Single-ion Conducting Polymer Electrolytes Research Articles

Construction of a lithium ion transport network in cathode with lithiated bis(benzene sulfonyl)imide based single ion polymer ionomers

We demonstrate a novel method to construct a lithium ion transport network in cathode materials by replacing PVDF with lithiated poly(bis(4-carbonyl benzene sulfonyl)imide-co-bis(4-amino benzene sulfonyl)imide) as the binder. The single ion conducting polymer was synthesized via polycondensation of bis(4-carbonyl benzene sulfonyl)imide and bis(4-amino benzene sulfonyl)imide followed by lithium ion exchange. By blending the ionomers with LiFePO4 and acetylene carbon, the ionic network was well constructed, resulting in a maximum use of active cathode material inside the cathode. The membrane of the polymer electrolyte exhibits an ionic conductivity of 0.14 mS cm−1 at room temperature, a high ion transference number of 0.92 and a wide electrochemical window of 4.5 V (vs. Li+/Li). A lithium ion battery assembled with the single ion conducting polymer electrolyte delivers excellent performance at room temperature with various C-rates.

A new single-ion polymer electrolyte based on polyvinyl alcohol for lithium ion batteries

In this study, a novel single-ion conducting polymer electrolyte, lithium polyvinyl alcohol oxalate borate (LiPVAOB), from the reaction of poly(vinyl alcohol) (PVA) with different molar ratio of boric acid, oxalic acid and lithium carbonate was prepared. The prepared materials were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential thermal analysis (DTA), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry. Ionic conductivity of these polymer electrolytes from adding an assistant (about 20wt.% propylene carbonate) is dependent on molar ratio of the reactants and can up to 6.11×10−6Scm−1 at ambient temperature. Their electrochemical window can be stable up to 7V (vs. Li+/Li), which is of great attraction for high voltage lithium ion batteries with high energy density.

A Single Ion Conducting Gel Polymer Electrolyte Based on Poly(lithium 2-Acrylamido-2-Methylpropanesulfonic Acid-Co-Vinyl Triethoxysilane) and its Electrochemical Properties

Single ion conducting polymer electrolytes synthesized through a copolymer poly(lithium 2-acrylamido-2-methylpropanesulfonic acid-co-vinyl triethoxysilane) and a crosslinker poly(etheylene glycol) dimethacrylate (PEGDMA) were prepared. Scanning electron microscope (SEM) was used to observe the morphology of the surface and cross-section of the polymer electrolyte membrane. AC impedance and linear sweep voltammetry were used to investigate the electrochemical properties of the polymer electrolytes. It was found that the obtained membrane had a typical amorphous structure and possessed a smooth surface. The bulk resistance of the polymer electrolyte increased with the increase in the plasticizer uptake. The electrochemical stability increased with the increase in the content of VTES.

Electrospun poly(lithium 2-acrylamido-2-methylpropanesulfonic acid) fiber-based polymer electrolytes for lithium-ion batteries

Novel single-ion conducting polymer electrolytes based on electrospun poly(lithium 2-acrylamido-2-methylpropanesulfonic acid) (PAMPSLi) membranes were prepared for lithium-ion batteries. The preparation started with the synthesis of polymeric lithium salt PAMPSLi by free-radical polymerization of 2-acrylamido-2-methylpropanesulfonic acid, followed by ion-exchange of H+ with Li+. Then, the electrospun PAMPSLi membranes were prepared by electrospinning technology, and the resultant PAMPSLi fiber-based polymer electrolytes were fabricated by immersing the electrospun membranes into a plasticizer composed of ethylene carbonate and dimethyl carbonate. PAMPSLi exhibited high thermal stability and its decomposition did not occur until 304°C. The specific surface area of the electrospun PAMPSLi membranes was raised from 9.9 m2/g to 19.5 m2/g by varying the solvent composition of polymer solutions. The ionic conductivity of the resultant PAMPSLi fiber-based polymer electrolytes at 20°C increased from 0.815 × 10−5 S/cm to 2.12 × 10−5 S/cm with the increase of the specific surface area. The polymer electrolytes exhibited good dimensional stability and electrochemical stability up to 4.4 V vs. Li+/Li. These results show that the PAMPSLi fiber-based polymer electrolytes are promising materials for lithium-ion batteries. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

