期刊
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
卷 167, 期 11, 页码 -出版社
ELECTROCHEMICAL SOC INC
DOI: 10.1149/1945-7111/ab9e7f
关键词
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资金
- BASF SE within its BASF SE Battery Research Network
Li- and Mn-rich layered oxides are a promising class of cathode active materials (CAMs) for future lithium-ion batteries. However, they suffer from fast capacity fading in standard EC-containing electrolytes, and therefore fluorinated alternatives, such as FEC, are required to improve their full-cell performance, which unfortunately increases the cost of the electrolyte. In this study, we will analyze the reasons for the poor cycling performance of EC-containing electrolytes with CAMs that release lattice oxygen at high degrees of delithiation, i.e., either of Li- and Mn-rich NCMs (LMRNCMs) during activation or of NCMs at high cutoff voltages. By on-line electrochemical mass spectrometry (OEMS), we will show that the stability of EC towardselectrochemicaloxidation is sufficient up to potentials of 4.7 V vs Li+/Li, but that itschemicalreaction with lattice oxygen released from CAMs negatively affects cycle-life. Furthermore, we will show that the use of EC-based electrolytes above the onset potential for oxygen release leads to a resistance build-up causing a rapid rollover fading, while FEC does not show such a dramatic impedance increase. Last, we will demonstrate that the lattice oxygen release from NCM-622 above 4.5 V vs Li+/Li requires the use of EC-free electrolytes for stable cycling.
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