• Mckeon, Lorcan
• Coelho, João
• Long, Edmund
• Park, Sang Hoon
• Zhang, Chuanfang
• Coull, Richard
• Shmelov, Aleksey
• Nicolosi, Valeria

Abstract

<jats:p>Supercapacitors composed of nano-layered material electrodes represent a new generation of energy storage technology. Understanding and analyzing the mechanism of how the electrode material changes and degrades during the charge and discharge process is fundamental to maximizing the efficiency of supercapacitors. </jats:p><jats:p>The primary objective of this body of work was to develop a method whereby the electrode-electrolyte interface of a supercapacitor could be analyzed by real time <jats:italic>in-situ</jats:italic> TEM imaging during the charge-discharge process. This experimental approach combines advanced microscopy techniques and electrochemical testing. This approach is in the preliminary stages of experimental development, with very few major published works exploring the specific use of this technique. First, an effective method for repeatable deposition of our layered electrode material was developed, using inkjet printing methods. Our selected active material, MnO<jats:sub>2</jats:sub>-Graphene nanoflakes suspended in Isopropanol was used as our material ink for printing. This suspension was printed onto a specialized electrochemistry TEM chip, featuring Au electrodes and a transparent SiN<jats:sub>2</jats:sub> window for TEM viewing. A low concentration dispersion of 0.5 mg mL<jats:sup>-1</jats:sup> was first used to optimize the printing process and to find the printing parameters that minimized the spreading of the printed line. Having fully optimized the printing process, a high concentration 10 mg mL<jats:sup>-1</jats:sup> suspension of MnO<jats:sub>2</jats:sub>-Graphene was used to deposit the working electrodes of our micro electrochemical cell. </jats:p><jats:p>This cell was tested with a range of potential windows and multiple material deposition thicknesses. In most potential ranges, responses from the active material were difficult to observe due to the noise created by the inherent double layer capacitance of the Au electrode. Higher amounts of deposited material produced slightly higher responses but were for the most part unobservable above the aforementioned noise. These high layer depositions were also electron opaque. During <jats:italic>in-situ</jats:italic> TEM CV testing of these cells, prominent dendritic growth outward from our electrodes were observed. </jats:p><jats:p>Higher CV responses <jats:italic>ex-situ</jats:italic> could be achieved with higher amounts of deposited active material, overcoming the noise generated by the Au-electrolyte reactions. For <jats:italic>in-situ</jats:italic> tests, morphological changes could be observed with lower amounts of material, so that the individual flakes of the Solid-Electrolyte interface can be resolved via TEM analysis.</jats:p>

Topics

• Deposition
• impedance spectroscopy
• dispersion
• layered
• transmission electron microscopy