Improving high voltage stability of lithium cobalt oxide/graphite battery via forming protective films simultaneously on anode and cathode by using electrolyte additive

• The cyclic stability of LiCoO2/graphite battery in voltage range of 3.0-4.5 V is improved by VEC.
• VEC inhibits dimension change of the battery after cycling at 4.5 V cutoff voltage.
• The SEI formed by VEC on cathode is able to inhibit the cobalt dissolution.
• The anodic SEI formed by VEC suppresses the cobalt deposition and the electrolyte decomposition.

We report a new finding that high voltage stability of lithium cobalt oxide (LiCoO2)/graphite battery can be improved by using vinyl ethylene carbonate (VEC) as an electrolyte additive. Charge/discharge tests demonstrate that the battery using VEC exhibits significantly improved cyclic and dimensional stability of the 053048-type LiCoO2/graphite pouch cell up to 4.5 V. The capacity retention is 87.0% and the swell value in thickness is 3.1% for the cell with 2.0 wt.% VEC after 400 cycles between 3.0 V and 4.5 V, compared to the values of 38.4% and 38.6%, respectively, for the cell without additive. The characterizations from scanning electron spectroscopy and X-ray photoelectron spectroscopy demonstrate that VEC facilitates the formation of stable solid electrolyte interfaces simultaneously on anode and cathode of the LiCoO2/graphite battery, yielding effective protections for anode and cathode and preventions of the electrolyte decomposition on both electrodes.