Preparation of gel polymer electrolytes using PMMA interpenetrating polymeric network and their electrochemical performances

A gel polymer electrolyte (GPE) is prepared from polymethylmethacrylate interpenetrating polymer network, benzoyl peroxide, and 1.1 M LiPF₆/EC-DEC (1:1 vol.%). The LiCoO₂/graphite cells are prepared and their electrochemical properties were evaluated at various current densities and temperatures. The viscosity of the precursor containing 5 vol.% curable mixture is around 4.6 mPa s. The ionic conductivity of the GPE at 20 °C is around 5.8×10⁻³ S cm⁻¹. The GPE has good electrochemical stability up to 4.8 V vs. Li/Li⁺. The capacity of the cell at 1.0C rate is 82% of the discharge capacity at 0.2C rate. The capacity of the cell at −10 °C is 86% of the discharge capacity at 20 °C. Discharge capacity of the cell with GPE is stable with charge-discharge cycling.     

Electrochemical performances of gel polymer electrolytes using tetra(ethylene glycol) diacrylate

A gel polymer electrolyte (GPE) was prepared using tetra(ethylene glycol) diacrylate monomer, benzoyl peroxide, and (). The LiCoO₂/GPE/graphite cells were prepared and their electrochemical properties were evaluated at various current densities and temperatures.The viscosity of the precursor containing the tetra(ethylene glycol) diacrylate monomer was around . The ionic conductivity of the gel polymer electrolyte at 20°C was around . The gel polymer electrolyte had good electrochemical stability up to vs. Li/Li⁺. The capacity of the LiCoO₂/GPE/graphite cell at rate was 63% of the discharge capacity at rate. The capacity of the cell at −10°C was 81% of the discharge capacity at 20°C. Discharge capacity of the cell with gel polymer electrolyte was stable with charge-discharge cycling.     

Preparation and electrochemical performance of gel polymer electrolytes with a novel star network

Well-defined star shaped polymers with α-Cyclodextrin (α-CD) core linking PMMA-block arms were synthesized by atom transfer radical polymerization (ATRP). Gel polymer electrolytes (GPEs) were prepared by encapsulating electrolyte solution of 1 mol L⁻¹ of LiClO₄/EC-PC (volume 1:1) into the obtained star shaped polymer host. The ionic conductivity of the GPEs and the cycling characteristics of LiCoO₂/GPEs/Graphite cell were studied by electrochemical impedance spectroscopy and charge-discharge testing, respectively. The results indicate that the GPEs have a high ionic conductivity up to 1.63 × 10⁻³ S cm⁻¹ at room temperature and exhibit a high electrochemical stability potential of 4.5 V (vs. Li/Li⁺). The discharge capacity of LiCoO₂/GPEs/Graphite cell is about 98% of its initial discharge capacity after 20 cycles at 0.1 C rate. Discharge capacity of the model cell with GPEs is stable with charge-discharge cycling.     

A novel lithium/sulfur battery based on sulfur/graphene nanosheet composite cathode and gel polymer electrolyte

A novel sulfur/graphene nanosheet (S/GNS) composite was prepared via a simple ball milling of sulfur with commercial multi-layer graphene nanosheet, followed by a heat treatment. High-resolution transmission and scanning electronic microscopy observations showed the formation of irregularly interlaced nanosheet-like structure consisting of graphene with uniform sulfur coating on its surface. The electrochemical properties of the resulting composite cathode were investigated in a lithium cell with a gel polymer electrolyte (GPE) prepared by trapping 1 mol dm⁻³ solution of lithium bistrifluoromethanesulfonamide in tetraethylene glycol dimethyl ether in a polymer matrix composed of poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methylmethacrylate)/silicon dioxide (PVDF-HFP/PMMA/SiO₂). The GPE battery delivered reversible discharge capacities of 809 and 413 mAh g⁻¹ at the 1st and 50th cycles at 0.2C, respectively, along with a high coulombic efficiency over 50 cycles. This performance enhancement of the cell was attributed to the suppression of the polysulfide shuttle effect by a collective effect of S/GNS composite cathode and GPE, providing a higher sulfur utilization.     

