Polymer electrolyte based on polyethylene glycol for quasi-solid state dye sensitized solar cells

A gel polymer electrolyte containing I⁻/I₃⁻ redox couple was prepared using polyethylene glycol (PEG) as polymer matrix and propylene carbonate (PC) as organic solvent by sol-gel method. A dye sensitized solar cell (DSSC) employing the gel polymer electrolyte gives an open-circuit voltage of 0.7 V and a short-circuit current of 8.1 mA cm⁻² at an incident light intensity of 100 mW cm⁻². Fourier transform infrared spectroscopy was utilized to examine the chemical properties of produced gel electrolytes. Unlike the conventional covalent bond that bridges the different polymer segments, in this study, it was observed that hydrogen bonds bridged polyethylene glycol and propylene carbonate. Influences of different synthetic parameters such as reaction time and temperature were also investigated. Optimal DSSC performance was observed at electrolyte reaction temperature and time of 100 °C and 24 h, respectively, with a maximum photoelectric energy conversion efficiency of 2.2%.     

Gelled composite electrolyte comprising thermoplastic polyurethane and poly(ethylene oxide) for lithium batteries

Composite polymer electrolyte films consisting of poly(ethylene glycol) based thermoplastic polyurethane blended with poly(ethylene oxide) (denoted as TPU(PEG)/PEO) incorporating LiClO₄–PC have been prepared and their electrochemical properties were studied. The thermal analysis of the composite films were performed to demonstrate the miscibility of the polymer blend by using differential scanning calorimeter (DSC). TPU(PEG)/PEO based polymer electrolyte shows ionic conductivity of the order 6.4×10⁻⁴ S/cm at room temperature, irrespective of time evolution. Cyclic voltammogram shows that this composite electrolyte has good electrochemical stability in the working voltage ranging from 2 to 4.5 V. Cycling performances of Li/polymer electrolyte/LiCoO₂ cells are also followed. From AC impedance results, the recharging ability of the cells is proved to be dominated by the passive layer formation at Li electrode–polymer electrolyte interface.     

PEO/PS/PMMA聚合物电解质膜的制备及性能研究

聚合物电解质是解决锂离子电池安全性问题的有效途径之一。考察了由聚环氧乙烷(PEO)、聚苯乙烯(PS)、聚甲基丙烯酸甲酯(PMMA)、聚乙二醇(PEG)和双三氟甲烷磺酰亚胺锂盐(LiTFSI)组成的固体聚合物电解质膜的性能。采用聚合物共混技术制备了一系列复合聚合物电解质膜,通过扫描电子显微镜(SEM)和X射线衍射(XRD)对膜的形态和晶体结构进行了分析,并详细考察了离子电导率、孔隙率和吸液率等性能。PS和PMMA的加入降低了PEO的结晶度,提高了它的拉伸强度。结果表明,当PEO/PS/PMMA膜中各组成质量比为75:10:15时,聚合物电解质膜具有优良的性能,膜的离子电导率为3.56×10^-4S·cm^-1,拉伸强度为11.56MPa,孔隙率达到57.6%,吸液率高达164.3%。     

Photocured PEO-based solid polymer electrolyte and its application to lithium–polymer batteries

A solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) is prepared by photocuring of polyethylene glycol acrylates. The conductivity is greatly enhanced by adding low molecular weight poly(ethylene glycol) dimethylether (PEGDME). The maximum conducticity is 5.1×10⁻⁴ S cm⁻¹ at 30°C. These electrolytes display oxidation stability up to 4.5 V against a lithium reference electrode. Reversible electrochemical plating/stripping of lithium is observed on a stainless steel electrode. Li/SPE/LiMn₂O₄ as well as C(Li)/SPE/LiCoO₂ cells have been fabricated and tested to demonstrate the applicability of the resulting polymer electrolytes in lithium–polymer batteries.     

