AlF3-coating to improve high voltage cycling performance of Li[Ni1/3Co1/3Mn1/3]O-2 cathode materials for lithium secondary batteries

Abstract

Li[Ni1/3Co1/3Mn1/3]O-2 powders were modified by coating their surface with amorphous AlF3 as a new coating material. The AlF3-coated Li[Ni1/3Co1/3Mn1/3]O-2 electrode showed improved cycle performance and rate capability under a high cutoff voltage range of 4.5 and 4.6 V. AC impedance results showed that the AlF3-coated Li[Ni1/3Co1/3Mn1/3]O-2 has stable charge transfer resistance (R-ct) regardless of the cycle number. Electron diffraction analysis also showed that no structural transition of the primary particles was observed for the AlF3-coated electrode. Electrochemical impedance spectroscopy and electron microscopy indicate that AlF3 coating plays an important role of stabilizing the interface between cathode and electrolyte.