The present invention provides a lithium-ion secondary battery whose power characteristic has been improved without widening a battery size. A cylindrical lithium-ion battery 20 accommodates a winding group 6 and a non-aqueous electrolytic solution within a battery container 7. The winding group 6 is structured by winding a positive electrode using lithium manganate (Li1+xMn2-xO4 or Li1+xMn2-x-yAlyO4) where an average particle diameter of primary particles is in a range of from 0.1 mu m to 2 mu m as a positive electrode active material and a negative electrode using amorphous carbon as a negative electrode active material via a separator. The reaction area of the positive electrode active material is optimized.
