Design of plasticized proton conducting Chitosan:Dextran based biopolymer blend electrolytes for EDLC application: Structural,impedance and electrochemical studies

In this work, for the use of an electrical double-layer capacitor (EDLC) device applications, the fabrication and characterization of solid polymer electrolytes (SPEs) based on chitosan-dextran (CS-DN) blended polymer doped and plasticized with ammonium thiocyanate (NH₄SCN) and glycerol are studied, respectively. The Fourier transform infrared (FTIR) spectroscopy method has been used to investigate the structural behavior of electrolytes. It was observed that the FTIR bands are shifted and decreased in their intensities with the increased glycerol plasticizer content and it results in the complex formation. According to the electrical impedance spectra (EIS), the electrolyte incorporated with high contents of plasticizer (42 wt%) revealed the highest ionic conductivity of (3.08 × 10⁻⁴ S/cm). The electrical equivalent circuits (EEC) were used to investigate the circuit elements of the electrolytes further. Increasing glycerol plasticizers verified an improvement in ions density number (n), mobility (μ), and diffusion coefficient (D). The transference number measurements (TNM) indicated that the predominant charge carriers in the conduction process are ions where the (t_ion) is 0.95. According to the linear sweep voltammetry (LSV) study, the uppermost conducting sample was found to have sufficient anode stability with a breakdown voltage of 1.9 V that can be used in electrochemical devices. The absence of peaks in the cyclic voltammetry (CV) demonstrated that the charge storage mechanism within the constructed EDLC is fully capacitive. Based on this finding, the starting specific capacitance (C_s), energy density (E_d), and power density (P_d) have been identified to be 118F/g, 13.2 Wh/kg, and 1560 W/kg, respectively. Throughout its 100 cycles, the equivalence series resistance ESR value was between 53 and 117 Ω.     

The study of EDLC device fabricated from plasticized magnesium ion conducting chitosan based polymer electrolyte

Plasticized biopolymer electrolytes based on chitosan (CS) doped with magnesium acetate (Mg(CH₃COO)₂) and various amounts of glycerol have been prepared for energy storage electrochemical double-layer capacitor (EDLC) application. In this work the dielectric and electrochemical properties have been examined using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). It is confirmed from the frequency changing of the impedance spectra that relatively high dielectric constant has been recorded at low frequency region. From tan δ and M″ spectra, relaxation peaks are clearly seen. It has been found that as the glycerol concentration increased, the DC conductivity increases. In the fabricated system (CS: Mg(CH₃COO)₂: glycerol.), ions are responsible for charge carrying as the ion transference number is higher than the electron transference number. The electrochemical stability of the system extends to 2.4 V as shown in the LSV. The mechanism of the charge storage has been investigated and indicated that the non-Faradaic dominates where the specific capacitance is significantly affected by scan rate. The fabricated EDLC possessed a constant value of specific capacitance (78.2 F/g), energy density (8.8 Wh/kg), and ESR (78.2 F/g). The EDLC has an tremendous cycleability as high number of Columbic efficiency has accomplished. The value of efficiency of the EDLC has been in the range of 97%–99%.     

Role of plasticizer's dielectric constant on conductivity modification of PEO-NH4F polymer electrolytes

The addition of plasticizer to the polyethylene oxide (PEO)-ammonium fluoride (NH₄F) polymer electrolytes has been found to result in an increase in conductivity value and the magnitude of increase has been found to depend upon the dielectric constant of the plasticizer used. The addition of dimethylacetamide as a plasticizer with dielectric constant (?=37.8) higher than that of PEO (?∼5) results in an increase of conductivity by more than three orders of magnitude whereas the addition of diethylcarbonate as a plasticizer with dielectric constant (?=2.82) lower than that of PEO does not enhance the conductivity of PEO-NH₄F polymer electrolytes. The increase in conductivity has further been found to depend upon the concentration of plasticizer, the concentration of salt in the polymer electrolyte as well as on the dielectric constant value of the plasticizer used. The conductivity modification with the addition of plasticizer has been explained on the basis of dissociation of ion aggregates formed in PEO-NH₄F polymer electrolytes at higher salt concentrations.     

