Efficient conversion of lignin waste and self-assembly synthesis of C@MnCo2O4 for asymmetric supercapacitors with high energy density

Lignin waste from the papermaking and biorefineries industry is a significantly promising renewable resource to prepare advanced carbon materials for diverse applications, such as the electrodes of supercapacitors; however, the improvement of their energy density remains a challenge. Here, we design a green and universal approach to prepare the composite electrode material, which is composed of lignin-phenolformaldehyde resins derived hierarchical porous carbon (LR-HPC) as conductive skeletons and the self-assembly manganese cobaltite (MnCo2O4) nanocrystals as active sites. The synthesized C@MnCo2O4 composite has an abundant porous structure and superior electronic conductivity, allowing for more charge/electron mass transfer channels and active sites for the redox reactions. The composite shows excellent electrochemical performance, such as the maximum specific capacitance of similar to 726 mF cm(-2) at 0.5 mV s(-1), due to the significantly enhanced interactive interface between LR-HPC and MnCo2O4 crystals. The assembled all-solid-state asymmetric supercapacitor, with the LR-HPC and C@MnCo2O4 as cathode and anode, respectively, exhibits the highest volumetric energy density of 0.68 mWh cm(-3) at a power density of 8.2 mW cm(-3). Moreover, this device shows a high capacity retention ratio of similar to 87.6% at 5 mA cm(-2) after 5000 cycles. (c) 2022 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Lignin waste from the papermaking and biorefineries industry is used to prepare a composite electrode material with hierarchical porous carbon and manganese cobaltite nanocrystals. The composite exhibits excellent electrochemical performance and high capacity retention after 5000 cycles. This green and universal approach shows promising potential for improving the energy density of renewable carbon materials.