Hydrothermal synthesis and electrochemical performance studies of Al2O3-coated LiNi1/3Co1/3Mn1/3O2 for lithium-ion batteries

LiNi1/3Co1/3Mn1/3O2 nanocrystallites were synthesized by a one-step hydrothermal method, and uniform second particles were formed by a subsequent calcination process. X-ray diffraction results indicate that the as-synthesized material can be indexed by alpha-NaFeO2 layered structure with R-3 m space group. The results of Rietveld refinements show the I (003)/I (104) value of the material is 2.032, and the nanostructured material presents low cation mixing, small cell volume, and a consequent suppression of lattice strain. The rate performances of the as-synthesized material can be further improved by coating Al2O3. The discharging capacity of Al2O3-coated material reaches 154.4 mAh g(-1), and the capacity retention maintains 80.3 % after 50 cycles at 5 C in the voltage range of 2.5 to 4.5 V, while those of the bare one is only 139.0 mAh g(-1) and 71.6 %, respectively. The transmission electron microcopy observation shows no zigzag layer exists on the surface of particle after cycles for Al2O3-coated LiNi1/3Co1/3Mn1/3O2. Compared to bare LiNi1/3Co1/3Mn1/3O2, the de-intercalation potential difference before and after cycles of Al2O3-coated one is smaller. This indicates that Al2O3 coating can reduce the electrochemistry polarization in the electrode bulk.