The power trio: CoS-CoFe2O4-rGO ternary composite to enhance energy density of all-solid-state asymmetric supercapacitors

This study addresses a critical challenge in supercapacitors by boosting their energy density without compromising the power density. For this, cobalt sulfide-cobalt ferrite-reduced graphene oxide (CS-CFO-rGO) nano- composite was prepared using the hydrothermal method and employed as an electrode for supercapacitors. Detailed analysis of X-ray photoelectron spectroscopy and ab initio density functional theory confirmed the presence of cobalt ferrite nanocrystals with both normal and inverse occupation types, which is the most suitable phase of CFO for the supercapacitor applications. The CS-CFO-rGO composite synergistically combined the large specific surface area offered by the flower-like structure of CS, significant conductivity of rGO, and abundant electroactive sites of both the CFO and CS which led to improved overall supercapacitive performance. The ternary composite exhibited a superior specific capacitance of 1381 F g- 1 at 0.5 A g- 1 . An asymmetric super- capacitor (ASC) device was fabricated which achieved 55.25 Wh kg- 1 energy density and 375 W Kg- 1 power density with notable stability. The practical applicability of the ASC device was demonstrated by powering LEDs.