Crystallization and gelation of poly(vinylidene fluoride) in organic solvents

Tazaki, Michiko; Wada, Risei; Abe, Machiko; Homma, Takeshi

doi:10.1002/(sici)1097-4628(19970822)65:8<1517::aid-app9>3.3.co;2-t

Cited by 33 publications

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“…10 m • , typical of the crystalline form II of this polymer. 40 The differences in particle shape and crystallinity do not influence the morphologies of the polymer films resulting from binder dissolution and solvent evaporation. Indeed, the spectra of the dry SA and PVdF films obtained after dispersing the binders in H 2 O and NMP, respectively, are almost identical and completely amorphous as shown by the XRD patterns reported in Figure 2c.…”

Section: Resultsmentioning

confidence: 99%

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

Bigoni

Giorgio

Soavi

et al. 2016

J. Electrochem. Soc.

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Binders are electrochemically inactive electrode components. However, their chemical and physical nature greatly affects battery performance and plays a key role in electrode integrity and interface reactivity. The binders thus have a strong impact on battery capacity retention and cycle life. Water-processable binders would make the electrode preparation process cheap and environmentally friendly and provide a viable alternative to polyvinylidene difluoride (PVdF). Here we report the use of sodium alginate (SA) as binder for LiNi 0.5 Mn 1.5 O 4 (LNMO), one of the most promising cathode materials for high-voltage and high-energy LIBs. We demonstrate that electrodes with high mass loading containing SA have excellent specific discharge capacity (120 mAh g −1 at C/3 and 100 mAh g −1 at 5C) with negligible overpotentials in conventional electrolyte based on ethylene carbonate (EC): dimethyl carbonate (DMC) and 1 M LiPF 6 , where the reactivity of LNMO is known to negatively affect stability. The electrodes with SA also show a good stability over subsequent cycles of charge and discharge at 1C with capacity retention of 95% and 86% with respect to the initial cycles at the 100th and 200th cycle. Lithium-ion batteries (LIBs) have been on the market for 25 years and recently are being widely used in electric vehicles.1,2 Research is currently focused on improving the safety and performance of LIBs in terms of gravimetric and volumetric energy and power as well as reducing the costs and toxicity of battery components and of the manufacturing process.3,4 While the three main active battery components, i.e. anode, cathode and electrolyte, are widely studied, as shown by numerous review papers, [5][6][7][8] it is worth noting that such inactive battery components as separators are extremely important in overall operation. 9 The same holds true for the conductive agent (usually carbon black) and the binder that support the electrochemical processes even if present in low weight percentages in electrode composite. The former improves electronic conductivity and, hence, the rate capability of the electrode. The latter acts as glue for active material and the conductive agent and can also improve adhesion with the current collector. Although electrochemically inactive, the chemical and physical nature of polymeric binders can enhance battery performance, control the interface structure of the electrode and has a strong impact on battery capacity retention and cycle life. 10The most widely used binder for LIBs is polyvinylidene difluoride (PVdF). While displaying all the desirable binder properties, such as good adhesion strength to the current collector and good electrochemical stability, it can also soak up a large amount of liquid electrolyte, a property that has its pros and cons.11 A facile penetration of the electrolyte inside the composite electrode results in a high interfacial area of active material in contact with the electrolyte. While this facilitates Li + transport, it also promotes unwanted side-reactions. Furth...

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Section: Resultsmentioning

confidence: 99%

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

Bigoni

Giorgio

Soavi

et al. 2016

J. Electrochem. Soc.

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“…In the previous study, 14 the present authors measured the gelation times (t gel ) of two systems: PVdF/γ-butyrolactone and PVdF/cyclohexanone. In that study, t gel of PVdF in cyclohexanone was found to be smaller than that in γ-butyrolactone.…”

Section: In Situ Ft-ir Spectramentioning

confidence: 99%

“…[9][10][11][12][13] The present authors investigated gelation process of PVdF homopolymer in many organic solvents from measurements of both time-resolved Fourier transform infrared (FT-IR) spectroscopy and dilatometry. [14][15][16][17] Tashiro et al studied the structural change during the gelation process and the resultant aggregation structure of PVdF polymer and solvent molecules in the gel through measurement of the time-resolved FT-IR. 18 Hong and Chou studied the relation between phase separation behavior and gelation kinetics in PVdF/tetra(ethylene glycol) dimethyl ether (TG) solution.…”

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confidence: 99%

The Flory-Huggins Interaction Parameter and Thermoreversible Gelation of Poly(vinylidene fluoride) in Organic Solvents

