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.

Automated summary

The Co3O4-RGOC composite and 3D rGO-PANI aerogel, prepared by solvothermal method and in situ polymerization/chemical reduction process respectively, exhibit excellent electrochemical performance as positive and negative electrode materials. Combining these two materials as asymmetric supercapacitors results in high energy density and excellent cycle performance.