Production of an energy-storage electrode paper using a pilot-scale paper machine

The global electrification of our society requires an enormous capacity of electrical energy storage. This drives the demand for low-cost and sustainable solutions, where the electrode materials are key components. In the present work, all-organic supercapacitor electrodes have successfully been demonstrated to be produced on a pilot-scale paper machine, thereby showing the feasibility of large-scale production of “paper-based energy storage”. The material concept was based on activated charcoal from pyrolyzed coconut and cationized cellulose pulp, the latter having small amounts of electrostatically adsorbed PEDOT:PSS in order to create a conducting, percolating network. In a pre-trial lab experiment, it was evident that even small addition of 1 wt% PEDOT:PSS gave a large increase in capacitance compared to samples with only activated charcoal. In the pilot trials, the addition of carboxymethylated nanocellulose and/or carbon black was further investigated. The different additions significantly affected several paper properties such as tensile strength and conductivity, but the specific capacitance of the activated charcoal was not affected and was found to be around 65-70 F/g. As more than half of the electrodes mass consisted of pulp fibers, the specific capacitance of the paper electrodes was about 25-30 F/g, which is in the same order of commercial supercapacitor electrodes. The successful production of several 10-meter-long rolls of supercapacitor electrode paper shows the feasibility of producing energy storage devices with papermaking methods, and the work as a whole provides valuable insights on how to further advance bio-based energy storage solutions.