Heavy Metal-Free Tannin from Bark for Sustainable Energy Storage

Abstract

A novel renewable cathode made from earth abundant, low-cost materials can contribute to the intermittent storage needs of renewable energy-based society. In this work, we report for the first-time tannin from Nature as a cathode material. Our approach exploits the charge storage mechanism of the redox active quinone moiety. Tannins extracted from tree bark using environmental friendly aqueous solvents have the highest phenol content (5.56 mol g) among all the natural phenolic biopolymers, 5000 times higher than lignin. Tannins coupled with a conductive polymer polypyrrole acquire high specific capacitance values of 370 F g at 0.5 A g as well as excellent rate performance of 196 F g at 25 A g. Additionally, we employed carbonized wood as an electrode substrate to produce a sustainable electrochemical device with dramatically improved performance compared to conventional devices. The high surface area provided by the well-aligned, cellular porosity of wood-derived substrate combined with the high mobility of ions and electrons in the carbonized cell walls and deposited tannin can achieve an areal capacitance of 4.6 F cm at 1 mA cm, which is 1.5 times higher than activated wood carbon.

Interplay of Porosity, Wettability, and Redox Activity as Determining Factors for Lithium–Organic Electrochemical Energy Storage Using Biomolecules

“…Catechol groups in hybrid materials with microporous carbons contribute to the overall capacity both through the increased wettability of carbon surfaces by the electrolytes and redox activity. Still, catechol groups are rather rare in nature, notable exceptions are dopamine and tannic acid, which have been described previously for electrochemical energy storage . In contrast, guaiacol groups (which are chemically similar; cf.…”

“…[34] Comparison of the electrochemical performanceofc atechol and guaiacol groups Catecholg roups in hybrid materials with microporous carbons contributet ot he overall capacity both through the increased wettability of carbon surfacesb yt he electrolytes and redox activity.S till, catechol groups are rather rarei nn ature, notable exceptionsa re dopamine and tannic acid, which have been described previously for electrochemical energy storage. [35][36][37][38][39][40] In contrast, guaiacol groups (which are chemically similar;c f. Scheme1)a re abundanti nn ature,f or example, in low-value biogenic materials such as lignin. To our knowledge,s uch materials have never been used in secondaryl ithium ion batteries without additional redox active polymers to date.…”

Sustainable Battery Materials from Biomass

“…Another class of abundant naturally occurring polyphenols is tannins, which are widespread, for example, in wood bark and often bear a high density of catechol‐like functionalities. Similar to lignin, some tannins may be used in combination with conjugated polymers or carbons for charge storage applications. Moreover, in combination with biomass‐based carbons, the omittance of fluorinated binders or hazardous solvents is especially appealing for fabricating sustainable electrodes…”

Enhancing Energy Storage Devices with Biomacromolecules in Hybrid Electrodes

“…These natural products can be found in certain plant tissues, such as bark, fruit and wood, and can be removed from these sources by extraction with water . Mukhopadhyay et al used tannins extracted from bark of the chestnut tree to fabricate tannin/PPy electroactive hybrid materials by oxidative electropolymerization on gold‐coated silicon chips and on sustainable carbonized wood in order to prepare a free‐standing cathode entirely from biomass . PPy effectively prevents the dissolution of tannins into the aqueous solution and provides electronic conductivity to facilitate electron transport from its active quinone sites.…”

“…[64,86] Mukhopadhyay et al used tannins extracted from bark of the chestnut tree to fabricate tannin/PPy electroactive hybrid materials by oxidative electropolymerization on goldcoated silicon chips and on sustainable carbonized wood in order to prepare a free-standing cathode entirely from biomass. [87] PPy effectively prevents the dissolution of tannins into the aqueous solution and provides electronic conductivity to facilitate electron transport from its active quinone sites. As a result, the tannin/PPy cathode possesses a discharge capacity of ≈370 F g −1 at 0.5 A g −1 current rate and retained 196 F g −1 at a high current rate of 25 A g −1 , due to their rapid and reversible conversion between the quinone and phenol moiety.…”