Comparative study on high-voltage safety performance of LiNixMnyCozO2 cathode with different nickel contents

Abstract

In this article, systematic comparison of the safety performance of LiNixMnyCozO2 is made to find a balance among nickel content, energy density, and thermal stability. Three kinds of LiNixMnyCozO2 cathodes with different nickel contents are charged to different cut-off voltages from 4.2 to 4.6 V (vs Li+/Li) to obtain different energy densities, and their safety is evaluated through differential scanning calorimetry. Different characteristic temperatures are proposed to describe the cathode safety comprehensively and a relationship between energy density and thermal stability is established. It is found that cathode with lower nickel content (LiNi0.5Mn0.3Co0.2O2 and LiNi0.6 Mn0.2Co0.2O2) charging to high voltage exhibits better thermal stability compared to high nickel cathode (LiNi0.8Mn0.1Co0.1O2) at a conventional voltage. Numerical simulation based on a lumped thermal model is also performed to predict the real thermal behaviors of batteries using different cathodes. The discussion of the impact of the cut-off voltage for NMC cathodes provides a new dimension to further improve the comprehensiveness of battery material safety database and a new viewpoint on the trade-off between cathode energy density and safety.