Electrochemical properties of amorphous comb-shaped composite PEO polymer electrolyte

The electrochemical behaviour of a polyethylene oxide (PEO)-based composite polymer electrolyte are studied. The crystallinity of the PEO is suppressed by using a comb-shaped polymer to improve polymer chain mobility. An amorphous comb-shaped polymer, ‘TEC-24’, with a side-chain content of 24 mol%, is designed and fine silica powder is dispersed within it to enhance the mechanical properties above the melting point. The composite polymer electrolyte has an ionic conductivity of 1.6×10⁻⁴ and 1.6×10⁻³ S cm⁻¹ at 30 and 90 °C, respectively, with an electrochemical stability window close to 5.0 V, even at 80 °C (versus Li/Li⁺). The polymer electrolyte is evaluated using CuS as a cathode material and shows better cycle performance than that obtained with a liquid electrolyte.     

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.     

Alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte for Zn–air battery

An alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte with high ionic conductivity (10⁻² S cm⁻¹) at room temperature has been prepared and applied to solid-state primary Zn–air batteries. The electrolyte shows excellent mechanical strength. The electrochemical characteristics of the batteries were experimentally investigated by means of ac impedance spectroscopy and galvanostatic discharge. The results indicate that the PEO–PVA–glass-fibre-mat composite polymer electrolyte is a promising candidate for application in alkaline primary Zn–air batteries.     

Quasi-solid-state dye-sensitized solar cells with a novel efficient absorbent for liquid electrolyte based on PAA–PEG hybrid

A novel efficient absorbent for liquid electrolyte based on poly(acrylic acid)–poly(ethylene glycol) (PAA–PEG) hybrid is prepared. The highest value of liquid electrolyte absorbency about 3.65 is achieved. The polymer gel electrolyte shows a moderate value of ionic conductivity about 3.24 mS cm⁻¹ and high chemical stability. Based on the polymer gel electrolyte, a quasi-solid-state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of 3.19% was obtained under irradiation of 100 mW cm⁻².     

Electrochemical characteristics of room temperature Li/FeS2 batteries with natural pyrite cathode

Electrochemical characteristics of Li/FeS₂ batteries having natural pyrite as cathode and liquid electrolytes have been studied at room temperature. The organic electrolytes used were 1 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) or a mixture of TEGDME and 1,3-dioxolane (DOX), and 1 M LiPF₆ in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The pyrite powder and FeS₂ cathode were characterized by SEM, EDS, XRD and charge/discharge cycling. The discharge capacities of Li/FeS₂ cells with 1 M LiTFSI dissolved in TEGDME were 772 mAh g⁻¹ at the 1st cycle and 313 mAh g⁻¹ at the 25th cycle at 0.1C. The cycling performance could be improved by using a mixture of TEGDME and DOX as the electrolyte. It was found that TEGDME contributed to high initial discharge capacity, whereas, DOX contributed to better stabilization of the performance. The first discharge capacities of Li/FeS₂ cells showed a decreasing trend with higher current densities (615 and 534 mAh g⁻¹, respectively, at 0.5C and 1.0C). Li/FeS₂ cells with the battery grade electrolyte 1 M LiPF₆ in EC/DMC had lower initial discharge capacity and cycling capability compared to the TEGDME system. The natural pyrite cathode with 1 M LiTFSI dissolved in a mixture of TEGDME and DOX showed reasonably good first discharge capacity and overall cycling performance, suitable for application in room temperature lithium batteries.     

PVDF–PEO blends based microporous polymer electrolyte: Effect of PEO on pore configurations and ionic conductivity

A novel microporous polymer electrolyte based on poly(vinylidene fluoride) and poly(ethylene oxide) (PVDF–PEO) blends was prepared by a simple phase inversion technique, in which the addition of PEO can obviously improve the pore configuration, such as pore size, porosity, and pore connectivity of PVDF-based microporous membranes, and hence, the room temperature ionic conductivity was greatly enhanced. The highest porosity of about 84% and ionic conductivity of about 2 mS cm⁻¹ can be obtained when the weight ratio of PEO to PVDF is 50%. This implies that PVDF–PEO blends based microporous polymer electrolyte can be used as candidate electrolyte and/or separator material for high-performance rechargeable lithium batteries.     

