3D nitrogen and boron dual-doped carbon quantum dots/reduced graphene oxide aerogel for advanced aqueous and flexible quasi-solid-state zinc-ion hybrid capacitors

As prospective energy storage devices, zinc-ion hybrid capacitors (ZHCs) still suffer from unsatisfactory cathode materials. Herein, the three dimensional (3D) N, B dual-doped carbon quantum dots/reduced graphene oxide (N, B-CQDs/rGO) composite aerogel is prepared via a one-pot hydrothermal method. Thanks to the synergism of CQDs modification and N, B dual-doping, the resultant N, B-CQDs/rGO composite aerogel delivers superior electrochemical properties. Furthermore, the as-obtained N, B-CQDs/rGO composite aerogel is served as a cathode for aqueous and flexible quasi-solid-state ZHCs for the first time. Impressively, the aqueous N, B-CQDs/rGO//Zn ZHC manifests a large energy density of 96.2 Wh·kg⁻¹ at 80 W·kg⁻¹ and still remains a high energy density of 54.7 Wh·kg⁻¹ at a superb power density of 80 kW·kg⁻¹. Meanwhile, kinetic analyses are employed to elucidate the prominent power performance, and various ex situ tests are undertaken to explore the energy storage mechanism of aqueous ZHC. More notably, the flexible quasi-solid-state N, B-CQDs/rGO//Zn ZHC displays a desirable energy density (89.1 μWh·cm⁻²), a superior power density (96,000 μW·cm⁻²) and exceptional flexible performance. The present study offers a valuable reference for designing and developing advanced cathode materials for aqueous and flexible quasi-solid-state ZHCs.