Laser Raman and conductivity studies of plasticized polymer electrolyte P(ECH-EO):propylenecarbonate:<Emphasis Type="Italic">γ</Emphasis>-butyrolactone:LiClO<Subscript>4</Subscript>

The plasticized polymer electrolytes composed of poly(epichlorohydrin-ethyleneoxide) (P(ECH-EO)) as host polymer, lithium perchlorate (LiClO₄) as salt, γ-butyrolactone (γ-BL), and propylene carbonate (PC) as plasticizer have been prepared by simple solution casting technique. The effect of mixture of plasticizers γ-BL and PC on conductivity of the polymer electrolyte P(ECH-EO):LiClO₄ has been studied. The band at 457 cm⁻¹ in the Raman spectra of plasticized polymer electrolyte is attributed to both the ring twisting mode of PC and the perchlorate ν ₂(ClO₄⁻) bending. The maximum conductivity value is observed to be 4.5 × 10⁻⁴ S cm⁻¹ at 303 K for 60P(ECH-EO):15PC:10γ-BL:15LiClO₄ electrolyte system. In the present investigation, an attempt has been made to correlate the Raman and conductivity data.     

Structural and electrical properties of polyvinyl alcohol (PVA):Methyl cellulose (MC) based solid polymer blend electrolytes inserted with sodium iodide (NaI) salt

This paper studies the structural and electrical properties of solid polymer blend electrolytes based on polyvinyl alcohol (PVA) and methylcellulose (MC) incorporated with sodium iodide (NaI). The polymer electrolyte films were assembled through a solution casting technique. The host matrix, which is doped with different NaI salt concentrations between 10 and 50 wt%, utilizes the most amorphous blend compositions (60 wt% Polyvinyl alcohol and 40 wt% methylcellulose). The structural behaviour of the electrolyte films was examined utilizing X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) techniques. The semi crystalline nature of PVA:MC with inserted NaI was derived from the X-ray diffraction studies, while the XRD analysis suggests that the highest ion conductive sample displays the minimum crystalline nature. The interaction between polymer blends and inserted salt was conceived from the FTIR investigation. Shifting of peaks and variation in the intensity of FTIR bands was detected. To investigate the structural properties and calculate the degree of crystallinity of the films, the (XRD) technique was employed, while electrical impedance spectroscopy (EIS) was utilized for studying the conductivity of the samples. In order to comprehend all of the electrical properties of the ion-conducting systems, the EIS outcome of each electrolyte was matched with Equivalent Electrical Circuits (EEC) s. Ion transport parameters including mobility, carrier density and diffusion are well assessed for the samples and the dielectric properties were compared with the conductivity measurement. At lower frequencies, the dielectric constant was elevated and dielectric loss was detected. Loss tangent and electric modulus plots were used to study the relaxation nature of the samples. The highest ambient temperature conductivity of PVA loaded 50 wt% of NaI was determined to be 1.53 × 10⁻⁵ S/cm. The loss tangent relaxation peak shifts towards high-frequency side which indicates the decrease of relaxation time and faster ion dynamics.     

Glycerol as an efficient plasticizer to increase the DC conductivity and improve the ion transport parameters in biopolymer based electrolytes: XRD,FTIR and EIS studies

In the current work Plasticized sodium ion conducting solid polymer electrolytes (SPEs) based on polyvinyl alcohol: methylcellulose (PVA: MC) and sodium iodide (NaI) as the electrolytic salt are fabricated. The SPE films are created using a renowned solution casting procedure, and the results of the experiments are provided. The development of polymers-salt complexes is supported by the Fourier-transform infrared transform (FTIR) analysis. The degrees of crystallinity of the polymers are noticeably decreased as a result of the glycerol plasticizer, according to X-ray diffraction test. The sample inserted with 40 wt% glycerol has the maximum ionic conductivity, according to electrical impedance spectroscopy (EIS). Electrical equivalence circuits (EEC) are used to explore the electrolytes circuit components. For the highest conducting electrolyte, the number density (n), mobility (µ), and diffusion coefficient (D) of ions are found to be 2 × 10²¹, 1.79 × 10^?6, and 4.59 × 10^?8, respectively. A high dispersion of the real component of dielectric permittivity at a lower frequency are used to infer the space charge influence induced by stainless-still (SS) electrodes. The tangent loss spectra show that the bouncing chance per unit time decreases as the glycerol concentration rises.     

