Impact of silicon content on mechanical abuse and thermal runaway of Li-ion battery cells

Abstract

In order to increase the energy density of lithium-ion batteries, the use of silicon alongside graphite is spreading in the application. However, the high energy densities are accompanied with safety risks, as high energy density materials can be more prone to thermal runaway. Therefore, the effect of five different silicon contents (0, 2.5, 5, 10, 15 wt%) on the safety performance during mechanical abuse were investigated. Anodes were produced, characterized and processed into cells with a NCM-83-11-6 cathode. The electrochemical performance was analyzed, and the thermal runaway in pouch cells was investigated using crush tests with a hemispherical punch. The results disclose an up to 30 % increase in load capacity with increasing silicon content while the thermal runaway reaction is more severe. The reaction time decreases with a rate of 0.035 s %_Si⁻¹ and the cell surface temperature as well as the mass loss increase with 6.1 °C %_Si⁻¹ and 0.47 % %_Si⁻¹. This study provides insights into the influence of electrode and cell parameter from production to the safety behavior in a mechanical abuse test and can help to develop batteries that exhibit high energy density as well as sufficient safety characteristics.