Modern generation of polymer electrolytes based on lithium conductive imidazole salts

In this paper the application of completely new generation imidazole-derived salts in a model polymer electrolyte is described. As a polymer matrix, two types of liquid low molecular weight PEO analogues e.g. dimethyl ether of poly(ethylene glycol) of 500 g mol⁻¹ average molar mass (PEGDME500) and methyl ether of poly(ethylene glycol) of 350 g mol⁻¹ average molar mass (PEGME350) were used. Room temperature conductivities measured by electrochemical impedance spectroscopy were found to be as high as 10⁻³-10⁻⁴ S cm⁻¹ in the 0.1-1 mol dm⁻³ range of salt concentrations. Li⁺ transference numbers higher than 0.5 were measured and calculated using the Bruce-Vincent method. For a complete electrochemical characterization the interphase resistance stability over time was carefully monitored for a period of 30 days. Structural analysis and interactions between electrolyte components were done by Raman spectroscopy. Fuoss-Kraus semiempirical method was applied for estimation of free ions and ionic agglomerates showing that fraction of ionic agglomerates for salt concentration of 0.1-1 mol dm⁻³ is much lower than in electrolytes containing LiClO₄ in corresponding concentrations.     

Photovoltaic activity in a ZnTe/PEO–chitosan blend electrolyte junction

A ZnTe/polymer junction has been fabricated and the photovoltaic properties studied. The polymer is a blend of 50 wt% chitosan and 50 wt% polyethylene oxide (PEO). The polymer blend was complexed with ammonium iodide (NH₄I) and some iodine crystals were added to the polymer–NH₄I solution to provide the I⁻/I³⁻ redox couple. The ionic conductivity of the polymer electrolyte is 4.32×10⁻⁶ S cm⁻¹ at room temperature. ZnTe was electrodeposited on ITO conducting glass. The polymer film was sandwiched between the ZnTe semiconductor and an ITO glass to form a ZnTe/polymer electrolyte/ITO photovoltaic cell. The open circuit voltage (V_oc) of the fabricated cells ranges between 300 and 400 mV and the short circuit current between 2 and 5 μA.     

Improved performance of Li hybrid solid polymer electrolyte cells

The seminal research by Wright et al. on polyethylene oxide (PEO) solid polymer electrolyte (SPE) generated intense interest in all solid-state rechargeable lithium batteries. Following this a number of researchers have studied the physical, electrical and transport properties of thin film PEO electrolyte containing Li salt. These studies have clearly identified the limitations of the PEO electrolyte. Chief among the limitations are a low cation transport number (t₊), high crystallinity and segmental motion of the polymer chain, which carries the cation through the bulk electrolyte. While low t₊ leads to cell polarization and increase in cell resistance high T_g reduces conductivity at and around room temperatures. For example, the conductivity of PEO electrolyte containing lithium salt is <10⁻⁷ S cm⁻¹ at room temperature. Although modified PEO electrolytes with lower T_g exhibited higher conductivity (∼10⁻⁵ S cm⁻¹ at RT) the t₊ is still very low ∼0.25 for lithium ion. Numerous other attempts to improving t₊ have met with limited success. The latest approach involves integrating nano domains of inorganic moieties, such as silcate, alumosilicate, etc. within the polymer component. This approach yields an inorganic–organic component (OIC) based polymer electrolyte with higher conductivity and t₊ for Li⁺_. This paper describes the improved electrical and electrochemical properties of OIC-based polymer electrolyte and cells containing Li anode with either a TiS₂ cathode or Mag-10 carbon electrode. Several solid polymer electrolytes derived from silicate OIC and salt-in-polymer constituent based on Li triflate (LiTf) and PEO are studied. A typical composition of the SPE investigated in this work consists of 600 kDa PEO, lithium triflate (LiTf, LiSO₃CF₃) and 55% of silicate based on (3-glycidoxypropyl)trimethoxysilane and tetramethoxysilane at molar ratio 4:1 and 0.65 mol% of aluminum(tri-sec-butoxide) (GTMOS-Al1-900k-55%). Several pouch cells consisting of Li/OIC-based–SPE/cathode containing OIC-based–SPE–LiTf binder were fabricated and tested, these cells are called modified cells. The charge/discharge and impedance characteristics of the new cells (also called modified cells) are compared with that of the pouch cells containing the conventional PEO–LiTf electrolyte as the cathode binder, these cells are called non-modified cells. The new cells can be charged and discharged at 70 °C at higher currents. However, the old cells can be charged and discharged only at 80 °C or above and at lower currents. The cell impedance for the new cells is much lower than that for the old cells.     