Preparation of rechargeable lithium batteries with poly(methyl methacrylate) based gel polymer electrolyte by <Emphasis Type="Italic">in situ</Emphasis>γ-ray irradiation-induced polymerization

An admixture of commercial liquid electrolyte (LB302, 1 M solution of LiPF₆ in 1:1 EC/DEC) and methyl methacrylate (MMA) was enclosed in CR2032 cells. The assembled cells were then -ray-irradiated using configurations of half cells and full cells. Through this in situ irradiation polymerization process, we obtained rechargeable lithium ion cells with poly(methyl methacrylate) (PMMA) based gel polymer electrolytes (GPE). Galvanostatic cycling, AC impedance spectroscopy, and cyclic voltammetry were employed to investigate the electrochemical properties of the cells and the gel polymer electrolyte. This PMMA-based gel polymer electrolyte was found to exhibit a high ionic conductivity (at least 10^–3 S cm^–1) at room temperature. Due to a significant increase in the charge transfer resistance between the GPE and the cathode, the cell impedance of a PMMA-based lithium ion cell is greater than that of a liquid-electrolyte-based cell. The discharge capacity of a LiNi_0.8Co_0.2O₂/GPE/graphite is approximately 145 mAh g^–1 for the first cycle and decreases to123 mAh g^–1 after 20 cycles. In addition, a large initial cell impedance (LICI) was observed in the irradiated positive half cell. In this paper, we propose a possible mechanism related to the detachment of the PMMA layer from the lithium electrode. This detachment of the PMMA layer from the lithium electrode has not been explicitly discussed previously.     

Electrochemical studies of electrospun organic/inorganic hybrid nanocomposite fibrous polymer electrolyte for lithium battery

Poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-co-HFP)/magnesium aluminate (MgAl₂O₄) hybrid fibrous nanocomposite polymer electrolyte membranes were newly prepared by electrospinning method. The as-prepared electrospun pure and nanocomposite fibrous polymer membranes with various MgAl₂O₄ filler contents were characterized by X ray diffraction, differential scanning calorimetry and scanning electron microscopy techniques. The fibrous nanocomposite polymer electrolytes were prepared by soaking the electrospun membranes in 1 M LiPF₆ in EC:DEC (1:1, v/v). The fibrous nanocomposite polymer electrolyte membrane with 5 wt.% of MgAl₂O₄ show high electrolyte uptake, enhanced ionic conductivity is found to be 2.80 × 10⁻³ S cm⁻¹ at room temperature and good electrochemical stability window higher than 4.5 V. Electrochemical performance of commercial celgard 2320, fibrous pure and nanocomposite polymer electrolyte (PE, NCPE) membranes with different MgAl₂O₄ filler content is evaluated in Li/celgard 2320, PE, NCPE/LiCoO₂ CR 2032 coin cells at current density 0.1 C-rate. The NCPE with 5 wt.% of MgAl₂O₄ delivers an initial discharge capacity of 158 mAhg⁻¹ and stable cycle performance compared with the other cells containing celgard 2320 separator and pure membrane.     

A zinc–air cell employing a porous zinc electrode fabricated from zinc–graphite-natural biodegradable polymer paste

Porous zinc anodes have been fabricated from a mixture of zinc and graphite powder using gelatinized agar solution as the binding agent. Agar is a biodegradable polysaccharide polymer extracted from marine algae. The graphite content and the agar solution concentration were varied to find the best electrode composition. Zinc–air cells were fabricated using the porous zinc anode, a commercially available air cathode sheet and KOH electrolyte in the form of elastic jelly granules. The electrode performance was evaluated from the zinc–air cell galvanostatic discharge capability. In the cell design, a thin agar layer was introduced between the electrode-gelled electrolyte interfaces, resulting in substantially improved cell discharge performance. The inclusion of particulate graphite into the electrode did not enhance the electrode performance due to the formation of a graphite-rich layer, which obscured the electrode porosity. A zinc–air cell employing the optimized porous zinc electrode demonstrated a capacity of 2066 mA h and specific energy density of 443 Wh kg^–1.     

