All-solid-state electrochromic device based on poly(butyl viologen), Prussian blue, and succinonitrile

A new complementary electrochromic device (ECD) is described; it is based on poly(butyl viologen) (PBV) and Prussian blue (PB) confined to the electrode surfaces. PBV is a cathodically colored organic polymer, while PB is an anodically colored inorganic material. The two electrochromic materials were individually characterized in a 0.5 M KCl aqueous solution. On the basis of their properties, a PBV–PB ECD containing a solid-state electrolyte prepared by adding lithium tetrafluoroborate (LiBF₄) as a salt to succinonitrile (SN) was investigated. This all-solid-state ECD system showed good optical contrast with a coloration efficiency of ca. 163 cm²/C at 650 nm and good stability during 4000 cycles. The transmittance of the ECD at 650 nm changed from 73% (bleached) to 8% (darkened), with an applied potential of 1.7 V (−1.0 to 0.7 V) across the two electrodes. After 4000 cycles, the transmittance attenuation (ΔT) of the device was still at 86% of its original value, i.e. the ΔT value had decreased from 65% to 56%.     

An all-thiophene electrochromic device fabricated with poly(3-methylthiophene) and poly(3,4-ethylenedioxythiophene)

A novel all-organic electrochromic device (ECD) is presented. By electrodepositing poly(3-methylthiophene) (PMeT) in boron fluoride ethyl ether (BFEE), a strong Lewis acid, a good-quality PMeT film was obtained. On the basis of studies of PMeT, it can be regarded as a pseudo-anodic coloring material for ECDs. On the other hand, poly(3,4-ethylenedioxythiophene) (PEDOT) is an ideal cathodic coloring electrochromic material known for its high optical contrast, long-term stability, and high coloration efficiency. By combining these two thiophene derivatives, the application potential of this device was determined. The color of the ECD switches between deep blue at −1.4 V (PEDOT vs. PMeT) and light red at 0.6 V. The device exhibits stable electrochromic performance, with a maximum optical attenuation (ΔT_max) at 655 nm reaching 46% (from 9% to 55%), and achieves a high coloration efficiency of 336 cm²/C. After 100 repeated cycles, the cell still retained at 91.3% of its ΔT_max at 655 nm.     

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.     

Characteristics of laminated electrochromic devices using polyorganodisulfide electrodes

The application of polyorganodisulfides as optically passive counter-electrodes in a variety of electrochromic smart glazing devices are discussed. Characteristic data is presented for electrochromic devices using proton, and lithium coloration ions with modified polyethylene oxide electrolyte and polydimercaptothiadiazole positive electrodes. Solid state devices consisting of molybdenum doped WO₃, amorphous polyethylene oxide electrolyte (a-PEO), and a polyorganodisulfide counter-electrode colored rapidly from a pale yellow to a deep blue-green, upon application of −1.2 V DC. The photopic transmittance (T_p) changes from 61 to 9%, and the solar transmittance (T_s) changes from 45 to 5% during the coloration process. Also, our experiments with polyimidazole are detailed. This family of compounds due to its unique electrical and ion conduction properties allow a single composite ion storage and ion conductor electrode to be made, simplifying the device construction. Devices made from this family of compounds color to deep blue-gray upon application of −1.2–1.5 V DC. Bleaching occurs at −0.4 to −0.5 V DC. The photopic transmittance changed from 55 to 9%, and the solar transmittance from 34 to 4% during coloration. Both coloration and bleaching are quite rapid.     

A complementary electrochromic device based on Prussian blue and poly(ProDOT-Et2) with high contrast and high coloration efficiency

A complementary electrochromic device (ECD) based on Prussian blue (PB) and poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine) (PProDOT-Et₂) has been systematically investigated. PB is regarded as an anodic coloring material with high electrochemical stability, while PProDOT-Et₂ is a cathodic coloring polymer with high contrast and high coloration efficiency (η). The electro-optical properties of the two electrochromic (EC) materials are characterized separately in a 0.1 M LiClO₄ in propylene carbonate (PC). A complementary ECD is assembled based on the two EC materials. The maximum transmittance of the ECD at 590 nm can be changed reversibly from 11.3% to 70.6% at the applied voltages of 1.2 and −1.3 V, and achieved a high coloration efficiency of 1214 cm²/C. Moreover, this ECD still remains at 98% of its maximum transmittance window (ΔT_max) even after 1,200 cycles, namely, the ΔT value decreases from 59% to 58%.     

