Crystallinity and morphology of PVdF–HFP-based gel electrolytes

Abbrent, Sabina; Pleštil, Josef; Hlavatá, D.; Lindgren, Jan; Tegenfeldt, Jörgen; Wendsjö, Å.

doi:10.1016/s0032-3861(00)00517-6

Cited by 303 publications

(189 citation statements)

References 25 publications

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“…T 0 values of B1, B2, and B3 are close to T g values reported for swollen polymer electrolytes. 32 Low values of E a are obtained, consistent with conductivities slightly dependent on the temperature in liquid electrolytes. .…”

Section: Resultssupporting

confidence: 60%

Swollen Polymethacrylonitrile Urethane Networks for Lithium Batteries

Bélières

Maréchal

Saunier

et al. 2003

J. Electrochem. Soc.

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Copolymers of methacrylonitrile are reported. Surprisingly, their curing through urethane cross-links acts as an internal plasticization. This cross-linking prevents any dissolution or leakage, up to 90°C, when the networks are swollen by liquid organic electrolytes. These provide high conductivities, and the increase in resistivity with respect to pure liquid electrolytes remains р2. The specifications of lithium batteries intended for electronic application imposes an operation at low temperature which can be obtained only with liquid organic electrolytes. In parallel these batteries must be able to tolerate a temperature of 80°C over a period of several days. Within the framework of cellular phone application, the tendency is to decrease volume and weight, but operational requirements, i.e., accessibility of the keys, reading of the screen, make it impossible to envisage a reduction in the surface of the telephone.1 Consequently, it is desirable to substitute prismatic batteries by flexible and thin batteries. The majority of the commercial batteries, in particular, prismatic, use a microporous polyolefin separator, which confers a particular safety, shut-down effect, to the battery with respect to a great increase in temperature. However, this type of separator exhibits poor affinities for the polar organic electrolytes and makes difficult their use for the manufacture of flexible and thin batteries. An alternative to these microporous separators consists in using a polymer swollen by the liquid organic electrolytes. Thirty years ago, 2 these polymers swollen by the electrolyte were intended to manufacture ''thin-layer'' electrochemical elements. The polymers proposed were polyacrylonitrile ͑PAN͒, 3,4 copolymer poly͑methyl methacrylate͒ P͑AN-co-PMMA͒, 5-6 polyvinyl chloride ͑PVC͒, 7 polyacetals as polyvinylbutyral ͑PVB͒, fluoropolymers as polyvinylidene fluoride-co-polyhexafluoropropene ͑VDF/HFP͒, [8][9][10] or PMMA copolymers. [11][12][13] The solvent retention ability of polymer gels decreases in the order of PMMA у PAN ϭ poly͑vinylidene difluoride͒ P͑VdF-HFP͒ у PVdF.14 The lowaffinity polymers are advantageous with respect to the mechanical strength of polymer gels but are a disadvantage with respect to ionic conductivity. It was also proposed to use poly͑oxyethylene͒ ͑POE͒ networks. 15 These adapted well to dry lithium-polymer applications but are much less interesting compared to organic solvents.We chose to use a polynitrile because of the strong dipole moment of the nitrile group and the affinity of PAN for the usual lithium salts and the polar solvents which constitute the liquid electrolyte. However, the electrochemical instability of PAN with a lithium negative electrode has been known for a long time and has been highlighted from measurements of PAN electrolyte/lithium interface resistances and their evolution with time. 16 We attributed much of the PAN instability to the existence of the rather ''acidic'' hydrogen in the alpha position of the nitrile group. To solve this we chose polymethacryloni...

