3,3'-(Ethylenedioxy)dipropiononitrile as an Electrolyte Additive for 4.5 V LiNi_1/3Co_1/3Mn_1/3O₂/Graphite Cells

3,3'-(Ethylenedioxy)dipropiononitrile (EDPN) has been introduced as a novel electrolyte additive to improve the oxidation stability of the conventional carbonate-based electrolyte for LiNi_1/3Co_1/3Mn_1/3O₂/graphite pouch batteries cycled under high voltage. Mixing 0.5 wt % EDPN into the electrolyte greatly improved the capacity retention, from 32.5% to 83.9%, of cells cycled for 100 times in the range 3.0-4.5 V with a rate of 1C. The high rate performance (3C and 5C) was also improved, while the cycle performance was similar to that of the cell without EDPN when cycled between 3.0 and 4.2 V. Further evidence of a stable protective interphase film can be formed on the LiNi_1/3Co_1/3Mn_1/3O₂ electrode surface due to the presence of EDPN in the electrolyte. This process effectively suppresses the oxidative decomposition of electrolyte and the growth in the charge-transfer resistance of the LiNi_1/3Co_1/3Mn_1/3O₂ electrode and greatly improves the high-voltage electrochemical properties for the cells. In contrast, EDPN has no positive effect on the cyclic performance of the LiNi_0.5Co_0.2Mn_0.3O₂-based cell under high operating voltage.