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Yoichi Tominaga - One of the best experts on this subject based on the ideXlab platform.
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Ion-conductive polymer electrolytes based on poly(Ethylene Carbonate) and its derivatives
Polymer Journal, 2017Co-Authors: Yoichi TominagaAbstract:Ion-conductive polymer electrolytes are remarkable materials that have recently been proposed for use as flexible solid electrolytes in next-generation energy storage devices. In particular, the author has proposed the synthesis of novel polymer electrolytes with very high ionic conductivities and the essential properties of polymeric materials. This review describes the synthesis of alternating copolymers of CO_2 with epoxides and their application as novel ion-conductive polymers in the place of typical polyether-based systems. The Li salt electrolytes of poly(Ethylene Carbonate) (PEC) and of other polyCarbonates with different side groups exhibit unique ion-conductive properties, such as increasing conductivity with higher salt concentrations, very high Li transference numbers and good electrochemical stability. The Li-ion conductivity of a PEC-lithium bis(fluorosulfonyl)imide LiFSI electrolyte was estimated to be greater than 10^−4 S cm^−1, and excellent battery performance of this material was also demonstrated at room temperature. In this focus review, alternating copolymers of carbon dioxide with epoxides have been synthesized and studied as novel ion-conductive polymers. The Li salt electrolytes of poly(Ethylene Carbonate) (PEC) and of other polyCarbonates having different side groups exhibited remarkable ion-conductive properties including the following: increased conductivity with increasingly higher salt concentrations, very high values for the Li^+ transference number, and good electrochemical stability. The Li-ion conductivity of a highly concentrated PEC-LiFSI electrolyte was estimated to be greater than 10^−4 S cm^−1, and excellent battery performance was demonstrated at room temperature.
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correlation between solvation structure and ion conductive behavior of concentrated poly Ethylene Carbonate based electrolytes
Journal of Physical Chemistry C, 2016Co-Authors: Kento Kimura, Joh Motomatsu, Yoichi TominagaAbstract:Solid polymer electrolytes are important materials in realizing safe and flexible energy storage devices. The present study looks at correlation between solvation structure and the ion-conductive behavior of poly(Ethylene Carbonate) (PEC)/lithium bis(fluorosulfonyl)imide (LiFSI) electrolytes which have high Li transference number (t+) and show unusual salt-concentration dependence of conductivity. From FT-IR and Raman spectroscopy, we determined that Li ions interact with carbonyl (C═O) groups and also with FSI ions, which can be referred to as contact ion pair or aggregate. 7Li magic-angle-spinning NMR spectroscopy and density functional theory calculations for model species suggest that a loose coordination structure, in which Li ions interact with C═O groups and FSI ions with appropriate strength, allows the electrolytes to have both reasonable conductivity and high t+ with a flexible and transparent character. A high salt dissociation rate is generally considered essential in SPEs, but the presence of...
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a highly concentrated poly Ethylene Carbonate based electrolyte for all solid state li battery working at room temperature
Electrochemistry Communications, 2016Co-Authors: Kento Kimura, Mari Yajima, Yoichi TominagaAbstract:Abstract We report an all-solid-state Li rechargeable battery based on a hybrid membrane comprising a highly-concentrated poly(Ethylene Carbonate) (PEC) electrolyte with 80 wt.% of lithium bis(fluorosulfonyl)imide (LiFSI) and a three-dimensionally ordered macroporous polyimide matrix operating at room temperature. The PEC-LiFSI 80 wt.% electrolyte showed an ionic conductivity of the order of 10 − 5 S cm − 1 at 30 °C and a quite high Li transference number, and was employed as a good ion-conductive solid polymer membrane for all-solid-state Li battery. To assure the mechanical stability, the polyimide matrix was combined as a porous substrate to support the electrolyte. A Li | PEC-LiFSI | LiFePO 4 cell with the hybrid membrane delivered a reversible charge–discharge capacity close to 120 ~ 130 mAh g − 1 at 30 °C and C/20 rate.
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electrochemical properties of a poly Ethylene Carbonate litfsi electrolyte containing a pyrrolidinium based ionic liquid
Ionics, 2015Co-Authors: Kento Kimura, Jusef Hassoun, S Panero, Bruno Scrosati, Yoichi TominagaAbstract:A novel polymer electrolyte membrane comprising poly(Ethylene Carbonate) (PEC), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, and N-n-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) ionic liquid is prepared by a solvent-free procedure, combining annealing and hot-pressing. The electrochemical properties of the electrolyte are investigated in terms of ionic conductivity, Li transference number (tLi+), and electrochemical stability by a combined study involving electrochemical impedance spectroscopy (EIS), chronoamperometry, and voltammetry. The thermal characteristics are assessed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results reveal an ionic conductivity of a PEC-Pyr14TFSI-LiTFSI electrolyte of the order of 10−5 S cm−1 at 80 °C and tLi+ as high as 0.66 with the intrinsic amorphous nature of the PEC matrix. Furthermore, a Li polymer cell coupling LiFePO4 cathode and the electrolyte is assembled and galvanostatically cycled. The result of this charge-discharge test demonstrates a 3.5-V battery which can be used at 80 °C and a current rate of C/20, delivering a reversible capacity of the order of 150 mAh g−1.
