In recent years, cordless electronic devices such as personal computers, cellular phones, and digital cameras have become very popular. Faster development of electric vehicles and fuel-cell cars is eagerly anticipated. For these devices and machines, one of the essential parts is the power source. As the power source, many types of batteries are used; batteries are usually composed of anode, cathode, and electrolyte. For the electrolyte, flammable liquids are generally used, which involves the issues of leakage and combustion of the liquids. If excellent solid electrolytes were developed and replaced the liquid electrolytes, these issues could be solved at once. In the twentieth century our daily life was drastically changed by the innovative development of many electronic devices; the key to the development was the invention of the transistor. In other words, the invention of the solid device transistor resulted in a kind of revolution in our daily life. The transistor is, of course, a solid device composed of semiconductors. The functions of transistors are controlled with the movement of electrons and holes in semiconductors.