NOVELTY - A lithium transition metal phosphate powder comprises lithium transition metal phosphate containing a composition containing lithium-metal phosphate complex (a) (I), and has a specific surface area of more than 15 m2/g. The solid solution lithium non-stoichiometry of lithium transition metal phosphate powder at room temperature is more than 2 mol%, which is higher than the solid solution lithium non-stoichiometry of lithium transition metal phosphate of same ideal composition prepared in bulk form or powder.    USE - Lithium transition metal phosphate powder is used in lithium storage battery for storing and delivering electrical energy (all claimed) in hybrid electric vehicle, cell phone, and laptop computer. Can also be used for battery-capacitor hybrid devices and high-rate electrochromic devices.    ADVANTAGE - The lithium transition metal phosphate powder has excellent electroconductivity, electromechanical stability, and intercalation rate, and provides battery with high charge and discharge rate capabilities.    DETAILED DESCRIPTION - A lithium transition metal phosphate powder comprises lithium transition metal phosphate containing a composition containing lithium-metal phosphate complex (a) of formula: Li1-xMPO4 (I), and has a specific surface area of more than 15 m2/g. The solid solution lithium non-stoichiometry of lithium transition metal phosphate powder at room temperature is more than 2 mol%, which is higher than the solid solution lithium non-stoichiometry of lithium transition metal phosphate of same ideal composition prepared in bulk form or powder having specific surface area of less than 10 m2/g. The solid solution contains lithium-metal phosphate complex (a) and lithium-metal phosphate complex (b) of formula: LiyFePO4 (II).    M=first row transition metal;    x=0-0.3;and    y=0.01-0.2.    INDEPENDENT CLAIMS are included for the following:    (1) partially lithiated iron phosphate composition, which contains the solid solution, and has a specific surface area of more than 15 m2/g and a single crystalline phase of olivine structure at room temperature;    (2) lithium transition metal phosphate compound, which exhibits a continuously decreasing charging current upon charging in a potentiostatic intermittent titration procedure at a constant overpotential of 50 mV higher than the open-circuit voltage of the cell, when using a lithium storage electrode in a standard electrochemical cell with lithium metal as counter electrode. The open-circuit voltage is measured after charging to 50% state of charge and holding for more than 12 hours;    (3) method for storing electrical energy, which involves charging a lithium storage battery comprising the transition metal phosphate compound at a current rate of more than 2 C which is an average current rate applied for a period of more than 5 seconds; and    (4) method for storing and delivering electrical energy, which involves charging the lithium storage battery comprising the lithium transition metal phosphate compound at current rate of more than 2 C and discharging at a rate of more than 2 C.