The present disclosure is intended to design a secondary battery with improved boosting charge performance by estimating reaction in the thickness-wise direction of the electrode, and provides a method or estimating reaction of a secondary battery including (a) preparing a battery cell having a structure of first electrode/separator/reference electrode/separator/second electrode, wherein the second electrode has a structure of upper layer/porous film/lower layer, (b) setting a charging condition to estimate reaction of the battery cell, (c) measuring voltage and current of each of the upper layer, the lower layer and the battery cell while the set charging condition is reached, (d) after the charging condition, measuring an open-circuit voltage of the upper layer, the lower layer and the battery cell, and (e) comparatively analyzing a capacity obtained using the measured current with the measured open-circuit voltage, and a battery cell used for the same.