Optimization of Non‐Pyrolyzed Lignin Electrodes for Sustainable Batteries

Abstract

Lignin, a byproduct from the pulp industry, is one of the redox active biopolymers being investigated as a component in the electrodes for sustainable energy storage applications. Due to its insulating nature, it needs to be combined with a conductor such as carbon or conducting polymer for efficient charge storage. Herein, the lignin/carbon composite electrodes manufactured via mechanical milling (ball milling) are reported. The composite formation, correlation between performance and morphology is studied by comparison with manual mixing and jet milling. Superior charge storage capacity with ≈70% of the total contribution from the Faradaic process involving the redox functionality of lignin is observed in a mechanically milled composite. In comparison, manual mix shows only ≈30% from the lignin storage participation while the rest is due to the electric double layer at the carbon–electrolyte interface. The significant participation of lignin in the ball milled composite is attributed to the homogeneous, intimate mixing of the carbon and the lignin leading the electronic carrier transported in the carbon phase to reach most of the redox group of lignin. A maximum capacity of 49 mAh g−1 is obtained at charge/discharge rate of 0.25 A g−1 for the sample milled for 60 min.

Lignin Functionalized with Catechol for Large‐Scale Organic Electrodes in Bio‐Based Batteries

“…I capacitive is mostly due to the creation of electric double layer between the conducting carbon phase and the electrolyte, while I redox activity reflects the amount of phenol redox groups involved in the charge storage on the lignin phase. [ 23 ] Because the electric double‐layer contribution is small and likely similar between the various four samples, the large current ratios R found for the two catechol modifications (C‐AIKL with R = 7.87 and C‐ ASKL with R = 7.61) compared to the nonfunctionalized fraction (ASKL with R = 5.35 and AIKL with R = 5.27) clearly indicate the success of the approach to increase charge storage capacity by the introduction of aromatic phenolic groups in lignins.…”

“…[ 14 ] Kraft lignin composited with carbon black via ball milling led to a much cheaper alternative with slightly better performance (49 mAh g −1 ). [ 23 ] A significant improvement is obtained by fine tuning the composition of a synthetic polymer made of syringol (S), guaiacol (G), and hydroquinone (HQ). S and G are monomers in natural lignins.…”

Bioelectronic Approaches for On-Demand Generation of Reactive Oxygen Species

“…78 Since lignin and LS contain hydroquinone structures which are known redox species 79 (see Figure 7) and are a shared features of known organic compounds which can photochemically convert O2 to H2O2 8 , they were therefore investigated for H2O2 generation. Further applications of lignins which make use of this redox-active unit are in batteries 80 and supercapacitors 79,81 . Additionally, lignin is reported to enhance the photocatalytic activity when used as a composite material for photocatalytic systems.…”

Wood Templated Organic Electronics

“…Subsequently, multiple endeavors have been undertaken to advance lignin-based energy storage devices. Kraft lignin 55 , lignosulfonate 15 , and various lignin sources have been employed in combination with electroactive materials like carbon and conducting polymers to fabricate sustainable supercapacitors and batteries 15,56,57 . Lignin has also found application as an electrolyte in redox flow batteries 58 and other electrochemical systems 15,54 .…”