Structural,ion transport parameter and electrochemical properties of plasticized polymer composite electrolyte based on PVA: A novel approach to fabricate high performance EDLC devices

In this study a novel polymer composite electrolytes (PCEs) based on poly (vinyl alcohol) (PVA): Ce(III)-complex:NH₄SCN plasticized with glycerol are prepared by solution cast technique. XRD and FTIR routes are used to study the film structure. The crystalline and amorphous areas are determined through the deconvolution of XRD spectra and their values were used to calculate the degree of crystallinity. The deconvolutions of the FTIR of asymmetric C≡N stretching mode are carried out to establish the bands coupled with free ions, contact ion pairs and ion aggregates. The maximum ambient temperature DC conductivity of 2.07 × 10⁻³ S cm⁻¹ is recorded for the sample with the lowest degree of crystallinity. It was found that the number density (n), mobility (μ) and diffusion coefficient (D) of ions are increased with the glycerol concentration. Field emission scanning electron microscopy (FESEM) is used to examine the effect of plasticizer on film morphology. The DC conductivity trend is interpreted in detail with the help of dielectric properties. It is found that the transference numbers of ions (t_ion) and electrons (t_el) are 0.965 and 0.035, respectively. It is shown by the linear sweep voltammetry (LSV) that the potential window of the PCE is 2.1 V. A shape, which is nearly rectangular at lower scan rates, is identified from cyclic voltammetry (CV). Specific capacitance and energy density are exhibited by EDLC with average of 161.5 F/g and 18.17 Wh/kg, respectively within 400 cycles. The initial power density is shown by EDLC to be 2.825 × 10³ W/kg.     

Mg-ion conducting gel polymer electrolyte membranes containing biodegradable chitosan: Preparation,structural, electrical and electrochemical properties

A biodegradable gel polymer electrolyte system based on chitosan/magnesium trifluoromethanesulfonate/1-ethyl-3-methylimidazolium trifluoromethanesulfonate (CA/Mg (Tf)₂/EMITf) is developed. The structure, thermal performance, mechanical properties, ionic conductivity, relaxation time, electrochemical stability and ionic transport number of the membranes are analyzed by various techniques. The ion migration mainly depends on the complexation and decomplexation of Mg²⁺ with amine band (NH₂) in chitosan. The 90CA-10Mg (Tf)₂ system plasticized with 10% EMITf (relative to the amount of 90CA-10Mg (Tf)₂) is identified as the optimum one and the temperature dependence of ionic conductivity obeys the Arrhenius rule. Moreover, the relaxation time of the electrolyte is very short, being just 1.25 × 10⁻⁶ s, and its electrochemical stability window is quite wide, being up to 4.15 V. The anodic oxidation and cathodic reduction of Mg at the Mg-electrode/electrolyte interface is facile, and the ionic transference number of this electrolyte is 0.985, indicating that it could be a potential electrolyte candidate for Mg-ion devices.     

Solid polymer electrochemical capacitors using heteropoly acid electrolytes

An electrochemical capacitor utilizing a polyvinyl alcohol (PVA) and H₄SiW₁₂O₄₀ (SiWA) solid polymer electrolyte was developed. The electrolyte was deposited via precursor solution coating followed by thermal pressing and exhibited an ionic conductivity of 0.01 S/cm. The electrolyte has also shown good stability and cycle life. The performance of the solid polymer electrolyte-based capacitor was characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and was compared to a similar capacitor with an aqueous electrolyte.     

