To provide a lithium manganese composite oxide capable of improving the initial discharge capacity of secondary batteries by removing more Li ions than the conventional lithium manganese composite oxide does when used in the positive electrode used for secondary batteries. The first and second supports are connected to different ones of the side surfaces of the rim, and the spinner assembly is rotatably mounted between the first and second supports, such that the first, second, third, and fourth axes are aligned. The shield is pivotally secured to the winged needle assembly to enable pivotal movement from a position away from the needle to a position enclosing the needle.