Abstract
The aging and performance of natural graphite/PEO-based gel electrolyte/LiFePO
4 cells are 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 LiBF4-EC/GBL exhibited high reversible capacity (345
mAh/g) and high coulombic efficiency (91%). The LiFePO
4 cathode in the same gel-polymer exhibited a reversible capacity of 160
mAh/g and 93% coulombic efficiency. Better performance was obtained at high-rate discharge with 6% carbon additive in the cathode, however the graphite anode performance suffers at high rate. The Li-ion gel polymer battery shows a capacity fade of 13% after 180 cycles and has poor performance at low temperature due to low diffusion of the lithium to the graphite in the GBL system. The LiFePO
4/gel/Li system has an excellent rate capacity. LiFePO
4 cathode material is suitable for HEV application.