Cycle life improvement of ZrO2-coated spherical LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries

A modified synthesis process was developed based on co-precipitation method followed by spray drying process. In this process, a spherical shaped (Co1/3Ni1/3Mn1/3)(OH)2 precursor was synthesized by co-precipitation and pre-heated at 500 °C to form a high structural stability spinel (CoNiMn)O4 to maintain its shape for further processing. The spherical LiNi1/3Co1/3Mn1/3O2 was then prepared by spray drying process using spherical spinel (CoNiMn)O4. LiNi1/3Co1/3Mn1/3O2 powders were then modified by coating their surface with a uniform and nano-sized layer of ZrO2. The ZrO2-coated LiNi1/3Co1/3Mn1/3O2 material exhibited an improved rate capability and cycling stability under a high cut-off voltage of 4.5 V. X-ray diffraction (XRD) measurements revealed that the material had a well-ordered layered structure and Zr was not doped into the LiNi1/3Co1/3Mn1/3O2. Electrochemical impedance spectroscopy measurements showed that the coated material has stable cell resistance regardless of cycle number. The interrupt charging/discharging test indicated that the ZrO2 coating can suppress the polarization effects during the charging and discharging process. From these results, it is believed that the improved cycling performance of ZrO2-coated LiNi1/3Co1/3Mn1/3O2 is attributed to the ability of ZrO2 layer in preventing direct contact of the active material with the electrolyte resulting in a decrease of electrolyte decomposition reactions.