Efficient Electrochemical Performance of Sr(OH)₂:MnO₂ Binary Composites for Solid State Symmetric Supercapacitor

In this study, we synthesized a binder‐free composite electrode based on Sr(OH) 2 /MnO 2 material. The active electrode was prepared using the layer‐by‐layer (LBL) technique. The surface architecture of the sample was examined through scanning electron microscopy (SEM) and high‐resolution scanning electron microscopy (FE‐SEM). Further, the microstructural information of the electrode was revealed via transmission electron microscopy (TEM). The composite confirmation was ensured through X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and energy‐dispersive X‐ray spectroscopy (EDX) spectra with mapping analysis. The electrode exhibited the maximum specific capacitance of 554.7 F g −1 at 5 mVs −1 in the 6 M KOH electrolyte. The electrode maintained ~65 % capacitance retention after 10,000 galvanostatic charge‐discharge (GCD) cycles. Furthermore, the assembled symmetric supercapacitor device exhibited the highest specific capacitance value of 124.7 F g −1 @ 5 mVs −1 within a potential span of 1.2 V. This device demonstrated the capability to illuminate light‐emitting diodes (LEDs) of different colors. The energy and power densities of the device were calculated as 26.66 Wh kg −1 and 9884.54 W kg −1 respectively. The stability performance of the device was ~57 % after 10,000 GCD cycles. These findings strongly suggest that the material and the device represent promising options for future energy storage applications.