Microvoltammetry for cathode materials at elevated temperatures: electrochemical stability of single particles

The electrochemical stability of single particles of cathode materials (LiMn2O4, Li1.10Cr0.048Mn1.852O4, LiCoO2 and LiNi0.85Co0.15O2) was investigated by means of a microelectrode technique at 25°C and 50°C. The cycle stability was evaluated by multi-cyclic voltammetry. LiMn2O4 showed good cycle stability in LiClO4/propylene carbonate (PC)+ethylene carbonate (EC) and LiBF4/PC+EC solutions even at 50°C. On the contrary, in LiPF6/PC+EC, significant capacity fading during charge–discharge was observed at 50°C. The cycle stability of LiMn2O4 in the latter solution was improved by partial substitution of Mn by Cr and Li. Regarding LiCoO2, its cycle life in LiClO4/PC+EC at 50°C was unsatisfactory when the potential was scanned between 3.60 and 4.30 V. On the other hand, LiCoO2 retained 90% of its capacity when the potential scan was limited to 4.00 V. LiNi0.85Co0.15O2 showed similar trend at 50°C.