Structure and electrochemical properties of multiple metal oxide nanoparticles as cathodes of lithium batteries

Multiple metal oxide nanoparticles, which are the solid solutions of various kinds of divalent and trivalent metal ion oxides containing a certain amount of cation vacancy, with a uniform particle size less than 20 nm and huge surface area were synthesized by the calcination of layered double hydroxide (LDH) precursors, and their structures were analyzed using XRD and EXAFS. The electrochemical properties of these metal oxide nanoparticles as the cathode electrodes of Li batteries were also investigated by charge-discharge tests and AC-impedance measurements. Among the three kinds of multiple metal oxide nanoparticles prepared in this paper, Ni-V oxide showed the highest charge-discharge capacity of 327 mA h g(-1) in the voltage range 4.2-1.0 V. According to the results of ex situ XRD, ex situ EXAFS and AC-impedance measurements, we have concluded that the discharge-charge process proceeds in the two stage reactions of (i) Li+ intercalation-deintercalation to the cation vacancy and (ii) formation and decomposition of new surface phase reversibility without significant structural change.