Electrolyte Reactions with the Surface of High Voltage LiNi[sub 0.5]Mn[sub 1.5]O[sub 4] Cathodes for Lithium-Ion Batteries

The reaction of an electrolyte (1 M in ethylene carbonate/dimethyl carbonate/diethyl carbonate, 1:1:1) with the surface of at various voltages (4.0–5.3 V vs Li) was investigated. Coin cells stored at low voltage (4.0–4.5 V vs Li) show low residual current, and ex situ analysis of the surface by X-ray photoelectron spectroscopy (XPS) and IR spectroscopy suggests low concentrations of electrolyte decomposition products. Coin cells stored at high voltage (4.7–5.3 V vs Li) show increased residual current, and ex situ analysis of the cathode surface by XPS and IR supports the presence of poly(ethylenecarbonate).