Out‐of‐Plane CuSe/WS ₂ Heterostructure Array as a High‐Performance Electrode Material in Ammonium Ion Supercapacitor in Harsh Environment of Extreme Temperature

Abstract Ammonium‐ion supercapacitor (AISC), being technology innovation for next generation energy storage devices has been limited in practical application. Conventional in‐plane structure leads to short circuit and less participated electro‐active sites in the redox process. However, out‐of‐plane heterostructure array provides rapid charge transport across vertically arranged nanoflakes, and forms less heat pockets due to less contact area between vertically arranged ensembles and in‐plane nanoflake, making them suitable for advanced energy storage applications. Here, the energy storage performances of AISC based on out‐of‐plane heterostructure array is studied, which provides large surface area with ample active sites for rapid charge transport at the surfaces of vertically arrayed nanoflakes. The developed electrode material achieves a high specific capacitance of 555.6 F g ⁻¹ and capacitance retention of 82.3% after 5500 cycles. The assembled quasi‐solid‐state supercapacitor achieves high energy‐power densities, and significant capacitance retention after 5000 cycles. The assembled device can illuminate different colored LEDs and power the scientific calculator. Importantly, the developed heterostructure array can dissipate heat and inhibit short circuit due to limited overlap between 2D CuSe ensemble and 2D WS ₂ nanoflake. Hence, the device can endure a wide range of temperatures with remarkable energy and power densities even in harsh environments of differential temperatures.