Ion scavenger for lithium ion secondary cell, liquid electrolyte, separator, and lithium ion secondary cell

The present invention provides an ion scavenger for a lithium ion secondary cell with which it is possible to extend the service life of a lithium ion secondary cell, substantially without affecting a liquid electrolyte due to being imparted with a neutral liquid, the ion scavenger highly selectively scavenging impure metal ions generated from the structural components of the lithium ion secondary cell and minimizing short-circuiting caused by such impurities, and having a high adsorption capacity per unit mass. This ion scavenger for a lithium ion secondary cell contains at least one phosphate selected from (A) α-zirconium phosphate having a specific composition in which ion-exchange groups within a prescribed range are substituted by lithium ions, (B) α-titanium phosphate having a specific composition in which ion-exchange groups within a prescribed range are substituted by lithium ions, and (C) aluminum dihydrogen tripolyphosphate having a specific composition in which ion-exchange groups within a prescribed range are substituted by lithium ions.