The excellent daily utility of the lithium-ion battery is due to three inventors who were honored with the Nobel Prize for Chemistry last year. The British-American solid-state chemist Stanley Whittingham (photo, right) conducted experiments with tantalum sulfide and potassium for the multinational oil company Exxon in the 1970s. He discovered that layered sulfide takes up ions from a metal anode in its interstices. Experts call this process “intercalation.” It generates an electric voltage between the anode and the cathode. Whittingham subsequently replaced the tantalum sulfide in the cathode with the lighter substance titanium and used the less volatile element lithium instead of potassium as the ion donor in the anode. Whittingham’s first battery cell already generated two volts of electrical power, but it was highly explosive. After several charging cycles, the anode metal forms needle-like structures called dendrites. If they penetrate the cell and reach the cathode, they cause a short circuit. Back then, the local fire department had to rush to Whittingham’s laboratory so often that it threatened to send him a bill for its services. Not long after that, the American physicist John Goodenough (middle), who was working at the University of Oxford, took up Whittingham’s idea. He suspected that oxides could take up more ions than sulfides do — and he was proven right. His cathode, which was made of lithium cobalt oxide, promptly generated four volts instead of two. In addition, Goodenough was the first scientist to realize that the batteries did not have to be manufactured in the charged state; they could also be charged after they had been assembled. The last component of lithium-ion batteries, which was the key element of their safety, was contributed by the Japanese scientist Akira Yoshino (left). Unlike his forerunners, he was employed by a company that had its own electronics department, the Asahi Kasei Corporation in Japan. In the early 1980’s, the company was placing great hopes in portable consumer electronics. Sony had just recently scored a global success with the first Walkman. Yoshino developed an anode made of cobalt that smoothly intercalated the lithium ions. If no metallic lithium is present, the danger of dendrites is eliminated. Thus Yoshino had discovered the structural design of the lithium-ion battery that is still valid today. Sony launched the first one on the market in 1991. BERND KALTWASSER