1T-MoS₂/Mxene//?-MnO₂ Study On Assembly And Performance Of Asymmetric Supercapacitor

Metallic 1T phase MoS₂(1T-MoS₂)nanosheet has the advantages of large layer spacing,high conductivity,good hydrophilicity,etc.,and can obtain more pseudocapacitance.However,its energy storage mechanism involves intercalation of ions,limiting its capacitive storage at high current densities,resulting in poor magnification performance of 1T-MoS₂.In this paper,the 1T-MoS₂nanosheet was grown on the surface of highly conductive MXene(Ti₃C₂T_x)by one-step hydrothermal method,and the 1T-MoS₂/Ti₃C₂T_x heterostructure was successfully constructed to improve the magnification performance of 1T-MoS₂,and the physical phase,crystal structure,micromorphology,and elemental binding energy of the1T-MoS₂/Ti₃C₂T_x heterostructure were systematically analyzed,and the supercapacitor performance was studied and the energy storage mechanism of the heterogeneous structure was revealed.In addition,in order to assemble the asymmetric supercapacitor device,we also successfully prepared the?-Mn O₂nanoflower cathode material,and successfully assembled the1T-MoS₂/Ti₃C₂T_x//?-Mn O₂ flexible asymmetric supercapacitor and systematically tested its electrochemical properties.The main contents of the paper are as follows:(1)Two different crystal structures of MoS₂,namely semiconductor phase2H-MoS₂ and metal phase 1T-MoS₂,were prepared by hydrothermal method,and when the two were used as supercapacitor electrode materials,the specific capacitance of 2H-MoS₂ at a current density of 1 A g^-1 was only 37.3 F g^-1.The large layer spacing of 1T-MoS₂ favors the intercalation of ions,and can obtain more intercalation-type pseudo-capacitance,showing a higher specific capacitance value,which can reach 228.8 F g^-1(1 A g^-1),much higher than 2H-MoS₂.However,its specific capacitance drops sharply to 70 F g^-1 at a high current density of 20 A g^-1,with a retention rate of only 31%and poor magnification performance.(2)In order to further improve the magnification performance of 1T-MoS₂,1T-MoS₂/Ti₃C₂T_x heterostructure was constructed by one-step hydrothermal method,and when this heterogeneous structure was used as the supercapacitor electrode material,the energy storage advantages of 1T-MoS₂ and Ti₃C₂T_xcan be combined by synergistic effects,and the high specific capacitance can be combined by the large layer spacing of 1T-MoS₂ component to produce intercalation-type pseudocapacitance,and the ultra-high magnification performance of the heterogeneous structure originates from the ultra-fast electron transport of Ti₃C₂T_x.The 1T-MoS₂/Ti₃C₂T_xelectrode has a specific capacitance of 206.3 F g^-1 at a current density of 1 A g^-1,and despite a 20-fold increase in current density,its capacitance value remains at 150 F g^-1with a magnification performance of up to 73%.In addition,the heterostructure exhibits excellent cyclic stability,with a capacitance retention rate of 94.4%after10,000 cycles(20 A g^-1).As a result,the 1T-MoS₂/Ti₃C₂T_x heterostructure has excellent performance and provides an excellent negative electrode material for the next step of asymmetric device assembly.(3)In order to further assemble the asymmetric supercapacitor device,potassium permanganate decomposition was induced by hydrothermal method by cetyltrimethylammonium bromide(CTAB),and the cathode material?-Mn O₂nanoflower was prepared.?-Mn O₂ is used as an electrode material for supercapacitor performance testing,its voltage window is 0-1 V and the specific capacitance value is up to 205 F g^-1(1 A g^-1).Finally,in this paper,1T-MoS₂/Ti₃C₂T_x as the negative electrode material,?-Mn O₂ as the positive electrode material,and PVA-Na₂SO₄ gel as the solid electrolyte,the flexible asymmetric supercapacitor device was successfully assembled,with a voltage window of 1.8V and an energy density of 68.8?Wh cm^-2,and the two devices were connected in series to successfully drive the LED.