ARC studies of the thermal stability of three different cathode materials: LiCoO 2; Li[Ni 0.1Co 0.8Mn 0.1]O 2; and LiFePO 4, in LiPF 6 and LiBoB EC/DEC electrolytes

Abstract

Accelerating rate calorimetry (ARC) has been used to compare the thermal stability of three different cathode materials, LiCoO 2, Li[Ni 0.1Co 0.8Mn 0.1]O 2, and LiFePO 4, in EC/DEC solvent and in 1.0 M LiPF 6 EC/DEC or 0.8 M LiBoB EC/DEC electrolytes. The cathode materials were charged to 4.2 V vs. Li metal before analysis. In EC/DEC solvent, the onset temperatures for self-sustained exothermic reactions are 150, 220 and 310 °C for LiCoO 2, Li[Ni 0.1Co 0.8Mn 0.1]O 2 and LiFePO 4 (all charged to 4.2 V), respectively. In LiPF 6 EC/DEC or LiBoB EC/DEC, Li[Ni 0.1Co 0.8Mn 0.1]O 2 (0.2 μm diameter particles) shows higher stability than LiCoO 2 (5 μm diameter particles). For both of these charged electrode materials, the reactivity with LiBoB EC/DEC is more severe than with LiPF 6 EC/DEC. For charged LiFePO 4, however, LiBoB EC/DEC presents higher thermal stability than LiPF 6 EC/DEC. Since the reactivity of lithiated graphite with LiBoB-based electrolytes is less severe than with LiPF 6-based electrolytes, the results in this paper suggest that graphite/LiBoB-based electrolyte/LiFePO 4 Li-ion cells will be very abuse-tolerant.