First a-SiC : H photovoltaic-powered monolithic tandem electrochromic smart window device

We report on the first monolithic, amorphous-silicon-based, photovoltaic-powered electrochromic window coating. The coating employs a wide band gap a-Si_1−xC_x : H n–i–p photovoltaic (PV) cell as a semitransparent power supply, and an Li_yWO₃/LiAlF₄/V₂O₅ electrochromic (EC) device as an optical-transmittance modulator. The EC device is deposited directly on top of a PV device that coats a glass substrate. The a-Si_1−xC_x : H PV cell has a Tauc gap of 2.2 eV and a transmittance of 80% over a large portion of the visible light spectrum. We reduced the thickness of the device to about 600 Å while maintaining a 1-sun open-circuit voltage of 0.9 V and short-circuit current of 2 mA/cm². By employing the LiAlF₄ as the Li⁺ ion electrolyte, the parasitic electronic current through the device has been significantly reduced (<10 μA/cm² under 1 V bleaching voltage). By properly controlling y and the thickness of each layer, the coloration and bleaching voltage of the EC device could be adjusted within the range of −0.6 to −1.3 V (coloring) and 0.1–0.6 V (bleaching) for compatibility with the underlying PV cell. Our prototype 16 cm² PV/EC device modulates the transmittance by more than 60% over a large portion of the visible spectrum. Its color is pale yellow at bleached state and dark blue at colored state. The coloring and bleaching times of the electrochromic device are approximately 2 min under normal operating conditions (±1 V). The device is hermetically sealed for a long lifetime.     

Electrochromic device of PEDOT–PANI hybrid system for fast response and high optical contrast

An organic–organic hybrid system composed of the polyaniline (PANI) and poly-(3,4-ethylenedioxythiophene) (PEDOT) with controlled thickness was developed successfully in order to realize synergetic effects in electrochromic (EC) properties such as optical contrast and color-switching rate. From the UV transmittance spectra, we found that the optical contrast (Δ%T) was enhanced up to 6–72% at the wavelength of 580 nm compared with the previous PANI–PEDOT ECDs. Furthermore, the optimized ECD showed an extremely fast response time of less than 160 ms. It is therefore concluded that such a complementary full .cell system of PEDOT–PANI ECD is applicable as an optical device.     

Influence of coloring voltage on the optical performance and cycling stability of a polyaniline–indium hexacyanoferrate electrochromic system

An electrochromic system based on the multielectrochromic polyaniline (PANI) and pseudo-transparent indium hexacyanoferrate (InHCF) thin-film electrodes was studied in this work. In combination with a hybrid H⁺/K⁺-conducting solid polymer electrolyte—KCl-doped poly(2-acrylamido-2-methylpropanesulfonic acid) (K-PAMPS), a precoloring-free PANI–InHCF electrochromic device (ECD) with an active area of 3×3 cm² was fabricated and exhibited yellowish-green-blue multicolor electrochromism. From in situ spectroelectrochemical experiments, we found that the performance of a PANI/K-PAMPS/InHCF ECD was significantly affected by the operating voltages, especially by the coloring voltage. Both the bleached and yellowish state of the ECD could be attained reversibly by applying a voltage ranging from +1.5 to +1.7 V (InHCF vs. PANI). Different coloring voltages resulted in different optical properties and cycling stabilities, however. For instance, the device biased at −1.6 V (InHCF vs. PANI) showed a deep blue color, but the optical activity decayed quickly (less than 50 cycles) when the device was switched between +1.6 and −1.6 V. Nevertheless, the device could be reversibly operated between +1.6 and 0 V for several hundred cycles, although a narrower electrochromic extent (yellowish-to-green) was observed correspondingly. The optimization of the coloring voltage is therefore of paramount importance to the PANI/K-PAMPS/InHCF ECD.     