Thermal and dielectric properties of PEO/EC/Pr4N+I− polymer electrolytes for possible applications in photo-electro chemical solar cells

The anion-conducting polymer electrolyte polyethylene oxide (PEO)/ethylene carbonate (EC)/Pr₄N⁺I⁻/I₂ is a candidate material for fabricating photo-electrochemical (PEC) solar cells. Relatively high ionic conductivity values are obtained for the plasticized electrolytes; at room temperature, the conductivity increases from 7.6 × 10⁻⁹ to 9.5 × 10⁻⁵ S cm⁻¹ when the amount of EC plasticizer increases from 0% to 50% by weight. An abrupt conductivity enhancement occurs at the melting of the polymer; above the melting temperature, the conductivity can reach values of the order of 10⁻³ S cm⁻¹. The melting temperature decreases from 66.1 to 45.1 °C when the EC mass fraction is increased from 0% to 50%, and there is a corresponding reduction in the glass transition temperature from −57.6 to −70.9 °C with the incorporation of the plasticizer. The static dielectric constant values, , increase with the mass fraction of plasticizer, from 3.3 for the unplasticized sample to 17.5 for the 50% EC sample. The dielectric results show only small traces of ion-pair relaxations, indicating that the amount of ion association is low. Thus, the iodide ion is well dissociated, and despite its large size and relatively low concentration in these samples, the iodide ion to ether oxygen ratio is 1:68, a relatively efficient charge carrier. A further enhancement of the ionic conductivity, especially at lower temperatures, is however desired for these applications.     

Ionic transport studies on (PEO)6:NaPO3 polymer electrolyte plasticized with PEG400

Conduction characteristics of the poly(ethylene oxide) based new polymer electrolyte (PEO)₆:NaPO₃, plasticized with poly(ethylene glycol) are investigated. Free standing flexible electrolyte films of composition (PEO)₆:NaPO₃ + x wt.% PEG₄₀₀ (30 ? x ? 70) are prepared by solution casting method. A combination of X-ray diffraction (XRD), optical microscopy and differential scanning calorimetry (DSC) studies have indicated enhancement in the amorphous phase of polymer due to the addition of plasticizer. Further, a reduction in the glass transition temperature observed from the DSC result has inferred increase in the flexibility of the polymer chains. The cationic transport number (t_Na⁺) of 0.42 determined through combined ac-dc technique has confirmed ionic nature of conducting species. Ionic conductivity studies are carried out as a function of composition and temperature using complex impedance spectroscopy. The electrolyte with maximum PEG₄₀₀ content has exhibited an enhancement in the conductivity of about two orders of magnitude compared to the host polymer electrolyte. The complex impedance data is analyzed in conductivity, permittivity and electric modulus formalism in order to throw light on transport mechanism. A solid state electrochemical cell based on the above polymer electrolyte with a configuration Na|SPE|(I₂ + acetylene black + PEO) has exhibited an open circuit voltage of 2.94 V. The discharge characteristics are found to be satisfactory as a laboratory cell.     

Metal framework as a novel approach for the fabrication of electric double layer capacitor device with high energy density using plasticized Poly(vinyl alcohol): Ammonium thiocyanate based polymer electrolyte

High performance electric double-layer capacitors (EDLCs) based on poly (vinyl alcohol) (PVA): ammonium thiocyanate (NH₄SCN):Cu(II)-complex plasticized with glycerol (GLY) have been fabricated. The maximum DC ionic conductivity (σ_DC) of 2.25 × 10^-3 S cm⁻¹ is achieved at ambient temperature. The X-ray diffraction (XRD) patterns confirmed that the addition of both Cu(II)–complex and GLY enhanced the amorphous region within the samples. Through the Fourier transform infrared (FTIR) the interactions between the host polymer and other components of the prepared electrolyte are observed. The FESEM images reveal that the surface morphology of the samples showed a uniform smooth surface at high GLY concentration. This is in good agreement with the XRD and FTIR results. Transference numbers of ion (t_ion) and electron (t_el) for the highest conducting composite polymer electrolyte (CPE) are recognized to be 0.971 and 0.029, respectively. The linear sweep voltammetry (LSV) revealed that the electrochemical stability window for the CPE is 2.15 V. These high values of t_ion and potential stability established the suitability of the synthesized systems for EDLC application. Cyclic voltammetry (CV) offered nearly rectangular shape with the lack of Faradaic peak. The specific capacitance and energy density of the EDLC are nearly constant within 1000 cycles at a current density of 0.5 mA/cm² with average of 155.322F/g and 17.473 Wh/Kg, respectively. The energy density of the EDLC in the current work is in the range of battery specific energy. The EDLC performance was found to be stable over 1000 cycles. The low value of equivalent series resistance reveals that the EDLC has good electrolyte-electrode contact. The EDLC exhibited the initial high power density of 4.960 × 10³ W/Kg.     

