Room Temperature Single Phase Li Insertion/Extraction Material for Use in Li-Based Battery

Abstract

The invention relates to active materials for the manufacture of Li-based batteries. A crystalline nanometric powdered material with formula Li x (M, M′)PO 4 , in particular Li x FePO 4 (0≦x≦1), is disclosed, exhibiting single phase Li insertion/extraction mechanism at room temperature when used as positive electrode material in Li-based batteries. Compared to current LiFePO 4 , the novel material results in smooth, sloping charge/discharge voltage curves, greatly simplifying the monitoring of the state of charge of the batteries. The coexistence of mixed valence states for Fe (i.e. Fe III VFe II ) is believed to increase the electronic conductivity in the room temperature single phase Li x FePO 4 material, compared to state of the art two-phase materials. This, together with the nanometric size of the particles and their sharp monomodal size distribution, contributes to the exceptional high-rate capability demonstrated in batteries.

1 . A Li insertion/extraction powdered material comprising particles of a crystalline material, the particles having a size distribution d50 of less than 50 nm, wherein during Li extraction (discharging) from said material and Li insertion (charging) in said material, the Li insertion/extraction powdered material remains a single phase material that is thermodynamically stable at 25° C. for any amount of Li present in said material. 
     
     
         2 . The material of  claim 1 , wherein d50 is between 10 and 50 nm. 
     
     
         3 . The material of  claim 1 , having a d99 of less than 300 nm. 
     
     
         4 . The material of  claim 1 , having a ratio (d90−d10)/d50 of less than 1.5. 
     
     
         5 . A secondary Li-based battery with an electrode comprising the Li insertion/extraction powdered material of  claim 1  as an active component wherein during discharging and charging of the active component, the contribution of said electrode to the EMF of the battery at 25° C. varies continuously with the state of charge by more than 0.05 V, for any amount of Li present in said material.