A self-discharging reaction mediated by imide salt enables the prevention of explosive thermal runaway in high-Ni material/graphite full cells

Abstract

High Ni cathode materials have attracted much interest in the Li-ion battery field due to high capacity, but their poor phase stability at the end of charge state can cause severe issues, such as rapid capacity fading and safety problems. Although they have been successfully commercialized as a high capacity cathode material, strategies to ensure safety of LIBs have been consistently required. Here, we demonstrate that a thermally driven spontaneous self-discharge reaction activated by a LiFSI containing electrolyte can prevent severe thermal runaway of charged high Ni/graphite based full cells at >100 °C. At >100 °C, a large amount of Li ions is spontaneously leached out from the lithiated graphite due to its thermodynamic stability, and is then re-inserted into the fully delithiated high Ni material by using the self-discharging reaction. The self-discharging reaction is achieved by the diffusion of Li_xS, which can be formed by the reaction of the leached Li with the LiFSI salt, from the anode surface to the delithiated cathode. We suggest electrolyte modification as a new strategy for suppressing explosive thermal runaway of a cell even when it is exposed to high temperature (>100 °C).