Determination of fluorine in lithium cobalt oxide samples by acid digestion-ion chromatography - A preliminary study

An analytical method combining sample pretreatment with ion chromatography (IC) was established for the determination of fluorine content in lithium cobalt oxide (LiCoO₂) samples. The samples were treated using a sulfuric acid-hydrogen peroxide system, and volatile fluorine-containing species were transferred by nitrogen purging, absorbed in alkaline solution, and finally determined as F^- by IC. Preliminary spike experiments and condition screening were conducted to evaluate the feasibility of the pretreatment procedure and to investigate the effects of sulfuric acid solution volume, sulfuric acid volume fraction, reaction time, and reaction temperature. The results showed that selection of pretreatment conditions should not be based solely on the F^- response in the absorption solution, but should also take the sample decomposition state into account. The final pretreatment conditions were determined as follows: sulfuric acid solution volume, 20.0 mL; sulfuric acid volume fraction, 60%; reaction time, 120 min; and reaction temperature, 190 °C. Under these conditions, the fluorine contents in five batches of LiCoO₂ samples were 0.25, 0.32, 0.26, 0.19, and 0.39 mg g^-1, respectively. These results indicate that the proposed method is preliminarily applicable to fluorine determination in LiCoO₂ samples.