Correlation between dissolution behavior and electrochemical cycling performance for LiNi_1/3Co_1/3Mn_1/3O₂-based cells

LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) cathode has wide operation voltage window. Dissolution behavior of the NCM cathode at different charge states in 1 M LiPF₆/EC:DEC (1:1) electrolyte is determined with inductively coupled plasma (ICP) technique. Electrochemical cycling performance of the NCM-based cells in the electrolyte with different charge voltage limits is correlated with the dissolution of the active material. With increasing charge voltage limit, specific capacity and energy density of the electrode are significantly enhanced. However, cycle life of the cell based on NCM cathode and meso-carbon micro-bead (MCMB) anode is compromised at cutoff voltages >4.3 V. Mechanisms of the capacity decay for the full cell cycled with high charge voltage limit are investigated. Impedance rise of the graphite anode, which is resulted from deposition of the dissolved metal ions from the NCM cathode, is specified to be the main factor responsible for the cell failure. SEM observation and EDX analysis confirm the presence of Mn, Co, and Ni elements on the MCMB anode surface when the cell is cycled with high charge voltage limits.