Construction of an Ultra‐High‐Energy Density Hybrid Supercapacitor with Self‐Assembled 3D Hydrangea Flower‐like Mo‐rich CoMoO₄ Microstructures

Abstract The accumulation of two‐dimensional nanoflake‐like units into three‐dimensional (3D) hierarchical mesoporous flower‐like microstructures can introduce abundant electroactive surface sites and large contact areas with the electrolyte and enable fast ion/electron transport during the electrochemical process. We propose a simple method of constructing a 3D hydrangea flower‐like mesoporous Mo‐rich CoMoO₄ (CMO) electrode via the solvothermal route (CMO‐ETH) with excellent electrochemical characteristics. This morphology arises from the self‐assembly of primary nanoparticles into flake‐like units, then transformed into hydrangea flower‐like microstructures. Compared with the CMO‐DIW battery‐type electrode (hydrothermally synthesized electrode), the CMO‐ETH had a higher specific capacity of 678 C g⁻¹ at a current density of 1 A g⁻¹. The fabricated CMO‐ETH//activated carbon hybrid supercapacitor (HSC) exhibited an ultra‐high energy density of 103.4 Wh kg⁻¹ at a power density of 750.5 W kg⁻¹. We also successfully turned on the red and green LEDs for 3 minutes after connecting two HSCs in series.