A rapid increase in energy demand has strained natural resources. As such, there is an urgent need to develop novel materials with higher performance capabilities and promote green technology. In this regard, advanced manufacturing and tribological characterization of novel and green materials are of high importance. The conventional materials used in energy storage devices, such as batteries and supercapacitors, suffer from problems of electric wastes, high-cost, toxicity, and non-biodegradability. There is an impending need to find novel energy storage materials that can provide high electrochemical performance while being environmentally sustainable. Lignin is a naturally occurring source of carbon that holds a high promise for energy storage applications due to its abundance, low-cost, and bio-degradability. However, unprocessed lignin has several issues that limit its electrochemical performance. Uneven pore size and distribution, highly complex surface chemistry, largely unknown surface functional groups, and an intricate 3D network of chains in unprocessed lignin, create hindrance to charge transport and ion mobility. As a result, the lignin-based electrochemical devices are prone to instability, poor performance, and low cycle life. Hence, it is of utmost importance to understand the surface morphology and characteristics of lignin electrodes in detail. In this research, MnO~2~ deposited alkali lignin-based electrode is synthesized for application in a flexible supercapacitor. MnO~2~ particles deposited on alkali lignin, via hydrothermal treatment, was used as the electroactive material with an Al substrate. An asymmetric supercapacitor, with Al/lig/MnO~2~ as the anode, was assembled using an aqueous gel electrolyte of PVA/H~3~PO~4~ and Al/AC as the cathode. To study the morphology and microstructure of the electrode, synchrotron X-ray microtomography was employed. Data analysis was performed using image processing and several surface parameters were calculated and compared. The 3D concatenated images revealed details on surface morphology, surface packing density, roughness, chain length, and 3D structure of chains. The electrochemical system performance was assessed using cyclic charge-discharge (CCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Three varying ratios of lignin and MnO~2~ were tested and analyzed to achieve optimal performance. The highest specific capacitance obtained was 379 mF cm^-2^ at a current density of 40 mA g^-1^, which is 900 times greater than currently reported. The supercapacitor exhibited high capacitance retention of 80%, an energy density of 6 Wh kg^−1^, and a power density of 355 W kg^−1^. The exhibited remarkable performance makes this supercapacitor suitable for several applications. Thus, this work utilizes synchrotron tomography in revealing several important surface characteristics of a novel and green supercapacitor electrode. The electrode is of high performance and sustainable. This knowledge from this research can be used to drive further research and development in the tribology of novel and green materials.


Tribological Characteristics of Green Supercapacitors

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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