Search

Abstract: A high temperature polymer electrolyte membrane water electrolyser (PEMWE) was investigated at temperatures between 80 and 130°C and pressures between 0.5 and 4bar. Nanometer size Ru0.7Ir0.3O2 and Pt/C were employed as anode and cathode catalysts respectively. The catalyst coated on membrane (CCM) method was used to fabricate the membrane electrode assemblies. The membrane, oxygen evolution catalysts and MEAs were characterized with SEM, XRD and TEM. The influence of high temperature and pressure was investigated using in situ electrochemical measurements. Increasing temperature and pressure produced higher current densities for oxygen evolution, and smaller terminal voltages. The high temperature PEMWE achieved a voltage of 1.51V at a current density of 1Acm−2, at 130°C and 4bar pressure. [Copyright &y& Elsevier]

Oligoether branched-and-spaced “acid-in-chain” polymers, with variable length side chains attached to the acidic borons have been prepared by a simple two-step reaction sequence. These may be used as anion-retarding hosts for “salt-in-polymer” electrolytes or, alternatively, may be converted to polyanionic electrolytes by reacting with strong Lewis base anions. High ionic conductivities, reaching 7.6×10−5 S cm−1 at 25 °C have been obtained for the former case, using LiTFSI:B proportions of 1:1, and optimized side chain and spacer lengths. The electrochemical windows are wide enough (>4.5 V) for most applications. [Copyright &y& Elsevier]

Lithium polyMOB has been investigated as the polymer in a polymer-in-salt type electrolyte incorporating the salts lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium tetrafluoroborate (LiBF4). While all salts give rubbery solids at high salt contents, only LiClO4 provides high conductivity because only in the case of LiClO4 is the lithium cation motion highly decoupled from the structural relaxation. The crystallization of the salt at high salt contents prevents a favorable combination of mechanical and electrical properties, but the system provides an excellent example of the principle of the polymer-in-salt ionic rubber electrolyte and the factors determining its performance. [Copyright &y& Elsevier]

Plasticized and crosslinked versions of poly(lithium oligoetherato mono-oxalato borate), called lithium polyMOBs, have been studied. In heavily plasticized forms of both polyMOB, and a LiBH4-crosslinked polyMOB, the ionic conductivity reaches 10−3 S cm−1 at room temperature while single ion conductivity is automatically retained. The electrochemical stability window is up to 5 V, for both stainless steel (SS) electrodes. The plasticized forms are fluid, not a gel, due to the low molecular weight of the polyanions. Freestanding gel electrolytes with high single ionic conductivity of 10−4 S cm−1 at ambient can be obtained by incorporation of high molecular weight poly(methyl methacrylate) (PMMA) into the solution. Electrochemical cells using these electrolytes will not suffer from concentration polarization. [Copyright &y& Elsevier]

We describe the synthesis of new chain polymers that contain weakly basic anionic mono-oxalato orthoborate (MOB) moieties in a polyether backbone at controllable anionic separations. The conductivities of these lithium-conducting polymers are found to be high relative to those of most conventional dry salt-in-polymer electrolytes. An ambient conductivity of about 10−5 S cm−1 has been obtained for a solid polymer with 14 ethyleneoxy repeating units. The electrochemical window for these materials is in excess of 4.5 V. These inexpensive benign materials should be very suitable as electrolytes for rechargeable lithium batteries. [Copyright &y& Elsevier]