Polyaniline-Assisting Construction of Highly Phosphomolybdate-Loading Electrode with Nano-Morphology Towards Aqueous Supercapacitor and Zinc-Ion Battery.

The development of a high-mass-loading-based electrode represents a pivotal breakthrough for achieving high capacitance. Polyoxometalates (POMs) possess obvious redox activity and theoretical specific capacity, demonstrating potential value as an electrode material for aqueous supercapacitors and zinc-ion batteries. Herein, phosphomolybdate was deposited in a highly mass-loading form around carbon fibers via an electrochemical method. Polyaniline effectively immobilized the phosphomolybdate and led to the formation of nanofibrous morphology. Moreover, a multilevel nanostructure can be observed: the outermost layer exhibited a nanoarray architecture, and the interior consisted of densely packed nanofibers. The nanofibrous morphology provided abundant exposed active sites, thereby significantly enhancing the capacitance and rate performance. The fabricated PANI@POM/CC electrode showed a high areal capacitance of 7679.46 mF cm-2 in H2SO4 solution with the high loading of 12 mg cm-2. 64.4% of its capacitance can be retained, when the charge/discharge current density was increased by 30 times. The factors influencing the immobilization and accumulation of nanofibers were investigated. An asymmetric supercapacitor assembled by using PANI@POM/CC and PANI/CC-1 as the cathode and the anode achieved a volumetric capacitance of 4.7 F cm-3. The zinc-ion battery cells with PANI@POM/CC as the cathode delivered a high specific capacity of 244 mAh g-1 at 0.1 A g-1 and 84.8% of capacity retention over 500 cycles.