Thermogalvanic conversion of heat to electricity

A thermogalvanic (nonisothermal) cell was constructed for carrying out power conversion efficiency measurements. The design departed from that of traditional thermogalvanic cells which have largely been used only for studies of open-circuit voltage. The cell was used to obtain temperature coefficients, ∂E/∂T, of the open circuit voltage and power conversion efficiencies, Φ, for an interelectrode temperature difference, ΔT, of 20 K, using various redox couples. The values obtained were the following: Cu²⁺/Cu (1.0 mol dm⁻³), ∂E/∂T = 785 μV K⁻¹; Zn²⁺/Zn (1.0 mol dm⁻³), ∂E/∂T = 790 μV K⁻¹; Fe phen(CN)₄⁻/Fe phen(CN)₄²⁻ (10⁻³ mol dm⁻³), ∂E/∂T = 1046 μV K⁻¹, Φ = 4.17 × 10⁻⁵%; Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ (0.07 mol dm⁻³), ∂E/∂T = 1600 μV K⁻¹, Φ = 1.4 × 10⁻²%. More detailed studies of the latter system when [Fe(CN)₆³⁻] = [Fe(CN)₆⁴⁻] = 0.26 mol dm⁻³ and [KCl] = 0.80 mol dm⁻³, using platinum electrodes, with ΔT = 20 K, gave a current density of 1.45 mA cm⁻² and a power conversion efficiency, Φ, of 2.8 × 10⁻²%. This approaches 0.5% of the maximum theoretical efficiency of a Carnot engine operating across the same temperature difference.     

Imidazolium-based ionic liquid derivatives for application in electrochromic devices

Novel proton-conducting electrolytes were prepared from the sol–gel precursor 1-[3-(trimethoxy-λ⁴-silyl)propyl]imidazole with the addition of either trifluoroacetic or acetic acid. The presence of trimethoxysilyl groups enabled the solvolysis and condensation reactions of silsesquioxane species. IR spectroscopy revealed that more cube-like species formed in the electrolyte prepared from trifluoroacetic acid, while cube- and ladder-like silsesquioxanes were present in the electrolyte with acetic acid. This assignation was independently confirmed by ²⁹Si NMR analyses revealing the T³ signals of trisiloxane bonding. IR spectroscopy also pointed to the formation of hydrogen bonding in the latter electrolyte, since the frequencies of the observed bands at 1710, 1409, and 1272 cm⁻¹ approached those of acetic acid. In contrast, the IR bands at 1662, 1204, and 1130 cm⁻¹ confirmed the existence of trifluoroacetate anions in the case when the electrolyte was prepared from trifluoroacetic acid. The presence of free trifluoroacetate anions contributed to the moderately higher specific conductivity of this electrolyte (4.6×10⁻⁵ S/cm) compared to that of acetic acid (1.6×10⁻⁵ S/cm). The specific conductivity of the electrolytes could be further increased by the addition of a lithium salt. All electrolytes were employed in electrochromic devices with optically active WO₃ and various inorganic counter-electrodes (CeVO₄, V₂O₅, Ti/V-oxide). Photopic transmittance changes from 30% to 40% were achieved.     

Incorporation of a stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) in an electrochromic device

A stable organic radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), was studied. We employed TEMPO as a cathodic radical provider in propylene carbonate (PC) and poly(3,4-propylenedioxythiophene) derivatives (PProDOT-Et₂) as an anodic electrochromic (EC) thin film, which was obtained through electropolymerization. On assembling them together in a device, the electrochemical and optical performances of this hybrid electrochromic device (ECD) showed reversible cycling stability and high absorbance attenuation in the visible range. By selecting proper electrolytes (LiClO₄/PC) and controlling the deposited charge of the PProDOT-Et₂ thin film, it was possible to obtain a transmittance change (ΔT) of up to 59% at 590 nm with no noticeable degradation after operating between 0 and 0.9 V for 1000 cycles. Furthermore, an electrochemical quartz crystal microbalance (EQCM) was used to investigate ion migrations in the PProDOT-Et₂ thin film, which influenced its long-term stability.     

