| abstract |
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 non-aqueous electrochemical cells. In particular, the invention relates to crystalline nanometric olivine-type LiFe 1-x M x PO 4 powder with M is Co and/or Mn, and 0<x<1, with small particle size and narrow particle size distribution. A direct precipitation process is described, comprising the steps of:—providing a water-based mixture having at a pH between 6 and 10, containing a dipolar aprotic additive, and Li (I) , Fe (II) , P (V) , and Co (II) and/or Mn (II) 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 LiFe 1-x M x PO 4 powder. An extremely fine particle size is obtained of about 80 nm for Mn and 275 nm for Co, both with a narrow distribution. The fine particle size is believed to accounts for excellent high-drain properties, while minimizing the need for conductive additives. The narrow distribution facilitates the electrode manufacturing process and ensures a homogeneous current distribution within the battery. |