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 degrees C and 50 degrees 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 degrees C. On the contrary, in LiPF6/PC + EC, significant capacity fading during charge-discharge was observed at 50 degrees 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 degrees 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 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.