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

Highlights Incorporation of Schottky Junction increases the pseudocapacitive mechanism at higher current rate. The pseudocapacitance behavior of the positive and negative electrodes is balanced to construct a solid-state supercapattery device. An energy density of 236.14 Wh kg −1 is achieved for solid-state supercapattery device. 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.