IR spectroscopy and quantum mechanical calculations of lithium ion transport conditions in a single ion conducting polymer electrolyte

Lithium single ion conducting polymers with good conductive properties has the potential of boosting the performance of lithium batteries considerably. Recently, lithium single ion conducting polymer electrolytes were obtained by solvating ‘polymeric salts’ into polyether matrices. Of the polymeric salts developed, the highest ion conductivity was obtained using poly(5-oxo-3-oxy-4-trifluoromethyl-1,2,4-pentafluoro-pentylene sulphonyl imide lithium) (LiPPI). In the present study ab initio calculations have been used to determine limitations for ion transport in a model system similar to the LiPPI. The lithium ion coordination and the flexibility of the polymer backbone have been studied using monomers and dimers of our model system. Comparisons with calculated IR spectra from our model system and experimental IR spectra of LiPPI in solution show that our model is a good description of the LiPPI system. The present results are used to propose structural changes that may increase the single ion conductivity.

Blended polymer electrolytes based on poly(lithium 4-styrene sulfonate) for the rechargeable lithium polymer batteries

Single ion conducting polymer electrolytes composed of poly(ethylene oxide) (PEO) and poly(lithium 4-styrenesulfonate) (PLSS) were prepared and characterized. Transference number of lithium ion in the blended polymer electrolyte was 0.85. For the blended polymer electrolytes under this study, the optimum concentration for maximum ionic conductivity was found to be [EO]/[Li] = 8.0.

Li-Ion Conductivity of Aluminate and Borate Complex Polymers Containing Fluoroalkane Dicarboxylate

Single-ion conducting polymer electrolytes which contain fluoroalkane dicarboxylate substituted aluminate or borate backbone and two methoxy [oligo (ethyleneoxide)] side chains directly bonded to the ate complex centers (aluminum, borate, etc.) were prepared. Borate polymers containing a long ether chain exhibited high ionic conductivity S cm−1 at 30°C) and high electrochemical stability. The relationship between polymer structure and ionic conductivity is discussed with the partial charge density on oxygen atoms of the ate complex from the calculations in MOPAC. © 2004 The Electrochemical Society. All rights reserved.

Enhancement of ion dissociation in polyelectrolyte gels

High conductivity in single ion conducting polymer electrolytes is still the ultimate aim for many electrochemical devices such as secondary lithium batteries. Achieving effective ion dissociation in these cases remains a challenge since the active ion tends to remain in close proximity to the backbone charge as a result of a low degree of ion dissociation. A unique aspect of this dissociation problem in polyelectrolytes is the repulsion between the backbone charges created by dissociation. One way of enhancing ion dissociation in polyelectrolyte systems is to use copolymers in which only a fraction (<20%) of the mer units are charged and where the comonomer is itself chosen to be polar and preferably to be compatible with potential solvents. We have also found that certain dissociation enhancers based on ionic liquids or boroxine ring compounds can lead to high ionic conductivity. In the cases where an ionic liquid is used as the solvent in a polyelectrolyte gel, the viscosity of the ionic liquid and its hydrophilicity are critical to achieving high conductivity. Compounds based on the dicyanamide anion appear to be very effective ionic solvents; polyelectrolyte gels incorporating such ionic liquids exhibit conductivities as high as 10 −2 S/cm at room temperature. In the case of boroxine ring dissociation enhancers, gels based on poly(lithium-2-acrylamido-2-methyl-1-propanesulfonate) and ethylene carbonate produce conductivities approaching 10 −3 S/cm. This paper will discuss these approaches for achieving higher conductivity in polyelectrolyte materials and suggest future directions to ensure single ion transport.

Single-Ion Conducting Polymer Electrolytes: Synthesis and Characterization

AbstractTwo classes of alkali metal single-ion conducting polymer electrolytes have been characterized and their conductivities examined. Both polymers are sodium ion conductors. The first class is based upon a tetra(alkoxy)-aluminate counterion incorporated into a polyether network, and the second has a sulfonate counterion covalently bonded to a phosphazene backbone. The temperature dependent and concentration dependent conductivities of these polymers are contrasted. Phosphazene polymers that are anion conductors are also discussed.