染料敏化太阳电池用聚合物电解质

综述了本研究小组近年来用于染料敏化太阳电池中聚合物电解质的研究概况.设计合成了几类性能优良的聚合物电解质,较好地改进了液体电解质染料敏化太阳电池(DSSC)的使用稳定性,研究结果具有实际应用的价值,并提出了此领域研究今后的发展方向.     

Fabrication and evaluation of a polymer Li-ion battery with microporous gel electrolyte

This paper introduces an easy method for the fabrication of polymer Li-ion batteries with microporous gel electrolyte (MGE). The MGE is a multiphase electrolyte, which is composed of liquid electrolyte, gel electrolyte, and polymer matrix. The MGE not only has high ionic conductivity and good adhesion to the electrodes at low temperatures, but also retains good mechanical strength at elevated temperatures. Therefore, the MGE batteries are able to operate over a wide temperature range. During battery fabrication, the MGE is formed in situ by introducing liquid electrolyte into a swellable microporous polymer membrane and then heating or cycling the battery. In this work, the chemical compatibility of MGE with metal lithium during 60 °C storage and with LiMn₂O₄ cathode during cycling was studied. In addition, graphite/MGE/LiMn₂O₄ Li-ion batteries were made and evaluated.     

Protective layer with oligo(ethylene glycol) borate anion receptor for lithium metal electrode stabilization

The gel polymer electrolyte based on semi-IPN (interpenetrating polymer network) structure for the protection of lithium metal electrode was successfully developed by ultraviolet (UV) radiation-curing method. A curable mixed solution consists of linear polymer (Kynar 2801), crosslinking agent (1,6-hexanediol diacrylate), liquid electrolyte (ethylene carbonate (EC)/propylene carbonate (PC)/1 M LiClO₄), oligo(ethylene glycol) borate (OEGB) anion receptor, and photoinitiator (methyl benzoylformate). The OEGB was synthesized by the dehydrocoupling reaction of hydroxyl group in di(ethylene glycol) methyl ether with hydrogen in BH₃ and characterized by ¹H NMR. The presence of OEGB anion receptor in the protection layer could lead to an enhancement in the ionic conductivity, electrochemical stability, and the interfacial properties. The deposited lithium exhibited particle-like shape resulting from the introduction of the protection layer onto the lithium electrode surface. The unit cell based on the lithium anode protected with gel polymer electrolyte containing OEGB showed higher discharge capacity than that of the unit cell without OEGB after 100 cycles at C/2 rate (1.25 mA cm⁻²).     

A novel gel polymer electrolyte based on poly ionic liquid 1-ethyl 3-(2-methacryloyloxy ethyl) imidazolium iodide

Poly ionic liquid 1-ethyl 3-(2-methacryloyloxy ethyl) imidazolium iodide (PEMEImI) as a single-ion conductor was designed and synthesized. When appropriate amount of suitable plasticizers, I₂ and polyacrylonitrile (PAN) were incorporated into it, the complex formed gel polymer electrolyte. Chemical structure, thermal behavior and ionic conductive properties of the gel polymer electrolyte were investigated by Raman spectra, UV-Vis spectra, differential scanning calorimetry (DSC), and complex impedance analysis, respectively. For the new gel polymer electrolyte, the ionic conductivity of about 1 × 10⁻³ S cm⁻¹ at room temperature was achieved.     

The network gel polymer electrolyte based on poly(acrylate-co-imide) and its transport properties in lithium ion batteries

Poly (acrylate-co-imide)-based gel polymer electrolytes are synthesized by in situ free radical polymerization. Infrared spectroscopy confirms the complete polymerization of gel polymer electrolytes. The ionic conductivity of gel polymer electrolytes are measured as a function of different repeating EO units of polyacrylates. An optimal ionic conductivity of the poly (PEGMEMA₁₁₀₀-BMI) gel polymer electrolyte is determined to be 4.8 × 10^–3 S/cm at 25 °C. The lithium transference number is found to be 0.29. The cyclic voltammogram shows that the wide electrochemical stability window of the gel polymer electrolyte varies from −0.5 to 4.20 V (vs. Li/Li⁺). Furthermore, we found the transport properties of novel gel polymer electrolytes are dependent on the EO design and are also related to the rate capability and the cycling ability of lithium polymer batteries. The relationship between polymer electrolyte design, lithium transport properties and battery performance are investigated in this research.     

