Comparison of the chemical stability of the high energy density cathodes of lithium-ion batteries

With an objective to assess the chemical stabilities and their consequences in cell performance, the variations of oxygen content with lithium content (1−x) in chemically delithiated Li1−xCoO2, Li1−xNi0.85Co0.15O2, and Li1−xMn2O4 cathodes have been monitored with redox titrations. The Li1−xCoO2 system tends to lose oxygen from the lattice at deep lithium extraction, while the Li1−xNi0.85Co0.15O2 system does not lose oxygen at least for (1−x)>0.3. The chemical instability with a tendency to lose oxygen at deep lithium extraction could be the reason for the limited practical capacity of the Li1−xCoO2 system (140 mA h/g) compared to that realized with the Li1−xNi0.85Co0.15O2 system (180 mA h/g). The Li1−xMn2O4 spinel maintains an oxygen content of 4.0 without losing any oxygen for 0.15⩽(1−x)⩽1.