Okabe

Wada

Tazaki

et al. 2003

Polym J

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ABSTRACT:The Flory-Huggins interaction parameter (χ 12 ) between poly(vinylidene fluoride) (PVdF) and organic solvent was estimated experimentally over wide range of temperature by an inverse gas chromatography (IGC) using many kinds of solvents such as alkane, alkene, ketone, lactone, and nitrogen-containing solvent. The thermoreversible gelation of PVdF solution was discussed from the magnitude of interaction parameter χ 12 between PVdF and solvent. The parameter χ 12 was measured for a concentrated PVdF solution by the usual IGC technique. The parameter χ 12 obtained for each PVdF/solvent system increased slowly with decreasing temperature. The present systems were divided broadly into three groups according to the magnitude of χ 12 in the vicinity of room temperature, i.e., group (a) with χ 12

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“…In a previous study, we reported our investigation of the gelation process of PVdF in a number of organic solvents without a lithium salt using time-resolved Fourier transform infrared (FT-IR) spectroscopy and dilatometry. [12][13][14][15] In addition, we experimentally estimated the Flory-Huggins interaction parameters (w 12 ) between PVdF and the organic solvents over a wide temperature range using inverse gas chromatography and then clarified the correlation between the thermoreversible gelation of a PVdF solution and the magnitude of w 12 . 16 Here, we report the results of a preliminary study of the gelation process and the structural morphology of a PVdF gel in the presence of a lithium salt, LiBF 4 .…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Sol-gel transitions of poly(vinylidene fluoride) in organic solvents containing LiBF4

Shimizu

Arioka

Ogawa

et al. 2011

Polym J

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Poly(vinylidene fluoride) (PVdF) dissolved in organic solvents containing lithium tetrafluoroborate (LiBF 4 ) forms stable gels when the solution is cooled to room temperature. Here, we describe the effects of LiBF 4 concentration and different gelation solvents on the gelation process, and characterize the resulting structural morphology using several techniques. Diethyl carbonate (DEC), propylene carbonate (PC) and c-butyrolactone (GBL) were used as gelation solvents. Time-resolved Fourier transform infrared spectroscopic measurements showed that the conformational transition from TGT G to T 3 GT 3 G occurred with the addition of lithium salts to the PVdF/DEC gel. In addition, PVdF produces thermoreversible gels in GBL and PC containing LiBF 4 , by assuming a T 3 GT 3 G conformation regardless of the LiBF 4 concentration. Scanning electron microscopy studies have indicated the presence of spherulites in the gels. Spherulite size decreased with increasing LiBF 4 concentration, whereas gel-melting temperatures increased with an increase in LiBF 4 concentration. These results indicate that gelation of PVdF in the presence of LiBF 4 occurs as polymer chains assuming the T 3 GT 3 G conformation, imparting the resulting gels with increased thermal stability. Polymer Journal (2011) 43, 540-544; doi:10.1038/pj.2011.21; published online 13 April 2011Keywords: lithium ion; molecular conformation; polymer gel electrolyte; poly(vinylidene fluoride); thermoreversible gel INTRODUCTION Polymer electrolytes have attracted much attention in lithium-battery technology because they enable fabrication of safe and reliable highenergy, high-power secondary lithium batteries. 1 Typical examples of polymer electrolytes include complexes of a lithium salt (LiX) with PEO (polyethylene oxide). The conductivity of PEO-LiX electrolytes reaches practically useful values of B10 À4 S cm À1 at temperatures of 60-80 1C but decreases to 10 À7 S cm À1 at room temperature. 2 Decrease in the conductivity on cooling is because fast ion transport occurs only in the amorphous state of the polymer.The most promising approach for improving conductivity at room temperature is to immobilize a highly conductive liquid electrolyte within a polymer matrix. This type of electrolyte is called a polymer gel electrolyte. This system demonstrates high ionic conductivity at room temperature with sufficient mechanical strength. 3,4 Among the matrices used for polymer gel electrolytes are PVdF, 5,6 poly(methyl methacrylate), 7,8 and poly(acrylonitrile). 9,10 Gel electrolytes based on PVdF are of great interest because of their good thermal, mechanical and electrochemical stability. Recent studies have shown that the ionic conductivity of PVdF gel electrolytes is related to the morphology of the gel. 11 However, a detailed characterization of these gels with regard to the gelation process and structural morphology has not been undertaken. In a previous study, we reported our investigation of the gelation process of PVdF in a number of organic solvents without a lith...

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Crystallization and gelation of poly(vinylidene fluoride) in organic solvents

Cited by 33 publications

References 0 publications

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

Sodium Alginate: A Water-Processable Binder in High-Voltage Cathode Formulations

The Flory-Huggins Interaction Parameter and Thermoreversible Gelation of Poly(vinylidene fluoride) in Organic Solvents

Sol-gel transitions of poly(vinylidene fluoride) in organic solvents containing LiBF4

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