Science For Everyone: Welcome back to "Science For Everyone", ABP Live's weekly science column. Last week, we discussed the different stages in the life cycle of a star, and the difference between a supernova, nebula, neutron star and black hole, astronomical terms that are often mistaken for one another. John Goodenough, the 2019 Chemistry Nobel Laureate who pioneered the development of lithium-ion batteries, passed away last week at 100 years of age. Therefore, this week, we discuss the science behind lithium-ion batteries, and how Goodenough and other scientists developed it.
The 2019 Nobel Prize in Chemistry was jointly awarded to Goodenough, M Stanley Whittingham and Akira Yoshino for their contributions to the development of the lithium-ion battery. In 2019, Goodenough became the oldest person to win a Nobel Prize.
What are lithium-ion batteries?
A lithium-ion battery is the most powerful battery in the world. It is extremely important, more than one can imagine. Thanks to the invention of the rechargeable battery, the world is able to enjoy wireless electronic devices such as mobile phones and laptops.
Lithium-ion batteries also enable a fossil fuel-free world because they can power electric cars and are a form of renewable energy source.
Solar and wind energy can also be stored using lithium-ion batteries.
The development of the lithium-ion battery
Before we understand how lithium-ion batteries were developed, and the science behind their working, it is important to know why lithium is used in making the world's most powerful battery. Lithium is an element with three electrons and two electron shells. Two electrons are located in the inner shell, and the third electron is present in the outer shell. However, this electron is not tightly bound to the nucleus, and hence, the electron has a tendency to leave lithium's outermost shell and form a bond with a positively-charged ion.
Lithium's tendency to easily lose its outermost electron, also called the valence electron, makes it a highly reactive element. A positively-charged lithium ion is more stable than lithium in its pure form.
Therefore, it is difficult to find pure metallic lithium in nature. The element is mostly found in the form of salt. Since lithium is extremely unstable, and highly reactive with air, chemists store it in oil.
Lithium's reactivity is its weakness as well as its strength. Whittingham, Goodenough and Yoshino separately worked on lithium to leverage its strength.
Whittingham developed the world's first functional lithium battery in the 1970s, by taking advantage of the element's strong tendency to release its valence electron.
In the 1980s, Goodenough increased the battery's potential by two times by creating the right conditions for a more powerful and useful battery.
Yoshino, in 1985, successfully eliminated pure lithium from the battery, and instead, used lithium ions, which are more stable than pure lithium, and hence, safer. Yoshino's feat made it possible to use the lithium-ion battery for practical purposes.
Why was there a need for alternative energy sources?
The need for alternatives to oil arose in the mid-20th century because of the increase in the number of petrol-driven cars. Also, such cars contributed to air pollution through the emission of exhaust fumes. The companies also realised that oil is an exhaustible resource, and hence, there is an urgent need for an alternative source of energy.
However, electric vehicles and alternative energy sources require powerful batteries that can store large amounts of energy, and before the mid-20th century, there were only two types of rechargeable batteries in the market. One of them was the heavy lead battery that had been invented in 1859, and the other was the nickel-cadmium battery that was developed in the first half of the 20th century. Petrol-driven cars still use the heavy lead battery as the starter battery.
Since there was a threat of oil running out, Exxon, an oil giant, recruited researchers in the field of energy to conduct experiments and find renewable sources of energy that could serve as alternatives to oil. .
Whittingham’s lithium battery
Whittingham was one of those researchers. He started working on this project in 1972. Before this, he was at Stanford University, where he conducted research on solid materials with atom-sized spaces in which charged ions can attach. The phenomenon of charged ions attaching to atom-sized spaces in materials is called intercalation.
Whittingham and his colleagues investigated superconducting materials as part of their project at Exxon. One of these materials was tantalum disulphide. Since it can intercalate ions, the researchers added ions to the material to check how its conductivity was affected.
They unexpectedly observed that potassium ions affected the conductivity of tantalum disulphide. Whittingham found that tantalum disulphide had a very high energy density.
