Building Safe Lithium-Ion Batteries for Electric Vehicles: A Review

Lithium-ion batteries (LIBs), with relatively high energy density and power density, have been considered as a vital energy source in our daily life, especially in electric vehicles. However, energy density and safety related to thermal runaways are the main concerns for their further applications. In order to deeply understand the development of high energy density and safe LIBs, we comprehensively review the safety features of LIBs and the failure mechanisms of cathodes, anodes, separators and electrolyte. The corresponding solutions for designing safer components are systematically proposed. Additionally, the in situ or operando techniques, such as microscopy and spectrum analysis, the fiber Bragg grating sensor and the gas sensor, are summarized to monitor the internal conditions of LIBs in real time. The main purpose of this review is to provide some general guidelines for the design of safe and high energy density batteries from the views of both material and cell levels.Graphic AbstractSafety of lithium-ion batteries (LIBs) with high energy density becomes more and more important in the future for EVs development. The safety issues of the LIBs are complicated, related to both materials and the cell level. To ensure the safety of LIBs, in-depth understanding of the safety features, precise design of the battery materials and real-time monitoring/detection of the cells should be systematically considered. Here, we specifically summarize the safety features of the LIBs from the aspects of their voltage and temperature tolerance, the failure mechanism of the LIB materials and corresponding improved methods. We further review the in situ or operando techniques to real-time monitor the internal conditions of LIBs.