Provided is a lithium ion battery having a long service life by improving an adhesion strength between a binder resin and a metal foil. A binder resin, which is a compound having a chemical structure that contains a polyvinylidene fluoride molecular chain, a six-membered ring such as a cyclohexane ring, and an end group selected from the group consisting of SiX3, SH, NH2, GeX3, and TiX3 (wherein X is a functional group that undergoes a condensation reaction), wherein the six-membered ring is disposed in a region between the polyvinylidene fluoride molecular chain and the end group, is mixed with an active material and applied to a metal foil, and the binder resin is chemically bonded to metal atoms such as copper atoms on the surface of the metal foil.