A comparative study on the reactivity of charged Ni-rich and Ni-poor positive electrodes with electrolyte at elevated temperatures using accelerating rate calorimetry

The reactivity of four promising positive electrode materials was investigated using Accelerating Rate Calorimetry. A “library” was built which may provide guide for battery engineers and researchers from a safety perspective. The reactivity between charged Li(Li 0.115 Mn 0.529 Ni 0.339 Al 0.017 )O 2 (Li-rich), single crystal Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 (SC-NMC811), LiFePO 4 (LFP) and LiMn 0.8 Fe 0.2 PO 4 (LMFP) positive electrodes at different states of charge (SOCs) and traditional carbonate-based electrolyte at elevated temperatures is systematically studied using accelerating rate calorimetry (ARC). The results show that the SOC greatly affects the thermal stability of the Li-rich and SC-NMC811 when traditional carbonate-based electrolyte is used. Although an increase in the SOC increases the energy density of lithium-ion cells, it also increases the reactivity between charged Li-rich and SC-NMC811 samples with electrolyte at elevated temperatures. In comparison with SC-NMC811, the Li-rich samples are much more stable at elevated temperatures, and the latter have higher specific capacity. SC-NMC811 samples are less reactive than traditional polycrystalline NMC811. Both LFP and LMFP samples show excellent thermal stability at elevated temperatures. The substitution of Fe by Mn in the olivine series positive materials does not impact the reactivity with electrolyte.