ARC studies of the thermal stability of three different cathode materials:: LiCoO2; Li[Ni0.1Co0.8Mn0.1]O2; and LiFePO4, in LiPF6 and LiBoB EC/DEC electrolytes

Accelerating rate calorimetry (ARC) has been used to compare the thermal stability of three different cathode materials, LiCoO2, Li[Ni0.1Co0.8Mn0.1]O-2, and LiFePO4, in EC/DEC solvent and in 1.0 M LiPF6 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 degreesC for LiCoO2, Li[Ni0.1Co0.8Mn0.1]O-2 and LiFePO4 (all charged to 4.2 V), respectively. In LiPF6 EC/DEC or LiBoB EC/DEC, Li[Ni0.1Co0.8Mn0.1]O-2 (0.2 mum diameter particles) shows higher stability than LiCoO2 (5 mum diameter particles). For both of these charged electrode materials, the reactivity with LiBoB EC/DEC is more severe than with LiPF6 EC/DEC. For charged LiFePO4, however, LiBoB EC/DEC presents higher thermal stability than LiPF6 EC/DEC. Since the reactivity of lithiated graphite with LiBoB-based electrolytes is less severe than with LiPF6-based electrolytes, the results in this paper suggest that graphite/LiBoB-based electrolyte/LiFePO4 Li-ion cells will be very abuse-tolerant. (C) 2003 Elsevier B.V. All rights reserved.