LiClO4 In Propylene Carbonate Research Articles

Electrospun polyaniline nanofibers web electrodes for supercapacitors

AbstractPolyaniline nanofibers (PANI‐NFs) web are fabricated by electrospinning and used as electrode materials for supercapacitors. Field‐emission scanning electron microscope micrographs reveal nanofibers web were made up of high aspect ratio (>50) nanofibers of length ∼30 μm and average diameter ∼200 nm. Their electrochemical performance in aqueous (1M H2SO4 and Na2SO4) and organic (1M LiClO4 in propylene carbonate) electrolytes is compared with PANI powder prepared by in situ chemical oxidative polymerization of aniline. The electrochemical properties of PANI‐NFs web and PANI powder are studied using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. PANI‐NFs web show higher specific capacitance (∼267 F g−1) than chemically synthesized PANI powder (∼208 F g−1) in 1M H2SO4. Further, PANI‐NFs web demonstrated very stable and superior performance than its counterpart due to interconnected fibrous morphology facilitating the faster Faradic reaction toward electrolyte and delivered specific capacitance ∼230 F g−1 at 1000th cycle. Capacitance retention of PANI‐NFs web (86%) is higher than that observed for PANI powder (48%) indicating the feasibility of electro spun PANI‐NFs web as superior electrode materials for supercapacitors. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Atmospheric-pressure plasma-enhanced chemical vapor deposition of electrochromic organonickel oxide thin films with an atmospheric pressure plasma jet

Deposition of electrochromic organonickel oxide (NiOxCy) films onto glass/indium tin oxide (ITO) substrates using atmospheric-pressure plasma-enhanced chemical vapor deposition with an atmospheric pressure plasma jet under various precursor injection angles is investigated. A precursor [nickelocene, Ni(C5H5)2] vapor, carried by argon gas and mixed with oxygen gas, is injected into an air plasma torch for the deposition of NiOxCy films by a short exposure of the substrate, 20s, in the plasma. Uniform light modulation on glass/ITO/NiOxCy is produced while the moving glass/ITO substrate is exposed to the plasma torch at room temperature (~23°C) and under atmospheric pressure. Light modulation with up to a 40.9% transmittance variation at a wavelength of 513.9nm under Li+ intercalation and de-intercalation in a 1M LiClO4–propylene carbonate electrolyte is achieved.

Electrochemical properties of PEO/PMMA blend-based polymer electrolytes using imidazolium salt-supported silica as a filler

In this study, the composite polymer electrolytes (CPEs) were prepared by solution casting technique. The CPEs consisted of PEO/PMMA blend as a host matrix doped with LiClO4. Propylene carbonate (PC) was used as plasticizer and a small amount of imidazolium salt-supported amorphous silica (IS-AS) as a filler was prepared by the sol–gel method. At room temperature, the highest conductivity was obtained for the composition having PEO–PMMA–LiClO4–PC–4wt. % IS-AS with a value of 1.15 × 10−4 S/cm. In particular, the CPE using the IS-AS filler showed a higher conductivity than any other sample (fumed silica, amorphous silica). Studies of differential scanning calorimetry and scanning electron microscopy indicated that the ionic conductivity increase was due to an expansion in the amorphous phase which enhances the flexibility of polymeric chains and the homogeneous structure of CPEs. It was found that the ionic conductivity and interfacial resistance stability of CPEs was significantly improved by the addition of IS-AS. In other words, the resistance stability and maximum ambient ionic conductivity of CPEs containing IS-AS filler were better than CPEs containing any other filler.

Preparation and electrochemical properties of the ternary nanocomposite of polyaniline/activated carbon/TiO2 nanowires for supercapacitors

We herein report the synthesis of ternary nanocomposites consisting of polyaniline (PANI), activated carbon, and TiO2(B) components, which involves the preparation of activated carbon/TiO2(B) nanowires (ACTB) using sonochemical–hydrothermal method, and their subsequent composites with PANI via in situ polymerization. The morphology and structure of ACTB/PANI ternary nanocomposites are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD). Morphology analysis shows that the porous network layer of PANI homogeneously coated on the outer surface of ACTB support. The electrochemical properties of the ternary nanocomposite as the electrode material for electrochemical capacitors are examined by cyclic voltammetry and galvanostatic charge/discharge test in an organic electrolyte (1.0M LiClO4 in propylene carbonate). The results show that the ternary nanocomposites have a specific capacitance as large as 286Fg−1 in the potential range from −3 to 3V (vs. SCE) at a charge–discharge current density of 1.0Ag−1, which is a significant improvement compared to those of the three separate components, demonstrating that the ACTB/PANI nanocomposites are promising materials for supercapacitor electrode.

