Improvement of Interfacial Stability for LiNi0.5Mn1.5O4 Cathode: Insight into the Effect and Mechanism of Additive with Special Structure

Abstract

AbstractThe development of a suitable high voltage electrolyte system is of great importance for high energy density system. However, solving the interfacial stability of high voltage cathode materials remains a challenge. Herein, methyl benzenesulfonate (MBS) with a special structure as a “victim” additive has been introduced to construct a protective interface film on the surface of lithium nickel manganese oxide (LiNi0.5Mn1.5O4, LNMO) cathode. Charge‐discharge cycling and rate capability performances demonstrate that introducing MBS additive has positive effect on interfacial stability, especially for power property. In 3.0 C rate, the cell with MBS electrolyte has about 63.5 % of capacity retention compared with the discharge capacity using 0.2 C rate, nevertheless, the baseline electrolyte is only 24.2 %. Besides, electrolyte with MBS additive shows some advantages in suppressing overcharge. The excellent performance can be attributed to the special molecular structure of MBS, which can further optimize the properties of interface film. The preferential oxidizability of MBS is able to construct a protective film on the electrode to hinder the further breakdown of electrolyte. The aromatic ring ensures the chemical stability of interface film and the sulfur provides the interface film with high ionic conductivity. These contributions are confirmed by further electrochemical measurements, detailed physical characterizations and theoretical calculations.