Abstract
We have determined the electrochemical characteristics of the high voltage,
high capacity Li-ion battery cathode material Li[Li2/12Ni3/12Mn7/12]O2 prepared
using three different synthesis routes: sol-gel, hydroxide co-precipitation, and
carbonate co-precipitation. Each route leads to distinct morphologies and surface
areas while maintaining the same crystal structures. X-ray photoelectron
spectroscopy (XPS) measurements reveal differences in their surface chemistries
upon cycling, which correlate with voltage fading. Indeed, we observe the valence
state of Mn on the surface to decrease upon lithiation, and this reduction is
specifically correlated to discharging below 3.6V. Furthermore, the data shows a
correlation of the formation of Li2CO3 with Mn oxidation state from the