Cross-linking copolymers of acrylates’ gel electrolytes with high conductivity for lithium-ion batteries

The cross-linking gel copolymer electrolytes containing alkyl acrylates, triethylene glycol dimethacrylate, and liquid electrolyte were prepared by in situ thermal polymerization. The gel polymer electrolytes containing 15 wt% polymer content and 85 wt% liquid electrolyte content with sufficient mechanical strength showed the high ionic conductivity around 5?×?10^?3 Scm^?1 at room temperature. The gel electrolytes containing different polymer matrices were prepared, and their physical observation and conductivity were discussed carefully. The cross-linking copolymer gel electrolytes of alkyl acrylates with other monomers were designed and synthesized. The results showed that copolymerization can improve the mechanical properties and ionic conductivities of the gel electrolytes. The polymer matrices of gels had excellent thermal stability and electrochemical stability. The scanning electron microscope analysis showed the gel electrolyte was the homogeneous structure, and the cross-linking polymer host was the porous three-dimensional network structure, which demonstrated the high conductivity of the gel electrolytes. The gel polymer Li-ion battery was prepared by this in situ thermal polymerization. The cell exhibited high charge-discharge efficiency at 0.1 C. The results of LiFePO4-PEA-Li cell and graphite-PEA-Li cell showed that gel polymer electrolytes have good compatibility with the battery electrodes materials.     

Highly porous LiMnPO4 in combination with an ionic liquid-based polymer gel electrolyte for lithium batteries

A porous well defined LiMnPO₄ cathode material is synthesized by a sol-gel method. The electrochemical performance of the cathode material is evaluated in a cell with an ionic liquid-based polymer electrolyte (0.5 M LITFSI in EMImTFSI) and a lithium metal electrode. The results are compared to a cell with a traditional organic carbonate-based electrolyte (1 M LiPF₆ in EC/DMC). The cell with the ionic liquid-based polymer electrolyte presents an enhanced electrochemical intercalation performance of lithium ions, a high electrochemical stability window of 5 V, and an excellent cycling ability as compared with the organic based counterpart. Furthermore, the ionic liquid-based polymer gel electrolyte effectively prevents the dissolution of manganese — otherwise a common problem.     

The effects of polymer gel electrolyte composition on performance of quasi-solid-state dye-sensitized solar cells

Polymer gel electrolytes based on poly(acrylic acid)-poly(ethylene glycol) (PAA–PEG) hybrid have been prepared and applied to developed quasi-solid-state dye-sensitized solar cells (DSCs). PAA–PEG hybrid was synthesized by polymerization reaction. Quasi-solid-state DSCs were fabricated with synthesized PAA–PEG electrolyte. The effects of alkali iodides LiI, KI, and I₂ concentrations on liquid electrolyte absorbency and ionic conductivity of PAA–PEG were investigated. The evolution of the solar cell parameters with polymer gel electrolyte compositions was revealed. DSCs based on PAA–PEG with optimized KI/I₂ concentrations showed better performances than those with optimized LiI/I₂ concentrations. The electrochemical impedance spectroscopy technique was employed to examine the electron lifetime in the TiO₂ electrode and quantify charge transfer resistances at the TiO₂/dye/electrolyte interface and the counter electrode in the solar cells based on the PAA–PEG hybrid gels. A maximum conversion efficiency of 4.96% was obtained for DSCs using KI based quasi-solid electrolyte under 100 mW cm⁻². Our work suggests that KI can be the promising alkali metal iodide for improving the performance of PAA–PEG hybrid gel DSCs.     

