Facile synthesis of spherical nanostructured LiCoPO4 particles and its electrochemical characterization for lithium batteries

Spherical nanostructured LiCoPO₄ (SN-LiCoPO₄) particles were facilely synthesized by citric acid assisted spray pyrolysis at 600 °C in air atmosphere. The X-ray diffraction pattern of the synthesized LiCoPO₄ samples was indexed to olivine structure with a Pnma space group. Scanning electron microscopy analysis showed that the primary particle size of LiCoPO₄ reduced due to citric acid additive into a precursor solution. This fact might indicate that the citric acid additive restricted the agglomeration and growth of primary particles in a droplet to solid particle conversion process of spray pyrolysis synthesis. The first discharge capacity of SN-LiCoPO₄ electrode was 135 mAh g⁻¹ at 0.05 C in a voltage range of 2.0–5.1 V, corresponding to approximately 81% of its theoretical capacity (167 mAh g⁻¹). Moreover, the rate capability of SN-LiCoPO₄ electrode was superior to that of bare LiCoPO₄ electrode_, delivering a discharge capacity of 73 mAh g⁻¹ even at 0.5 C. Cyclic voltammetry and electrochemical impedance spectroscopy data demonstrated that the SN-LiCoPO₄ electrode had lower polarization and faster redox reaction kinetics for the charge and discharge processes. These results were attributed to the reduced primary particle sizes that shortened the lithium ion diffusion pathway during the charge and discharge processes for lithium batteries.