ARC studies of the thermal stability of three different cathode materials: LiCoO_2; Li[Ni_(0.1)Co_(0.8)Mn_(0.1)]O_2; and LiFePO_4, in LiPF_6 and LiBoB EC/DEC electrolytes

摘要

Accelerating rate calorimetry (ARC) has been used to compare the thermal stability of three different cathode materials, LiCoO_2, Li[Ni_(0.1)Co_(0.8)Mn_(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 ℃ for LiCoO_2, Li[Ni_(0.1)Co_(0.8)Mn_(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_(0.1)Co_(0.8)Mn_(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.