Switchable Polyacrylonitrile‐Copolymer for Melt‐Processing and Thermal Carbonization—3D Printing of Carbon Supercapacitor Electrodes with High Capacitance

Abstract

allowing fast charge-discharge kinetics, long cycling stability, and high capacitance. [1][2][3][4] Typically, such carbon electrodes are produced from active carbon powders. [5] The required structural integrity of the electrode can only be achieved by mixing the active carbon powder with binders; however, these binders are often electrochemically inert and decrease the overall performance of the electrodes by blocking the surface and porosity of the active material. To produce electrodes without binder, carbon fiber non-wovens present ideal materials for components in fuel cells, batteries, and supercapacitors. [5][6][7][8][9][10][11] The most widely used precursor for carbon fibers and materials is polyacrylonitrile (PAN). [12] PAN can be converted into carbon materials in a two-step thermal conversion process. The first step is called stabilization, in which the nitrile groups engage in mostly intramolecular cyclization reactions, forming polymer ribbons. Stabilization is conducted in an oxidative atmosphere between 200 and 300 °C. [13][14][15] Strong dipolar interactions between the nitrile groups entail a high melting temperature T m , well above the activation energy for the cyclization reaction-or stabilization. The second step is the carbonization, in which the polymer ribbons fuse to graphitic domains. Carbonization is conducted in an inert atmosphere above 1000 °C. [13,16,17] Because of its sensitivity towards high temperatures-with potential for thermal run-away, due to the exothermic nature of the stabilization reaction-PAN is typically processed from solution.However, solution processing limits the final architectures of the desired carbon materials to fibers and films. [18][19][20] Fiber spinning and film formation processes are energy consuming and costly, as they require large amounts of solvents, which on an industrial scale have to be recovered and eventually disposed of. [21][22][23][24] A much more economic manufacturing approach would be to process PAN from its melt. [17,25,26] This strategy would enable 3D printing techniques such as polymer extrusion-based additive manufacturing (EAM) with full freedom-ofdesign, expanding the possible shapes of carbon materials from 1D fibers and 2D films to monolithic 3D workpieces. To our advantage, EAM would allow fully automated shaping of PAN into complex structures. EAM is scalable, fast, solvent-free, and Polyacrylonitrile (PAN) represents the most widely used precursor for carbon fibers and carbon materials. Carbon materials stand out with their high mechanical performance, but they also show excellent electrical conductivity and high surface area. These properties render carbon materials suitable as electrode material for fuel cells, batteries, and supercapacitors. However, PAN has to be processed from solution before being thermally converted to carbon, limiting its final format to fibers, films, and non-wovens. Here, a PAN-copolymer with an intrinsic plasticizer is presented to reduce the melting temperature and avoid undesired entering of the t...

Design and 3D Printing of Polyacrylonitrile‐Derived Nanostructured Carbon Architectures

“…The stabilization of 3D printed PAN materials was carried out by heating from ambient temperature to 220 °C in air at a rate of 1 °C min −1 . The color of samples changed from orange to black, indicating both the dehydrogenation of PAN and cyclization of the nitrile groups to form a ladder‐like, conjugated polymer, [ 14 ] as well as partial degradation of Sudan II dye ( Figure ).…”

“…However, PAN‐based materials are not typically prepared using digital light processing techniques, arguably one of the most utilized 3D printing methods. [ 14 ] Common approaches for 3D printing of PAN‐containing materials include the use of an AN–butadiene–styrene thermoplastic polymer, [ 15 ] or PAN copolymers with switchable melting temperature, [ 14 ] as a feedstock for fused filament fabrication. Subsequently, the as‐printed structures are pyrolyzed to produce carbonaceous objects.…”

Capillary Evaporation on High‐Dense Conductive Ramie Carbon for Assisting Highly Volumetric‐Performance Supercapacitors

“…According to the peak fitting of carbon element, C 1s spectrum is divided into four peaks at 284.80, 285.66, 288.75, and 291.37 eV, corresponding to the CC/CC, CO, CO, and OCO, respectively (Figure 2m). [ 33 ] Among them, content of CC peak is obviously higher than that of natural conductive ramie carbon (NCRC), presenting the greatly‐improved crystallinity. This high crystallinity helpfully improves the thickness of pseudo‐graphite layer (Table S2, Supporting Information).…”

Trendbericht: Makromolekulare Chemie 2023

“…24) Auch an Elektrodenmaterialien wurde geforscht: Kühne und Mitarbeitende entwickelten ein 3-D-druckbares Polyacrylnitrilcopolymer für Kohlenstoffsuperkondensatorelektroden mit hoher elektrischer Kapazität. 25) Abseits von Batterien entwickelten Abetz, Klassen und Mitarbeitende bessere Speicherpolymere für H 2 . 26) Energiewende bedeutet auch, bewusster mit Energie umzugehen und den Energiebedarf bei gleichzeitigem Erhalt der Lebensqualität zu senken.…”