Temperature dependent electrochemical performance of LiNi 0.6 Co 0.2 Mn 0.2 O 2 coated with Li 2 ZrO 3 for Li-ion batteries

We tried to form an Li2ZrO3(LZO) coating layer on LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material to improve its thermal and electrochemical properties using a sol-gel technique. A homogeneous coating of LZO on NCM622 was obtained with different weight ratio (1.0, 2.0, and 4 wt.%) of LZO:NCM622. The surface morphology and elemental analysis of LZO@NCM622 were carried out by FE-SEM with EDS mapping. FE-TEM images showed that ~13 nm nanolayer of LZO was coated on the NCM622 surface (1 wt.% LZO@NCM622). The LZO coating improved the electrohcemical reaction kinetics and galvanostatic charge-discharge performance than bare NCM622. The LZO coating can protect the NCM622 surface from HF attack, and restricts the degradation of the active cathode material. The thermal properties of the NCM622 cathode at the high temperature of 60 °C were remarkably improved by the LZO coating layer because of a blocking in the direct contact between the cathode and organic electrolyte. In addition, galvanostatic intermittent titration technique (GITT) and potentiostatic intermittent titration technique (PITT) showed diffusion kinetics of Li-ion intercalation were maintained in 50 cycles at 1 wt.% LZO@NCM622. Finally, full-cell cycle performance using 1 wt.% LZO@NCM622 exhibited better cycle retention until 99% compared with 83% of pure NCM622. Given these results, LZO coating is widely considered to be a viable surface coating material for improving the excellent thermal and electrochemical properties of NCM622.