(¹ Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008)
(² Graduate School of Chinese Academy of Sciences, Beijing 100039)
(³ Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190) Abstract LiBF₄ was prepared via aqueous solution process and its properties were examined by X-ray diffraction (XRD), IR, and thermogravimetry and differential thermogravimetry (TG-DTG). H₃BO₃, HF and Li₂CO₃ were used as starting materials to prepare LiBF₄ solution, followed by concentrating, crystallizing and dehydrating to obtain LiBF₄. The incomplete dehydration caused by traditional rapid heating was avoided through gradient heating dehydration. The obtained LiBF₄ crystal belongs to the hexagonal system with space group P3₁2₁, confirmed by its XRD spectrum which conformed to powder diffraction file (PDF) card 00-040-1431. The infrared absorption bands of the obtained LiBF₄ were observed, one band located at 1050 cm^－1, and splitted off two bands which are located at 1055 and 1038 cm^－1; the other band located at 650 cm^－1; attributed to ν₃ (as) vibration and δ₃ (s) vibration, respectively. In TG-DTG spectrum, a weak decomposition peak was observed at 341.31 K and a strong decomposition peak appeared at 516.48 K, the weight loss rate was 72.33%. The decomposition was regarded as the LiBF₄ decomposed into LiF and BF₃.

Key words: LiBF₄, electrolyte, lithium-ion battery, lithium salt, aqueous solution process