Electrochemical synthesis and properties of CoO2, the x=0 phase of the AxCoO2 systems (A=Li,Na)

Single-phase bulk samples of the exotic CoO2, the x=0 phase of the A(x)CoO(2) systems (A=Li,Na), were successfully synthesized through electrochemical deintercalation of Li from pristine LiCoO2 samples. The samples of pure CoO2 were found to be essentially oxygen stoichiometric and possess a hexagonal structure consisting of stacked triangular-lattice CoO2 layers only. The magnetism of CoO2 is featured with a temperature-independent susceptibility of the magnitude of 10(-3) emu/mol Oe, being essentially identical to that of a Li-doped phase, Li0.12CoO2. It is most likely that the CoO2 phase is a Pauli-paramagnetic metal with itinerant electrons. (C) 2008 American Institute of Physics.