A bifunctional additive bi(4-flurorophenyl) sulfone for enhancing the stability and safety of nickel-rich cathode based cells

LiNi0.8Co0.1Mn0.1O2 is regarded as a promising cathode material in lithium ion batteries (LIB) for its high specific capacity and low cost. While the short cycle life, severe cathode deterioration as well as the poor safety characteristic hinder its wide application. In this work, we introduce a novel additive, bis(4-fluorophenyl) sulfone (BFS), which enhances the capacity retention from 75.19% to 83.04% after 100 cycles at the rate of 1C. Moreover, linear sweep voltammetry (LSV), cyclic voltammetry (CV), galvanostatic test, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy were carried out to further demonstrate the superiority of this additive. We prove that this additive can decompose preferentially and form a desirable cathode electrolyte interface on the positive cathode according to the LSV and TEM results. Furthermore, the smooth and robust film not only can effectively enhance the cycling stability, but also can prevent the cathode from severe deterioration. We deduce a proper function mechanism of this additive. This additive can be oxidized at state of charge into two sulfonates, which prevent the carbonate electrolyte from decomposition. This mechanism has been proved by DFT calculations. In addition, the overcharging performance also has been tested in this work by charging cells till 5 V. (C) 2019 Elsevier B.V. All rights reserved.