Redox molecule decorated polyaniline/graphene porous composite cathode materials for enhancing the energy storage of Zn-ion capacitor

The high energy density requirements of electronics stimulate Zn-ion capacitors (ZICs) to develop new electrode-active materials with high electrochemical performances. As the important cathode materials, the reduced graphene oxide (rGO) sheets easily stack, and the polyaniline (PANI) has the problem of structural expansion/contraction caused by deprotonation thus deteriorating the performance of ZIC. In this work, we developed the porous rGO anchored with 1-Anthraquinonesulfonic acid sodium salt (AQS) decorated PANI (RAP) for high-performance ZICs via a facile one-step solvothermal method. The AQS molecules decorated PANI nano-particles prevent the stacking of rGO nanosheets to form the porous network, and the rGO provides sufficient buffer space for the PANI expansion/contraction process. Moreover, the AQS not only improves the structure stability of PANI by the electrostatic interaction and ionic coordination but also supplies additional pseudocapacitance during the electrochemical process. Therefore, the ZIC based on RAP cathode and Zn anode exhibits a high capacity of 205.1 mAh g−1, and delivers the maximum energy and power density of 175.5 Wh kg−1 and 15.6 kW kg−1, respectively. It also shows 86.2% capacity retention after 10000 cycles at 10 A g−1, indicating the remarkable practicability of RAP cathode materials for ZICs.