Recently, rechargeable batteries with high energy density are in great demand as energy sources for various purposes, e.g. handy electronic machines, zero emission electric vehicles, load leveling in electric power. Lithium secondary batteries are the most promising to fulfill such needs because of their intrinsic discharge voltage with relatively light weight. In 1991, the first lithium secondary battery of high quality and revolutionary concept was put on the market by Sony. In the commercial battery, called the “lithium ion battery,” lithium ions swing between the anode and the cathode through an organic liquid elctrolyte dissolving an inorganic lithium salt, like a rocking chair rocking from side to side. The principal concept is based on the intercalation reaction and is rather different from conventional secondary batteries which are based on chemical reactions. The past excellent results of fundamental research and technology have been used to develop the lithium ion battery. The needs of the time, however, do not stop and require further quality and better cost-performance for this type of battery, and given this favorable environment excellent fundamental concepts, idea and technology regarding electrodes and electrolytes in the battery are being published in articles and proceedings. However, the description is not always sufficient for complete understanding due to limited space.