Abstract not Available.

The single-ion conductor, BF3-incorporated poly[(oxyethylene)(9) methacrylate-ran-lithium methacrylate]- graft-poly(dimethyl siloxane), P(OEM-r-LiMA)-g-PDMS, was used as an electrolyte in cells containing a lithium anode and a thin-film vanadium oxide cathode. Cycle testing revealed an unanticipated high polarization which resulted in a significant drop in capacity compared to that of cells constructed with conventional salt-doped electrolytes produced by the addition of a lithium salt to an uncharged electrolyte poly (oxyethylene)(9) methacrylate-graft-polydimethyl siloxane. Impedance spectra obtained from a vanadium oxide symmetric cell fitted with a single-ion electrolyte showed a large resistance associated with the cathode/electrolyte interface. Further battery testing illustrated that the polarization remained even when lithium triflate was added to the single-ion electrolyte. In contrast, cells consisting of a lithium anode, single-ion electrolyte, and an alloying cathode showed no rise in polarization over what is found in similar cells constructed with a salt-doped electrolyte. These observations are consistent with the hypothesis that diffusion of lithium ions into the bulk vanadium oxide may be coulombically hindered by single-ion electrolytes. (C) 2006 The Electrochemical Society.

Graft copolymer electrolytes (GCEs) of poly[(oxyethylene)(9) methacrylate]-g-poly(dimethyl siloxane) (POEM-g-PDMS) (70: 30) have been synthesized by simple free radical polymerization using a macromonomer route. Differential scanning calorimetry, transmission electron microscopy, and small angle neutron scattering confirmed the material to be microphase-separated with a domain periodicity of similar to25 nm. Over the temperature range 290 < T < 360 K, the electrical conductivities of the lithium triflate-doped POEM-g-PDMS, which exhibited solid-like mechanical behavior, were nearly identical to those of the liquid POEM homopolymer. Thermal and electrochemical stability studies showed the electrolyte to be stable over a wide temperature range and voltage window. Solid-state, thin-film batteries comprised of a metallic lithium anode, a similar to0.2 mum thick vanadium oxide cathode, and an electrolyte of POEM-g-PDMS doped with LiCF3SO3 proved resistant to capacity fade during extended cycling at room temperature (>200 cycles) at a discharge rate of 2/3 C and could be cycled (charged and discharged) at subambient temperature (0degreesC). (C) 2004 The Electrochemical Society.

A microphase-separating single-ion conductor, poly[(oxyethylene)(9) methacrylate-ran-lithium methacrylate]-graft-poly(dimethyl siloxane), P(OEM-r-LiMA)-g-PDMS, was prepared by lithiating a precursor polymer synthesized by free radical methods using commercially available macromonomers. This material possessed a low conductivity, stemming from high ion-pairing interactions that severely restricted the number of charge carriers available for conduction. Subsequent conversion of the LiMA units via the addition of BF3, a Lewis acid, resulted in a 2 orders-of-magnitude rise in conductivity, a gain that could be attributed to a large increase in the number of mobile cations. By blending this material with uncharged POEM-g-PDMS, the room-temperature conductivity was optimized to 7x10(-6) S/cm. With a lithium transference number of unity, these materials exhibit higher dc-measured conductivities at elevated currents than their salt-doped counterparts and are electrochemically stable to similar to 4.5 V. (c) 2005 The Electrochemical Society.

Student self-assessment survey results indicate that a virtual lab experience improved understanding of many key laboratory learning objectives and that the Materials Digital Library (MatDL) has potential value in supporting a virtual lab

Solid-state polymer–silicate nanocomposite electrolytes based on an amorphous polymer poly[(oxyethylene)8 methacrylate], POEM, and lithium montmorillonite clay were fabricated and characterized to investigate the feasibility of their use as ‘salt-free’ electrolytes in lithium polymer batteries. X-ray scattering and transmission electron microscopy studies indicate the formation of an intercalated morphology in the nanocomposites due to favorable interactions between the polymer matrix and the clay. The morphology of the nanocomposite is intricately linked to the amount of silicate in the system. At low clay contents, dynamic rheological testing verifies that silicate incorporation enhances the mechanical properties of POEM, while impedance spectroscopy shows an improvement in electrical properties. With clay content ≥15 wt.%, mechanical properties are further improved but the formation of an apparent superlattice structure correlates with a loss in the electrical properties of the nanocomposite. The use of suitably modified clays in nanocomposites with high clay contents eliminates this superstructure formation, yielding materials with enhanced performance.