Application of a solid polymer electrolyte reactor to remove nitrate ions from wastewater

The application of a zero gap solid polymer electrolyte (ZGSPE) reactor to deminealise nitrate ions in aqueous wastewater is described. The following performance data for the reduction of a simulated alkaline solution with 16.1 mM nitrate ions under galvanostatic operation were achieved: percentage of nitrate removal up to 100%, rates of nitrate removal up to 0.057 mol cm^–2 h^–1, space–time yields up to 5.4 kg m^–3 h^–1, current efficiencies up to 24.5% and energy consumption between 40.1 and 63.3 kW h kg^–1. The beneficial effects of higher temperatures and nitrate ion concentrations and using a suitable electrolyte flow rate on the activity, selectivity and efficiency is reported. PdRh_1.5/Ti mini-mesh electrode used in the study was stable after a cumulative use of 1000 h.     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(methylmethacrylate)—magnesium triflate gel polymer electrolyte for solid state magnesium battery application

A gel polymer electrolyte (GPE) film of poly(methylmethacrylate) and magnesium triflate is studied in view of its potential application in a solid state rechargeable magnesium battery. Experimental data of a.c. impedance and cyclic voltammetric studies of symmetrical cells made of blocking and non-blocking electrodes, and also data of charge/discharge cycles of Mg/GPE/MnO₂ cells are reported. The composition of the GPE is optimized in view of a minimum quantity of the liquid components (propylene carbonate and ethylene carbonate) required for the gel formation and a maximum conductivity. Specific conductivity (σ) of the GPE of optimum composition is (4.2±0.45)×10⁻⁴ S cm⁻¹ at 20 °C. The σ values follow the Arrhenius equation and the activation energy for GPE of optimum composition is 0.038 eV. The effects of temperature and ageing on Mg/GPE interface are studied. Discharge capacity of about 90 mAh g⁻¹ of MnO₂ is obtained during the discharge of Mg/GPE/MnO₂ cells. On repeated charge/discharge cycling of the cell, the discharge capacity decreases to about 70 mAh g⁻¹. The cycle-life is limited by the problems associated with passivation of the Mg surface.     

Study of lithiated Nafion ionomer for lithium batteries

Lithiated Nafion 112 ionomer was characterized by FT-IR spectroscopy, AC impedance, and cyclic voltammetry. The ionomer swollen with mixed solvents of propylene carbonate (PC) and ethylene carbonate shows ionic conductivity of 8.18×10^–5Scm^–1 at 25°C and good electrochemical stability to allow operation in Li/ionomer/LiCoO₂ cells. The discharge capacity of the first cycle is 126mAhg^–1. Significant capacity loss occurs during cycling due to the presence of PC. AC impedance shows that the passive layer formed at the Li/ionomer interface dominates the cycling performance of the cell.     

All-solid secondary polyaniline-zinc battery

A solid state battery based on polyaniline (PANI), Zinc (Zn) and a gel polymer electrolyte (GPE) is reported for the first time. Poly (ethylene oxide)–zinc sulphate-nanoclay-H₂O based GPE was used as the separator. The GPEs with a varying composition of salt were evaluated for their electrochemical performance. The highest conductivity at ambient temperature for the GPEs was found to be 5.54 × 10⁻⁴ S cm⁻¹. Cyclic voltammetry and impedance studies, with the Zn/GPE/Zn cell, showed reversibility with respect to Zn/Zn²⁺ couple. The battery showed a capacity of 43.9 Ah kg⁻¹ of PANI and a coulombic efficiency higher than 100%. However, a decrease in capacity was observed for the system during the cycling.     

Ionic conductivity and physical stability study of gel nework polymer electrolytes

Gel polymer electrolytes (GPE) were prepared by a crosslinking reaction between poly(ethylene glycol) and a crosslinking agent with three isocyanate groups in the presence of propylene carbonate (PC) and ethylene carbonate (EC) or their mixture, and their ionic conducting behavior was carefully investigated. When the plasticizer amount was fixed, the ionic conductivity was greatly influenced by the nature of plasticizers. It was found that the conductivity data followed the Arrhenius equation in the GPE. Whatever plasticizer was used, a maximum ambient conductivity was found at a salt concentration near [Li⁺]/[EO] equal to 0.20. The physical stability of GPE was studied qualitatively by weight loss of GPE under pressure. It was shown that the stability was greatly affected by the network structure of the GPE and the most stable one in our research was the GPE containing the PEO₁₀₀₀ segment, which has a strong interaction between network and plasticizers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2957–2962, 2000     

