Boosting Pseudocapacitive Behavior of Supercapattery Electrodes by Incorporating a Schottky Junction for Ultrahigh Energy Density

Abstract

Pseudo-capacitive negative electrodes remain a major bottleneck in the development of supercapacitor devices with high energy density because the electric double-layer capacitance of the negative electrodes does not match the pseudocapacitance of the corresponding positive electrodes. In the present study, a strategically improved Ni-Co-Mo sulfide is demonstrated to be a promising candidate for high energy density supercapattery devices due to its sustained pseudocapacitive charge storage mechanism. The pseudocapacitive behavior is enhanced when operating under a high current through the addition of a classical Schottky junction next to the electrode–electrolyte interface using atomic layer deposition. The Schottky junction accelerates and decelerates the diffusion of OH‒/K+ ions during the charging and discharging processes, respectively, to improve the pseudocapacitive behavior. The resulting pseudocapacitive negative electrodes exhibits a specific capacity of 2,114 C g−1 at 2 A g−1 matches almost that of the positive electrode’s 2,795 C g−1 at 3 A g−1. As a result, with the equivalent contribution from the positive and negative electrodes, an energy density of 236.1 Wh kg−1 is achieved at a power density of 921.9 W kg−1 with a total active mass of 15 mg cm−2. This strategy demonstrates the possibility of producing supercapacitors that adapt well to the supercapattery zone of a Ragone plot and that are equal to batteries in terms of energy density, thus, offering a route for further advances in electrochemical energy storage and conversion processes.

Hierarchical Mn3O4/NiSe2–MnSe2: A Versatile Electrode Material for High-Performance All-Solid-State Hybrid Pseudocapacitors with Supreme Working Durability

“…In the discharge profiles of the GCD plots under all applied current density conditions, the signature of quasi-capacitive discharging profiles is clearly evident, which accentuates redox-mediated charge transfer in the Mn 3 O 4 /NiSe 2 –MnSe 2 ||N-rGO ASSHPC device . During discharging under all applied current density conditions, an insignificant iR (voltage) drop (0.09 V) is observed, which further shows negligible charge-transfer resistance exerted by Mn 3 O 4 /NiSe 2 –MnSe 2 , PVA-KOH, and N-rGO during the discharging process. ,, The mass and areal specific energy storage are the crucial parameters of the pseudocapacitors in the context of their real-world applicability in electronic integrations. , In this regard, the mass specific capacity ( Q S , C g –1 ) and areal specific capacity ( Q A , mC cm –2 ) values of the Mn 3 O 4 /NiSe 2 –MnSe 2 ||N-rGO ASSHPC device at various applied current densities ( i in mA cm –2 ) were estimated by utilizing the discharge time ( Δt in s) under the respective current density condition, total mass ( m in g) of Mn 3 O 4 /NiSe 2 –MnSe 2 and N-rGO, and the active working area ( A = 1 cm 2 ) of the device in equations and . ,,, italicQ italicA = italici × normalΔ italict italicA The Q S and Q A values of the Mn 3 O 4 /NiSe 2 –MnSe 2 ||N-rGO hybrid pseudocapacitor at applied current densities of 3, 6, 8, 10 and 12 mA cm –2 were estimated to be 71, 56, 48, 41, and 35 C g –1 and 121, 95, 81, 69, and 60 mC cm –2 , respectively, and the resultant ( Q S and Q A ) vs applied current density plots are drafted in inset I of Figure E. Similarly, the mass specific capacitance ( C S , F g –1 ) and areal specific capacitance ( C A , mF cm –2 ) values of the Mn 3 O 4 /NiSe 2 –MnSe 2 ||N-rGO ASSHPC device at various applied current densities ( i in mA cm –2 ) were estimated by utilizing the discharge time ( Δt in s) under the respective current density condition, total mass ( m in g) of Mn 3 O 4 /NiSe 2 –MnSe 2 and N-rGO, active working area ( A = 1 cm 2 ) of the device, and the operating potential window of the device in equations and . , italicC italicA = italici × normalΔ italict italicA × normalΔ italicV The C S and C A values of the Mn 3 O 4 /NiSe 2 –MnSe 2 ||N-rGO hybrid pseudocapacitor at applied current densiti...…”

“…Among several essential electrochemical energy storage devices, supercapacitors are significant in the context of delivering equally high power and energy density, extended operational stability, and diverse applicability . Therefore, supercapacitors have evolved as the most contemporary energy storage systems, which are being modernized to assist technological revolutions . Based on the operating principles, two key categories of supercapacitors have been identified, i.e., electrical double layer capacitors (EDLCs) and redox capacitors/pseudocapacitors, where the charge accumulation occur via adsorption/desorption of electroactive ions (formation of dynamic double layers) and fast/reversible redox reactions on the electrode/electrolyte interface, respectively .…”

Enhancing high-performance supercapattery electrodes: harnessing structural and compositional synergies via phosphorus doping on bimetallic boride for rapid charging

“…The oxygen vacancy sites are mainly responsible for the surface to store charges. 14 The increase in intensity of M–OH peak and decrease in O V peak indicates the usage of oxygen vacancy sites for OH − ions interactions. Fig.…”

“…13 The basic requirements for an electrode material with supercapattery behavior include a nanometer scale a high surface area, a shorter diffusion length for electrolyte ions, 3D structures with high porosity, and a high electrical conductivity. 14 In addition, a supercapattery requires an electrolyte with high ionic conductivity, and positrode and negatrode materials that attain a high specific capacity with a wide operational potential window. 15 In an EES device, the negatrode is responsible for power capability and positrode is responsible for energy capability.…”

Evaluation of Supercapacitor Properties of Radio Frequency Sputter Binder‐Free and Nanosandwich WO3/SiO2/WO3 Thin Film

“…The specific capacitance “ C sp ” was calculated using the GCD of the thin film electrode demonstrated in Figure 9 and the equation:where “ I ” is the applied charge–discharge current, “ A ” the electrode area in contact with electrolytes, “Δ V ” is voltage after the IR drop, “ ∫Vdt ” is integral area under discharge curve after IR drop. [ 73–75 ] C sp is further calculated through the area under the discharge curve of GCDs (Figure 9). The capacitance values of WO 3 /SiO 2 /WO 3 are 10.13, 8.95, 8.28, 4.34, and 5.66 mF cm −2 at the current densities of 0.06, 0.2, 0.4, 0.8, and 1.2 mA cm −2 , respectively.…”