Conductivity Of Gel Polymer Electrolyte Research Articles

Poly-acrylonitrile-based gel-polymer electrolytes for sodium-ion batteries

Research and development activities on sodium-ion batteries are becoming prominent in the past few years. Compared to lithium-based batteries, the sodium-based batteries will be cheaper because of the abundancy of sodium raw materials in the earth’s crust and also in seawater. In the current study, we synthesized and characterized poly-acrylonitrile (PAN)-based gel-polymer electrolytes formed with NaClO4 and dissolved in ethylene carbonate (EC) and propylene carbonate (PC). By systematically varying the weight ratios of polymer, salt, and the solvents, we obtained an optimum room temperature ionic conductivity of 4.5 mS cm−1 for the composition 11PAN-12NaClO4-40EC-37PC (wt.%), which is reasonably good for practical applications. This value of conductivity is comparable to a few other Na+ ion conducting gel-polymer electrolyte systems studied in the recent past. Variation of ionic conductivity with inverse temperature showed Arrhenius behavior. Activation energies estimated for all the samples showed only a slight variation suggesting that a single activation process which depends on the EC/PC co-solvent governs the ionic mobility in these gel-polymer electrolytes. Thermo-gravimetric analysis (TGA) revealed that there is no noticeable weight loss of these electrolytes up to 100 °C and hence the electrolytes are thermally stable for operating temperatures up to 100 °C.

A long persistence phosphor tailored quasi-solid-state dye-sensitized solar cell that generates electricity in sunny and dark weathers.

An all-weather quasi-solid-state dye-sensitized solar cell is built using a long persistence phosphor tailored mesoscopic TiO2 photoanode and a three-dimensional conducting polymer gel electrolyte. The so-called all-weather solar cell yields a maximum efficiency of 28.7% in the dark, making a promising photovoltaic revolutionary for state-of-the-art photovoltaics.

Thiol–ene synthesis and characterization of lithium bis(malonato)borate single-ion conducting gel polymer electrolytes

The development of high capacity anodes and high voltage cathodes for advanced lithium-ion batteries motivates the search for new polymer electrolytes that exhibit superior electrochemical stabilities and high ionic conductivities. We report a convenient, three-step synthesis of lithium bis(non-8-enyl-malonato)borate (LiBNMB) as a α,ω-diene monomer, which undergoes thermally initiated thiol-ene crosslinking polymerizations in propylene carbonate to yield gel polymer electrolytes with high lithium ion concentrations (∼0.9 M). By conducting these crosslinking polymerizations using mixtures of di- and tri-thiols and LiBNMB with [thiol] : [ene] = 1 : 1, we synthesized a series of gel networks with dynamic elastic moduli ranging from G' = 40-79 kPa that increase monotonically with trifunctional crosslinker content. While ionic conductivities for these polymer gels measured by electrochemical impedance spectroscopy at 22 °C are σ = 0.82-2.5 × 10-6 S cm-1, we show that the conductivity of propylene carbonate-solvated lithium ions though the bulk of these gel electrolytes is 8.5 × 10-5 S cm-1 independent of crosslinker density. However, the conductivities of the gel interfaces depend sensitively on crosslinker content, suggesting the importance of segmental rearrangement dynamics at the electrode interface in limiting the rate of ion motion. Thus, the design of highly conductive polymer electrolytes for advanced batteries demands careful design of both the internal and interfacial properties of these new materials.

Electrical Characterization of PVdF based Proton Conducting Polymer Gel Electrolytes

