Alkaline Polymer Electrolyte Research Articles

Preparation and characterization of PVA/PAA membranes for solid polymer electrolytes

Solid polymer electrolyte (SPE) membranes with varying composition ratios were prepared from poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The acrylic acid monomer with cross-linker was first blended with PVA polymer. A free radical polymerization was then carried out to form an alkaline polymer electrolyte. The solution casting method was used to form the solid polymer membranes. The solid polymer membranes were then immersed in 32 wt.% KOH solution to form different types of electrolyte, and the characteristic properties were examined with ac impedance, differential scanning calorimetry (DSC), stress–strain test, X-ray diffraction (XRD) and SEM morphology analysis. The results showed that the highest room temperature ionic conductivity for the PVA/PAA/KOH solid polymer membrane electrolyte system was 0.301 S cm −1, which is a four-fold increase from that of the PVA–KOH electrolyte. These PVA/PAA composite polymer membranes also exhibited excellent thermal and mechanical properties. The membranes were stable for a wide temperature range. The PVA/PAA polymer membrane had good mechanical strength and ductility and would be a suitable polymer membrane electrolyte for the alkaline batteries and other electrochemical systems.

Composite alkaline polymer electrolytes and its application to nickel–metal hydride batteries

In order to enhance the ionic conductivity of polyethylene oxide (PEO)-KOH based alkaline polymer electrolytes, three types of nano-powders, i.e., TiO 2, β-Al 2O 3 and SiO 2 were added to PEO-KOH complex, respectively, and the corresponding composite alkaline polymer electrolytes were prepared. The experimental results showed that the prepared polymer electrolytes exhibited higher ionic conductivities at room temperature, typically 10 −3 S cm −1 as measured by ac impedance method, and good electrochemical stability. The electrochemical stability window of ca. 1.6 V was determined by cyclic voltammetry with stainless steel blocking electrodes. The influence of the film composition such as KOH, H 2O and nano-additives on ion conductivity was investigated and explained. The temperature dependence of conductivity was also determined. In addition, polyvinyl alcohol (PVA)-sodium carboxymethyl cellulose (CMC)-KOH alkaline polymer electrolytes were obtained using solvent casting method. The properties of the polymer electrolytes were characterized by ac impedance, cyclic voltammetry and differential thermal analysis methods. The ionic conductivity of the prepared PVA-CMC-KOH-H 2O electrolytes can reach the order of 10 −2 S cm −1. The effect of CMC addition on the alkaline polymer electrolytes was also explained. The experimental results demonstrated that the PVA-CMC-KOH-H 2O polymer electrolyte could be used in Ni/MH battery.

Study of ionic transport properties of alkaline poly(vinyl) alcohol-based polymer electrolytes

The ionic transport properties of alkaline polymer electrolytes based on poly(vinyl) alcohol (PVA) have systematically been studied using a Hittorf's method. The ionic transport numbers for three types of alkaline PVA-based polymer electrolytes, including PVA, PVA/PECH blend, PVA/TEAC blend, were measured in this work. It was found that the anionic transport number ( t −) was in the range of between 0.82 and 0.99; it strongly depends on the types of alkali metal salts, and the chemical compositions of polymer electrolytes. However, it only slightly depends on the applied current densities. Experimental results indicated that alkaline PVA/TEAC blend polymer electrolytes showed the highest value of anionic transport number, as compared with PVA and PVA/PECH blend polymer electrolytes.

Chemical composition and XRD analyses for alkaline composite PVA polymer electrolyte

Alkaline composite polymer electrolyte films, which composed of PVA polymer with a glass–fiber–cloth mat and various alkali hydroxides, were obtained by a solution cast method. The crystal structure properties of composite PVA polymer electrolyte films were examined by XRD. The XRD results revealed that the amorphous domain of PVA polymer matrix was increased when the KOH was blended. It was found that the ionic conductivity of composite electrolyte films with different alkali hydroxides is at the level of 10 −2 S/cm at room temperature. The ionic conductivity of the alkaline polymer electrolyte is highly dependent on the composition of KOH and H 2O in the films. The chemical composition of composite PVA polymer electrolytes was quantitatively examined by ionic chromatographic (IC) analysis. The IC composition results reveal that the chemical composition of alkaline PVA polymer electrolyte films can be tailored to optimum the performance of alkaline composite polymer films.