Structure and ion transport in an ethylene carbonate-modified biodegradable gel polymer electrolyte

The influence of ethylene carbonate (EC) addition on 85poly(ε-caprolactone):15Lithium thiocyanate (85PCL:15LiSCN) polymer electrolyte is investigated using X-ray diffraction, impedance spectroscopy, Wagner's polarization and electrochemical measurements. The results reveal that the amorphicity of the 85PCL:15LiSCN system increases with increase of EC content up to an optimal level of 40 wt.%. This is reflected in the electrical properties of the gel polymer electrolytes, i.e., the 40 wt.% EC-incorporated gel polymer electrolyte exhibits both high amorphicity and high electrical conductivity as compared to the other samples. The EC concentration dependences of dielectric constant and electrical conductivity show a similar trend, indicating that these properties are closely related to each other. The total ionic transference numbers of EC-incorporated gel polymer electrolytes are in the range 0.989–0.993, demonstrating that they are almost completely ionic conductors. The electrochemical stability window of the 40 wt.% EC-incorporated gel polymer electrolyte is ∼4.1 V along with the electrical conductivity of 2.2 × 10⁻⁴ S cm⁻¹, which is significantly improved as compared to the 85PCL:15LiSCN system (3.0 V and 1.04 × 10⁻⁶ S cm⁻¹). Consequently, the addition of EC in the 85PCL:15LiSCN polymer electrolyte leads to a promising improvement in its various properties.     

Application of chitosan/iota-carrageenan polymer electrolytes in electrical double layer capacitor (EDLC)

In this work, a chitosan/iota (ι)-carrageenan blended film doped with orthophosphoric acid (H₃PO₄) as ionic dopant and poly(ethylene glycol) (PEG) as plasticizer has been used as a separator and electrolyte in an electrical double layer capacitor (EDLC). A set of samples were prepared by the solution cast technique to see the effect of the different weight ratios of the proton donor and plasticizer on the conductivity. The highest conducting sample has composition 37.50 wt.% chitosan–37.50 wt.% ι-carrageenan–18.75 wt.% H₃PO₄–6.25 wt.% PEG. The conductivity value is 6.29 × 10⁻⁴ S cm⁻¹. The conductivity–temperature relationship is Arrhenian, and the activation energy for the highest conducting sample is 0.09 eV. The specific discharge capacitance of the EDLC is 35 F g⁻¹ at 0.11 mA cm⁻² current drain and was constant for 30 cycles.     

A polymer electrolyte containing ionic liquid for possible applications in photoelectrochemical solar cells

Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt = 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4 × 10⁻⁴ S cm⁻¹ and that of the annealed sample was 4.6 × 10⁻⁴ S cm⁻¹ at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (I _SC), the open circuit voltage (V _OC), and the power conversion efficiency of the cell are 0.63 mA cm⁻², 0.76 V, and 0.47% under the irradiation of 600 W m⁻² light.     

室温离子液体增塑的纳米复合聚合物电解质研究

在室温离子液体N-乙基-N'-甲基咪唑四氟硼酸盐(EMIBF₄)增塑的凝胶聚合物电解质中加入氧化铝纳米粒子, 制备了一种纳米复合聚合物电解质(nanocomposite polymer electrolyte, NCPE). 通过示差扫描量热(DSC)、X射线衍射(XRD)、热重分析(TGA)、电化学阻抗谱(EIS)等手段对其进行了表征. 结果显示, 随着氧化铝纳米粒子含量的增加, NCPE的结晶度降低, 离子导电率升高. 但是, 纳米粒子的加入量过大时反而引起NCPE的离子导电率降低. 当纳米粒子填充量为w＝10%时, NCPE具有最高的室温离子导电率1.25×10^－3 S•cm^－1.     

