Hierarchical Flower Array NiCoOOH@CoLa‐LDH Nanosheets for High‐Performance Supercapacitor and Alkaline Zn Battery

Abstract Nickel oxyhydroxide based energy storage materials have been largely confined by insufficient exposure of active sites which results in low energy efficiency and poor stability. In order to resolve the problems, hierarchical flower array heterostructure NiCoOOH@CoLa‐LDH (denoted as NC@CL) nanosheets are designed with NiCo oxyhydroxide (NiCoOOH, denoted as NC) being tightly covered on CoLa layered double hydroxide (CoLa‐LDH, denoted as CL) nanosheet. This rational design creates more active sites, enlarges the electrode‐electrolyte contact area, improves electron conductivity, and prevents agglomeration during the cycling charge–discharge processes. Density functional theory calculations and differential charges concurrently illustrate that heterostructure formation optimizes the reaction kinetics and promotes electron redistribution. Benefiting from the heterogeneous structure and rich electro‐active sites caused by NC, NC@CL displays outstanding reversible specific capacitance (3228 F g⁻¹ at 1 A g⁻¹). The aqueous rechargeable alkaline Zn battery NC@CL//Zn exhibits a high capacity of 381.1 mA h g⁻¹ at 0.5 A g⁻¹ and cycling durability (98% capacity retention after cycling at 5 A g⁻¹ for 2000 cycles). The excellent electrochemical performances indicate that NC@CL has great application potential as electrode material for aqueous energy storage device.