Characterisation and stability of low-emittance multiple coatings for glazing applications

We present experimental studies on the deposition and characterisation of ZnS/Ag/ZnS low-e coatings carried out to assess their optical performance and stability. Theoretical predictions of the coatings optical properties were combined with measured emissivity () values to derive a figure of merit (η) defined as the ratio of luminous transmittance over emissivity. A coating consisting of 37.0 nm ZnS/21.5 nm Ag/37.0 nm ZnS was found to maximise η. Long-term experiments on the produced ZnS/Ag/ZnS coatings, under solar irradiation have revealed that a moderate vacuum (10⁻²–10⁻³ mbar) is required to avoid degradation of the film properties. Four-layer ZnS/Al/Ag/ZnS and five-layer ZnS/Ag/ZnS/Ag/ZnS coatings were produced and tested for thermal stability. They were both found to withstand heating at 300°C for 3 h. The four-layer structures however, present low transmittance in the visible, due to absorption by the Al layer.     

A polymer gel electrolyte composed of a poly(ethylene oxide) copolymer and the influence of its composition on the dynamics and performance of dye-sensitized solar cells

A polymer gel electrolyte composed of a poly(ethylene oxide) derivative, poly(ethylene oxide-co-2-(2-methoxyethoxy) ethyl glycidyl ether), mixed with gamma-butyrolactone (GBL), LiI and I₂ is employed in dye sensitized solar cells (DSSC). The electrolyte is characterized by conductivity experiments, Raman spectroscopy and thermal analysis. The influence of the electrolyte composition on the kinetics of DSSC is also investigated by transient absorption spectroscopy (TAS). The electrolyte containing 70 wt.% of GBL and 20 wt.% of LiI presents the highest conductivity (1.9 × 10⁻³ S cm⁻¹). An efficiency of 4.4% is achieved using this composition. The increase in I_SC as a function of GBL can be attributed an increase in the mobility of the iodide (polyiodide) species. The increase in the yield of the intermediate species, I₂⁻, originating in the regeneration reaction, is confirmed by TAS. However, the charge recombination process is faster at this composition and a decrease in the V_oc is observed. Photovoltage decay experiments confirm an acceleration in charge recombination for the DSSC assembled with the electrolyte containing more GBL. Raman investigations show that in this electrolyte the I₅⁻/I₃⁻ ratio is higher. Theoretical calculations also indicate that the I₅⁻ species is a better electron acceptor.     

Photoresponse of n-TiO2 thin film and nanowire electrodes

Thin film and nanowire electrodes of n-type titanium oxide (n-TiO₂) were fabricated and their photoresponses towards water-splitting reaction were studied. A more than twofold increase in maximum photoconversion efficiency was observed when a single-layer thin film of n-TiO₂ was replaced by nanowires. Highest photoconversion efficiency was observed at an applied potential of 0.61 V vs. E_aoc where the electrode potential at open circuit, E_aoc was found to be −1.0 V SCE⁻¹ at illumination intensity of 40 mW cm⁻² in 5.0 M KOH solution. The maximum photoconversion efficiency was approximately of another twofold increase for water splitting at nanowire electrodes when methanol was used as a sacrifacial hole scavenger (depolarizing agent) in the electrolyte. Also, this maximum photoconversion efficiency was found at a lower applied potential of 0.41 V vs. E_aoc in presence of methanol. The band-gap energy of the n-TiO₂ films and nanowires annealed at 750°C was found to be 2.98 eV, which indicates their rutile structure.     