Electrodeposition and stripping of zinc from an ionic liquid polymer gel electrolyte for rechargeable zinc-based batteries

In this paper, we report on zinc deposition and stripping in an ionic liquid polymer gel electrolyte on gold and copper substrates, respectively. The ionic liquid-based polymer gel electrolyte is prepared by combining the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py_1,4]TfO), with Zn(TfO)₂ and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP). The ionic liquid polymer gel electrolyte exhibits good conductivity (2.2 mS cm^?1) and good mechanical stability. Zinc deposition and stripping in the ionic liquid polymer gel electrolyte were studied by cyclic voltammetry, potentiostatic, and galvanostatic cycling (charging/discharging) experiments. The gel electrolyte exhibits a promising electrochemical stability and allows a quasi-reversible zinc deposition/stripping. The morphology of the zinc deposits after 10 cycles of zinc deposition/stripping is compact and dense, and deposits without any dendrite formation can be obtained. The quasi-reversibility of the electrochemical deposition/stripping of zinc in this ionic liquid polymer gel electrolyte is of interest for rechargeable zinc-based batteries.     

Room temperature cross-linkable gel polymer electrolytes for lithium ion batteries by in situ cationic polymerization of divinyl ether

We demonstrated room temperature cross-linkable gel polymer electrolytes (GPE) prepared by in situ cationic polymerization of tri(ethylene glycol) divinyl ether (TEGDVE) with LIBF₄ that yields protonic acid and Lewis acid as an acidic initiating system by the reaction with water as an impurity in the liquid electrolyte. FTIR analysis reveals that TEGDVE in the liquid electrolyte is successfully polymerized into gel polymer electrolyte. The resulting gel polymer electrolyte showed promising electrochemical properties including ionic conductivity, wide range in working potential and stable cycle performance as a lithium ion conducting medium.     

锂离子电池PMMA-VAc聚合物电解质的制备与性质研究

以甲基丙烯酸甲酯(MMA)和醋酸乙烯酯(VAc)为单体, 用乳液聚合法合成聚甲基丙烯酸甲酯-醋酸乙烯酯聚合物(PMMA-VAc), 并以此聚合物制备了新型聚烯烃膜支撑的聚合物膜及聚合物电解质. 用红外光谱(FTIR)、凝胶色谱(GPC)、差热和热重分析(DSC/TG)、扫描电镜(SEM)及电池充放电实验等方法研究了聚合物、聚合物膜和聚合物电解质的性质. 红外光谱结果表明, MMA与VAc通过各自的C＝C双键打开聚合成PMMA-VAc. PMMA-VAc易于分散在混合碳酸酯溶剂中并形成凝胶, 凝胶粘度随PMMA-VAc浓度的增加而增加, 当浓度为4%时成膜效果最佳. PMMA-VAc膜具有大量的微孔结构, 具有极强的吸液性能. PMMA-VAc膜具有良好的热稳定性: 在380 ℃范围内保持稳定. 聚烯烃膜支撑的PMMA-VAc膜室温下的离子电导率为1.85×10^－3 S•cm^－1, 用作为锂离子电池的聚合物电解质时, 电池具有良好的循环稳定性和倍率性能.     

Effect of EMIMBF4 ionic liquid addition on the structure and ionic conductivity of LiBF4-complexed PVdF-HFP polymer electrolyte films

New polymer electrolyte films of lithium tetrafluoroborate (LiBF₄)-complexed poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) embedded with different quantities of 1-ethyl-3methylimidazolium tetrafluoroborate (EMIMBF₄) ionic liquid were prepared by solution casting. The prepared films were characterized using various techniques: X-ray diffraction, scanning electron microscopy, impedance spectroscopy and electrochemical measurements. The pure PVdF-HFP possessed a semi-crystalline structure and its amorphicity increased with the addition of LiBF₄ salt and EMIMBF₄ ionic liquid. The size and interconnection of pores in the films were enhanced by EMIMBF₄. Impedance measurements indicated that the room-temperature ionic conductivity of the films increased with increasing EMIMBF₄ concentration until 15 wt.%, being up to 0.202 × 10⁻⁴ S cm⁻¹, and then decreased with further increasing EMIMBF₄ concentration. In addition, the temperature-dependent ionic conductivity of the polymer electrolyte films followed an Arrhenius relation and the 15 wt.% EMIMBF₄-incorporated gel polymer electrolyte film exhibited a low activation energy for ionic conduction, being about 0.28 eV. Finally, the electrochemical stability window of the 85PVdF-HFP:15LiBF₄+15 EMIMBF₄ gel polymer electrolyte films was evaluated as approximately 4.4 V, which is a promising value for ion battery applications.     