Single-ion conducting block copolymer electrolytes were prepared in which counter ions were tethered to the polymer backbone to achieve a lithium transference number of unity. Through tailored anionic synthesis, the influence of counter ion placement on conductivity was investigated. Incorporating the anions outside the ion-conducting [poly(ethylene oxide)-based] block, such as in poly(lauryl methacrylate)-block-poly(lithium methacrylate)-block-poly[(oxyethylene)(9) methacrylate], known as PLMA-b-PLiMA- b-POEM, and P(LMA-r-LiMA)-b-POEM, caused lithium ions to dissociate from the carboxylate counter ions upon microphase separation of the POEM and PLMA blocks, yielding conductivities of 10(-5) S/cm at 70 degreesC. In contrast, incorporating anions into the conducting block, as in PLMA-b- P(LiMA-r-OEM), rendered the majority of lithium ions immobile, resulting in conductivities one to two orders of magnitude lower over the range of temperatures studied for equivalent stoichiometries. Converting the carboxylate anion to one that effectively delocalized charge through complexation with the Lewis acid BF3 raised the conductivity of the latter system to values comparable to those of the other electrolyte architectures. Ion dissociation could thus be equivalently achieved by using a low charge density counter ion (COOBF3-) or by spatially isolating the counter ion from the ion-conducting domains by microphase separation. (C) 2004 The Electrochemical Society.

Block copolymer electrolytes of poly[(oxyethylene)(9) methacrylate]-b-poly(butyl methacrylate) (POEM-b-PBMA) (60:40 by mass) synthesized for the first time by atom transfer radical polymerization (ATRP) exhibited mechanical and electrical properties indistinguishable from those of materials made by the more difficult anionic polymerization method. ATRP offers distinct processing advantages as it is easily scalable and almost solvent-free. Solid-state, thin-film batteries comprised of a metallic lithium anode, a binder-free, additive-free, fully dense vanadium oxide cathode, and an electrolyte of ATRP-synthesized POEM-b-PBMA (60:40) doped with LiCF3SO3 demonstrate resistance to capacity fade during extended cycling at a discharge rate of C/2, and perform comparably to otherwise identical batteries operated with the liquid electrolyte 1 M LiPF6 in ethylene carbonate: dimethyl carbonate (1:1 by mass). (C) 2002 The Electrochemical Society.

Department of Chemistry, Northeastern University, Boston, Massachusetts 02115-5000, USAA self-organizing, nanocomposite electrode~SONE! system was developed as a model lithium alloy-based anode for rechargeablelithium batteries. In situ X-ray adsorption spectroscopy, galvanostatic testing, cyclic voltammetry, X-ray diffraction, and trans-mission electron microscopy were used to analyze the electrode, which was fabricated from a polyethylene oxide-based blockcopolymer, single-walled carbon nanotubes, and gold salt. Processing involved a single mixing step without need of a reducingagent. It was found that thermodynamic self-assembly of the block copolymer could provide a template for incorporation of boththe gold salt and nanotubes. Electrochemical testing and subsequent analysis showed that owing to the small particle size and thesurrounding block copolymer matrix, the SONE system could cycle over 600 cycles with rates varying between C/1.8 and 8.8Cwith little evidence of decrepitation or coarsening.© 2002 The Electrochemical Society. @DOI: 10.1149/1.1518482# All rights reserved.Manuscript submitted February 6, 2002; revised manuscript received June 13, 2002. Available electronically October 31, 2002.

In an attempt to raise the transference number of Li+ to nearly unity in a solid polymer electrolyte, block copolymer materials have been prepared in which the counterions are tethered to the polymer backbone. This immobilizes the “anion” and, in effect, renders the material a single-ion conductor. For such so-called self-doped block copolymer electrolytes (SDBCEs) Li+ transference numbers of ∼0.9 have been measured. In parallel, these materials possess significant ionic conductivity (∼10−5Scm−1 at 35°C). Cyclic voltammetry has shown the SDBCE to be immune to electrochemical breakdown at voltages exceeding 5V.