Atmospheric pressure plasma jet-synthesized electrochromic organomolybdenum oxide thin films for flexible electrochromic devices

An investigation is conducted into fast synthesis of electrochromic organomolybdenum oxide (MoOxCy) thin films onto 40Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates via atmospheric pressure plasma jet. A precursor [molybdenum carbonyl, Mo(CO)6] vapor, carried by argon gas, is injected into air plasma torch to synthesize MoOxCy films for offering extraordinary electrochromic performance. Only low driving voltages from −1V to 1V are needed to offer reversible Li+ ion intercalation and deintercalation in a 1M LiClO4-propylene carbonate electrolyte. Light modulation with transmittance variation of up to 61%, optical density change of 0.54 and coloration efficiency of 37.5cm2/C at a wavelength of 550nm after 200cycles of cyclic voltammetry switching measurements is achieved.

Reversible Incorporation of Lithium-Ions into Electrodeposited Layers of TiO2

Thin layers of titanium oxide were deposited electrochemically from potassium titanium oxalate solution on ITO glasses and on QCM sensor. Any treatment at elevated temperature caused mechanical damage of the layers. The thickness of the layers was estimated within 200 - 400 nm. Dry layers were able to incorporate and reversibly released lithium ions from LiClO4 in propylene carbonate; this process was apparent visually by occurrence of brownish color. The material could be used in an electrochromic window or similar device.

Low-temperature ozone exposure technique to modulate the stoichiometry of WOx nanorods and optimize the electrochromic performance

A low-temperature ozone exposure technique was employed for the post-treatment of WOx nanorod thin films fabricated from hot-wire chemical vapor deposition (HWCVD) and ultrasonic spray deposition (USD) techniques. The resulting films were characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV–vis–NIR spectroscopy and x-ray photoelectron spectroscopy (XPS). The stoichiometry and surface crystallinity of the WOx thin films were subsequently modulated upon ozone exposure and thermal annealing without particle growth. The electrochromic performance was studied in a LiClO4–propylene carbonate electrolyte, and the results suggest that the low-temperature ozone exposure technique is superior to the traditional high-temperature thermal annealing (employed to more fully oxidize the WOx). The optical modulation at 670 nm was improved from 35% for the as-deposited film to 57% for the film after ozone exposure at 150 °C. The coloration efficiency was improved and the switching speed to the darkened state was significantly accelerated from 18.0 s for the as-deposited film to 11.8 s for the film after the ozone exposure. The process opens an avenue for low-temperature and cost-effective manufacturing of electrochromic films, especially on flexible polymer substrates.

Lithium electrochromism of atmospheric pressure plasma jet-synthesized NiO x C y thin films

Reversible lithium intercalation and deintercalation behavior of atmospheric pressure plasma jet (APPJ)-synthesized organonickel oxide (NiO x C y ) thin films under various substrate distances is testified in an electrolyte (1 M LiClO4–propylene carbonate solution) at low driving voltages from −0.5 to 1.5 V. Fast responses of 2 s bleaching at −0.5 V and 6 s coloration at +1.5 V are accomplished for the nano-porous NiO x C y thin films. This study reveals that a rapid synthesis of electrochromic NiO x C y thin films in a single process via APPJ by 21 s is investigated. This study presents a noteworthy electrochromic performance in a light modulation with up to 43% of transmittance variation and a coloration efficiency of 36.3 cm2/C at a wavelength of 830 nm after 200 cycles of cyclic voltammetry measurements.

