Electrochemical Study of Functional Additives for Li-Ion Batteries

Abstract

In the battery industry, the performance of lithium-ion batteries operating at a high voltage is enhanced by utilizing functional additives in electrolytes to achieve higher energy densities and longer lifetimes. These additives chemically stabilize the electrolyte and aid in the formation of a stable cathode electrolyte interphase (CEI). In this paper, the investigation of oxidative potentials of more than 100 additives, using density functional theory calculations to determine the best candidates for CEI formation, is reported. The method was validated by comparing the calculated oxidation potentials and the experimental data obtained using linear sweep voltammetry based on the evaluation of 18 candidates. Further electrochemical studies (AC impedance and cycling stability) on six selected additives were conducted. Among the tested additives, the addition of quinacridone at 0.03% weight concentration resulted in the formation of a less resistive surface film on the cathode in Li/Ni0.5Mn0.3Co0.2O2 coin cells. Moreover, the capacity retention in Gr/Ni0.5Mn0.3Co0.2O coin cells increased from 62% to 77% after 200 cycles at 1C and approximately 4.4 V. The derived results suggest that the combination of the oxidation potential prediction with impedance study could be used as a powerful tool to properly and efficiently select CEI-forming additive candidates for improved battery performance.