Novel alkaline polymer electrolytes based on tetramethyl ammonium hydroxide

In this work, novel alkaline solid polymer electrolytes (SPEs) with tetramethyl ammonium hydroxide (Me 4NOH· xH 2O) have been developed, without addition of any volatile solvent. It was found that some polymers such as poly(sodium acrylate) had good compatibility with Me 4NOH· xH 2O. The polymer-Me 4NOH· xH 2O electrolytes thus prepared in this work appeared to have improved mechanical properties as compared with the pure hydroxide and remained highly conductive in the solid state (10 2 S cm −1 at ∼40 °C). The thermal properties of the alkaline SPEs and the dependence of conductivity on composition and temperature are presented, and the relationships between properties and composition as well as conductivity mechanism for these new systems are discussed.

A novel alkaline Zn/MnO 2 cell with alkaline solid polymer electrolyte

For the first time, all solid-state Zn/MnO 2 cells have been fabricated using an alkaline polymer electrolyte prepared from PVA and KOH aqueous solution. Galvanostatic discharge and electrochemical impedance measurement have been used to examine the electrochemical performance of prototype cells. The results demonstrated that the Zn/MnO 2 cell exhibited good discharge characteristics and stability.

GEA TO SHED ITS AIR TREATMENT BUSINESS

In recent years, integrated fuel cell (FC) type primary and secondary batteries attracted a great deal of attention as integrated on-chip power sources due to their high theoretical power densities. Unfortunately, the costs of these devices have been rather high. This is partially due to the involved clean-room processes, but also due to the fact that these devices generally rely on expensive precious-metals such as Pd and Pt. Therefore we developed a novel integrated FC type accumulator that is based on non-precious-metals only. The key component of the presented accumulator is its alkaline polymer electrolyte membrane that allows not only the usage of a low-cost AB5 type hydrogen storage electrode, but also the usage of La0.6Ca0.4CoO3 as a precious-metal free bifunctional catalyst for the air-breathing electrode. Additionally the presented design requires only comparatively few cleanroom processes which further reduces the overall production costs. Although abdicating precious-metals, the presented accumulator shows an open circuit voltage of 0.81 V and a maximum power density of 0.66 mW cm−2 which is comparable or even superior to former precious-metal based cells.

Polymer Ni–MH battery based on PEO–PVA–KOH polymer electrolyte

An alkaline polymer electrolyte film has been prepared by a solvent-casting method. Poly(vinyl alcohol), PVA is added to improve the ionic conductivity of the electrolyte. The ionic conductivity increases from 10 −7 to 10 −2 S cm −1 at room temperature when the weight percent ratio of poly(ethylene oxide), PEO to PVA is increased from 10:0 to 5:5. The activation energy of the ionic conductivity for the PEO–PVA–KOH polymer electrolyte is 3–8 kJ mol −1. The properties of the electrolyte film are characterized by a wide variety of techniques and it is found that the film exhibits good mechanical stability and high ionic conductivity at room temperature. The application of such electrolyte films to nickel–metal-hydride (Ni–MH) batteries is examined and the electrochemical characteristics of a polymer Ni–MH battery are obtained.

Supercapacitor based on activated carbon and polyethylene oxide–KOH–H 2O polymer electrolyte

For the first time, a totally solid state electric double layer capacitor has been fabricated using an alkaline polymer electrolyte and an activated carbon powder as electrode material. The polymer electrolyte serves both as separator as well as electrode binder. The capacitor has a three-layer structure: electrode–electrolyte–electrode with a final thickness of ca. 1.5–2 mm, diameter of 1.8 cm (surface of 2.5 cm 2) and a mass of ca. 300–500 mg. Cyclic voltammetry, galvanostatic cycling and impedance spectroscopy have been used for the determination of the electrochemical performance of prototype capacitors and a capacity of ca. 1.7–3.0 F for a 1 V voltage range has been measured.

Recent advances in solid polymer electrolyte fuel cell technology with low platinum loading electrodes

Of all the fuel cell systems, only alkaline and solid polymer electrolyte fuel cells are capable of achieving high power densities (1 W cm −2) required for terrestrial and extraterrestrial applications. Electrode kinetic criteria for attaining such high power densities are discussed. Attainment of high power densities in solid polymer electrolyte fuel cells has been demonstrated earlier by different groups using high platinum loading electrodes (4 mg cm −2). Recent work at Los Alamos National Laboratory and at Texas A&M University (TAMU) demonstrated similar performance for solid polymer electrolyte fuel cells with ten times lower platinum loading (0.45 mg cm −2) in the electrodes. Some of the results obtained at TAMU are discussed in terms of the effects of type and thickness of membrane, and of the methods of platinum localization in the electrodes, on the performance of a single cell.