Preparation and Characterization of Li_1.05[Ni_0.35Co_0.25Mn_0.4]O₂ as a Cathode Material for Rechargeable Lithium Cells

A lithium insertion material Li_1.05[Ni_0.35Co_0.25Mn_0.4]O₂ was synthesized by a sol-gel method. The structural and electrochemical properties of the sample were investigated using X-ray diffraction spectroscopy (XRD) and the galvanostatic charge-discharge method. Rietveld analysis of the XRD patterns shows this compound as having the α-NaFeO₂ structure (R3m; a = 2.8670(4) Å, and 14.279(3) Å in hexagonal setting). Li_1.05[Ni_0.35Co_0.25Mn_0.4]O₂ has a discharge capacity of 164 mAh/g in the voltage range 2.8-4.5 V vs Li/Li⁺, a stable capacity on cycling, and good rate capability in the current range 0.1-4.0 C. When the voltage range is increased to 2.8-4.8 V, it yields a capacity of 187 mAh/g, but exhibits a significant loss of capacity during cycling. The results indicate that this novel cathode material should be useful for lithium-ion cells because it has a lower cost than LiCoO₂-containing cells, and high performance.