Technologies of lithium ion secondary batteries (LIB) were pioneered by Sony. Since the introduction of LIB on the market first in the world in 1991, the LIB has been applied to consumer products as diverse as cellular phones, video cameras, notebook computers, portable minidisk players and others. Years of assiduous efforts and researches to improve LIB performances enabled LIB to play a leading role in the portable secondary battery market. In this article, the past 10 years’ technological achievement is traced and future possibilities are discussed.