This year’s Nobel Prize in Chemistry recognises the work that led to the development of something that we all are familiar with, and depend very heavily upon – the rechargeable lithium-ion batteries that power most of the portable devices that we use, such as mobile phones.
The prize has been given jointly to Stanley Whittingham, now with Binghamton University, State University of New York; John B Goodenough, now with the University of Texas at Austin; and Akira Yoshino of Asahi Kasei Corporation. Whittingham developed the first functional lithium-ion battery in 1976, Goodenough brought in a major improvement in 1980, while Yoshino made the first practical-use lithium-ion battery in 1985. Commercially manufactured lithium-ion batteries, based on what Yoshino had developed, made their first appearance in 1991.
How batteries work
Batteries convert chemical energy into electricity. A battery comprises two electrodes, a positive cathode and a negative anode, which are separated by a liquid chemical, called electrolyte, which is capable of carrying charged particles. The two electrodes are connected through an electrical circuit. When the circuit is on, electrons travel from the negative anode towards the positive cathode, thus generating electric current, while positively charged ions move through the electrolyte.
Single-use batteries stop working once a balance is established between the electrical charges. In rechargeable batteries, an external power supply reverses the flow of electric charges, so that the battery can be used again.
STANLEY WHITTINGHAM: When Whittingham began working on batteries in the 1970s, rechargeable batteries were already available, but were bulky and inefficient. Whittingham worked with newer materials to make his battery lighter and more efficient. The older rechargeable batteries used to have solid materials in the electrodes which used to react with the electrolyte and damage the battery. Whittingham’s innovation came from the fact that he used the atom-sized spaces within the cathode material, titanium disulphide, to store the positive lithium ions. The choice of lithium was dictated by the fact that it let go of its electron quite easily and was also very light.
JOHN B GOODENOUGH: Whittingham’s battery worked at room temperature, making it practical, but was prone to short-circuits on repeated charging. An addition of aluminium, and a change of electrolyte, made it safer, but the big breakthrough was made by Goodenough who changed the cathode to a metal oxide instead of metal sulphide (titanium disulphide) that Whittingham had been using. Goodenough’s battery was almost twice as powerful as Whittingham’s.
AKIRA YOSHINO: Yoshino started working on Goodenough’s battery and tried using various lighter carbon-based materials as the anode in order to bring down the weight further. He got excellent results with petroleum coke, a byproduct of the oil industry. This battery was stable, lightweight, and as powerful as Goodenough’s.
Lithium-ion still best
Researchers have continued to look for other materials to make more efficient batteries, but so far none of these has succeeded in outperforming lithium-ion battery’s high capacity and voltage. The lithium-ion battery itself has, however, gone several modifications and improvements so that it is much more environment friendly than when it was first developed.