Thermal runaway aspect of ultrahigh-nickel cathode-based lithium-ion batteries at increasing charge states

Abstract

High-nickel cathode-based lithium-ion batteries (LIBs) are the core of sustainable innovation in electric vehicles (EV). However, there exists a fire hazard associated with thermal runaway (TR) during charging due to chemical instability of the abundant nickel oxides produced. While the subject of TR in LIBs has been considered in the past, research on the ultrahigh-nickel (Ni content >90 wt%) cathode materials subjected to a wide range of state of charge (SOC) is limited. The LIB is transforming towards going ultrahigh in Ni content to improve the performance of EVs, and ultimately resolving safety issues associated with TR related fire accidents is an immediate goal. The current study presents a correlation amongst the LIB components, SOCs, and Ni contents on two classes of cathodes, namely high-Ni at 88 % and ultrahigh-Ni at 91 % Ni. The exothermic reaction involving anode and electrolyte in a full cell was intensified at SOCs >75 %, leading to the dissociation of cathode materials and a significant self-heating via repeated reactions. When self-heating rate exceeded 1000 °C/min, the reaction developed into a TR, elucidating that a 3 % increase from 88 % to 91 % Ni content brought forward the likelihood of TR with a much shorter delay time.