CRYSTALLINE NANOMETRIC LIFEPO4

摘要

The present invention relates to lithium secondary batteries and more specifically to positive electrode materials operating at potentials greater than 2.8 V vs. Li⁺/Li in nonaqueous electrochemical cells. In particular, the invention relates to crystalline nanometric carbon- free olivine-type LiFePO₄ powders with enhanced electrochemical properties. A direct precipitation process is described for preparing crystalline LiFePO₄powder, comprising the steps of: - providing a water-based mixture having at a pH between 6 and 10, containing a water -miscible boiling point elevation additive, and Li^(I), Fe^(II) and P^(V) as precursor components; - heating said water-based mixture to a temperature less than or equal to its boiling point at atmospheric pressure, thereby precipitating crystalline LiFePO4 powder. An extremely fine 50 to 200 nm particle size is obtained, with a narrow distribution. The fine particle size accounts for excellent high-drain properties without applying any carbon coating. This allows for a significant increase in the active material content of the electrode. The narrow distribution facilitates the electrode manufacturing process and ensures a homogeneous current distribution within the battery.