Stable, easily sintered BaCe0.5Zr0.3Y0.16Zn0.04O3−δ electrolyte-based protonic ceramic membrane fuel cells with Ba0.5Sr0.5Zn0.2Fe0.8O3−δ perovskite cathode

A stable, easily sintered perovskite oxide BaCe_0.5Zr_0.3Y_0.16Zn_0.04O_3−δ (BCZYZn) as an electrolyte for protonic ceramic membrane fuel cells (PCMFCs) with Ba_0.5Sr_0.5Zn_0.2Fe_0.8O_3−δ (BSZF) perovskite cathode was investigated. The BCZYZn perovskite electrolyte synthesized by a modified Pechini method exhibited higher sinterability and reached 97.4% relative density at 1200 °C for 5 h in air, which is about 200 °C lower than that without Zn dopant. By fabricating thin membrane BCZYZn electrolyte (about 30 μm in thickness) on NiO–BCZYZn anode support, PCMFCs were assembled and tested by selecting stable BSZF perovskite cathode. An open-circuit potential of 1.00 V, a maximum power density of 236 mW cm⁻², and a low polarization resistance of the electrodes of 0.17 Ω cm² were achieved at 700 °C. This investigation indicated that proton conducting electrolyte BCZYZn with BSZF perovskite cathode is a promising material system for the next generation solid oxide fuel cells.     

Effect of the Cu underlayer on the optoelectrical properties of ITO/Cu thin films

Sn doped indium oxide (ITO) single layer films and ITO/Copper (Cu) bi-layer films were prepared on polycarbonate substrates by DC and RF magnetron sputtering without intentional substrate heating. In order to consider the influence of the Cu underlayer on the optoelectrical properties and microstructures of the films, the thickness of the Cu bottom layer in the ITO/Cu films was varied from 5 to 20 nm.Conventional ITO films had a constant optical transmittance of 74% and an electrical resistivity of 3.1 × 10⁻³ Ω cm, while ITO/Cu films had different optoelectrical properties that were influenced by the thickness of the Cu bottom layer. The lowest electrical resistivity, 5.7 × 10⁻⁵ Ω cm, was obtained from ITO 80 nm/Cu 20 nm films and the highest optical transmittance of 72%, was obtained from the ITO 95 nm/Cu 5 nm films. From the figure of merit (_TC) which is defined by _TC = T¹⁰/R_s, where T is the optical transmittance at 550 nm and R_s is the sheet resistance, it can be concluded that the most effective Cu thickness in the ITO/Cu films on the optoelectrical properties was 5 nm.     

Current transport in copper indium gallium diselenide solar cells comparing mesa diodes to the full cell

Mesa diodes were formed on CdS/CIGS/stainless steel solar cells to investigate current transport when edge leakage and spot defects are avoided. Current conduction mechanisms in the device were determined from current–voltage (I–V) and current–voltage–temperature (I–V–T) characteristics. Space charge limited (SCL) current in the mobility regime with an exponential distribution of traps was found in the voltage range of V>0.6 V based on I∝V^m where m>2. In the voltage region of 0.2V<V<0.6V, recombination was the dominant mechanism based on the ideality factor, n, in the equation I=Ae^(qV/nkT), close to 2. For −0.2V<V<0.2V, a combination of tunneling and SCL current in the ballistic regime was suggested because of the weak temperature dependency and approximation to I∝V^1.5. For the reverse bias region where V<−0.2 V, the device exhibited either SCL current in the velocity saturation regime or tunneling based on the unity I–V relation and the weak temperature dependency. A previous report on full size CIGS cells indicated a higher degree of tunneling for V<0.2 V. Thus, the mesa diodes show some difference in mechanism compared to “good” full cells and much difference compared to “poor” full cells.     

Electrochromic thin films prepared by sol–gel process

New methods are shown for lower temperature preparation of amorphous tungsten oxide thin film and preparation of crystalline iridium oxide thin film by sol–gel process using metal chloride as the starting materials and ethanol as a solvent. These electrochromic materials were combined with gel solid electrolyte, and preparation of fully solid-state electrochromic display (ECD) was made. The transmittance of the ECD could be made to change by 35% by applying a voltage of 3 V for 0.2 sec.     

