Structures and interfaces of CNT: pyrolytic C coated Al foil and its performance as current collector of electrochemical double layer capacitor

摘要

Al foil with CNT—pyrolytic C composite layer of 300 nm (CNT-C/A1) has been prepared by coating Al foil with CNT and polymeric precursors and heating it in rolls at 585 ℃ in argon flow. By Raman analysis, both sp3 and sp2 mode carbon are formed in pyrolytic C produced in-situ in the coating, and has interacted with walls of CNTs. Well—combined interfaces of CNT with pyrolytic C and carbon coating with Al matrix are seen in CNT-C/ Al by scanning electron microscope and high resolution transmission electron microscopy. Metallurgical bonding of carbon layer and Al matrix is confirmed by X-ray Diffraction for generation of Al_4C_3 in CNT-C/Al. Interfacial resistances of Al foil with carbon coating are evaluated by resistances of "sample piece/PEDOT layer/sample piece" stacks, which is 12 ±2 mΩ for CNT-C/A1 and 44 ±2 mΩ for CNT-C/Al-control with generation of Al_4C_3 restrained. Researches on electrochemical double layer capacitor (EDLC) electrodes reveal that samples using etched Al foil (E-Al) as current collector present higher sheet resistances than CNT-C/Al. EDLCs using CNT-C/A1 as current collector show higher capacitances and lower resistances than those using E-Al, and the differences become bigger when current flow increases. Notably, EDLCs using CNT-C/Al prove outstanding stability in resistance during galvanostatic charge—discharge cycles at current of 4.0 A for 10,000 times and accelerate lifetime test at 85 ℃/2.85 V for 64 h, while the corresponding increase rates for EDLC using E-Al are 19.6% and 30% respectively.