| With the depletion of fossil energy and the continuous consumption of natural resources,it is increasingly urgent to develop single materials or devices with multiple functions.Electrochromic devices have the same working structure and principle as supercapacitors.Therefore,it is feasible to combine electrochromic and capacitive properties into one single device.However,there are some contradictions between electrochromic and capacitive properties in some aspects.For example,the contradiction between high optical modulation/high energy storage level and high response speed,the contradiction between energy storage level and coloration efficiency,and the trade-off between fast response/high rate performance and cycle stability.To solve the above problems,in this thesis,WO3-based ordered nano arrays were used as the electrode materials.The electrochromic and capacitive properties of the above materials in LiClO4-propylene carbonate(LiClO4-PC)electrolyte and AICl3 aqueous electrolyte(AICl3-H2O)were discussed in detail.The synergistic mechanism between electrochromic and charging-discharging processes was clarified,and the key parameters for the comprehensive improvement of electrochromic-capacitive bifunctional performance were obtained.Moreover,the repair mechanism of electrode materials was also clarified.Furthermore,a real device prototype was constructed based on the electrode materials.All the above factors provided a new idea for the design and development of new electrochromiccapacitive bifunctional devices.The hexagonal WO3 nanorod arrays were successfully prepared by a hydrothermal method.The effects of different hydrothermal time on the micro morphology,structure and electrochromic-capacitive properties of WO3 nanorod arrays in LiClO4-PC electrolyte were systematically investigated.The results indicated that the overall performance of WO3 nanorod arrays reached its best under the hydrothermal growth of 5 h.And it possessed good electrochromic-capacitive dual-function characteristics,which proved the feasibility of integrating electrochromic and capacitive properties into one single material.In addition,by using AlCl3-H2O as the electrolyte,the effects of Al3+ions on the electrochromic and capacitive properties of WO3 nanorods were discussed in detail.Results showed that Al3+ion gave the WO3 material more excellent comprehensive properties because of its trivalent characteristic and small ion radius.The material achieved excellent performance in all four aspects of electrochromism.The optical modulation reached 81.5%,the response time was as low as 9/14 s,the coloration efficiency was as high as 149.9 cm2·C-1,and the optical modulation decreased only 1.8%in the 10000 s in-situ response cycle.Even limited by the voltage range of aqueous solution,the specific capacitance of the electrode material still reached 235.4 F·g-1(at the current density of 1 A·g-1),showing good energy storage performance.After 4000 charging-discharging cycles,the specific capacitance still maintained 86.2%of the initial value.The hexagonal/amorphous core-shell WO3 nanorod arrays were successfullysynthesized by a hydrothermal-spin coating method.The influences of different annealing temperatures and amorphous shell thickness on the overall electrochromic and capacitive properties of the materials were systematically studied.Results demonstrated that the comprehensive properties of the core-shell heterostructure material achieved its best performance when the annealing temperature was 250? and the amorphous shell thickness was 4 nm.In terms of electrochromic properties measured in LiClO4-PC electrolyte,the optical modulation,response time and coloration efficiency reached 67.7%,15/21 s and 101 cm2·C-1,respectively.While in the capacitive aspects,the specific capacitance achieved the highest value of 885.8 F·g-1 at the current density of 1 A·g-1,the coulomb efficiency was 91.8%,and in the meantime,the good rate performance and long-term charging-discharging cycle stability(57.8%of the initial capacitance value was retained after 2000 cycles)were also obtained.The transfer process and kinetic mechanism of ions/electrons at the interface of "core-shell nanorod array/electrolyte" were clarified.The core-shell nanorod arrays combined the excellent electrochemical stability of crystalline WO3,rapid ion mass transfer and rich internal active pore structure characteristics of amorphous tungsten oxide,which promoted the acquisition of more excellent electrochromic-capacitive bifunctional performance.In addition,in AICl3-H2O electrolyte,WO3 core-shell nanorod array electrode also showed certain electrochromic-capacitive bifunctional properties(the optical modulation,response time and coloration efficiency reached 82%,8/12 s and 154.7 cm2·C-1,respectively.And the specific capacitance remained 79%of the initial value after 1000 CV cycles.Besides,the specific capacitance reached 283.4 F·g-1 at a current density of I A·g-1.And the specific capacitance still remained 73.2%of the initial value after 4000 cycles).The TiO2/WO3 composite nanorod arrays were successfully prepared by a twostep hydrothermal method.And the repair mechanism of electrode materials was deeply studied.The results showed that the TiO2/WO3 composite material had no any significant short board in both electrochromic and capacitive performance in LiClO4-PC electrolyte.In general,the material possessed high coloration efficiency(153.1 cm2·C-1),fast color switching speed(10/10 s)and high specific capacitance(557.7 F·g-1).The transport process and kinetic mechanism of ions/electrons at the interface of "composite nanorod array/electrolyte" were revealed.On this basis,all properties of degraded electrode materials were successfully restored by a high voltage de-trapping treatment,which confirmed the feasibility of performance recovery.In addition,the principle for judging the industrial stability of materials was put forward.The degradation of materials during cycles could be explained by a theoretical model of "ion trap",which included two categories of eliminable traps and non-eliminable traps.Among them,the eliminable traps could be removed by a de-trapping treatment,so as to restore all the properties of the degraded material.In contrst,however,the non-eliminable traps couldn't be removed,that is,the performance of degraded materials cannot be restored.In addition,the TiO2/WO3 composite nanorod array materials showed certain electrochromic-capacitive bifunctional properties in AlCl3-H2O electrolyte.All properties of the degraded electrode materials were successfully restored by high voltage de-trapping treatment. |
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