Investigation of plasticized UV-curable glycidyl methacrylate based solid polymer electrolyte for photoelectrochemical cell (PEC) application

A free standing electrolyte film containing poly glycidyl methacrylate (PGMA) as polymer host, lithium perchlorate (LiClO₄) as charge carrier and ethylene carbonate (EC) as plasticizer were successfully prepared with solution casting technique. Nuclear magnetic resonance spectroscopy (NMR) was used to investigate the chemical structure of the polymer. The analyses of polymer electrolytes were performed by impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and fourier transform infrared spectroscopy (ATR-FTIR). The solid polymer electrolyte exhibited the highest conductivity at room temperature and 373 K with the values of 3.4 × 10⁻⁴ S cm⁻¹ and 1.2 × 10⁻³ S cm⁻¹ at 80 wt.% of EC, respectively, in the presence of 80 wt.% of EC. FTIR spectroscopy analysis confirmed the interaction between lithium salt and oxygen atoms in polymer host in the presence of EC. Moreover, the electrolytes containing EC showed good electrochemical stability (−1500 to 3000) mV which reveals the potential of this polymer electrolyte for photoelectrochemical cell (PEC) application.     

Enhanced saccharification of SO2 catalyzed steam-exploded corn stover by polyethylene glycol addition

Corn stover is a renewable, low cost and abundant feedstock in China. Its effective utilization is crucial for providing bioenergy, releasing environmental pollution and increasing farmers’ income. This aim of this study was to obtain the efficient saccharification of SO₂ catalyzed steam-exploded corn stover (SSECS) by polyethylene glycol (PEG) addition. According to the results, adding PEG6000 could lower the enzyme loading by 33.3%. With 20% solid loading, the highest glucose concentration of 102 g L⁻¹ and 91.3% saccharification yield were obtained using 30 CBU (g glucan)⁻¹ ??-glucosidase and 10 FPU (g glucan)⁻¹ cellulase in presence of PEG6000. In addition, protein and enzyme activities assays in the supernatants revealed that PEG could facilitate the desorption of enzyme protein from lignocellulose. These indicated that PEG addition not only can enhance enzymatic saccharification at high substrate concentration, but also can improve enzyme recycling by reducing the enzyme activity loss caused by adsorption during the hydrolysis.     

Effect of ball milling on structural and electrochemical properties of (PEO)nLiX (LiX = LiCF3SO3 and LiBF4) polymer electrolytes

Polymer electrolytes consisting of poly(ethylene oxide) (PEO) and lithium salts, such as LiCF₃SO₃ and LiBF₄ are prepared by the ball-milling method. This is performed at various times (2, 4, 8, 12 h) with ball:sample ratio of 400:1. The electrochemical and thermal characteristics of the electrolytes are evaluated. The structure and morphology of PEO–LiX polymer electrolyte is changed to amorphous and smaller spherulite texture by ball milling. The ionic conductivity of the PEO–LiX polymer electrolytes increases by about one order of magnitude than that of electrolytes prepared without ball milling. Also, the ball milled electrolytes have remarkably higher ionic conductivity at low temperature. Maximum ionic conductivity is found for the PEO–LiX prepared by ball milling for 12 h, viz. 2.52×10⁻⁴ S cm⁻¹ for LiCF₃SO₃ and 4.99×10⁻⁴ S cm⁻¹ for LiBF₄ at 90 °C. The first discharge capacity of Li/S cells increases with increasing ball milling time. (PEO)₁₀LiCF₃SO₃ polymer electrolyte prepared by ball milling show the typical two plateau discharge curves in a Li/S battery. The upper voltage plateau for the polymer electrolyte containing LiBF₄ differs markedly from the typical shape.     

