Diammonium Hydrogen\nCitrate-Assisted Spray Pyrolysis\nSynthesis of Nanostructured LiCoPO<sub>4</sub> Microspheres as High-Voltage\nCathode Material for Lithium-Ion Batteries

Nanostructured LiCoPO<sub>4</sub> (LCP) microspheres\nwere successfully\nsynthesized by one-step spray pyrolysis, adding an appropriate amount\nof diammonium hydrogen citrate (DHC) additive to the precursor solution.\nComprehensive physical characterization confirmed that the obtained\nLCPs exhibited a desirable orthorhombic olivine structure with nanostructured\nmorphology and a significant increase in specific surface area. This\nenhancement was attributed to the dispersion effect due to the carboxyl\ngroup and the evolution of the ammonium group of DHC during the pyrolysis\nprocess. The resultant LCP delivered a high initial discharge capacity\nof 132 mA h g<sup>–1</sup> with 63.3% capacity retention (vs\n103 mA h g<sup>–1</sup> and 37.1% of bare-LCP) after 50 cycles\nat 0.1 C using the conventional electrolyte. Moreover, the electrochemical\nperformance showed additional enhancement when a fluorinated electrolyte\nwas introduced, resulting in initial and 50th discharge capacities\nof 141 and about 100 mA h g<sup>–1</sup>, respectively, at\n0.1 C.