Safe Li-ion polymer batteries for HEV applications

The performance of natural graphite/PEO-based gel electrolyte/LiFePO4 cells (5 mAh, 4 cm(2)) is reported. The gel polymer electrolytes were produced by electron-beam irradiation and then soaked in a liquid electrolyte. The natural graphite anode in gel electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI)-EC + PC + DMC exhibited high reversible capacity (360 mAh/g) and high coulombic efficiency (91.6%). The LiFePO4 cathode in the same gel polymer exhibited a reversible capacity of 160 mAh/g and 92% coulombic efficiency. Better performance was obtained at high-rate discharge with 6% carbon additive (carbon and graphite) in the cathode. The Li-ion gel polymer battery shows a very low capacity fade of 1% after 100 cycles. (C) 2004 Elsevier B.V. All rights reserved.