NOVELTY - A crystalline lithium manganese phosphate powder for use as electrode material in a battery, having a particle size distribution with an average particle size d50 of less than 60 nm (preferably more than 20 nm).    USE - In preparing electrode mix for the manufacture of lithium insertion-type electrode, secondary lithium-batteries with non-aqueous liquid electrolyte, non-aqueous gel-like polymer electrolyte or non-aqueous dry polymer electrolyte (claimed).    ADVANTAGE - Use of the crystalline lithium manganese phosphate powder in battery allows reducing kinetic limitations due to Li ions transport within the particle and thus fast charge/fast discharge of the battery; facilitates manufacturing of the electrode. The narrow particle size distribution ensures a homogeneous current distribution within the battery. Use of limited amount of conductive coating in the composite powder allows maintaining energy density of the battery within practical ranges.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) preparing crystalline manganese phosphate (LiMnPO4) powder involves heating a water-based mixture having at a pH of 6-10, containing a dipolar aprotic additive, lithium (I), manganese (II) and phosphorus (V) as precursor components to a temperature between 60 degrees C and its boiling point, to precipitating crystalline LiMnPO4 powder;    (2) an electrode mix for secondary lithium-batteries with non-aqueous liquid electrolyte, or with non-aqueous gel-like polymer electrolyte, comprising LiMnPO4 (at least 80 wt.%), a reversible capacity of at least 80 (preferably at least 85)% of the theoretical capacity, when used as an active component in a cathode which is cycled between 2.5-4.5 V vs. lithium ion (Li+)/lithium (Li) at a discharge rate of 0.1 C at 25 degrees C; and    (3) an electrode mix for secondary lithium-batteries with non-aqueous dry polymer electrolyte, comprises LiMnPO4 (at least 70 wt.%), a reversible capacity of at least 80 (preferably at least 85)% of the theoretical capacity, when used as an active component in a cathode which is cycled between 2.5-4.5 V vs. Li+/Li at a discharge rate of 0.1 C at 25 degrees C.