A method for making a vanadium pentoxide-based active material for a cathode of an alkali metal ion battery includes steps of: a) preparing an aqueous solution of a triazine derivative of Formula (I) wherein each R independently represents hydrogen or an amino group; and b) adding vanadium pentoxide to the aqueous solution of the triazine derivative under stirring, so as to permit condensation among hydrolyzed vanadium pentoxide along with self-assembly of the triazine derivatives to obtain a reaction solution containing the active material.