Umicore

Centre National De La Recherche Scientifique

Charles Delacourt

Christian Masquelier

Philippe Poizot

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 LiFePOpowders with enhanced electrochemical properties. A direct precipitation process is described for preparing crystalline LiFePOpowder, comprising the steps of: &#x2014;providing a water-based mixture having at a pH between 6 and 10, containing a water-miscible boiling point elevation additive, and Li, Feand Pas precursor components; &#x2014;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.

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Lignières-Châtelain, France

Charles Delacourt