Triisopropyl borate as an electrolyte additive for improving the high voltage stability of LiNi0.6Co0.2Mn0.2O2 cathode

Triisopropyl borate electrolyte additive is introduced to improve the cycled stability of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode operating under 4.5 V charging-cutoff voltage. Through characterizations analysis from SEM, TEM, XPS, ICP, XRD and EIS, it reveals that triisopropyl borate additive can be oxidized on the cathode and form a relatively stable protective film on the NCM622 cathode surface, which has the ability to inhibit the decomposition of carbonate electrolyte solvents and improve the electrochemical stability of LiNi0.6Co0.2Mn0.2O2 cathode. When 1.0 wt% triisopropyl borate additive adding, the NCM622/Li cells achieve the discharge capacity retention of 82.7% after 300 cycles at the voltage of 3.0-4.5 V, while that of the cells without additive is only 50. 0%.