ION TRAPPING AGENT, SEPARATOR FOR LITHIUM ION BATTERY, AND LITHIUM ION SECONDARY BATTERY

An ion trapping agent which is a layered phosphate compound that includes a proton as an ion exchange group, that supports lithium ions in excess of a theoretical exchange capacity of the layered phosphate compound, and that has no water of crystallization; and a separator for a lithium ion battery or a lithium ion secondary battery containing the ion trapping agent.