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effect of anions on lithium ion conduction in poly Ethylene Carbonate based polymer electrolytes
ECS Transactions, 2014Co-Authors: Yoichi Tominaga, Kenta Yamazaki, Vannasa NanthanaAbstract:Poly(Ethylene Carbonate)-based polymer electrolytes with lithium salts (LiX; X=TFSI, ClO4, BF4 and PF6) were prepared and measured their lithium transference numbers (t +) for the comparison between different anion radius and salt concentrations. The LiTFSI electrolytes showed highest t + and Li-ion conductivities of all samples at 80 oC, and these values increased with increasing salt concentration. From the results of FT-IR measurements for all concentrated samples, it was revealed that the changes of a band fraction divided at around 1720 cm-1 for interacted carbonyl groups with Li+ (C=O --- Li+) strongly relate to the mobility of Li+.
A Ghosh - One of the best experts on this subject based on the ideXlab platform.
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dynamics and relaxation of charge carriers in poly methylmethacrylate lithium salt based polymer electrolytes plasticized with Ethylene Carbonate
Journal of Applied Physics, 2016Co-Authors: Prabir Pal, A GhoshAbstract:In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with Ethylene Carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and Ethylene Carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high fr...
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dynamics and relaxation of charge carriers in poly methylmethacrylate lithium salt based polymer electrolytes plasticized with Ethylene Carbonate
Journal of Applied Physics, 2016Co-Authors: Prabir Pal, A GhoshAbstract:In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with Ethylene Carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and Ethylene Carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.
Prabir Pal - One of the best experts on this subject based on the ideXlab platform.
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dynamics and relaxation of charge carriers in poly methylmethacrylate lithium salt based polymer electrolytes plasticized with Ethylene Carbonate
Journal of Applied Physics, 2016Co-Authors: Prabir Pal, A GhoshAbstract:In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with Ethylene Carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and Ethylene Carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high fr...
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dynamics and relaxation of charge carriers in poly methylmethacrylate lithium salt based polymer electrolytes plasticized with Ethylene Carbonate
Journal of Applied Physics, 2016Co-Authors: Prabir Pal, A GhoshAbstract:In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with Ethylene Carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and Ethylene Carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.
Pinchas Aped - One of the best experts on this subject based on the ideXlab platform.
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the behaviour of lithium electrodes in propylene and Ethylene Carbonate te major factors that influence li cycling efficiency
Journal of Electroanalytical Chemistry, 1992Co-Authors: Doron Aurbach, Yosef Gofer, Moshe Benzion, Pinchas ApedAbstract:Abstract The Li cycling efficiency surface chemistry and Li morphology in Ethylene Carbonate (EC) and propylene Carbonate (PC) based electrolyte solutions were investigated and correlated. Surface sensitive ex situ FTIR spectroscopy, X-ray microanalysis and scanning electron microscopy were used in conjunction with standard electrochemical techniques. EC is more reactive than PC in electroreduction processes and is reduced on noble metals to Ethylene diCarbonate. The difference in reactivity between the two solvents is discussed, based on MO ab initio calculations of their radical anions (and Li+ stabilized radical anions). In spite of the high reactivity of these systems to lithium, the Li cycling efficiency is strongly dependent on the presence of additives and contaminants at the ppm level that modify the Li surface chemistry in solutions. The two alkyl Carbonate solvents decompose when stored over activated Al2O3 and CO2 is formed. The presence of CO2 in solutions increases the Li cycling efficiency considerably due to the formation of Li2CO3 on the Li surfaces.
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the behaviour of lithium electrodes in propylene and Ethylene Carbonate te major factors that influence li cycling efficiency
Journal of Electroanalytical Chemistry, 1992Co-Authors: Doron Aurbach, Yosef Gofer, Moshe Benzion, Pinchas ApedAbstract:Abstract The Li cycling efficiency surface chemistry and Li morphology in Ethylene Carbonate (EC) and propylene Carbonate (PC) based electrolyte solutions were investigated and correlated. Surface sensitive ex situ FTIR spectroscopy, X-ray microanalysis and scanning electron microscopy were used in conjunction with standard electrochemical techniques. EC is more reactive than PC in electroreduction processes and is reduced on noble metals to Ethylene diCarbonate. The difference in reactivity between the two solvents is discussed, based on MO ab initio calculations of their radical anions (and Li+ stabilized radical anions). In spite of the high reactivity of these systems to lithium, the Li cycling efficiency is strongly dependent on the presence of additives and contaminants at the ppm level that modify the Li surface chemistry in solutions. The two alkyl Carbonate solvents decompose when stored over activated Al2O3 and CO2 is formed. The presence of CO2 in solutions increases the Li cycling efficiency considerably due to the formation of Li2CO3 on the Li surfaces.
