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Lithium batteries; intercalation compounds; electrochemical characterization; diffusion.

Layered LiNi_0.8Co_0.2O₂ crystallizing in 𝑅$\bar{3}$𝑚 space group is synthesized by decomposing the constituent metal–nitrate precursors. Oxidizing nature of metal nitrates stabilizes nickel in +3 oxidation state, enabling a high degree of cation ordering in the layered LiNi_0.8Co_0.2O₂. The powder sample characterized by XRD Rietveld refinement reveals < 2% Li–Ni site exchange in the layers. Scanning electron microscopic studies on the as-synthesized LiNi_0.8Co_0.2O₂ sample reflect well defined particles of cubic morphology with particle size ranging between 200 and 250 nm. Cyclic voltammograms suggest that LiNi_0.8Co_0.2O₂ undergoes phase transformation on first charge with resultant phase being completely reversible in subsequent cycles. The first-charge-cycle phase transition is further supported by impedance spectroscopy that shows substantial reduction in resistance during initial de-intercalation. Galvanostatic charge–discharge cycles reflect a firstdischarge capacity of 184 mAh g^-1 which is stabilized at 170 mAh g^-1 over 50 cycles.

M Sathiya¹ K Hemalatha¹ K Ramesha¹ A K Shukla² A S Prakash¹

1. CSIR – Central Electrochemical Research Institute – Chennai Unit, CSIR – Madras Complex, Chennai 600 113, India
2. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India

Published

December 2011

Manuscript received

28 March 2011

Manuscript revised

6 May 2011