Design and Synthesis of Lignin-Based Flexible Supercapacitors

Abstract

Due to the immense demand for flexible supercapacitors, it is important to develop low-cost and smarter solutions. To date, supercapacitors made of eco-friendly materials have been either expensive or of limited use. Herein, we report a solid-state, lightweight, low-cost, and plant-based supercapacitor for applications in flexible electronics. The asymmetric supercapacitor is made of MnO 2 deposited on activated carbon and lignin as a substrate using hydrothermal deposition. With Al/AC/lig-MnO 2 anode and Al/AC cathode, the supercapacitor is assembled using a poly(vinyl alcohol) (PVA)/H 3 PO 4 gel electrolyte. Morphological characterization is conducted using microtomography and scanning electron microscope. Electrochemical performance is assessed using cyclic charge−discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. A series of compositions of AC:lignin:MnO 2 are optimized for best performance. After 2000 cycles, the specific capacitance obtained at 6.01 mA g −1 is 5.52 mF cm −2 , which is up to 13 times reported. Retention is 98.7% after 1000 cycles and 97.5% after 2000 cycles. The maximum energy density, power density, and Coulombic efficiency obtained are 14.11 Wh kg −1 , 1 kW kg −1 , and 98%, respectively. The favorable electrochemical performance makes it useful for a wide variety of electronics. This new approach to fabricate electrodes from green sources, with constituent optimization and cost-effectiveness, marks an important step toward green energy technology development.

Bimetallic tungstate nanoparticle-decorated-lignin electrodes for flexible supercapacitors

“…49,50 Recently, lignin-based carbon materials have shown promising activity in supercapacitors. 51,52 However, challenges exist in terms of achieving high power and energy densities, cyclic stability, and long term cyclic stability for application purposes. Besides, the state-of-art use of lignin emphasizes the use of hazardous processes such as using polyacrylonitrile (PAN) based fibers, or expensive and unsafe techniques like electrospinning.…”

Design and synthesis of high performance flexible and green supercapacitors made of manganese‐dioxide‐decorated alkali lignin

“…The PVA/H 3 PO 4 electrolyte gel was obtained in a similar manner in our recently published work. 21…”

“…In our recently published work, FTIR spectroscopy was done for lignin and AC based electrodes to identify the chemical bonds present in both the materials and understand their chemical structure. 21 The peaks were referenced with the literature report for both materials. [49][50][51] Detailed discussion will not be provided here.…”

“…[14][15][16] In recent years, flexible electronics have attracted great attention, there are many reports about the design, fabrication, and manufacturing of flexible solid-state and portable supercapacitors. [14][15][16][17][18][19][20][21][22][23][24] An asymmetric supercapacitor helps extend the range of the operating voltage past the thermodynamic voltage of the electrolyte decomposition. In addition, the asymmetric design overcomes the charge storage limitation seen frequently within symmetric supercapacitors' designs.…”

“…To eliminate the potential combustion risk of traditionally used liquid electrolytes, and for the ease of use and portability, a supercapacitor that is an all‐solid‐state is greatly desirable 14‐16 . In recent years, flexible electronics have attracted great attention, there are many reports about the design, fabrication, and manufacturing of flexible solid‐state and portable supercapacitors 14‐24 . An asymmetric supercapacitor helps extend the range of the operating voltage past the thermodynamic voltage of the electrolyte decomposition.…”