Goodenough’s great contribution: The Li-ion battery
The 2019 Nobel prize winners, Goodenough, Whittingham, and Yoshino's breakthroughs powered the mobile electronics revolution and electric vehicle transition
Nobel laureate John Goodenough, who died at age 100 earlier this week, is widely described as the inventor of the lithium-ion (Li-ion) battery, which powers most of the electronic devices we use today. The story of the evolution of Li-ion batteries, however, does not begin or end with Goodenough. It has at least two other central figures, both of whom shared the Nobel Prize for Chemistry with Goodenough in 2019.
British-American chemist M Stanley Whittingham, now 82, created a lithium-based battery in the early 1970s. Goodenough, an American, developed his lithium-ion version in 1980; Japanese chemist Akira Yoshino, now 75, took it a step further in 1985.
Hunt and discovery
By the middle of the 20th century, the growth of the automobile industry had brought home the realisation that the world’s petroleum resources would not last forever. A need was felt, therefore, to develop electric vehicles, but these would need to be powered by batteries more efficiently than the ones in use at the time.
An oil giant, Exxon, decided to diversify its activities and recruited a number of researchers in the field of energy. Among them was Whittingham, who joined Exxon in 1972. At Stanford University, he worked on solid materials, in which were tiny spaces where charged ions can attach. This is called intercalation, a process that would prove key in Li-ion batteries.
At Exxon, Whittingham investigated a compound called tantalum disulphide, which can intercalate potassium ions. He found that considerable energy was involved in the interactions between the ions and the compound. Seeing the promise of new technology for energy storage, Whittingham developed a battery.
Tantalum is very heavy, so Whittingham replaced it with a lighter metal, titanium. Titanium disulphide formed the cathode, while lithium metal was the anode, where it would give up its electron easily. This was a rechargeable lithium-based battery, and Exxon promptly decided to develop a commercial version.
There were setbacks, however. When the battery was repeatedly charged, thin whiskers of lithium grew from the lithium electrode. When these reached the other electrode, the battery would short-circuit. “The fire brigade had to put out a number of fires and finally threatened to make the laboratory pay for the special chemicals used to extinguish lithium fires,” a post on the Nobel Prize website says.
Alterations were made, and the battery went into commercial production on a small scale, for solar-powered timepieces. Before it could be scaled up for electric vehicles, however, Exxon discontinued the work as it needed to make cutbacks amid a fall in oil prices.
This is where Goodenough stepped in.
A quick lesson on batteries
All batteries, whatever their configuration, work on the same principle. A battery cell has two electrodes, one designated as positive (cathode) and the other as negative (anode). The two are separated by a solution called an electrolyte. Chemical reactions between the electrodes and the electrolyte result in the release of various charged particles, including electrons whose flow creates an electric current.
In a Li-ion battery, which is rechargeable, the cathode is made of a lithium compound, such as lithium-cobalt oxide. The electrolyte, too, is usually a salt of lithium. The battery relies on the flow of positively charged lithium ions between the electrodes. These ions have been separated from their electrons, which, in turn, move towards the device it is powering.
The key advantage of Li-ion batteries is their high energy density. This refers to the amount of energy that it can store relative to its mass. Lithium is the lightest metal and, in fact, one of the lightest elements, allowing for lighter batteries. Lithium is also highly reactive, releasing its outermost electron readily.
Today, Li-ion batteries power most electronic devices from our mobiles to our laptops. Soon their use will become even more widespread as electric vehicles replace fuel-driven ones. In fact, electric vehicles were central to the events leading to the development of such batteries.
The modern version
Back to Goodenough.
The American scientist wanted to replace the metal sulphide in Whittingham’s cathode with a metal oxide which, he knew, should have a higher electric potential. His research group at the University of Oxford began a systematic search for a suitable metal oxide, one that would intercalate lithium ions, produce a high voltage, and not collapse when the ions were removed.
They uncovered these properties in lithium-cobalt oxide. An obvious difference between Whittingham’s and Goodenough’s models was that the former used lithium metal in the anode, while the latter used the oxide of lithium in the cathode, replacing titanium sulphide. At 4V, Goodenough’s battery proved almost twice as powerful as Whittingham’s.
In 1980, Goodenough published the discovery of this new cathode material, which had low weight and yet resulted in powerful batteries. The immediate impact was on wireless technology.
On the other end of the globe, in Japan, electronics companies were looking for light batteries for devices such as video cameras and computers. Yoshino, who was then with the Asahi Kasei Corporation, began working on developing a functional rechargeable battery; Goodenough’s lithium-cobalt oxide would be the cathode, and suitable carbon-based materials would be the anode.
Yoshino’s first commercially viable Li-ion battery used petroleum coke as the anode. It is stable, lightweight, and stored a high amount of energy. Also, the lithium ions are intercalated in the electrodes, which means they do not react with their surroundings.
The work of Goodenough, Whittingham and Yoshino is not the last word in battery technology. Since then, newer cathode materials (all lithium-based) have been identified for specific battery uses, and more discoveries are expected to come in the future. But it was the work of these three scientists that laid the ground for a wireless society, and a future possibly free of fossil fuels.
In an overview of their work on the Nobel Prize website in 2019, Prof Olof Ramström, a member of the Nobel Committee for Chemistry, wrote: “The discoveries of John B Goodenough, M Stanley Whittingham, and Akira Yoshino have arguably had a tremendous impact on our world. The lithium-ion battery thus has been an important part of the mobile electronics revolution, as well as the ongoing switch from vehicles powered by fossil fuels to electrically-powered transportation.”