Behaviour of PEO-urethane in solutions of carbonates. Synthesis and electrochemical characterisation of PEO-urethane–coke electrodes

Abstract

We studied the behaviour of PEO-urethane, resulting from a polycondensationin situ of PEO [poly(ethylene oxide)] with urethane, towards organic carbonate electrolytes. We analysed the weight increase of the PEO-urethane with propylene carbonate (PC) or dimethyl carbonate (DMC) and a lithium salt at different concentrations at different times. Results indicate that the diffusion of the carbonate electrolyte is clearly controlled by the PEO-urethane–lithium salt interactions with PC based solutions and by the PEO-urethane–LiAsF₆ . (DMC)₂ interactions with DMC based solutions.

Comparing the transport properties of PEO-urethane with that of Celgard in a liquid electrolyte confirms the results for the weight increase as they suggest a preferential solvation of lithium species by the PEO-urethane network with PC and by DMC when the latter solvent is used.

Composite electrodes containing coke and PEO-urethane were prepared using chemical in situ curing. The dependence of the electrical properties of these composites on the coke content was studied. We found an electrical percolation weight loading close to 46%. The influence of the PEO-urethane on the electrochemical behavior of coke was also studied in a carbonate electrolyte using these composite electrodes. A passivation phenomenon always occurs with the first reduction but the stability of the lithiated coke is reduced little with the PEO-urethane.