Polyaniline, Vanadium Dioxide, and Nickel Hydroxide Nanocomposites for Rate Capable and Robust Aqueous Hybrid Supercapacitors

A series of PANI/VO₂/Ni(OH)₂ (PVN) nanocomposites with different weight compositions was synthesized by a single-step chemical method to determine the best weight composition and, in turn, to study their supercapacitive behavior. A composite with a weight composition of PANI58.33%:VO₂25.00%:Ni(OH)₂16.67% (PVN16) provided superior performance as a symmetric supercapacitor cell among the PVN composites synthesized. The obtained performances of PVN16 are a specific capacity (Q) of 60.44 C g^‒1, a specific energy (E) of 10.07 W h kg^‒1, a specific power (P) of 0.6 kW kg^‒1, and a coulombic efficiency (ƞ) of 98.18%. In addition, this symmetric device exhibited no reduction in its Q up to 5000 cycles at 0.4 V s^‒1. The asymmetric supercapacitor cells of the PVN16 were fabricated using activated carbon in the presence of two different aqueous electrolytes, which are 1 M H₂SO₄ and a liquid by-product that was obtained after the synthesis of PANI (SLP). The asymmetric cell in the presence (ITP) of SLP provided electrochemical stability up to 1.55 V, better performance, and the E comparable with vanadium redox flow batteries (VRFB). The obtained higher energy storage the parameters of a Q of 102.8 C g^‒1, an E of 22.13 W h kg^‒1, a P of 0.775 kW kg^‒1, and a ƞ of 70.44%. The asymmetric devices exhibited 95% and 73.88% retention of their initial Q up to 5000 cycles at 0.4 V s^‒1 ITP of 1 M H₂SO₄ and SLP, respectively. The symmetric and asymmetric devices exhibited 15.75% and 22.33% retention of their initial Q up to 17 and 30 A g^‒1, respectively, ITP of H₂SO₄ exhibiting their promising rate capability. Since, the PVN16 asymmetric cells ITP of SLP provide higher energy than those of the VRFB, they could be used to fabricate real-time hybrid supercapacitor devices at desirable working voltages for real applications as energy storage and conversion devices, where both high E and P are required.