Mechanistic Insight in the Function of Phosphite Additives for Protection of LiNi0.5Co0.2Mn0.3O2 Cathode in High Voltage Li-Ion Cells

• DOI: 10.1021/acsami.6b01544
• Publication Date: 2016-04-19T12:14:56Z
• Authors: Meinan He; Chi-Cheung Su; Cameron Peebles; Zhenxing Feng; Justin G. Connell; Chen Liao; Yan Wang; Ilya A. Shkrob; Zhengcheng Zhang
• Keywords: Trimethyl phosphate

Triethlylphosphite (TEP) and tris(2,2,2-trifluoroethyl) phosphite (TTFP) have been evaluated as electrolyte additives for high-voltage Li-ion battery cells using a Ni-rich layered cathode material LiNi0.5Co0.2Mn0.3O2 (NCM523) the conventional carbonate electrolyte. The repeated charge/discharge cycling containing 1 wt % of these was performed an NCM523/graphite full cell operated at voltage window from 3.0–4.6 V. During initial charge process, decompose on surface lower oxidation potential than baseline Impedance spectroscopy post-test analyses indicate formation protective coatings by both that prevent oxidative breakdown However, only TTFP demonstrate improved capacity retention Coulombic efficiency. For TEP, coating is also formed, but low Li+ ion mobility through interphase layer results in inferior performance. These observations are rationalized inhibition electrocatalytic centers present organophosphate deposits isolating difference between two phosphites clearly originates different properties resulting phosphate coatings, which may be conductivity such materials.