Calendar- and cycle-life studies of advanced technology development program generation 1 lithium-ion batteries

This paper presents the test results and life modeling of special calendar- and cycle-life tests conducted on 18650-size generation 1 (Gen 1) lithium-ion battery cells (nominal capacity of 0.9 Ah; 3.0–4.1 V rating) developed to establish a baseline chemistry and performance for the Department of Energy sponsored advanced technology development (ATD) program. Electrical performance testing was conducted at the Argonne National Laboratory (ANL), Sandia National Laboratory (SNL) and the Idaho National Engineering and Environmental Laboratory (INEEL).As part of the electrical performance testing, a new calendar-life test protocol was used. The test consisted of a once per day discharge and charge pulse designed to have minimal impact on the cell yet establish its performance over a period of time such that the calendar-life of the cell could be determined. The calendar-life test matrix included two states-of-charge (SOCs) (i.e. 60 and 80%) and four test temperatures (40, 50, 60 and 70 °C). Discharge and regen resistances were calculated from the test data. Results indicate that both the discharge and regen resistances increased non-linearly as a function of the test time. The magnitude of the resistances depended on the temperature and SOC at which the test was conducted. Both resistances had a non-linear increase with respect to time at test temperature. The discharge resistances are greater than the regen resistances at all of the test temperatures of 40, 50, 60 and 70 °C. For both the discharge and regen resistances, generally the higher the test temperature, the lower the resistance.The measured resistances were then used to develop an empirical model that was used to predict the calendar-life of the cells. This model accounted for the time, temperature and SOC of the batteries during the calendar-life test. The functional form of the model is given by: R(t,T,SOC)=A(T, SOC)F(t)+B(T, SOC), where t is the time at test temperature, T the test temperature and SOC the SOC of the cell at the start of the test. A(T, SOC) and B(T, SOC) are assumed to be functions of the temperature and SOC; F is assumed to only be a function of the time at test temperature. Using curve-fitting techniques for a number of time-dependent functions, it was found that both the discharge and regen resistances were best correlated with F(t) having a square-root of test time dependence. These results led to the relationship for the discharge and regen resistances: R(t,T,SOC)=A(T, SOC)t^1/2+B(T, SOC). The square-root of time dependence can be accounted for by either a one-dimensional diffusion type of mechanism, presumably of the lithium-ions or by a parabolic growth mechanism for the growth of a thin-film solid electrolyte interface (SEI) layer on the anode and/or cathode. The temperature dependence of the resistance was then investigated using various model fits to the functions A(T, SOC) and B(T, SOC). The results of this exercise lead to a functional form for the temperature dependence of the fitting functions having an Arrhenius-like form: A(T,SOC)=a(SOC){exp[b(SOC)/T]} and B(T,SOC)=c(SOC){exp[d(SOC)/T]}, where a and c are constants, and b and d are related to activation energy (E_b and E_d) by using the gas constant (R) such that b=E_b/R and d=E_d/R. The functional form, therefore, for the discharge and regen resistances, including the SOC, is then: R(t,T,SOC)=a(SOC){exp[b(SOC)/T]}t^1/2+c(SOC){exp[d(SOC)/T]}. The a, b, c and d parameters are explicitly shown as being functions of the SOC. However, due to the lack of testing at SOC values other than 60 and 80% SOC, the exact form of the SOC dependence could not be determined from the experimental data. The values of a, b, c and d were determined, thus permitting the function R(t, T, SOC) to be used to correlate the discharge and regen data and to predict what the resistances would be at different test times and temperatures.This paper also presents, discusses and models the results of a special cycle-life test conducted for a period of time at specified temperatures of 40, 50, 60 and 70 °C. This test, consisting of specified discharge and charge protocols, was designed to establish the cycle-life performance of the cells over a time interval such that their cycle-life