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

摘要

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.