Binder for negative electrode of lithium ion secondary battery, manufacturing method thereof, and lithium ion secondary battery using the negative electrode binder

摘要

PROBLEM TO BE SOLVED: To provide a binder for a negative electrode of a lithium ion secondary battery, excellent in followability to a volumetric change at charging and discharging, and capable of improving load characteristics.SOLUTION: A polymer, containing an acid anhydride group formed by condensing carboxyl groups themselves in a molecule of a copolymer of an acrylic acid and an itaconic acid is used as a binder for a negative electrode. It becomes easier to trap a lithium ion before an electrolyte decomposition reaction happens at charging, because there are many carboxyl groups, which results in heightening the acidity, and the acidity never becomes excessively high because a predetermined amount of a carboxyl group is changed to an acid anhydride group.