High performance asymmetric supercapacitor based on 3D microsphere-like 1T-MoS2 with high 1T phase content

Abstract

1T phase molybdenum disulfide (1T-MoS2) has aroused extensive concern in energy storage devices such as supercapacitors due to its large interlayer spacing, high conductivity and good hydrophilicity. However, it is struggle to synthesize 1T-MoS2 with stable 1T phase with high content. Herein, Ammonium ion intercalation molybdenum disulfide (A-MoS2) with high 1T content and stable 3D microsphere structure was successfully synthesized using a facile hydrothermal method. We explained the feasibility of ammonium ion (NH4+) intercalation through density functional theory (DFT) calculations and proved the successful intercalation of NH4+ by XRD and XPS. Through XPS fitting, the 1T phase content is calculated as high as 83.1%. The as-prepared A-MoS2 presents a stable 3D microsphere structure with the interlayer spacing expanded to 0.93 nm, which provides a wide ion diffusion channel that allows ions to pass through quickly. Moreover, the high 1T content increases the hydrophilicity of MoS2, thereby improving the wettability of the electrode, which contributes to the interaction between the electrolyte and electrode. In 1 M Na2SO4, A-MoS2 electrode material displays high specific capacitance of 228 F g−1 at 5 mV s−1 and retains 127 F g−1 at 80 mV s−1, which proves the good rate capability. Furthermore, the assembled α-MnO2//A-MoS2 asymmetric supercapacitor (ASC) displayed a wide operating voltage of 2.1 V. The assembled ASC displays a high energy density of 35.8 Wh∙kg−1 at a power density of 525.0 W kg−1, which indicates excellent energy storage performance.