Mesh-like vertical structures enable both high areal capacity and excellent rate capability

In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics, herein, 2D mesh-like vertical structures (NiCo₂S₄@Ni(OH)₂) with a high mass loading of 2.17 mg cm⁻² and combined merits of both 1D nanowires and 2D nanosheets are designed for fabricating flexible hybrid supercapacitors. Particularly, the seamlessly interconnected NiCo₂S₄ core not only provides high capacity of 287.5 μAh cm⁻² but also functions as conductive skeleton for fast electron transport; Ni(OH)₂ sheath occupying the voids in NiCo₂S₄ meshes contributes extra capacity of 248.4 μAh cm⁻²; the holey features guarantee rapid ion diffusion along and across NiCo₂S₄@Ni(OH)₂ meshes. The resultant flexible electrode exhibits a high areal capacity of 535.9 μAh cm⁻² (246.9 mAh g⁻¹) at 3 mA cm⁻² and outstanding rate performance with 84.7% retention at 30 mA cm⁻², suggesting efficient utilization of both NiCo₂S₄ and Ni(OH)₂ with specific capacities approaching to their theoretical values. The flexible solid-state hybrid device based on NiCo₂S₄@Ni(OH)₂ cathode and Fe₂O₃ anode delivers a high energy density of 315 μWh cm⁻² at the power density of 2.14 mW cm⁻² with excellent electrochemical cycling stability.