Discharge properties of all-solid sodium–sulfur battery using poly (ethylene oxide) electrolyte

An all-solid sodium/sulfur battery using poly (ethylene oxide) (PEO) polymer electrolyte are prepared and tested at 90 °C. Each battery is composed of a solid sulfur electrode, a sodium metal electrode, and a solid PEO polymer electrolyte. During the first discharge, the battery shows plateau potentials at 2.27 and at 1.76 V. The first discharge capacity is 505 mAh g⁻¹ sulfur at 90 °C. The capacity drastically decreases by repeated on charge–discharge cycling but remains at 166 mAh g⁻¹ sulfur after 10 cycles. The latter value is higher than that reported for a Na/poly (vinylidene difluoride)/S battery at room temperature.     

Carbon anode for dry-polymer electrolyte lithium batteries

A spherical carbon material of meso-carbon microbead (MCMB) was examined as an anode in a polyethylene oxide (PEO) based polymer electrolyte lithium battery. The electrochemical performance of the carbon electrode with the polymer electrolyte depended on the electrode thickness and the particle size of MCMB. The 30 μm-thick electrode of MCMB with the particle size of 20–30 μm showed a reversible capacity comparable with that in a liquid electrolyte, but the 100 μm-thick electrode showed a half of the 30 μm-thick electrode. The smaller particle size of 5–8 μm exhibited a high irreversible capacity at the first charge–discharge cycle. The reaction heat between MCMB and the polymer electrolyte was 0.5 J mAh^?1, which was much lower compared to those between lithium metal and the polymer electrolyte, 1.2 J mAh^?1, and MCMB and conventional liquid electrolyte, 4.3 J mAh^?1.     

Electrochemical properties of lithium sulfur cells using PEO polymer electrolytes prepared under three different mixing conditions

Lithium sulfur cells were prepared by composing with sulfur cathode (PEO)₆LiBF₄ polymer electrolyte and lithium anode. (PEO)₆LiBF₄ polymer electrolyte was prepared under three different mixing conditions: stirred polymer electrolyte (SPE), ball-milled polymer electrolyte (BPE) and ball-milled polymer electrolyte with 10 wt%Al₂O₃ (BCPE). The effects of ball milling and additive were investigated by discharge test according to depth of discharge. The initial discharge capacity of lithium sulfur cell using BCPE was 1670 mAh g⁻¹-sulfur, which was better than those of SPE and BPE, and approximately equal to the theoretical capacity. The cycle performance of Li/(PEO)₆LiBF₄/S cell was remarkably improved by the addition of Al₂O_3.     

Microfibrillated cellulose as reinforcement for Li-ion battery polymer electrolytes with excellent mechanical stability

Methacrylic-based thermo-set gel-polymer electrolyte membranes obtained by a very easy, fast and reliable free radical photo-polymerisation process and reinforced with microfibrillated cellulose particles are here presented. The morphology of the composite electrolytes is investigated by scanning electron microscopy and their thermal behaviour (characteristic temperatures, degradation temperature) are investigated by thermo-gravimetric analysis and differential scanning calorimetry. The composite membranes prepared exhibit excellent mechanical properties, with a Young's modulus as high as about 80 MPa at ambient temperature. High ionic conductivity (approaching 10⁻³ S cm⁻¹ at 25 °C) and good overall electrochemical performances are maintained, enlightening that such specific approach would make these hybrid organic, cellulose-based composite polymer electrolyte systems a strong contender in the field of thin and flexible lithium based power sources.