High energy density supercapacitors using macroporous kitchen sponges

Macroporous, low-cost and recyclable kitchen sponges are explored as effective electrode platforms for supercapacitor devices. A simple and scalable process has been developed to fabricate MnO2–carbon nanotube (CNT)–sponge supercapacitor electrodes using ordinary kitchen sponges. Two organic electrolytes (1 M of tetraethylammonium tetrafluoroborate (Et4NBF4) in propylene carbonate (PC), 1 M of LiClO4 in PC) are utilized with the sponge-based electrodes to improve the energy density of the symmetrical supercapacitors. Compared to aqueous electrolyte (1 M of Na2SO4 in H2O), the energy density of supercapacitors tripled in Et4NBF4 electrolyte, and further increased by six times in LiClO4 electrolyte. The long-term cycling performance in different electrolytes was examined and the morphology changes of the electrode materials were also studied. The good electrochemical performance in both aqueous and organic electrolytes indicates that the MnO2–CNT–sponge is a promising low-cost electrode for energy storage systems.

Low Temperature Plasma Enhanced Chemical Vapor Deposition-Synthesized Electrochromic MoOxCy Thin Films for Flexible Electrochromic Devices

An investigation is conducted into the electrochromic organomolybdenum oxide (MoOxCy) films synthesized onto 60 Ω/□ flexible poly(ethylene terephthalate) (PET)/indium tin oxide (ITO) substrates using low temperature (∼23 °C) plasma-enhanced chemical vapor deposition (PECVD). The PECVD-synthesized MoOxCy films are proven to offer remarkable electrochromic performance. Cyclic voltammetry switching measurements reveal that only low driving voltages from -1 to 1 V are needed to provide reversible Li+ ion intercalation and de-intercalation in a 1 M LiClO4-propylene carbonate (PC) electrolyte. Light modulation with transmittance variation of up to 65.2%, optical density change of 0.63 and coloration efficiency of 35 cm2/C are achieved at a wavelength of 608 nm for 150 cycles of Li+ intercalation and de-intercalation. PECVD-synthesized MoOxCy thin films show excellent electrochromic properties for applications in flexible electrochromic devices.

Li dendrite growth and Li+ ionic mass transfer phenomenon

Li metal dendrite growth in LiPF6–propylene carbonate (PC) electrolyte was observed in situ by a laser scanning confocal microscope (LSCM) with a metallographic microscope. The development of the electrodeposited Li dendrite length was analyzed, and compared with dendrites grown in LiClO4–PC electrolyte solution. Different anions make different Solid Electrolyte Interphase (SEI) layers on the electrodeposited Li metal. This difference is one factor which causes the morphological variation and the different dendrite growth behavior of Li metal in these electrolytes. The relationship between the Li dendrite growth and Li+ ionic mass transfer rate associated with the electrodeposition of Li metal is examined, and dendrite initiation and growth rate are discussed. The authors find that ionic mass transfer plays an important role in dendrite growth behavior.

Electrochromic performance of NiV xO y thin films deposited onto flexible PET/ITO substrates by reactive plasma sputtering for flexible electrochromic devices

An investigation was conducted on the electrochromic properties of plasma sputtered-nickel–vanadium oxide thin films on 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates. Metallic Ni 0.93V 0.07 target, sputtered by radio frequency power with argon gases and reacted with oxygen gases at room temperature (23 °C), was proven to provide extraordinary electrochromic performance. Cyclic voltammetry switching measurements found that only low driving voltages from − 1 V to 1 V were needed to provide reversible Li + ion intercalation and deintercalation. The light modulation with up to 52% of transmittance variation, optical density change of 0.446 and color efficiency of 63.8 cm 2/C at a wavelength of 550 nm was obtained for 200 cycles of Li + intercalation and deintercalation in a 1 M LiClO 4-propylene carbonate electrolyte.

