COMPOSITE PARTICLE FOR ELECTROCHEMICAL DEVICE AND METHOD OF PRODUCING THE SAME, AND ELECTRODE FOR ELECTROCHEMICAL DEVICE AND ELECTROCHEMICAL DEVICE

A composite particle for an electrochemical device contains an electrode active material, a conductive material, a binder, and 0.1 parts by mass or more and 5 parts by mass or less of a thermally decomposable foaming agent per 100 parts by mass of the composite particle. When a cross section of the composite particle perpendicular to the long axis of the composite particle, and including the midpoint of the long axis is subjected to a map analysis using an electron beam microanalyzer, the value of the ratio of the integrated values of the detection intensities of carbon atoms contained outside and inside the range of the circle the center of which is coincides with the midpoint of the long axis and the diameter of which is one half of the length of the long axis is 4 or more and 15 or less.