Study On High-Performance Supercapacitors Based On Multiple Metal Oxide

In recent years,with the development of science and technology,people increase their demand for high performance and multi-function energy storage systems.Supercapacitors has been considered as an efficient energy storage because of attractive advantages of high power density,fast charge-discharge rate and environment-friendly.As we all known,the performance of supercapacitors depends mainly on the electrode materials,so it is the most critical technology to research and develop new advanced active electrode materials as well as to adjust suitable morphology and structure of materials.Furthermore,the energy-storage devices flexibility requirements are quite varied because of the range of applications in wearable system and portable electronics.In addition,electrode support is one of the most important factors that decide the mechanical properties of the device,hence,the flexibility performance of the supercaacitors can be realized by using the flexible electrode support materials.In this paper,we aim to design such a new flexible supercapacitor which is based on the carbon fiber cloth and multiple metal oxide(Na₂Ti₅O₁₁,K₂Ti₆O₁₃,Na_0.66[Mn_0.66Ti_0.34]O₂)and its composites,and study the electrochemical performance and the mechanism of the new materials for energy storage.The main contents are as follows:?1?High performance flexible supercapacitors based on C/Na₂Ti₅O₁₁nanocomposite electrode materials.The carbon fiber fabric?CFF?served as an electrode support and also as a current collector,and the C/Na₂Ti₅O₁₁ coated on CFF is directly used as the composite electrode for the SCs.The as-prepared electrode of C/Na₂Ti₅O₁₁/CFF exhibits excellent electrochemical performance and the highest specific capacitance of 1066 F/cm² at a current density of 2 mA/cm²,which is superior to other titanates reported for electrodes in supercapacitors to date.The capacitance keeps 85%after 3000 cycles at a current density of 2.8 mA/cm² indicating an good long-term stability.It demonstrated that three as-fabricated supercapacitors in series can power up 100 light-emitting diodes?LEDs,2.3 V,20 mA?for about 18 mins when the potential is up to 4.8 V.Therefore,C/Na₂Ti₅O₁₁ nanocomposite indicated good properties for a practical supercapacitor electrode material and the device shows significant potential applications in advanced energy storage systems.?2?Based on the stable tunnel structure of C@K₂Ti₆O₁₃ hybrid compositions for supercapacitor.The K₂Ti₆O₁₃ with tunnel structure was synthesized by hydrothermal process.The K₂Ti₆O₁₃3 was enhanced by carbon modified with alcohol lamp roasting,and C@K₂Ti₆O₁₃ electrode materials was fabricated.Moreover,the stability of alkali-metal titanates could be improved further through the carbon modification compared with the other electrode materials.To attain the flexible and stretchable property,the C@K-TNBs supercapacitor has been encapsulated by the flexible and stretchable PDMS?polydimethylsiloxane?.The solid SC device based on C@K₂Ti₆O₁₃shows excellent rate capability,high cycle stability,that is a specific capacitance of 301F/g at the current of 3 mA and a high energy density 26.8 Wh/kg and power density 1.47kW/kg.The retention of specific capacitance remain 82.7%after 10000 cycles at high current value of 21 mA which is contribute to not only the complex transition metal elements but also the unique channel structure.In addition,three supercapacitors in series were successfully integrated to operate 100 LEDs for 16 minutes.?3?Electrochemical performance of Na_0.66[Mn_0.66Ti_0.34]O₂ nanoparticles as energy storage materials.Na_0.66[Mn_0.66Ti_0.34]O₂ nano-particles?NMTO-NPs?is synthesized by a facile and high-production method of solid state reaction followed by ball milling.The as prepared NMTO-NPs electrode exhibits the highest specific capacity of 1025.75 F/g.A maximum energy density of 77.81 Wh/kg at the power density of 125 W/kg is obtained,and maintains a high energy density of 54.79 Wh/kg even at an ultrahigh power density of 3750 W/kg.Density functional theory?DFT?calculations show that the minimum ions diffusion barrier energy is 0.272 eV,which demonstrates the sodium ions could insert into the system easily.By scan-rate dependence cyclic voltammetry analysis,the capacity value indicates mix charge storage of capacitive behavior and Na⁺intercalation process.