Synthesis of organic sulfobetaine‐based polymer gel electrolyte for dye‐sensitized solar cell application

We have synthesized eco‐friendly, economic, and equally efficient polysulfobetaine‐based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye‐sensitized solar cells (DSSCs) for the first time. This nitrogen‐rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10^?3 Scm^?1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm², FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte‐based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm², FF = 69%, and PCE = 7.07%, both at 100 mWcm^?2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine‐based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices. Copyright © 2017 John Wiley & Sons, Ltd.     

Electrical and electrochemical studies on magnesium ion-based polymer gel electrolytes

The development of polymer gel electrolyte system with high ionic conductivity is the main objective of polymer research. Electrochemical devices based on lithium ion-conducting polymer electrolyte are not safe due to the explosive nature of lithium. An attempt has been made to synthesize magnesium ion-conducting polymeric gel electrolytes, poly (vinylidene fluoride-co-hexafluoropropylene)–propylene carbonate–magnesium perchlorate, PVdF(HFP)-PC–Mg(ClO₄)₂ using standard solution-cast techniques. The maximum room temperature ionic conductivity of the synthesized electrolyte system has been observed to be 5.0 × 10⁻³ S cm⁻¹, which is quite acceptable from a device fabrication point of view. The temperature-dependent conductivity and the dielectric behavior were also analyzed. The pattern of the temperature-dependent conductivity shows the Arrhenius behavior. The dielectric constant ε _r and dielectric loss ε _i increases with temperature in the low-frequency region but almost negligible in the high-frequency region. This behavior can be explained on the basis of electrode polarization effects. The real part M _r and imaginary part M _i versus frequency indicate that the systems are predominantly ionic conductors. Further, the synthesized electrolyte materials have been checked for its suitability in energy storage devices namely redox supercapacitor with conducting polymer polypyrrole as electrode materials, and finally, it was observed that it shows good capacitive behavior in low-frequency region. Preliminary studies show that the overall capacitance of 22 mF cm⁻² which is equivalent to a single electrode specific capacitance of 117 F gm⁻¹ was observed for the above said supercapacitors.     

Photovoltaic performance of dye-sensitized solar cells assembled by in-situ chemical cross-linking

Quasi-solid state dye-sensitized solar cells (DSSCs) were assembled by in-situ chemical cross-linking of a gel electrolyte precursor containing liquid electrolyte. The DSSCs assembled with this cross-linked gel polymer electrolyte showed higher open circuit voltage and lower short-circuit photocurrent density than those of DSSCs with liquid electrolyte. Addition of SiO₂ nanoparticles into the cross-linked gel polymer electrolyte significantly improved the photovoltaic performance and long-term stability of the DSSCs. The optimized quasi-solid state DSSC showed high conversion efficiency, 6.2% at 100 mW cm^?2 with good durability.     

Quasi-solid-state dye-sensitized solar cells assembled by in-situ chemical cross-linking at ambient temperature

Cross-linked gel polymer electrolytes containing aluminum oxide nanoparticles are successfully prepared using in-situ chemical cross-linking at room temperature after injection of the gel precursor into a dye-sensitized solar cell (DSSC). This makes it possible to directly solidify the electrolyte in the cell without leakage of solvent and to maintain close interfacial contact with the porous TiO₂ electrode. The quasi-solid-state DSSC assembled with gel polymer electrolyte containing 20 wt.% Al₂O₃ particles yields an overall conversion efficiency of 5.25% under AM 1.5 illumination at 100 mW cm^{− 2}.     

