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Rational designing of electrode materials having high surface area can accomplish the enhanced charge‐storing ability of the electrochemical energy storage devices. Therefore, the surface area of cobalt vanadium oxide (CVO) material is controlled by changing growth dynamics in successive ionic layer adsorption and reaction methods. Structural analysis confirms the formation of hydrous cobalt vanadium oxide nanoparticles (Co3V2O8⋅nH2O) thin film electrodes, and alteration in the surface area with change in growth dynamics is observed in Brunauer–Emmett–Teller analysis. The CVO1:1 thin film electrode prepared at optimal growth dynamics illustrates high specific capacitance (Cs) (capacity) of 793 F g−1(396.7 C g−1) at 0.5 A g−1, respectively. Moreover, aqueous hybrid supercapacitor devices constructed using CVO1:1 as cathode exhibit high Csof 133.5 F g−1at 1.1 A g−1, specific energy (SE) of 47.7 Wh kg−1with specific power (SP) of 0.90 kW kg−1. The solid‐state hybrid supercapacitor devices also offer high Csof 102.9 F g−1at 0.3 A g−1, SE of 36.6 Wh kg−1at SP of 0.30 kW kg−1. In the SILAR approach, the dipping time plays a critical role in improving the surface area of the material and, consequently, electrochemical performance, as the current work amply indicates. The surface area of cobalt vanadium oxide (CVO) material is controlled by changing growth dynamics through dipping time variation in successive ionic layer adsorption and reaction method, and fabricated hybrid supercapacitor devices comprised with optimized CVO1:1 cathode demonstrate high electrochemical performance.

Developing self-supported electrode material in the absence of electro-inert binders considering the effortless transfer of charges and manipulating physicochemical properties of electrodes in energy storage devices is essential. Hence, the present attempt emphasizes the facile synthetic strategy of successive ionic layer adsorption and reaction (SILAR) for controlled nickel vanadate (NV) growth over the conducting plate. In SILAR synthesis, the growth rate is monitored by rinsing and adsorption/reaction time variation to tune the surface area, mesoporous structure, and surface morphology of NV thin films. As a result, the formation of mesoporous, amorphous, hydrous nanoparticles of NV over the stainless-steel substrate is affirmed by structural analysis. Furthermore, alteration in specific surface area with variation in growth rate is observed in BET analysis. As a result, the optimal NV(1:2) thin film electrode exhibited the highest specific capacity (capacitance) of 355C g−1(710 F g−1) at 1 A g−1current density. Moreover, the fabricated aqueous hybrid supercapacitor device (NV(1:2)//rGO) delivered 109 F g−1specific capacitance at 1.3 A g−1current density, and the device exhibited a maximum specific energy (SE) of 44 Wh kg−1at a particular specific power (SP) of 1.14 kW kg−1. Furthermore, the solid-state hybrid supercapacitor (NV(1:2)//PVA-KOH//rGO) device conferred a specific capacitance of 89 F g−1at 0.5 A g−1current density and an SE of 36 Wh kg−1at 0.482 kW kg−1SP. This research paved an avenue to the binder-free, scalable synthesis of NV electrodes and employed them as a cathode in practical applications of hybrid energy storage devices.

Recently, excellent electrochemical performance and good conductivity of transition metal phosphates (TMPs) have been obtained, assuring their potential as a cathode in hybrid supercapacitors. Also, amorphous, hydrous materials are supposed to be exemplary active materials for high-performing supercapacitors because of their unique porous structure, structural flexibility, and rich defects. Therefore, the present investigation describes a simple synthesis method for hydrous and amorphous cobalt phosphate thin-film preparation by the simple successive ionic layer adsorption and reaction (SILAR) method on flexible stainless steel (SS) substrate for supercapacitor application. The structural and morphological analyses reveal mesoporous, agglomerated nanoparticle-like, hydrous, and amorphous cobalt phosphate over the SS substrate. The mesoporous nanoparticles of cobalt phosphate material possess the uppermost specific capacitance of 1147 F g–1and 630.7 C g–1specific capacity at a 1 mA cm–2current density. To demonstrate practical relevance, hybrid supercapacitor devices were assembled with cobalt phosphate and rGO (reduced graphene oxide) as cathode and anode electrodes, respectively. Furthermore, the assembled hybrid aqueous supercapacitor device (S-CP4//KOH//rGO) delivers 44.8 Wh kg–1specific energy (SE) at a specific power (SP) of 4.8 kW kg–1with 126 F g–1specific capacitance. The accumulated all-solid-state hybrid supercapacitor device (S-CP4//PVA-KOH//rGO) achieved the uppermost 77 F g–1specific capacitance and SE of 27.37 Wh kg–1at SP of 1.5 kW kg–1with an outstanding 94% capacitive retention over 5000 cycles. Such remarkable supercapacitive performance results demonstrate that the SILAR method is an easy synthesis process for the binder-free preparation of cathode based on hydrous, amorphous cobalt phosphate thin films for hybrid supercapacitor devices.