n+1X_nT_x. This compound is composed of a transition metal (M), carbon or nitrogen (X), and the surface terminations (T). With this study, the primary MXene used for coating was Ti₃C₂T_x due to its conductivity, stability, and non-toxicity. Previous work demonstrated hand-knit TSCs using dip-coated wool. This process is physically tedious, time-consuming, and only allows for small-scale production. To enhance the utility of the coated material, scaling up TSCs’ electrodes are crucial for increasing energy storage capacity. This project specifically focused on automating the coating and knitting process. The previous dip-coating method often resulted in uneven coating; therefore, we used roll-to-roll coating by pulling the yarn from the main spool. The apparatus consisted of a vertical stand approximately four square feet in size. Dozens of holes were drilled into the surface in an alternating pattern, each hole was threaded with a bolt and small-scale pulleys were attached to the end of each bolt. At the top of the panel, a mini scale coating bath was fastened. The bath was made of plexiglass roughly 2cm in depth, and it was equipped with a corresponding plexiglass lid with small metallic prongs protruding out of the bottom. The dimensions of the bath were designed specifically to allow the yarn to be submerged in the solution and drawn continuously through the bath. At the base of the apparatus was a small 4” fan, as well as a larger bolt connected to a small motor. The mounting of the lower bolt allowed for it to be continuously rotated clockwise, away from the end of the pulley system. To coat the thread, first a sufficient length of leader yarn was threaded throughout the pulley system; afterwards, the coating bath was filled with prepared MXene solution, and the yarn was continuously drawn through the solution and air dried using the fan until it reached the spool. After the desired length of yarn was coated and wound onto the spool, the yarn was removed from the bath and allowed to proceed through the pulley system until the uncoated portion had reached the collection spool as well. With this process, single coated samples were prepared as well as quad-coated samples. This automated method resolved the time-limiting factor for the production of the TSCs which was the issue with the previous dip-coating method.