Lithium titanate powder for electrode of energy storage device, active material, and energy storage device using the same

A lithium titanate powder, comprising Li4Ti5O12 as a main component, wherein,

• when a volume surface diameter calculated from specific surface area determined by the BET method is represented as DBET, and when a crystallite diameter calculated from a half-peak width of the peak for (111) plane of Li4Ti5O12 by the Scherrer equation is represented as DX,
• DBET is 0.1 to 0.6 μm,
• DX is larger than 80 nm,
• DBET/DX (μm/μm), ratio of DBET to DX, is 3 or less,
• the lithium titanate powder comprises M, wherein M is at least one type of metal element selected from the group consisting of Mg, Zn, Al, Ga, and In, and
• in a cross-sectional analysis of a lithium titanate particle using a scanning transmission electron microscope, when atomic concentration of the M and atomic concentration of titanium measured by energy dispersive X-ray spectroscopy at the 5 nm inner position from a surface of the lithium titanate particle along a straight line drawn vertically to tangent of the lithium titanate particle surface are D1 (atm %) and Dti (atm %) respectively, and when atomic concentration of the M at 100 nm inner position from the surface of the lithium titanate particle along the straight line is D2 (atm %), following formulas (I) and (II) are satisfied:
• D1/D2≧5 (I)
• 0.02≦D1/Dti≦0.4 (II).