(378n) Composite Electrolytes of Pyrrolidone-Derivatives-PEO Enable to Enhance Performance of All Solid State Lithium-Ion Batteries

All-solid-state batteries with LiFePO₄ cathodes and polyethylene oxide (PEO) based electrolytes are optimized with organic polymer synthesized from allyl amine and tartaric acid which show better properties including ionic conductivity, electrochemical window, charge-discharge capacity and rate performance. The rate of PEO (= 4,000,000) and lithium salt (Lithium bis(trifluoromethanesulphonyl)imide, LiTFSI) is 75:20 (w/w) and polymers of different molecular weight are tested at a wide temperature range from 27 °C (ambient temperature) to 120 °C. Electrolytes with larger amount (weighting more than half of PEO) of low-molecular-weight polymer show conductivity of above 10^-4 S cm^-1, which is similar to typical gel-polymer-electrolyte. Electrolytes which are made from high-molecular-weight dopant, PEO and LiTFSI through ball milling show better conductivity (5.4×10^-6 S cm^-1) as well as better strength than electrolytes without dopant (1.3×10^-6 S cm^-1) at room temperature. And a sensitive dependence on temperature increasing is also observed constructing to the sample without dopant. Stability below 120 °C and an electrochemical window of 5.4 V at 80 °C also indicate promising use of this composite electrolyte in solid state lithium ion batteries.