The demand for Li-ion batteries (LIBs) for vehicles is increasing. However, LIBs use valuable rare metals, such as Co and Li, as well as environmentally toxic reagents. LIBs are also necessary to utilize for a long period and to recycle useful materials. The reduction, reuse, and recycle (3R) of spent LIBs is an important consideration in constructing a circular economy. In this paper, a flowsheet of the 3R of LIBs is proposed and methods to reduce the utilization of valuable rare metals and the amount of spent LIBs by remanufacturing used parts and design-ing new batteries considering the concept of 3R are described. Next, several technological processes for the reuse and recycling of LIBs are in-troduced. These technologies include discharge, sorting, crushing, binder removal, physical separation, and pyrometallurgical and hydrometal-lurgical processing. Each process, as well as the related physical, chemical, and biological treatments, are discussed. Finally, the problem of de-veloped technologies and future subjects for 3R of LIBs are described.