Controllable synthesis of vanadium-doped nickel-chalcogenide/graphene cathodes and MnV₂O₆·2H₂O/graphene anode for high-energy asymmetric supercapacitors

Exploring novel electrode materials with rational morphology and structure is crucial for the fabrication of high-performance supercapacitors. In this work, novel vanadium-doped nickel-chalcogenide/reduced graphene oxide cathodes (NiV-S/rGO and NiV-Se/rGO) and MnV₂O₆·2H₂O/rGO anode are controllably prepared through a facile solvothermal method. Benefiting from the two-dimensional structure and desirable surface electronic environment, the graphene-supported NiV-X/rGO (X = S and Se) cathodes exhibit outstanding capacitive performance (1734.2 and 1577.2C·g⁻¹ at 2 A·g⁻¹), remarkable cycling stability and exceptional rate performance. Meanwhile, with the encapsulation of graphene protect layers, the MnV₂O₆·2H₂O/rGO anode also shows a significantly enhanced specific capacity and superb cycling stability (95.8 % retention after 10,000 cycles). When assembled into asymmetric supercapacitors, the NiV-S/rGO//MnV₂O₆·2H₂O/rGO and NiV-Se/rGO//MnV₂O₆·2H₂O/rGO devices not only exhibit ultra-high energy densities (82.4 and 60.0 Wh·kg⁻¹ at a power density of 800.0 W·kg⁻¹), but also display superior cycling stabilities (91.5 % and 93.7 % retention after 10,000 cycles). These excellent properties demonstrate their potential application prospect in supercapacitor with high energy densities.