Enhancement Of Electrochemical Performance Of Dense Supercapacitor Electrode Materials Via Adding Electroactive Organic Molecules

Nowadays,the attention among the world's great powers and the scientific community is concentrated on energy.In response to the ever-changing global energy landscape,people are very interested in growing and improving more efficient energy storage devices.As a kind of energy storage device,the technology of supercapacitors has been significantly mature and has the potential to promote significant progress in energy storage technology.In addition,since the development of modern electronic devices largely relies on energy sources with high energy density and power density,for practical applications,people are encouraged to develop environmentally friendly and efficient electrode materials for supercapacitors(SCs).The main contents of this article are as follows:(1)A novel supercapacitors electrode material with high volume density was prepared by embedding redox quinone-hydroquinone into a cheap and available biomass carbon material,and it was named TQ.The structure and properties of TQ were studied by a series of structural characterization and electrochemical performance tests.The results show that TQ has high volume density(0.91 g cm^-3),high nitrogen oxygen(25.6%),and the advantages of good hydrophilic(contact angle 14.48°).Furthermore,TQ shows excellent electrochemical performance.In three-electrode system using acidic solution as electrolyte,the quality specific capacitance of TQ based electrode is as high as 601.5 F g^-1 and its volume specific capacitance is 547.4 F cm^-3 at the discharge current density of 1 A g^-1.Moreover,TQ has the great capacitance retention of 68%and 66%at the discharge current density of 1 A g^-1(1000 cycles)and 10 A g^-1(5000 cycles),respectively.Therefore,TQ has excellent practical value in energy storage and conversion equipment.(2)A dense electrode material based MXene intercalated with redox organic molecules(azure A)was prepared through HF acid etching,intercalating and annealing processes.And,this MXene/Azure A intercalated composite was named KMA.Through a series of structural characterization and performance tests,the specific capacitance of KMA is nearly 6 times higher than that of MXene,and the its volume is as high as 2.32 g cm^-3.At the discharge current density of 0.5,1,2,5 and 10 A g^-1,its volumetric capacitance is 473.9,422.6,394.4,364.6 and 344.7 F g^-1,respectively.In addition,KMA also has good cycle stability.After 1000 cycles,its capacitance retention is 85.3%at 1 A g^-1,and after 9000 cycles at 10 A g^-1,its capacitance retention is about 74.3%.(3)The electrochemical performances of the above two electrode materials intercalated with redox organic molecules were tested and evaluated in two electrode systems.An asymmetric device used TQ as the negative electrode and 1 mol L^-1 H₂SO₄ as electrolyte shows outstanding electrochemical performance.At the 0.5A g^-1 discharge current density,the volumetric capacitance of the device is 77.2 F cm^-3,its energy density is 22.6 Wh L^-1 and power density is 193.8 W L^-1.In 1 mol L^-1 H₂SO₄,a symmetrical device based KMA-electrodes shows the largest volumetric specific capacitance of 352.6 F cm^-3 at the current density of0.5 A g^-1.Its power density is 261 W L^-1,and its energy density is 9.9 Wh L^-1 at same discharge current density.