Background: Polymer gel electrolytes have attracted much intention due to their high ionic conductivity (10-2 - 10-3 S/cm) along with other suitable properties like good thermal stability, compatibility with electrode materials, easy workability, wider control of properties etc. These materials are also called smart materials due to their practical applications in various devices like high energy power devices, electrochromic devices, supercapacitors, devices for Infra-red systems etc. This paper mainly discusses the enhancement of an ionic conductivity with the addition of polymer. No appreciable change in conductivity of gel electrolytes has been observed with temperature, which makes them suitable for device applications. Methods: Liquid electrolytes were prepared by dissolving orto-nitro benzoic acid (o- NBA) in the ternary mixture of ethylene carbonate (EC), propylene carbonate (PC), and dimethylacetamide (DMA) (in 2:2:1 volume ratio). The homogeneous polymer solution of PVdF in acetone is prepared and then added to the liquid electrolyte along with continuous stirring. Polymer gel electrolytes are obtained after the evaporation of acetone. Ionic conductivity of liquid and polymer gel electrolytes is measured by HP4284A precision LCR meter (having frequency range from 20Hz-1MHz) using complex impedance spectroscopy. Results: The conductivity of liquid electrolytes increases by two orders of magnitude with an addition of ortho-nitro benzoic acid (10-6 to 10-4 S/cm) and maximum room temperature conductivity of 1.46 x 10-4 S/cm has been obtained at 2M concentration of o-NBA in ternary mixture of EC, PC and DMA. The conductivity of electrolytes increases with the addition of polymer and maximum conductivity of 5.91 x 10-4 S/cm has been obtained at room temperature. The increase in conductivity has been explained by using “Breathing Polymer Chain Model”. Ionic transference number was calculated and it was found out to be nearly 1, which suggests that gel electrolyte is principally ionic conductor. Conclusion: Maximum conductivity of 5.91 x 10-4 S/cm at room temperature has been observed for gel electrolyte containing 2M ortho-nitrobenzoic acid in EC:PC:DMA (2:2:1) with 8 wt% PVdF. The conductivity of polymer gel electrolytes has been found to increase with the addition of PVdF concentration. The conductivity of gel electrolytes is found to be higher than that of liquid electrolytes at all PVdF concentrations i.e. σ(gel) > σ(liquid). The increase in conductivity has been found to depend upon the concentration of acid, dissociation constant of acid and concentration of PVdF used. No appreciable change in conductivity of gel electrolytes has been observed with temperature, which make them suitable for device applications. Ionic transference number measurements suggest that these electrolytes are principally ionic conductors. Keywords: Conductivity, dimethylacetamide, ethylene carbonate, gel, transference number.

Study of quasi-solid electrolyte in dye-sensitized solar cells using surfactant as pore-forming materials in TiO2 photoelectrodes

A novel polymer gel electrolyte was used to improve the performance and long-term stability in dye-sensitized solar cells (DSSCs). The polymer gel electrolyte (PGE) was prepared by mixing 5 wt% poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 2 % TiO2 nanoparticles. The conductivity of PGE with P25 reached 9.98 × 10−3 S/cm, which increased by 34.9 % compared with 7.40 × 10−3 S/cm of PGE without P25, and the diffusion coefficient was also increased by 19.0 %. Different photoelectrodes were obtained by using three kinds of surfactants (cetylamine, octadecylamine, and P123) as pore-forming materials, and their morphologies were contrasted through scanning electron microscopy (SEM). The results showed that gel electrolyte can increase the short-circuit current density (Jsc) from 11.01 to 12.99 mA/cm2 in DSSCs. Moreover, unlike the liquid electrolyte, the gel electrolyte is more conducive to the TiO2 photoelectrodes with larger pores. In conclusion, the efficiency of DSSC with gel electrolyte and P123 as pore-forming material was 6.73 %, which was 12 % higher than the liquid electrolyte in the same test condition. In addition, the sealed gel electrolyte DSSCs showed better stability than did liquid electrolyte DSSCs during nearly 600 h.

Electrical characterization of nano-composite polymer gel electrolytes containing NH4BF4 and SiO2: role of donor number of solvent and fumed silica

Nano-composite polymer gel electrolytes were synthesized by using polyethylene oxide (PEO), ammonium tetrafluoroborate (NH4BF4), fumed silica (SiO2), dimethylacetamide (DMA), ethylene carbonate (EC), and propylene carbonate (PC) and characterized by conductivity studies. The effect of donor number of solvent on ionic conductivity of polymer gel electrolytes has been studied. The mechanical strength of the gel electrolytes has been increased with the addition of nano-sized fumed silica along with an enhancement in conductivity. Maximum room temperature ionic conductivity of 2.63 × 10−3 and 2.92 × 10−3 S/cm has been observed for nano-composite gel electrolytes containing 0.1 and 0.5 wt% SiO2 in DMA+1 M NH4BF4+10 wt% PEO, respectively. Nano-composite polymer gel electrolytes having DMA have been found to be thermally and electrically stable over 0 to 90 °C temperature range. Also, the change in conductivity with the passage of time is very small, which may be desirable to make applicable for various smart devices.