Highly ion-conductive solid polymer electrolytes based on polyethylene non-woven matrix

Highly ion-conductive solid polymer electrolyte (SPE) based on polyethylene (PE) non-woven matrix is prepared by filling poly(ethylene glycol) (PEG)-based crosslinked electrolyte inside the pores of the non-woven matrix. The PE non-woven matrix not only shows good mechanical strength for SPE to be a free-standing film, but also has very porous structure for high ion conductivity. The ion conductivity of SPE based on PE non-woven matrix can be enhanced by adding sufficient non-volatile plasticizer such as poly(ethylene glycol) dimethyl ether (PEGDME) into ion conduction phase without sacrificing mechanical strength. SPE with 20 wt.% crosslinking agent and 80 wt.% non-volatile plasticizer shows 3.1 × 10⁻⁴ S cm⁻¹ at room temperature (20 °C), to our knowledge, which is the highest level for SPEs. It is also electrochemically stable up to 5.2 V and has high transference number about 0.52 due to the introduction of anion receptor as an additive. The interfacial resistance between Li electrode and SPE is low enough to perform charge/discharge test of unit cell consisting of LiCoO₂/SPE/Li at room temperature. The discharge capacity of the unit cell shows 87% of theoretical value with 86% Coulombic efficiency.     

PVdF-HFP/P123 hybrid with mesopores: a new matrix for high-conducting, low-leakage porous polymer electrolyte

Highly conducting porous polymer electrolytes comprised of poly(vinylidene-fluoride-co-hexafluoropropylene) (PVdF-HFP), polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (P123), ethylene carbonate (EC), propylene carbonate (PC), and LiClO₄ were fabricated. The PVdF-HFP/P123 hybrid polymer membranes were made with a phase inverse method and the electrolyte solution uptake was carried out in glove box to avoid the moisture contamination. It was found that when a small amount of polymer surfactant (P123) was blended into the PVdF-HFP, mesopores with well-defined sizes were formed. Impedance spectroscopy showed that the room temperature conductivity of (PVdF-HFP)/P123 polymer electrolytes increased as the content of P123 increased up to 4×10⁻³ S/cm. Nitrogen adsorption isotherms, electrolyte solution uptake, porosity measurements, and SEM micrographs showed that the enhanced conductivity was due to increase the pore volume, pore density, and electrolyte uptake. The highest conduction was found when the weight ratio of P123 to PVdF-HFP was 70%, when big channels were formed in the hybrid polymer membrane. Furthermore, blending P123 in PVDF-HFP reduced the pore size of polymer membrane, therefore, the solution leakage was also reduced. These polymer electrolytes were stable up to 4.5 V (vs Li/Li⁺) and the performance of the model lithium ion battery made by sandwiching the polymer electrolyte between a LiCoO₂ anode and a MCMB cathode, showed great promise for the use of these polymer electrolytes in lithium ion batteries.     

Electrochemical characterizations on MnO2 supercapacitors with potassium polyacrylate and potassium polyacrylate-co-polyacrylamide gel polymer electrolytes

MnO₂·nH₂O supercapacitors with potassium polyacrylate (PAAK) and potassium polyacrylate-co-polyacrylamide (PAAK-co-PAAM) gel polymer electrolytes (GPEs) having the weight compositions of polymer:KCl:H₂O = 9%:6.7%:84.3% have been characterized for their electrochemical performance. Compared with the liquid electrolyte (LE) counterpart, the GPE cells exhibit remarkable (50–130%) enhancement in specific capacitance of the oxide electrode, and the extent of the enhancement increases with increasing amount of the carboxylate groups in the polymers as well as with increasing oxide/electrolyte interfacial area. In situ X-ray absorption near-edge structure (XANES) analysis indicates that the oxide electrodes of the GPE cells possess higher Mn-ion valences and are subjected to greater extent of valence variation than that of the LE cell upon charging/discharging over the same potential range. Copolymerization of PAAK with PAAM greatly improves the cycling stability of the MnO₂·nH₂O electrode, and the improvement is attributable to the alkaline nature of the amino groups. Both GPEs exhibit ionic conductivities greater than 1.0 × 10⁻¹ S cm⁻¹ and are promising for high-rate applications.     