Electrochemical properties of amorphous Li x V2O5−y thin film deposited by r.f.-sputtering

The electrochemical properties of amorphous vanadium pentoxide (V2O5) thin films deposited by reactive r.f.-sputtering were investigated using galvanostatic charge/discharge cycling and galvanostatic intermittent titration technique (GITT). As x in LixV2O5−y increased (x = 0–2.0), the electromotive force of the lithium (Li)∣1 M LiClO4–propylene carbonate∣LixV2O5−y cell decreased gradually without a potential plateau or an abrupt potential reduction, demonstrating that an irreversible structural change did not occur in the entire Li content. Chemical diffusivity of the Li ion in the LixV2O5−y thin film measured using GITT was determined to be 4 × 10−13–7 × 10−14 cm2 s−1 in the Li content range investigated.

Effect of heat treatment on electrochromic properties of TiO2 thin films

Electrochromic titanium oxide (TiO2) films were deposited on ITO/glass substrates by chemical solution deposition (CSD). The stock solutions were spin-coated onto substrates and then heated at various temperatures (200–500 °C) in various oxygen concentrations (0–80%) for 10 min. The effects of the processing parameters on the electrochromic properties of TiO2 films were investigated. X-ray diffraction measurements demonstrated that the amorphous TiO2 films were crystallized to form anatase films above 400 °C. The electrochromic properties and transmittance of TiO2 films were measured in 1 M LiClO4–propylene carbonate (PC) non-aqueous electrolyte. An amorphous 350 nm-thick TiO2 film that was heated at 300°C in 60% ambient oxygen exhibited the maximum transmittance variation (ΔT%), 14.2%, between the bleached state and the colored state, with a ΔOD of 0.087, Q of 10.9 mC/cm2, η of 7.98 cm2/C and x in Li x ClO4 of 0.076 at a wavelength (λ) of 550 nm.

스핀코팅법에 의한 리튬 2차전지용 산화물 양전극 LiCoO2 박막의 구조 및 전기화학적 특성에 대한 연구

박막은 Pt/Ti/SiO2/Si 기판 위에 구연산 졸을 이용하여 spin coating에 의해 제작하였다. 기판위에 코팅된 구연산 졸을 380oC에서 15분간 건조시킨 후 750oC에서 10분간 열처리하여 박막을 얻었다. 얻어진 박막은 X-선 회절분석 결과 R3m의 결정구조를 가짐을 알수 있었고, 전기화학적 특성의 측정결과 1차 방전용량은 0.35Ah/cm2-m로 측정되었다. The LiCoO2 thin films were prepared on the Pt/Ti/SiO2/Si substrate by spin coating using citrate sol. The citrate sol was spin-coated on substrate and dried at 380oC for 15 min. to evaporate the solvents and remove the organic materials. The as-deposited films were annealed at 750oC for 10 min. in air for crystallization. The X-ray diffraction patterns for the film have been indexed hexagonal system with space group R3m. The active area of LiCoO2 films for electrochemical test was about 11cm2. A Li foil and 1M LiClO4 in propylene carbonate(PC) and ethylene carbonate(EC) (1:1)were used as an anode and an electrolyte, respectively. The galvanostatic charge-discharge test was carried out at constant current density ranging from 5 A/cm2 in the voltage window between 4.2 and 3.0 V. The first discharge capacity of the film is 0.35Ah/cm2-m. The cycling behavior of the LiCoO2 film is also reported.

An investigation of cell-impedance-controlled lithium transport through LiCoO2/Li1−δMn2O4 bilayer film electrode prepared by rf magnetron sputtering

Lithium transport through LiCoO2/Li1−δMn2O4 bilayer film electrode prepared by radio-frequency (rf) magnetron sputtering was investigated in a 1M solution of LiClO4 in propylene carbonate. From the analyses of the AC-impedance spectra experimentally measured from the Li1−δMn2O4 single-layer and LiCoO2/Li1−δMn2O4 bilayer film specimens, the internal cell resistance of the LiCoO2/Li1−δMn2O4 bilayer film electrode was determined to be smaller in value than that of the Li1−δMn2O4 single-layer film electrode over the whole potential range, which can be accounted for by the kinetic facility for the interfacial charge-transfer reaction in the presence of the more conductive LiCoO2 surface film. Moreover, from the analyses of the anodic current transients measured from both the film specimens, it was suggested that the cell-impedance-controlled constraint at the electrode surface is changed to the diffusion-controlled constraint simultaneously characterised by the large potential step and the small amount of lithium transferred during lithium transport. In addition, in the case of the LiCoO2/Li1−δMn2O4 bilayer film electrode, it was found that the critical value of the applied potential step needed for the mechanism transition is reduced, which strongly indicates that the internal cell resistance plays a significant role in determining the cell-impedance-controlled lithium transport. Furthermore, from the comparison of the cathodic current transients measured on the Li1−δMn2O4 single-layer film specimens with various thicknesses, it was experimentally verified that the diffusion resistance is explicitly distinguished from the internal cell resistance.