A Quasi-Solid-State Li-Ion Capacitor Based on Porous TiO2 Hollow Microspheres Wrapped with Graphene Nanosheets.

The quasi-solid-state Li-ion capacitor is demonstrated with graphene nanosheets prepared by an electrochemical exfoliation as the positive electrode and the porous TiO2 hollow microspheres wrapped with the same graphene nanosheets as the negative electrode, using a Li-ion conducting gel polymer electrolyte. This device may be the key to bridging the gap between conventional lithium-ion batteries and supercapacitors, meanwhile meeting the safety demands of electronic devices.

Ionic Liquid Based Polymer Gel Electrolyte Membranes for Lithium Ion Rechargeable Batteries

Li-ion conducting polymer gel electrolyte membranes (PGEMs) based on polymer poly(vinylidene fluoride-co-hexafluoropropylene) PVdF-HFP, ionic liquid, 1-butyl-3-methylimidazolium tetrafluroborate BMIMBF4 and Lithium bis(trifluoromethanesulfonyl)imide) LiTFSI salt (having different anion i.e. BF4 - and TFSI-) have been synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), complex impedance spectroscopy and cyclic voltammetry. After incorporation of IL in polymer electrolyte, (i.e. PVdF-HFP+20wt.% LiTFSI) different physicochemical properties such as melting temperature (Tm), glass transition temperature (Tg), thermal stability, degree of crystallinity (Xc), and ionic transport behaviour of these materials are found to change. The pristine PVdF-HFP possessed a semi-crystalline structure and its amorphicity increased with the addition of LiTFSI salt and BMIMBF4 ionic liquid. An impedance measurement indicated that the room-temperature ionic conductivity of the membranes increased with increasing IL content and attains a maximum value of 3.2 *10-3 S/cm at 30 °C and ~ 8.7*10-3 S/cm at 130 °C. An schematic representation exhibiting increase in ionic conductivity with increasing amount of dopant ionic liquid has been shown in the given figure. In addition, temperature dependent ionic conductivity seems to obey Arrhenius type thermally activated behaviour. A high total ionic transference number > 0.99 and the cationic transference number (tLi +) ~0.33 with a wider electrochemical window (ECW) ~4.0–5.0 V for the PGEMs containing higher loading of IL have been obtained. Fig. Schematic representation exhibiting increase in ionic conductivity with increasing amount of dopant Ionic Liquid. Figure 1

Effect of electrospinning on the ionic conductivity of polyacrylonitrile/polymethyl methacrylate nanofibrous membranes: optimization based on the response surface method

A novel fibrous polymer electrolyte membrane was produced based on polymethyl methacrylate/polyacrylonitrile (PMMA/PAN) blend. This was achieved through optimization in the loadings of the two polymers and electrospinning method. Consequently, the effect of PMMA on the ionic conductivity was assessed. A quantitative relationship between ionic conductivity and the important parameters including voltage, solution concentration, and PMMA content was determined. The response surface method (RSM) was employed to obtain the quantitative relationship and to determine the ion conductivity of PAN/PMMA electrospun membrane. Analysis of variance technique was used to study the importance of parameters and their interactions. A regression model was applied to determine the most influential factors on the ionic conductivity and to find the maximum ionic conductivity of the electrolyte membrane as an optimal result. The average fiber diameter was in the range of 206–367 nm, and the membranes were associated with high porosities between 50 and 91 %, and the electrolyte uptakes were in the range of 285–460 %. For all samples, the ionic conductivity of gel polymer electrolytes at 25 °C was above the 1 mS/cm. The ionic conductivity changed with the voltage directly and with the solution concentration inversely. According to the results, the ionic conductivity showed its dependency with the PMMA content, increasing with the PMMA content up to 50 % and smoothly decreasing with PMMA further increases. Some important interactions between the parameters were also detected.