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Section: Resultssupporting

confidence: 60%

Swollen Polymethacrylonitrile Urethane Networks for Lithium Batteries

Bélières

Maréchal

Saunier

et al. 2003

J. Electrochem. Soc.

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“…From the above results it can be inferred that the shape and domain size considerably varies only with PC content and not with lithium salt. The results contradict observation of Abbrent et al 3) , and Shilov et al 4) who reported that there is a significant change in the structure when the lithium salt is added to the PVC and PVdF based gels, respectively. The significant change indicates that lithium ion is associating with the polymer matrix in the case of PVdF and PVC.…”

Section: Small Angle X-ray Scattering (Saxs)contrasting

confidence: 95%

“…(r ) (r ) 1 2 (r) 2 ( (0) ) (2) The correlation function (r) can be calculated from the scattering intensity profile by the Fourier transform 1 sin qr 2 (r) q I(q) dq q qr 0 (3) A peak in a scattering profile indicates the presence of two-phase structure. The position of the peak (q max ) provides information about the periodic variation in electron density by the Bragg equation [4]; 2 D q max (4) 3.3 Impedance spectroscopy Frequency dependent conductivities of gel electrolytes were measured with an Alpha high resolution analyzer coupled to a Novocool temperature controller.…”

Section: Small Angle X-ray Scattering (Saxs)mentioning

confidence: 99%

Structural Investigation of Polyurethane Based Gel Polymer Electrolytes Using Small Angle X-ray Scattering (SAXS)

2010

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Cross linked polymers PU (polyurethane) gel electrolytes have been synthesized from polyethylene oxide triol (PEO triol) and 4,4-methylenediphenyl diisocyanate (MDI). The minimum and maximum intake of liquid electrolyte by this gel is 35 and 65 wt% respectively. WAXD patterns for PU gel electrolytes shows featureless behaviour indicating absence of crystalline phase. SAXS pattern of polyurethane gel exhibits a broad peak at lower q value (~0.7nm -1 ) that is attributed to the presence of two phases, namely hard domains and soft domains. The structure of the gel was inferred as a continuous soft phase with dispersed hard domains. The shape and interface of the hard domains were determined from the slope of the curve in log(I(q)) versus log(q) plot. The slope of the curve decreases with increase in Propylene Carbonate (PC) content. The decrease in slope from -1.5 to -0.2 suggest that the shape of the hard domains changed from diffused ellipsoidal to the diffused spherical when the PC content was increased from 35 to 60wt% in gels. PU-PC(60wt%) gel electrolyte shows the maximum conductivity 2.53 x 10 -3 S/cm at room temperature.

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“…Figure 1 shows differential scanning calorimetry ͑DSC͒ thermograms of gel polymer samples without Li salts. The glass transition temperature (T g ) of neat PVdF-HFP copolymers usually spans a very wide range between Ϫ130 and Ϫ50°C, which implies random distribution of HFP domains, 12 and that of PEGDA is around Ϫ60°C. For miscible polymer blend systems, it is expected to be intermediate between those of the two polymer components.…”

Section: Methodsmentioning

confidence: 99%

Thermally Stable Gel Polymer Electrolytes

Song

Kim

et al. 2003

J. Electrochem. Soc.

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To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride (PEGDA/PVdF) blend gel polymer electrolytes, low molecular weight false(M=742false) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/ LiPF6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. normalLi/Li+. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte was likely to evaporate through large pores in PVdF-HFP at 80°C, while PEGDA/PVdF blend showed better liquid electrolyte retention ability. This result was in good agreement with more stable interfacial properties of PEGDA/PVdF blend at 80°C in ac impedance analysis. Consequently, both PVdF-HFP and PEGDA/PVdF gel polymer electrolytes delivered similar discharge capacity at room temperature, but PEGDA/PVdF blend gel polymer electrolyte showed much better cycle performance than pure PVdF-HFP at 80°C. © 2003 The Electrochemical Society. All rights reserved.

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Crystallinity and morphology of PVdF–HFP-based gel electrolytes

Cited by 303 publications

References 25 publications

Swollen Polymethacrylonitrile Urethane Networks for Lithium Batteries

Swollen Polymethacrylonitrile Urethane Networks for Lithium Batteries

Structural Investigation of Polyurethane Based Gel Polymer Electrolytes Using Small Angle X-ray Scattering (SAXS)

Thermally Stable Gel Polymer Electrolytes

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