The conductivity and characterization of the plasticized polymer electrolyte based on the P(AN-co-GMA-IDA) copolymer with chelating group (II): The effect of free ion in the plasticized polymer electrolyte

A new gel-type polymer electrolyte (GPE) was made by the copolymerizing acrylonitrile (AN) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). The copolymer mixed with a plasticizer—propylene carbonate (PC) and lithium salt to form GPE. The lithium salts are LiCF₃SO₃, LiBr and LiClO₄. FT-IR spectra show that the lithium ion in the LiClO₄ system has the strongest interaction with the group based on the plasticized polymer. FT-IR spectra also indicate that CF₃SO₃⁻ prefers producing anion-cation association. Moreover, the ¹³C solid state NMR spectra for the carbons attached to the PC of GPE exhibited different level of chemical shift (158.5 ppm) when the different lithium salts were added to the electrolyte. The results of differential scanning calorimeter (DSC) also indicate that the LiClO₄ system has more free lithium ions; therefore, it has the maximum conductivity. In this study, the highest conductivity 2.98 × 10⁻³ S cm⁻¹ exists in AG2/PC = 20/80 wt.% system which contain 3 mmole (g-polymer)⁻¹ LiClO₄. Additionally, the polymer electrolytes, which contain GMA-IDA have better interfacial resistance stability with lithium electrode.     

Semi-interpenetrating gel polymer electrolyte based on PVDF-HFP for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte (GPE) is considered one of the promising candidate electrolytes in the polymer lithium ion battery (LIB) because of its free standing, shape versatility, security, flexibility, lightweight, reliability, and so on. However, the pristine PVDF-HFP GPE cannot still meet the requirement of large-scale LIBs and other electrochemical devices due to its relatively low ionic conductivity and deterioration of mechanical strength caused by the incorporation of organic liquid electrolyte into the polymer matrix as well as high cost. In order to overcome above deficiencies of PVDF-HFP based GPE, ultraviolet (UV)-curable semi-interpenetrating polymer network is designed and synthesized through UV-irradiation technique, and the as-prepared semi-interpenetrating matrix is constituted by pentaerythritol tetracrylate polymer network and PVDF-HFP. The ionic conductivity of the optimized GPE is as high as 5 × 10⁻⁴ S/cm and electrochemical window is up to 4.8 V at room temperature. Especially, the LIB prepared by GPE shows the high initial discharge specific capacity of 151 mAh/g at 0.5 C and good rate capability. Therefore, the semi-interpenetrating GPE based on PVDF-HFP exhibits a promising prospect for the application of rechargeable LIBs.     

Gel-based composite polymer electrolytes with novel hierarchical mesoporous silica network for lithium batteries

In the present work, novel gel-based composite polymer electrolytes for lithium batteries were prepared by introducing a hierarchical mesoporous silica network to the poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based gel electrolytes. As compared with the PVDF-HFP-based gel electrolytes with/without conventional nano-sized silica fillers, the novel electrolytes have shown more homogeneous microstructure, higher ionic conductivity and better mechanical stability, which could be caused by the strong silica network and the effective interactions among the polymer, the liquid electrolytes and the silica. Moreover, the cell with this kind of electrolytes could achieve a discharge capacity as much as 150 mAh g⁻¹ at room temperature (LiCoO₂ as the cathode active material), with high Coulomb efficiency.     

PE-g-MMA polymer electrolyte membrane for lithium polymer battery

PE-g-MMA membranes with different degrees of grafting (DG) were prepared by electron beam radiation-induced graft copolymerization of methylmethacrylate (MMA) monomer onto polyethylene (PE) separator. The grafted membranes (GMs) were characterized using SEM, FTIR. The new polymer electrolytes based on GMs were prepared through immersion in a solution of LiPF₆-EC/DMC (1:1 by volume). It was found that the GMs with different DG exhibited the different uptake and retention ability of liquid electrolyte. Moreover, the ion conductivities of activated polymer electrolytes (APEs) were also found to vary with the different DG and reached a magnitude of 10⁻³ S cm⁻¹ at the DG of 42%. Compared with those containing PE separators, the LiCoO₂-MCMB coin cells containing GMs demonstrated better cycle life and excellent rate performance.