Poly(vinylidene fluoride-hexafluoropropylene) polymer electrolyte for paper-based and flexible battery applications

Paper-based batteries represent a new frontier in battery technology. However, low-flexibility and poor ionic conductivity of solid electrolytes have been major impediments in achieving practical mechanically flexible batteries. This work discuss new highly ionic conductive polymer gel electrolytes for paper-based battery applications. In this paper, we present a poly(vinylidene fluoride-hexafluoropropylene) (PVDH-HFP) porous membrane electrolyte enhanced with lithium bis(trifluoromethane sulphone)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP), with an ionic conductivity of 2.1 × 10−3 S cm−1. Combining ceramic (LATP) with the gel structure of PVDF-HFP and LiTFSI ionic liquid harnesses benefits of ceramic and gel electrolytes in providing flexible electrolytes with a high ionic conductivity. In a flexibility test experiment, bending the polymer electrolyte at 90° for 20 times resulted in 14% decrease in ionic conductivity. Efforts to further improving the flexibility of the presented electrolyte are ongoing. Using this electrolyte, full-cell batteries with lithium titanium oxide (LTO) and lithium cobalt oxide (LCO) electrodes and (i) standard metallic current collectors and (ii) paper-based current collectors were fabricated and tested. The achieved specific capacities were (i) 123 mAh g−1 for standard metallic current collectors and (ii) 99.5 mAh g−1 for paper-based current collectors. Thus, the presented electrolyte has potential to become a viable candidate in paper-based and flexible battery applications. Fabrication methods, experimental procedures, and test results for the polymer gel electrolyte and batteries are presented and discussed.

Fiber-Reinforced Gel Polymer Electrolyte Based on Cross-Linked PMMA for Sodium Ion Battery Application

Gel polymer electrolytes (GPEs), consisting of polymer matrix, organic solvents and salts, are an appealing choice of electrolytes for advanced energy storage systems as they combine high ionic conductivity, low cost, improved safety, and ease of fabrication into desired shape and size. Nevertheless, it should be pointed out that even with immense efforts directing towards GPEs, the conductivity of GPEs is still limited because the evaporation of the organic solvents in GPEs reduces the volume of electrolyte; thus decreasing the contact area across the electrode and reducing the conductivity. Cross-linked GPE can be a good candidate to remedy this drawback. In this research, the fiber-reinforced cross-linked GPEs, in which the fibers are held together to form a meshed sheet or web. This 3D scaffold is then loaded with an appropriate electrolyte to create an electrochemically and mechanically stable electrolyte layer for battery application. The combination of polymer and fibers forms a fiber-reinforced polymer composite which possesses a unique blend of electrical and mechanical properties to enhance the performance of these ionic conductors. Reinforcing the polymer material with inert fibers which are not subject to chemical attack improves their shear strength and stiffness. The fiber reinforcement of GPEs will preliminarily employ a non-woven polyester fabric as a substrate. It has high porosity and good chemical resistance to organic liquids while maintaining good contact with the polymer; the holes in the cloth also increase the surface area to offer the open spaces for ion transfer. The fiber-reinforced gel polymer based on cross-linked PMMA is fabricated by free radical polymerization. The prepared organic solution and polyester cloth are placed together between two pieces of 0.25” thick optical lenses with heating at 75oC. The sketch of the sample is shown in Fig. 1a. Upon completion of the fiber-reinforced GPE, the samples are subjected to comprehensive electrochemical testing in order to evaluate the properties of this novel ion conducting electrolyte. The conductivity will be evaluated using potentiostatic impendence spectroscopy based on testing protocols available in the Gamry Reference-600 potentiostat. For sodium-air battery application, the electrolyte is used as the separator between the anode and the cathode as shown in Fig. 1b. The sodium sheet is used as the anode, the reference electrode Ag/AgCl is placed next to the anode while the platinum wire used as the cathode exposes to the oxygen environment. The open circuit potential and cyclic voltammetry tests are adopted for characterizing the electrochemical performance of fiber-reinforced cross-linked GPE in sodium-air battery. This research has successfully developed fiber-reinforced GPE based on cross-linked PMMA capable of delivering ionic conductivity comparable to that of cross-linked GPE (10-3 S/cm), while also being a robust separator capable of withstanding the pressure generated while under long term use in sodium-air batteries. The ion transfer thermodynamics are also investigated by activation energy measurement. The electrochemical behavior of sodium-air battery accommodated this light-weight, mechanically stable fiber-reinforced cross-linked GPE indicate that the increased energy density could help the metal-air battery technique to take the leap from bench top to commercial application. Figure 1

