Copper sulfide nanoparticles on titanium dioxide (TiO2) nanoflakes: A new hybrid asymmetrical Faradaic supercapacitors with high energy density and superior lifespan

In this research work, we have prepared nanocomposites of copper sulfide (CuS) nanoparticles (NPs) with titanium dioxide (TiO 2 ) nanoflakes, with varying contents of CuS, via combined chemical precipitation and sol-gel methods. The effects of CuS concentration on the structural, morphological and electrochemical properties of TiO 2 /CuS nanocomposites for hybrid asymmetric Faradaic supercapacitors was studied for the first time. Electrochemical studies were carried out by using CV, CD, and EIS measurements in a three/two-electrode setups for both capacitive and practical aspects. When serving as an electrode material for the supercapacitors in three-electrode measurements, all the samples demonstrated a capacitive nature with a Faradaic charge storage mechanism due to the prominent redox peaks originating from their CV and voltage plateau in the CD profile. The optimized electrode ST-3 revealed the highest energy storage performance (capacitance: 853 F g −1 ) with low charge transfer and solution resistance compared with other electrodes (CuS: 440 F g −1 , TiO 2 : 326 F g −1 , ST-1: 535 F g −1 , ST-5: 672 F g −1 ) at 1 Ag −1 with the superior rate capability. The ST-3//AC//KOH ASC displayed a high capacitance of 226.5 F g −1 and 80.2 F g −1 at the discharge current was prolonged from 1 to 5 A g −1 after an optimized voltage of 1.8 V in a two-electrode setup. Interestingly, an outstanding energy density of 68.4 W h kg −1 was achieved at a high-power density of 8150 W kg −1 at a discharge current of 1 and 5 A g −1 , with the descent durability of 87 % at a high discharge current of 6 A g −1 when recycled for a large number of 25,000 cycles. These outstanding features highlight an appealing, low-cost, simple, and green route to synthesize other transition metal sulfides for the next-generation electronic devices. Some of the main features of this article are as follows: • TiO 2 /CuS//AC ASC is fabricated for the first time. • TiO 2 -30% CuS electrode had a greater specific capacitance of 853 F g -1 , than pure CuS (440 F g -1 ) • TiO 2 -30% CuS//AC ASC delivered an outstanding energy density of 68.4 W h kg -1 at a high-power density of 8150 W kg -1 • TiO 2 /CuS excellent stability of 87% retention after 25,000 cycles.