Search

The ongoing electrification of many energy systems has created a large demand for low-cost and scalable electrical energy storage solutions. Conducting polymer supercapacitors have received significant attention for this purpose due to the abundance of their constituent materials. Although there exists a large body of experimental work on conducting polymer supercapacitors, a detailed understanding of the mixed electronic-ionic transport processes within these devices and the included materials, is still lacking. Modelling, in combination with experimental data, is a powerful tool to facilitate a detailed understanding of the transport processes within the materials and devices. However, to date, there has been a shortage of physical models which account for the non-ideal capacitances typically found in conducting polymer-based supercapacitors. Here, we report a novel model which reproduces experimental data and provides insights into the cyclic voltammograms, galvanostatic charge-discharge curves, self-discharge characteristics, and impedance spectroscopy results of supercapacitors based on the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and cellulose nanofibrils. We find that the non-ideal capacitive characteristics of the supercapacitors can be reproduced by the incorporation of heterogeneous ion transport features within the electrodes, comprising low ion diffusivity regions. The difference in charging rates of the high and low ion diffusivity regions accounts for the experimentally observed trends in cyclic voltammograms and self-discharge characteristics. The developed model demonstrates how complex transport processes, which govern the specifications of organic energy devices, can be analysed beyond the scope of conventional equivalent circuit models. It also provides an insight into how various transport and polarization processes are manifested in real measurement data and thus defines the limiting processes of co, Funding Agencies|Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation; Linkoping University; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Foundation for Strategic ResearchSwedish Foundation for Strategic Research; Wallenberg Wood Science Centre

Eco-friendly and cost-effective materials and processes to manufacture functional substrates are crucial to further advance the area of printed electronics. One potential key component in the printed electronics platform is an electrically functionalized paper, produced by simply mixing common cellulosic pulp fibers with high-performance electroactive materials. Herein, an electronic paper including nanographite has been prepared using a standardized and scalable papermaking technique. No retention aid was needed to achieve a conducting nanographite loading as high as 50 wt %. The spontaneous retention that provides the integrity and stability of the nanographite paper, likely originates partially from an observed water-stable adhesion of nanographite flakes onto the fiber surfaces. The resulting paper exhibits excellent electrical characteristics, such as an in-plane conductivity of 107 S/cm and an areal capacitance of 9.2 mF/cm(2), and was explored as the back-electrode in printed electrochromic displays., Funding Agencies|Digital Cellulose Centre, a competence center set up by the Swedish Innovation Agency VINNOVA; consortium of Swedish forest industries; Wallenberg Wood Science Center (Knut and Alice Wallenberg Foundation); VINNOVA "EPIC" projectVinnova [2017-05413]; Karl-Erik Onnesjo Foundation

The conducive polymer poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) is widely used in organic electronics and printed electronics due to its excellent electronic and ionic conductivity. PEDOT:PSS films exhibit anisotropic conductivities originating from the interplay of film deposition processes and chemical structure. The previous studies found that high boiling point solvent treated PEDOT:PSS exhibits an anisotropy of 3-4 orders magnitude. Even though both the in-plane and out-of-plane conductivities are important for the device performance, the out-of-plane conductivity is rarely studied due to the complexity with the experiment procedure. Cellulose-based paper or films can also exhibit anisotropic behavior due to the combination of their intrinsic fibric structure and film formation process. We have previously developed a conducive paper based on PEDOT:PSS and cellulose which could be used as the electrodes in energy storage devices. In this work we developed a novel measurement set-up for studying the anisotropy of the charge transport in such composite materials. A tool with two parallel plates mounted with spring loaded probes was constructed enabling probing both lateral and vertical directions and resistances from in-plane and out-of-plane directions to be obtained. The measurement results were then input and analyzed with a model based on a transformation method developed by Montgomery, and thus the in-plane and out-of-plane conductivities could be detangled and derived. We also investigated how the conductivity anisotropy depends on the microstructure of the cellulose template onto which the conducive polymer self-organizes. We show that there is a relatively small difference between the in-plane and out-of-plane conductivities which is attributed to the unique 3D-structure of the composites. This new knowledge gives a better understanding of the possibilities and limitations for using the material in electronic and electrochemical de, Funding Agencies|Swedish Foundation for Strategic Research [GMT14-0058]

Durable, electrically conducting yarns are a critical component of electronic textiles (e-textiles). Here, such yarns with exceptional wear and wash resistance are realized through dyeing silk from the silkworm Bombyx mori with the conjugated polymer:polyelectrolyte complex PEDOT:PSS. A high Youngs modulus of approximately 2 GPa combined with a robust and scalable dyeing process results in up to 40 m long yarns that maintain their bulk electrical conductivity of approximately 14 S cm(-1) when experiencing repeated bending stress as well as mechanical wear during sewing. Moreover, a high degree of ambient stability is paired with the ability to withstand both machine washing and dry cleaning. For the potential use for e-textile applications to be illustrated, an in-plane thermoelectric module that comprises 26 p-type legs is demonstrated by embroidery of dyed silk yarns onto a piece of felted wool fabric., Funding Agencies|Swedish Research Council Formas; Knut and Alice Wallenberg Foundation through a Wallenberg Academy Fellowship; European Research Council (ERC) [637624]