Sodium-Ion Polymer Batteries Assembled with Composite Gel Polymer Electrolytes

Rechargeable sodium-ion batteries have become the promising energy storage system due to their high energy density, long cycle life and lower cost. However, safety issues surrounding these batteries must be addressed before they can be widely utilized in large-scale applications such as electric vehicles and grid-scale energy storage devices. Therefore, the quest for safer and more reliable electrolyte system is urgent and polymer electrolytes are promising candidates in this regard. However, they suffer from poor thermal stability and mechanical properties. In order to obtain the gel polymer electrolytes with improved thermal and mechanical properties, ceramic fillers such as SiO2, Al2O3, TiO2 and BaTiO3 have been incorporated into host polymers. In these composite gel polymer electrolytes, the ceramic particles promote electrochemical properties of the polymer electrolytes through physical interactions without directly contributing to the lithium ion transport process. As reported in our previous studies, the ionic conductivity of gel polymer electrolyte was improved by using ceramic fillers covered with poly(styrene sulfonated lithium)(PLSS) containing lithium cation end group [1,2,3]. It is of our interest to synthesize and introduce inorganic materials containing dissociative sodium ions in the electrolyte of sodium-ion batteries to improve the ionic conductivity, thermal stability and mechanical property. In this study, we prepared composite gel polymer electrolytes based on core-shell structured SiO2 nanoparticles containing dissociative sodium ions. The SiO2 particles have unique core-shell morphology with a thin layer of poly(sodium 4-styrene sulfonate) surrounding nano-sized SiO2core particle. The composite gel polymer electrolyte exhibited high ionic conductivity and good mechanical strength. The prepared gel polymer electrolytes were used to assemble sodium-ion polymer batteries, and their cycling performances were evaluated.

Role of Polymer in Enhancement of Conductivity of Proton and Lithium Conducting Polymer Gel Electrolytes

Role of Polymer in Enhancement of Conductivity of Proton and Lithium Conducting Polymer Gel Electrolytes

High thermal and electrochemical stability of PVDF-graft-PAN copolymer hybrid PEO membrane for safety reinforced lithium-ion battery

A PVDF-graft-PAN copolymer was prepared by ozone polymerization and hybrid with PEO as a conductive gel–polymer electrolyte for lithium-ion batteries.

Hydroxypropyl Cellulose Based Non-Volatile Gel Polymer Electrolytes for Dye-Sensitized Solar Cell Applications using 1-methyl-3-propylimidazolium iodide ionic liquid.

Gel polymer electrolytes using imidazolium based ionic liquids have attracted much attention in dye-sensitized solar cell applications. Hydroxypropyl cellulose (HPC), sodium iodide (NaI), 1-methyl-3-propylimidazolium iodide (MPII) as ionic liquid (IL), ethylene carbonate (EC) and propylene carbonate (PC) are used for preparation of non-volatile gel polymer electrolyte (GPE) system (HPC:EC:PC:NaI:MPII) for dye-sensitized solar cell (DSSC) applications. The highest ionic conductivity of 7.37 × 10−3 S cm−1 is achieved after introducing 100% of MPII with respect to the weight of HPC. Temperature-dependent ionic conductivity of gel polymer electrolytes is studied in this work. XRD patterns of gel polymer electrolytes are studied to confirm complexation between HPC polymer, NaI and MPII. Thermal behavior of the GPEs is studied using simultaneous thermal analyzer (STA) and differential scanning calorimetry (DSC). DSSCs are fabricated using gel polymer electrolytes and J-V centeracteristics of fabricated dye sensitized solar cells were analyzed. The gel polymer electrolyte with 100 wt.% of MPII ionic liquid shows the best performance and energy conversion efficiency of 5.79%, with short-circuit current density, open-circuit voltage and fill factor of 13.73 mA cm−2, 610 mV and 69.1%, respectively.

Ionic conductivity and battery characteristic studies of a new PAN-based Na+ ion conducting gel polymer electrolyte system

Sodium ion conducting gel polymer electrolytes based on polyacrylonitrile (PAN) with ethylene carbonate and dimethyl formamide as plasticizing solvents are prepared by the solution cast technique. These electrolyte films are free standing, transparent and dimensionally stable. Na+ ions are derived from NaI. The structural properties of pure and complex formations have been examined by X-ray diffraction, Fourier transform infrared spectroscopic studies and differential scanning calorimetric studies. The variation of the conductivity with salt concentration ranging from 10 to 40 wt% is studied. The sample containing 30 wt% of NaI exhibits the highest conductivity of 2.35 × 10−4 S cm−1 at room temperature (303 K) and 1 × 10−3 S cm−1 at 373 K. The conductivity–temperature dependence of polymer electrolyte films obeys Arrhenius behavior with activation energy in the range of 0.25–0.46 eV. The transport numbers both electronic (te) and ionic (ti) are evaluated using Wagner’s polarization technique. It is revealed that the conducting species are predominantly due to ions. The ionic transport number of highest conducting film is found to be 0.991. Solid-state battery with configuration Na/(PAN + NaI)/(I2 + C + electrolyte) is developed using the highest conducting gel polymer electrolyte system and the discharge characteristics of the cell are evaluated over the load of 100 KΩ.

