The present disclosure provides a lithium-ion secondary battery, having a case made from a conductive material; a cell received in the case; a cap assembly mounted to the case in a sealing way and equipped with electrode posts electrically connected to the cell, the electrode posts are a positive post and a negative electrode post; an electrolyte injected in the case; and at least one adapter member. Each adapter member is made from a conductive material and it has a connection portion fixedly connected to the corresponding one electrode post equipped to the cap assembly; and a contact portion extending downwardly into a space between the cell and the case from the connection portion at a lateral side of the cell. The contact portion contacts with the case to realize a short-circuit between the electrode posts when the case is crushed under an external force.