Syntheses And Capacitive Properties Of POMCPs@Ti₃C₂T_x Cathode Materials

Due to the unique properties of high power density,long cycle life and wide operating temperature range,supercapacitors have been widely used in electronic equipment,hybrid electric vehicles and aerospace industry,and have become a research hotspot of the new generation of energy storage devices.However,the low energy density limits the range of applications of supercapacitors.In supercapacitors,the selection of electrode materials plays a decisive role in its performance.Therefore,the development of cheap and environmentally friendly high-performance new electrode materials is the top priority.POM-based Coordination Polymers（referred to as POMCPs）are crystalline materials with long-range structural order,which are of great interest due to their easy structural tunability,fast redox rate and high specific capacity.This crystalline material is prepared by a simple hydrothermal method under acidic conditions,so it is more stable in the medium with lower p H value.Therefore,POMCPs has become one of the research hotspots in the field of energy storage devices in recent years.In this paper,A kind of POMCPs material,whose molecular formula is Ni（itmb）₄[H₂Si W₁₂O₄₀]·5H₂O（referred to as POMCPs-1）,was synthesized by one-step hydrothermal method using classical Keggin-type silicotungstic acid,and it was prepared into glass carbon electrode sample.When the current density condition of constant current charge-discharge test is5 A g^-1,Has a high specific capacitance value of 365.9 F g^-1.POMCPs-1 not only retains the parent acid rich REDOX activity,but also has the good structural stability of crystalline materials,is a kind of excellent performance of supercapacitor electrode material.In order to enhance the capacitive performance of POMCPs materials,a novel POMCPs-1@Ti₃C₂T_xmaterial was prepared in this paper using the strategy of mixing titanium carbide（Ti₃C₂T_x）with POMCPs-1 by abstraction,and the mass ratio of POMCPs to Ti₃C₂T_xwas continuously adjusted during the experiments to explore the best mixing mass ratio,and four POMCPs-1@Ti₃C₂T_xmaterials,denoted as P1@Ti₃C₂T_x-1,P1@Ti₃C₂T_x-2,P1@Ti₃C₂T_xand P1@Ti₃C₂T_x-4,respectively.The specific capacitance values of the glassy carbon electrodes modified with these materials at 5 A g^-1were in the order of 376.3,627.3,412.4 and 384.0 F g^-1.A more in-depth study of the materials before and after the composite revealed that the two monomeric materials had more performance advantages than the monomeric material due to the synergistic effect.The composite retains both the large charge storage capacity of POMCPs and the high electrical conductivity and large specific surface area of Ti₃C₂T_x,while using the crystal particles as interlayer support for Ti₃C₂T_x,effectively preventing its reaccumulation.To further investigate the practical application performance of using this composite material as a supercapacitor anode,POMCPs-2 with a double water-assisted proton channel structure was synthesized by changing the metal ions in POMCPs-1,which was milled and added to the Ti₃C₂T_xsuspension for vacuum filtration to obtain the P2@Ti₃C₂T_xcomposite film,and the storage performance of the composite film was investigated.The composite film was directly used as the negative electrode and the environmentally friendly and inexpensive lettuce leaf material was selected as the positive electrode for electrode matching,and the first asymmetric supercapacitor device designed and assembled with POMCPs@Ti₃C₂T_xmaterial was successfully lit with a red LED for 8 min 26 sec.The devices exhibit excellent energy density(32.2 Wh kg^-1)and power density(12002.0 W kg^-1)at 5 A g^-1,superior to existing Ti₃C₂T_xor polyacid-based supercapacitor devices reported in the literature.The results indicate that POMCPs@Ti₃C₂T_xis a new supercapacitor electrode material with great potential for application,and in this paper,the design,preparation and performance research of such materials provide new way for the development of new high-performance supercapacitors.