High-performance double “ion-buffering reservoirs” of asymmetric supercapacitors enabled by battery-type hierarchical porous sandwich-like Co3O4 and 3D graphene aerogels

The double ion-buffering reservoirs of asymmetric supercapacitors (ASC) have drawn enormous interest due to their excellent electrochemical performance. Herein, we have prepared the hierarchical porous sandwich-like Co3O4-rGO-CNT > N-PEGm (Co3O4-RGOC, in which rGO was short for reduced graphene oxide and CNT > N-PEGm was modified with methoxypolyethylene glycol by nitrene chemistry) ternary composites via a solvothermal method. Remarkably, the Co3O4-RGOC composites exhibited unique structural features of the opened honeycomb-like structures as “ion-buffering reservoirs.” Moreover, in Co3O4-RGOC composites, both the intermediate sandwich layers of rGO sheets and the interpenetrating CNT > N-PEGms can form double conductive networks as express electron transport channels to improve the electronic conductivity by synergistic effect. The promising Co3O4-RGOC composites can be summarized as capacity of 138.5 mAh g−1 (capacitance of 1420.5 F g−1) at 0.5 A g−1. Furthermore, the 3D rGO-PANI (PANI, polyaniline) aerogels as negative electrode materials also have been prepared by facile in situ polymerization and chemical reduction process. The 3D rGO-PANI presented excellent electrochemical performance of 218.8 F g−1 (capacity of 60.8 mAh g−1) at 0.5 A g−1 due to the hierarchical interconnected porous network structures. Finally, the corresponding asymmetric supercapacitors of Co3O4-RGOC//3D rGO-PANI devices exhibited a high energy density of 41.3 Wh kg−1 at power densities of 775 Wk g−1 with excellent electrochemical performance and long cycle performance. Our work can present a new concept to design the innovative asymmetric supercapacitors with double ion-buffering reservoirs as a combinatorial strategy for useful energy storage and conversion. Graphical abstract The novel double “ion-buffering reservoir” asymmetric supercapacitors are fabricated with the double conductive networks of battery-type Co3O4-RGOC ternary composites as positive electrode and 3D rGO-PANI aerogels as negative electrode for energy storage-conversion application.