Thermal and electrochemical characteristics of plasticized polymer electrolytes based on poly(acrylonitrile-co-methyl methacrylate)

The thermal and electrochemical characteristics of plasticized polymer electrolytes composed of poly(acrylonitrile-co-methyl methacrylate) [P(AN-co-MMA)], a plasticizer [a mixture of ethylene carbonate and propylene carbonate], and LiCF₃SO₃ were investigated. The incorporation of a MMA unit into the matrix polymer was effective for an increase in the compatibility between the matrix polymer and the plasticizer. The comparative investigation of the interfacial resistance of the Li/polymer electrolyte/Li cell for the PAN-based and the P(AN-co-MMA)-based polymer electrolytes showed that the MMA unit could improve the stability of the polymer electrolyte toward the Li electrode, which is probably due to the enhanced adhesion of the polymer electrolyte to the Li electrode. Received: 14 July 1997 / Accepted: 14 May 1998     

EC modified PEO/PVDF-LLZO composite electrolytes for solid state lithium metal batteries

The polymer-ceramic composite electrolytes have great application potential for next-generation solid state lithium batteries, as they have the merits to eliminate the problem of liquid organic electrolytes and enhancing chemical/electrochemical stability. However, polymer-ceramic composite electrolytes show poor ionic conductivity, which greatly hinders their practical applications. In this work, the addition of plasticizer ethylene carbonate (EC) into polymer-ceramic composite electrolyte for lithium batteries effectively promotes the ionic conductivity. A high ionic conductivity can be attained by adding 40 wt% EC to the polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)-Li₇La₃Zr₂O₁₂ (LLZO) based polymer-ceramic composite electrolytes, which is 2.64 × 10⁻⁴ S cm⁻¹ (tested at room temperature). Furthermore, the cell assembled with lithium metal anode, this composite electrolyte, and LiFePO₄ cathode can work more than 80 cycles at room temperature (tested at 0.2 C). The battery delivers a high reversible specific capacity after 89 cycles, which is 119 mAh g⁻¹.     

Plasticized polymer electrolyte membranes based on PEO/PVdF-HFP for use as an effective electrolyte in lithium-ion batteries

Plasticized polymer electrolytes were prepared using poly(ethylene oxide)(PEO)/poly(vinylidene fluoridehexafluoro propylene)(PVd F-HFP) with lithium perchlorate(Li Cl O4) and different plasticizers. XRD and FTIR spectroscopic techniques were used to characterize the structure and the complexation of plasticizer with the host polymer matrix. The role of interaction between polymer hosts and plasticizer on conductivity is discussed using the results of alternating current(a.c.) impedance studies. TG-DTA and SEM were used for thermal and physical characterizations. Maximum ionic conductivity(3.26 × 10~(-4) S·cm~(-1)) has been observed for ethylene carbonate(EC)-based polymer electrolytes. Electrochemical performance of the plasticized polymer electrolyte is evaluated in LiFePO_4/plasticized polymer electrolytes(PPEs)/Li coin cell. Good performance with low capacity fading on charge discharge cycling is demonstrated.     

LiTFSI as a plastic salt in the quasi-solid state polymer electrolyte for dye-sensitized solar cells

Ionic conductivity and the type of ions are important for the composite polymer electrolyte (CPE) of the dye-sensitized solar cells (DSSCs). Lithium bis(trifluoromethane sulphone)imide (LiTFSI for short) which is easy to dissociate, is added in the composite polymer electrolyte(CPE) as a plasticizer. The LiTFSI acts differently from the conventional LiClO₄. LiTFSI changes the conformation of the polymer chain and shows higher ionic conductivity than LiClO₄. That contributes to the improvement of the short current density of the DSSC. Furthermore, the DSSCs with LiTFSI modification show higher photovoltage than the LiClO₄. The anions of TFSI^? prohibit the interface recombination more effectively compared with the LiClO₄ as the electrochemical impedance spectroscopy indicated. With the LiTFSI modified electrolyte, the performances of the DSSCs under 1 Sun, AM1.5 are improved and reaches the highest of 4.82% at the LiTFSI:LiI = 0.116:1, much better than the original DSSC(3.6%) and the LiClO₄ modified CPE electrolyte DSSC(4.32%).