| Electrochromisim refers to phenomenon which enables certain materials to switch their optical properties between colored and bleached states reversibly and persistently under the influence of external potential difference.Due to their versatile optical properties,electrochrmic devices have been extensively studied for diverse applications like smart windows,electrochromic displays and dynamic camouflage,etc.However,the current research hotspots are focused on rigid monofunctional devices.The recent technological trend shows an increasing demand for smart and intelligent electronic devices which can ensure mechanical flexibility,versatility and compatibility with existing technologies.Electrochromism offers potential advantages like tunable spectral coloration range,tailorable molecular structure and ease of fabrication.Therefore,the development of flexible or wearable multi-functional electrochromic devices needs further research and development efforts.This dissertation is focused on development of multi-functional electrochromic devices based on polyaniline.As a part of this research,the electrochromic-supercapacitor and electrochromic-zinc ion battery based on reflective structure have been thoroughly studied.Particularly,stability of polyaniline based materials and its impact on performance of devices has been covered in this dissertation.Further,the electrochemical performance of film based device is improved by small molecule doping modification and structural modification.The electrochromic performance,energy storage properties,emissivity performance were investigated in detail.The specific research conclusions are as follows:（1）Because the structure of electrochromic device is similar to that of supercapacitor,so a multifunctional electrochromic-supercapacitor was developed.The electrochromic-supercapacitor can exhibit the energy storage function on the basis of color variation which is a highly desirable feature for smart and potentially robust applications.Polyaniline has been extensively studied as a organic electrochromic and supercapacitor material.However,the volume expansion and contraction of polyaniline caused by repeated doping of ions during coloration（charging）and discoloration（discharging）process causes the rupture of molecular chain and the degradation of cyclic properties.In order to improve the stability and electrochemical performance of polyaniline based electrochromic-supercapacitor,pyrene molecules（PTSA）with strong rigid structure were used as dispersant of aniline monomer and stabilizer of polyaniline skeleton to improve its cyclic stability.The film（PANI-PTSA）exhibits spherical particle accumulation morphology.The doping ratio of PTSA molecule was systematically optimized.The color of electrochromic-supercapacitor can be tuned from light green to green and to dark black at different voltages with response time lagging below 3 s.After 3000 cycles,the device maintained 79%of the initial performance,which is about 29%higher than that of the unmodified thin film device.The device showed a high specific capacitance of 169.15 m F cm-2 at the current density of 1 m A cm-2.The electrochromic-supercapacitor exhibit excellent electrochemical stability at different bending states.（2）PTSA molecule without electrochemical activity penetrated into PANI film in the form of anionic dopant which increases the electrode mass and limits energy storage performance of device.A novel doping strategy of polyaniline with small molecules of anthraquinone-1-sulfonate（AQS）with redox activity has been proposed and implemented which was further used as electrolyte additive.The properties of the film were improved by storing charge in the Faraday reaction of AQS inside the film or at the interface.The microscopic morphology of PANI-AQS film presents a nanoneedle-like surface with a large specific surface area,which is conducive to improve the electrochromic and electrochemical energy storage performance.The prepared thin film devices can transform from light green to dark black with a response speed of less than 2 s.At the current density of 1 m A cm-2,the special capacitance of film device reached 194.2 m F cm-2 by using AQS modified electrolyte.72.1%of the initial capacitance performance was retained after 5000 charging/discharge cycles,which is 31.5%higher than that of pure PANI in 1 mol L-1 electrolyte.（3）In addition to electrochromic-supercapacitor,electrochromic-battery is another integrated multifunctional device.Based on the extensive application scenarios of batteries,the versatile properties of electrochromic-battery possess huge commercialization potential.In this dissertation,the fabrication method and process of electrochromic-zinc ion battery has been presented.Generally,weak acidic electrolytes were used to prevent corrosion of zinc electrode in zinc-ion battery.In order to avoid the weak electrochemical activity of polyaniline electrode in weak acid electrolyte,self-doped polyaniline（SPANI）with sulfonic group on the polymer chain was prepared by electrochemical oxidation copolymerization of aniline monomer with aniline-2,5-disulfonic acid.The SPANI-based film electrode maintains high electrochemical activity over a wide p H range with the help of ion source groups of sulfonic moieties group on the polymer chain.The electrochromic zinc ion battery（EC-ZIB）thin film devices based on SPANI electrode showed obvious color change（from light yellow to dark green）.The device also possess high energy and power density of 181.1Wh kg-1@501.8 W kg-1 and 124.7Wh kg-1@9148.6 W kg-1,respectively,with excellent bi-functional characteristics.（4）The spectrum control range of reflective electrochromic zinc-ion battery was further extended to the middle and far infrared spectral regions.The electrochromic zinc-ion battery application scenarios were further extended,such as intelligent camouflage,thermal control,etc.The multifunctional thin film device（HWEC-ZIB）has been developed with the functions of visible and infrared spectral regulation and energy storage.The self-doped polyaniline thin film（SP（ANI-MA））was prepared by copolymerization of aniline monomer and 3-aminobenzene sulfonic acid.The device was encapsulated by hot-embossing process,and the transparent encapsulation film on the surface layer was optimized.The influence of electrolyte on infrared regulation performance was investigated.The infrared emissivity of the device is 0.28 at 3～5μm and 0.19 at 8～14μm,which has promising application potential in the field of thermal camouflage.In the visible waves,the HWEC-ZIB possess diverse coloration scheme,ranging from light-yellow to dark green.The camouflaging ability of HWEC-ZIB was simulated in the visible waves.The thin film device of HWEC-ZIB can be adapted to the visible range camouflaging in geographical features like soil,grass etc.The thin film device of HWEC-ZIB displayed discharge capacity of 72.15 m Ah cm-2 at the current density of 0.1 m A cm-2.These results demonstrate that HWEC-ZIB is a promising multi-function device. |
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