Development of ion conducting polymer gel electrolyte membranes based on polymer PVdF-HFP, BMIMTFSI ionic liquid and the Li-salt with improved electrical, thermal and structural properties

Figure (a) shows that the semi-crystalline nature of the polymer PVdF-HFP and Figure (b) shows that the polymer chain became flexible on the addition of LiTFSI salt. Furthermore, on the addition of IL in polymer electrolyte membranes, the membranes became more flexible and provide high ionic conduction (because of more availability of ions) in the system resulting in enhancement of the ionic conductivity (see Figure (c)).

A sodium ion conducting gel polymer electrolyte

A sodium ion conducting gel polymer electrolyte based on poly(vinylidene difluoride-co-hexafluoropropylene) porous membrane is reported, which is prepared through a simple phase separation process. It exhibits high safety, good mechanical properties and good electrochemical stability. The gel polymer electrolyte provides the sodium ionic conductivity of 0.60mScm−1 at ambient temperature, while the commercial separator (Celgard 2730) offers only 0.16mScm−1. The temperature dependence of the ionic conductivity from 25 to 75°C is consistent with an Arrhenius-behavior. The ionic transference number of sodium ion (tNa+) in the gel polymer electrolyte is 0.30, higher than that (0.17) in the commercial separator. This provides a new direction to improve the safety of sodium ion batteries.

Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries

Lithium poly(4-styrene sulfonyl (phenylsulfonyl)imide) (PSSPSI) was synthesized through the Hinsberg reaction. Since the bis(sulfonyl)imide anion is immobilized in the polymer chain, the lithium cation transference number was measured to be 0.87. The weight average number molecular weight (Mw) was found to be 105,343 determined by gel permeation chromatography (GPC). A gel polymer electrolyte membrane, comprising of PVDF and PSSPSI, was successfully prepared with the ionic conductivity of 1.1×10−3Scm−1 at room temperature. The membrane exhibits a wide electrochemical window up to 4.5V (vs. Li+/Li) and is thermally and mechanically stable. The material is well suited for applications in lithium-ion batteries.

Stability improvement of gel-state dye-sensitized solar cells by utilization the co-solvent effect of propionitrile/acetonitrile and 3-methoxypropionitrile/acetonitrile with poly(acrylonitrile-co-vinyl acetate)

Propionitrile (PPN) or 3-methoxypropionitrile (MPN) is mixed with acetonitrile (ACN) to prepare ACN/PPN and ACN/MPN co-solvents and used to fabricate polymer gel electrolytes (PGEs) of dye-sensitized solar cells (DSSCs), aiming at improving the stability of gel-state DSSCs. Co-solvents with various ratios are utilized to prepare PGEs using poly(acrylonitrile-co-vinyl acetate) (PAN-VA) as the gelator. The ratio effects of the co-solvents on the properties of PGEs and the performances of the corresponding DSSCs are studied. The results show that in-situ gelation of the gel-electrolytes can still be performed at the presence of 40% PPN or 30% MPN. However, increasing the composition of PPN and MPN in the co-solvents triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the viscosity. Therefore, the energy conversion efficiencies of the cells decrease as a result. However, the introduction of PPN and MPN elevates the gel-to-liquid transition temperature (Tp) of the PGEs which significantly increases the stability of the gel-state DSSCs. Comparing between the effects of the two co-solvents, PPN and MPN have similar effect on elevation of Tp, but the conductivity of PGEs and the corresponding cell efficiency are higher for the ACN/PPN system, attributed to its lower viscosity compared with ACN/MPN system. By using the ACN/PPN (60/40) co-solvent at the presence of TiO2 fillers, gel-state cell with an efficiency of 8.3% can be achieved, which is even higher than that obtained by the liquid state cell (8%). After 500 h test at 60 °C, the cell can retain 95.4% of its initial efficiency.