Electrochemical in-Situ Raman Spectroscopic Studies of Highly-Cycled Li(Ni/Co/Mn)O 2 Cathode Cells

1. Introduction Raman spectroscopy is a novel non-destructive, non-contact method to study lithium ion battery (LIB) electrode surfaces [1]. We have developed and constructed an original optical LIB cell, which allows for reproducible Raman spectroscopic measurement under electrochemical control. The capability of this EC in-situ Raman cell for spectro-electrochemical and distribution spatial mapping measurements were reported previously [2], where information of Li ion intercalation behavior could be effectively studied for a chosen graphite anode particle. In this study, we have applied the electrochemical in-situ Raman measurement to study the high-capacitance 18650 type LIB cell that was highly-cycled and compared to those of the initially cycled one. 2. Method A LIB coin-cell was constructed with commercially available 18650 type Li(Co 0.3 Ni 0.3 Mn 0.3 )O 2 ternary oxide cathode and graphite anode. LIB cells were highly-cycled (500 cycles) at rate of 1C and capacity found to deteriorate to 74% of the initial value. For EC in-situ Raman measurements, the cathode was retrieved from the coin-cell and a LIB half-cell was assembled in a dry and inert Ar atmosphere (