Electronic phase diagram of Li _xCoO ₂ revisited with potentiostatically deintercalated single crystals

Electronic phase diagram of Li _xCoO ₂ has been reexamined using potentiostatically de-intercalated single-crystal samples. Stable phases of x∼0.87, 0.72, 0.53, 0.50, 0.43, and 0.33 were found and isolated for physical property studies. A-type and chain-type antiferromagnetic orderings have been suggested from magnetic susceptibility measurement results in x∼0.87 and 0.50 below approximately 10 and 200 K, respectively, similar to those found in Na _xCoO ₂ system. There is no Li vacancy superlattice ordering observed at room temperature for the electronically stable phase Li _0.72CoO ₂ as revealed by synchrotron x-ray Laue diffraction. The peculiar magnetic anomaly near ∼175 K as often found in powder samples of x∼0.46-0.78 cannot be isolated through this single-crystal potentiostatic method, which supports the previously proposed explanation to be a surface stabilized phase of significant thermal hysteresis and aging character.