J R Dahn - One of the best experts on this subject based on the ideXlab platform.
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a guide to Ethylene Carbonate free electrolyte making for li ion cells
Journal of The Electrochemical Society, 2017Co-Authors: Stephen Glazier, R Petibon, Jian Xia, Jeremy M Peters, Qianqian Liu, J P Allen, Renny Doig, J R DahnAbstract:Li[Ni0.42Mn0.42Co0.16]O2 (NMC442)/graphite pouch cells demonstrate superb performance at high voltage when Ethylene Carbonate (EC)-free electrolytes, using a solvent mixture that is >95% ethyl methyl Carbonate (EMC) and between 2 and 5% of an "enabler", are used. The "enablers", required to passivate graphite during formation, can be vinylene Carbonate (VC), mEthylene-Ethylene Carbonate (MEC), fluoroEthylene Carbonate (FEC) or difluoro Ethylene Carbonate (DiFEC), among others. In order to optimize the amount of "enabler" added to EMC, gas chromatography coupled with mass spectrometry (GC-MS) was used to track the consumption of "enabler" during the formation step. Storage tests, electrochemical impedance spectroscopy (EIS), ultrahigh precision coulometry (UHPC), long-term cycling, differential voltage analysis and isothermal microcalorimetry were used to determine the optimum amount of enabler to add to the cells. It was found that the graphite negative electrode cannot be fully passivated when the amount of "enabler" is too low resulting in gas production and capacity fade. Using excess "enabler" can cause large impedance and gas production in most cases. The choice of "enabler" also impacts cell performance. A solvent blend of 5% FEC with 95% EMC (by weight) provides the best combination of properties in NMC442/graphite cells operated to 4.4 V. It is our opinion that the experiments and their interpretation presented here represent a primer for the design of EC-free electrolytes.
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dielectric constants for quantum chemistry and li ion batteries solvent blends of Ethylene Carbonate and ethyl methyl Carbonate
Journal of Physical Chemistry C, 2015Co-Authors: David S Hall, Julian Self, J R DahnAbstract:This work reports measurements of the dielectric constants of Ethylene Carbonate (EC)/ethyl methyl Carbonate (EMC) blends between 25 and 60 °C. Dielectric constants were measured using a cylindrical capacitance cell and a frequency response analyzer. EC and EMC form nonideal mixtures that cannot be described by a simple linear mixing model. A quadratic mixing rule was instead adopted, and the mixing parameter is reported for 25–60 °C. The results of this research may be used to calculate the dielectric constant of any EC/EMC mixture over this temperature range with ≤4% estimated error. By modeling the ionic dissociation of lithium hexafluorophosphate (LiPF6) in various solvents, the significance of the dielectric constant on quantum chemistry simulations of chemical processes is explored. The effect of the dielectric constant accuracy on electrochemical processes was similarly evaluated by calculating the solvation energy of neutral and singly oxidized vinylene Carbonate in various solvents. It is demonst...
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the impact of vinylene Carbonate fluoroEthylene Carbonate and vinyl Ethylene Carbonate electrolyte additives on electrode electrolyte reactivity studied using accelerating rate calorimetry
Journal of The Electrochemical Society, 2014Co-Authors: Jian Xia, Xin Xia, J R DahnAbstract:The effects of vinylene Carbonate (VC), fluoroEthylene Carbonate (FEC) and vinyl Ethylene Carbonate (VEC) electrolyte additives on electrode/electrolyte reactivity at elevated temperatures were investigated using accelerating rate calorimetry (ARC). Li(Ni1/3Mn1/3Co1/3)O2 (NMC) and graphite (mesocarbon microbeads (MCMB)) were utilized as the electrodes and 1.0 M LiPF6 in Ethylene Carbonate (EC):diethyl Carbonate (DEC) (1:2 by volume) was chosen as control electrolyte. Adding 10 wt% VC, FEC or VEC to the electrolyte does not significantly impact the reactivity of delithiated NMC compared to the control electrolyte. However, the three additives affected the reactivity between lithiated graphite and electrolyte at elevated temperatures in different ways. Adding VC (up to 10%) reduces the reactivity between lithiated graphite and electrolyte below about 200°C, adding VEC does not affect the reactivity at all, while adding over 5 wt% FEC causes a small exotherm beginning as low as 50°C. After this small exotherm completes, electrolytes with 10 wt% FEC show more reactivity with lithiated graphite than control electrolyte above 130°C. These results give a head to head comparison of the reactivity of electrolytes containing VC, VEC or FEC with charged electrode materials at elevated temperatures and show that the use of VC and VC at levels of 10 wt% or less should not compromise the safety of Li-ion batteries.