Optical and Electrochemical Properties of SnO2:Sb Thin Films Prepared by the Sol-Gel Process

The sol-gel route offers the advantages of large area deposition in controlling the microstructure of films and producing films containing multiple cations. Tin oxide semiconductors with metal and/or oxide dopants and additives are widely used as transparent-electronically conductive electrodes in electrochromic devices (ECD). The aim of this research is to improve the ion storage capacity of the SnO2 film by adding antimony. The Sn-doped SnO2 solutions were prepared using SnCl2. 2H2O and SbCl3 as precursor materials. The films were dip-coated at speed of 12 cm/min and thermally treated at 500°C for 5 min. The electrochemical responses of the films were determined from the cyclic voltammetry and chronoamperometry measurements using LiClO4 in propylene carbonate (1.0 M) as electrolyte. X-ray diffraction (XRD) technique was used to analyze the structure of the prepared film.

高温焼成によるＣｏ含有バーネサイト型二酸化マンガンの合成とリチウム二次電池正極特性

Birnessite type manganese dioxides doped with cobalt were synthesized by calcination of a mixture of KMnO4 and Co(NO3)2·6H2O at 600°C in air. The artificial birnessite was consisted of differently stacked slab phases depending on the cobalt content. These birnessites doped with Co exhibited different ratio of two phases; two-layer hexagonal (2H) and three-layer rhombohedral (3R) whose stacking sequences are different but belong to birnessite. The ratio of 3R/2H phases increased with increasing the Co quantity. Their electrochemical performances in Li cells were investigated in a LiClO4-propylene carbonate solution. As a result, the Co-doped birnessite demonstrated the smaller charge transfer resistance and higher reversible capacities than Co-free birnessite.

A complementary electrochromic device based on polyaniline and poly(3,4-ethylenedioxythiophene)

In this study, two conducting polymers, polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) (PEDOT), were used to construct an electrochromic device (ECD). PANI was employed as the anodic coloring polymer while PEDOT was used as the cathodic coloring polymer. The electrochemical and optical properties of PANI, which has a coloration efficiency of 25 cm2/C at 570 nm, were coupled with the complementary coloring material, PEDOT, which has a coloration efficiency of 206 cm2/C at 570 nm. A suitable operating potential window was switched between −0.6 and 1.0 V to explore the cycle life of the ECD. We tested the PANI–PEDOT ECD, which consisted of PANI, PEDOT, and an organic electrolyte containing 0.1 M LiClO4 in propylene carbonate and 1 mM HClO4. The transmittance of the ECD at 570 nm changed from 58% (−0.6 V) to 14% (1.0 V) with a coloration efficiency of 285 cm2/C. Within the selected operating voltage range, the PANI–PEDOT ECD could be cycled for up to 2×104 cycles.

Electrochromic properties of sputtered TiO2 thin films

TiO2 thin films were deposited on ITO/Glass substrates by the rf magnetron sputtering in this study. The electrochromic properties of TiO2 films were investigated using cyclic voltammograms (CV), which were carried out on TiO2 films immersed in an electrolyte of 1 M LiClO4 in propylene carbonate (PC). As- deposited TiO2 thin film was amorphous, while the films post-annealed at 300~600°C contained crystallized anatase and rutile. With the increase of the annealing temperature, the surface roughness of film increased from 1.232 nm to 1.950 nm. Experimental results reveal that the processing parameters of TiO2 thin films will influence the electrochromic properties such as transmittance, ion-storage capacity, inserted charge, optical density change, coloration efficiency and insertion coefficient.