A novel ternary polymer electrolyte for LMP batteries based on thermal cross-linked poly(urethane acrylate) in presence of a lithium salt and an ionic liquid

A new ternary polymer electrolyte based on thermally cross-linked poly(urethane acrylate) (PUA), lithium bis(trifluoromethansulfonyl)imide (LiTFSI) and the ionic liquid N-butyl-N-methylpyrrolidinium TFSI (PYR₁₄TFSI) was developed and tested for application in LMP batteries. The polymer electrolyte was a transparent yellow self-standing material with quite good mechanical properties, i.e., comparable to that of a flexible rubber. The room temperature ionic conductivity of the dry polymer electrolyte was found to be as high as 0.1 mS cm⁻¹ for the compound containing 40 wt% of ionic liquid (PYR₁₄TFSI) and a O/Li ratio of 15/1 (Li⁺ from LiTFSI). The thermal analysis of the new cross-linked electrolyte showed that it was homogeneous, amorphous and stable over a wide temperature range extending from −40 °C to 100 °C. The homogeneity of the polymer electrolyte was also confirmed by SEM analysis.     

Effect of solvents on properties of polymer gel-electrolyte based on polyester diacrylate

New polymer gel electrolytes based on polyester diacrylates and LiClO₄ salt solutions in organic solvents are developed for lithium ion and lithium polymer batteries with a high ionic conductivity up to 2.7 × 10^?3 Ohm^?1cm^?1 at the room temperature. To choose the optimum liquid electrolyte composition, the dependence is studied of physico-chemical parameters of new gel electrolytes on the composition of the mixture of aprotic organic solvents: ethylene carbonate, propylene carbonate, and λ-butyrolacton. The bulk conductivity of gel electrolytes and exchange currents at the gel electrolyte/Li interface are studied using the electrochemical impedance method in symmetrical cells with two Li electrodes. The glass transition temperature and gel homogeneity are determined using the method of differential scanning calorimetry. It is found that the optimum mixture is that of propylene carbonate and λ-butyrolacton, in which a homogeneous polymer gel is formed in a wide temperature range of ?150 to +50°C.     

A novel composite polymer electrolyte containing room-temperature ionic liquids and heteropolyacids for dye-sensitized solar cells

A novel composite polymeric gel comprising room-temperature ionic liquids (1-butyl-3-methyl-imidazolium-hexafluorophosphate, BMImPF₆) and heteropolyacids (phosphotungstic acid, PWA) in poly(2-hydroxyethyl methacrylate) matrix was successfully prepared and employed as a quasi-solid state electrolyte in dye-sensitized solar cells (DSSCs). These composite polymer electrolytes offered specific benefits over the ionic liquids and heteropolyacids, which effectively enhanced the ionic conductivity of the composite polymer electrolyte. Unsealed devices employing the composite polymer electrolyte with the 3% content of PWA achieved the solar to electrical energy conversion efficiency of 1.68% under irradiation of 50 mW cm⁻² light intensity, increasing by a factor of more than three compared to a DSSC with the blank BMImPF₆-based polymer electrolyte without PWA. It is expected that these composite polymer electrolytes are an attractive alternative to previously reported hole transporting materials for the fabrication of the long-term stable quasi-solid state or solid state DSSCs.     

Preparation of a Star Network PEG-based Gel Polymer Electrolyte and Its Application to Electrochromic Devices

A star network polymer with a pentaerythritol core linking four PEG-block polymeric arms was synthesized, and its corresponding gel polymer electrolyte based on lithium perchlorate and plasticizers EC/PC with the character being colorless and highly transparent has been also prepared. The polymer host was characterized and confirmed to be of a star network and an amorphous structure by FTIR, ^1H NMR and XRD studies. The polymer host hold good mechanical properties for pentaerythritol cross-linking. Maximum ionic conductivity of the prepared polymer electrolyte has reached 8.83 × 10 ^-4 S·cm^-1 at room temperature. Thermogravimetry （TG） of the polymer electrolyte showed that the thermal stability was up to at least 150 ℃. The gel polymer electrolyte was further evaluated in electrochromic devices fabricated by transparent PET-ITO and electrochromically active viologen derivative films, and its excellent performance promised the usage of the gel polymer electrolyte as ionic conductor material in electrochrornic devices.