Lignin Laser Lithography: A Direct‐Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

Abstract

In this work, a simple lignin‐based laser lithography technique is developed and used to fabricate on‐chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser‐scribed graphene (LSG) electrodes by a simple one‐step CO2 laser irradiation. This step is followed by a water lift‐off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm−1), and have a high specific surface area (338.3 m2 g−1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm−2), high volumetric energy density (≈1 mWh cm−3), and high volumetric power density (≈2 W cm−3). The versatility of lignin laser lithography opens up the opportunity in applications such as on‐chip microsupercapacitors, sensors, and flexible electronics at large‐scale production.

Synthesis Strategies of Porous Carbon for Supercapacitor Applications

“…High graphitization (conductivity) and high SSA are contradictory factors since amorphous carbons with relatively low conductivities (<1 S cm −1 ) are obtained from the traditional pyrolysis process. Laser scribing opens a new pathway for graphene‐based electrode materials with high conductivity (as high as 60 S cm −1 ) for SCs 228. Given the limited SSA of state‐of‐art LSG electrodes, we still need other ways to improve the SSA of LSG.…”

“…Furthermore, they developed inert‐gas‐protected laser scribing and multiple laser scribing processes which enable the successful transformation from wood,226 cloth,227 bread into LSG (Figure 15b). Alshareef et al developed the LSG from natural lignin and used LSG as electrodes for high‐energy microsupercapacitors through a direct‐write lignin laser lithography technique 228. Besides, Alshareef et al developed high‐power SC based on the LSG from amorphous carbon spheres 229.…”

3D Laser Scribed Graphene Derived from Carbon Nanospheres: An Ultrahigh‐Power Electrode for Supercapacitors

“…Similar to the CV test, in the GCD test, the CNS‐LSG shows high areal capacitance but low rate capability in the voltage range of 0–2 V. The CNS‐LSG electrodes show a capacitance of 0.800 mF cm −2 , and 38.5% of the capacitance is still retained when the GCD current density increased from 0.078 to 31.2 mA cm −2 (Figure E). The rate capability of CNS‐LSG is further compared with other LSGs from literature . In fact, CNS‐LSG shows the best rate capability among all previously reported LSGs with a high capacitance retention of ≈ 60%, after increasing the GCD current density by two order of magnitude (Figure F).…”

UV Laser‐Induced Polyimide‐to‐Graphene Conversion: Modeling, Fabrication, and Application

“…Graphene is an important material for both fundamental sciences and industrial applications such as in microelectronics, energy storage, flexible display, transparent conductive electrode, composite, biological, and biomimetic devices . In spite of the intense research efforts on achieving chemical‐free, low‐temperature processing of high‐quality graphene, cost‐effective synthetic methods to directly fabricate graphene sheets on a substrate are still lacking …”