could be determined. The cycle-life test was conducted at 60% SOC, with SOC swings of Δ3, Δ6 and Δ9%. During the cycle-life test, the discharge and regen resistances were determined after every 100 test cycles. The results of the cycle-life testing indicate that both the discharge and regen resistances increased non-linearly as a function of the test time at each Δ% SOC test. The magnitude of the resistances and the rate at which they changed depended on the temperature and Δ% SOC at which the test was conducted. Both resistances had a non-linear increase with respect to time at test temperature, i.e. as the number of test cycles increased the discharge and regen resistances increased also. For a given Δ% SOC test, the discharge resistances are greater than the regen resistances at all of the test temperatures of 40, 50, 60 and 70 °C. For both the discharge and regen resistances, generally the higher the test temperature, the lower the resistance. At each of the four test temperatures, the magnitude of the discharge and regen resistances was generally in the following order: Δ3% SOC>Δ9% SOC>Δ6% SOC, but the ordering was dependent on test time.A model was also developed to account for the time, temperature, SOC and Δ% SOC of the batteries during the cycle-life test. The functional form of the model is given by R(t,T,SOC,Δ% SOC)=A(T, SOC, Δ% SOC)F(t)+B(T, SOC, Δ% SOC) where t is the time at test temperature, T the test temperature, SOC the SOC of the cell at the start and end of the test and Δ% SOC the SOC swing during the test. A(T, SOC, Δ% SOC) and B(T, SOC, Δ% SOC) are assumed to be functions of the test temperature, SOC and Δ% SOC swing. F(t) is assumed to only be a function of the test time at test temperature. Using curve-fitting techniques for a number of time-dependent functions, it was found that both the discharge and regen resistances were best correlated by a square-root of test time dependence. These results led to the relationship for the discharge and regen resistances having the form R(t,T,SOC,Δ% SOC)=A(T, SOC, Δ% SOC)t^1/2+B(T, SOC, Δ% SOC). This model is essentially the same as used to analyze the calendar-life test data. The temperature dependence of the resistance was then investigated using various model fits to the functions A(T) and B(T). The results of this exercise lead to a functional form for the functions having again an Arrhenius-like form: A(T)=a[exp(b/T)] and B(T)=c[exp(d/T)] where a and c are constants, and b and d are related to activation energies. The functional form, therefore, for the discharge and regen resistances including the SOC and Δ% SOC is R(t,T,SOC,Δ% SOC)=a(SOC, Δ% SOC){exp[b(SOC, Δ% SOC)/T]}t^1/2+c(SOC, Δ% SOC){exp[d(SOC, Δ% SOC)/T]}. The a, b, c and d parameters are explicitly shown as being functions of the SOC and the Δ% SOC. However, due to the lack of testing at SOC values other than 60% SOC, the exact form of the SOC dependence could not be determined from the experimental data. In addition, no model was found that consistently correlated the observed resistance changes with the Δ% SOC of the tests. Eliminating the SOC and Δ% SOC from the resistance function, the function R(t, T) was then used to correlate the discharge and regen resistances data. This model also allows the prediction of what the resistances would be at different test times at a particular Δ% SOC test condition and temperature.     

All solid-state electrochromic devices with gelatin-based electrolyte

6×8 cm² electrochromic devices (ECDs) with the configuration K-glass/EC-layer/electrolyte/ion-storage (IS) layer/K-glass, have been assembled using Nb₂O₅:Mo EC layers, a (CeO₂)_0.81–TiO₂ IS-layer and a new gelatin electrolyte containing Li⁺ ions. The structure of the electrolyte is X-ray amorphous. Its ionic conductivity passed by a maximum of 1.5×10⁻⁵ S/cm for a lithium concentration of 0.3 g/15 ml. The value increases with temperature and follows an Arrhenius law with an activation energy of 49.5 kJ/mol. All solid-state devices show a reversible gray coloration, a long-term stability of more than 25,000 switching cycles (±2.0 V/90 s), a transmission change at 550 nm between 60% (bleached state) and 40% (colored state) corresponding to a change of the optical density (ΔOD=0.15) with a coloration efficiency increasing from 10 cm²/C (initial cycle) to 23 cm²/C (25,000th cycle).