Bimetallic transition metal sulfides (TMSs) exhibit considerable potential for energy storage. However, to keep improving the performance of electrochemical systems, effective synthetic techniques for advantageous electrode architecture still need to be developed. The present study involved the synthesis of a NiCo₂S₄/NiS₂/Co₉S₈ nanocomposite (NCS/NS/CS) employing polyethyleneimine by the solvothermal technique, resulting in the creation of an NiCo-precursor.   After that, we annealed the NiCo-precursor with S powder for two hours at 300 °C in an argon atmosphere. The enhanced morphology and NCS/NS/CS electrode conductivity allow for fast ion transport, giving them an excellent electrochemical energy storage feature. At 0.5 A/g, the NCS/NS/CS nanocomposite displays a capacitance of 326 F/g. Additionally, utilizing an NCS/NS/CS electrode for each of the positive and negative electrodes, an NCS/NS/CS//NCS/NS/CS symmetric device was created, providing an exceptional 18.9 Wh k/g of specific energy at a specific power of 529 W k/g at 1 A/g. According to these, the NCS/NS/CS nanocomposite is an excellent choice for an electrode material with remarkable performance in supercapacitors.