%0 Journal Article
%K Lithium batteries
%K Pyrrolidinium
%K Ionic liquid
%K Lifepo4
%K Lithium electrode
%K PEGDME
%K TEGDME
%A Joon Ho Shin
%A Pratyay Basak
%A John B Kerr
%A Elton J Cairns
%B Electrochimica Acta
%D 2008
%G eng
%N 2
%P 410-414
%R 10.1016/j.electacta.2008.07.062
%T Rechargeable LiFePO<sub>4</sub> Cells Using N-Methyl-N-butyl pyrrolidinium bis(trifluoromethane sulfonyl)imide-LiTFSI Electrolyte Incorporating Polymer Additives
%V 54
%8 12/2008
%X <p>We have incorporated polymer additives such as poly(ethylene glycol) dimethyl ether (PEGDME) and tetra(ethylene glycol) dimethyl ether (TEGDME) into <em>N</em>-methyl-<em>N</em>-butylpyrrolidinium bis(trifluoromethane sulfonyl)imide (PYR<sub>14</sub>TFSI)-LiTFSI mixtures. The resulting PYR<sub>14</sub>TFSI + LiTFSI + polymer additive ternary electrolyte exhibited relatively high ionic conductivity as well as remarkably low viscosity over a wide temperature range compared to the PYR<sub>14</sub>TFSI + LiTFSI binary electrolytes. The charge/discharge cyclability of Li/LiFePO<sub>4</sub> cells containing the ternary electrolytes was investigated. We found that Li/PYR<sub>14</sub>TFSI + LiTFSI + PEGDME (or TEGDME)/LiFePO<sub>4</sub> cells containing the two different polymer additives showed very similar discharge capacity behavior, with very stable cyclability at room temperature (RT). Li/PYR<sub>14</sub>TFSI + LiTFSI + TEGDME/LiFePO<sub>4</sub> cells can deliver about 127 mAh/g of LiFePO<sub>4</sub> (74.7% of theoretical capacity) at 0.054 mA/cm<sup>2</sup> (0.2C rate) at RT and about 108 mAh/g of LiFePO<sub>4</sub> (63.4% of theoretical capacity) at 0.023 mA/cm<sup>2</sup> (0.1C rate) at −1 °C for the first discharge. The cell exhibited a capacity fading rate of approximately 0.09-0.15% per cycle over 50 cycles at RT. Consequently, the PYR<sub>14</sub>TFSI + LiTFSI + polymer additive ternary mixture is a promising electrolyte for cells using lithium metal electrodes such as the Li/LiFePO<sub>4</sub> cell reported here. These cells showed the capability of operating over a significant temperature range (~0-~30 °C).</p>