Hiroyuki Ohno

A zwitterion is a neutral compound that has both a cation and an anion in the same molecule. Quaternary ammonium cations are frequently used for zwitterions. Zwitterions with quaternary ammonium cations are also common in biological molecules, such as phospholipids, which are the main components of cell membranes. Chemically, they have broad applicability because they are dielectric, non‐volatile, and highly polar compounds with a large dipole moment. In addition, after salt addition, ion exchange does not occur in the presence of zwitterions. Owing to these characteristics, zwitterions have been applied as novel electrolyte materials targeting high ionic conductivity. In this review, application of zwitterions and their polymers for Li‐ion batteries is addressed.