Mixed metal olivine electrode materials for lithium ion batteries

A lithium secondary cell, comprising:

• a positive electrode in electronic contact with a positive electrode current collector, said current collector in electrical connection with an external circuit;
• a negative electrode in electronic contact with a negative electrode current collector, said current collector in electrical connection with an external circuit;
• a separator positioned between and in ionic contact with the cathode and the anode;
• and an electrolyte in ionic contact with the positive and negative electrodes;
• wherein
• the positive electrode comprises an electroactive material having two or more phases comprising lithium (Li), an electroactive metal (M), and phosphate (PO4), wherein the overall composition in the electroactive material has a ratio of Li:M ranging from greater than 1.1 to about 1.3, a ratio of (PO4):M ranging from about 1.0 to about 1.14, the ratios Li:M and (PO4):M are as compared to a stoichiometric composition for an olivine lithium transition metal phosphate (LiMPO4), M is one or more metals selected from the group consisting of Cr, Mn, Fe, Co, and Ni, and wherein the electroactive material comprises an olivine lithium electroactive metal phosphate phase and less than 10 wt % of a lithium-rich secondary phase or a lithium-rich and phosphate-rich secondary phase.