Energy-rich interactions occurred between the potassium ions and tantalum disulphide, resulting in a couple of volts. Since tantalum is a heavy element, he replaced it with titanium. This element had similar properties, and was much lighter than tantalum. The market was in search of light batteries, and therefore, a battery which used titanium disulphide for one of the electrodes was a better option than other batteries of that time.
Whittingham used titanium disulphide for the positively-charged electrode, or cathode, and lithium for the negatively-charged electrode, or anode. An anode should be such that the elements it is made up of easily release electrons towards the cathode.
This battery had great potential, was rechargeable, and worked at room temperature. According to the Nobel Prize Organisation, Whittingham went to Exxon's headquarters at New York to discuss the project, and after a meeting which lasted about 15 minutes, the management group decided to make a commercially viable battery using Whittingham's discovery.
A problem with the first rechargeable batteries was that they used solid materials in the electrodes, which broke down when they chemically reacted with the electrolyte, destroying the batteries in the process.
Meanwhile, Whittingham's lithium battery, which used lithium in the anode, allowed lithium ions to flow from that electrode to the titanium disulphide in the cathode, when the battery was used, and the ions were stored in the spaces in titanium disulphide due to intercalation. Lithium ions flowed back to the anode when the battery was charged.
However, several challenges came up while producing the battery. One of the drawbacks was that repeated charging of the lithium battery caused thin whiskers of lithium to grow from the lithium electrode, and when the pure lithium reached the other electrode, the battery short-circuited. This increased the chances of an explosion. Several times, fire erupted, and the fire brigade threatened to make the laboratory pay for the special chemicals used to extinguish lithium fires.
The researchers tried to make the battery safer by adding aluminium to the metallic lithium electrode and changing the electrolyte between the electrodes. In 1976, Whittingham announced his discovery, following which the battery began to be produced on a small scale for a Swiss clockmaker.
Now, the battery had to be scaled up in a way such that it could be used to power electric cars. However, the development work was stalled because the price of oil decreased dramatically in the early 1980s, causing Exxon to make cutbacks. Whittingham's work was licensed to three different companies.
Goodenough replaced titanium disulphide with lithium cobalt oxide
This is when Goodenough came into the picture. He worked at the Lincoln Laboratory at the Massachusetts Institute of Technology (MIT) for many years, and his research there contributed to the development of random access memory.
Goodenough was also among the people affected by the oil crisis in the 1970s, and offered to work for Exxon to find alternative energy sources, but was not allowed because the Lincoln Laboratory, which was funded by the US Air Force, did not permit all kinds of research. However, he was offered a position as professor of inorganic chemistry at Oxford University in Great Britain, and this marked his venture into the field of energy research.
Goodenough had studied about Whittingham's battery. Goodenough had thorough knowledge of the interior of matter, which led him to realise that the battery would work better if a metal oxide was used in the cathode instead of a metal sulphide. Therefore, it was important to find a metal oxide which not only produced a high voltage when intercalated with lithium ions, but also did not collapse on being charged, because lithium ions were removed.
After a lot of research, Goodenough's team came up with the idea of using lithium cobalt oxide as the cathode.
Whittingham's battery produced more than two volts, while Goodenough's battery was about twice as powerful, and generated four volts. The scientist released that while manufacturing batteries, it is not necessary to keep them charged, and instead, could be charged afterwards. Therefore, Goodenough discovered a new, energy-dense cathode material which resulted in powerful, high-capacity batteries despite its low weight. This was a stepping stone towards the wireless revolution.
In the West, interest in alternate sources of energy technology and the development of electric vehicles decreased because oil had become cheaper. However, in Japan, electronic companies were searching for lightweight, rechargeable batteries that could power innovative electronics such as video cameras, cordless telephones and computers, according to the Nobel Prize Organisation.
Yoshino developed the world’s first battery that used lithium ions instead of pure lithium
Yoshino from the Asahi Kasei Corporation understood this need, and decided to develop a functional rechargeable battery.
He used Goodenough's lithium cobalt oxide as the cathode, and tried using different carbon-based materials as the anode. Previous studies had found that lithium ions can be intercalated in the molecular layers of graphite, but the material gets corroded by electrolytes. Therefore, Yoshino chose petroleum-coke, a byproduct of the oil industry, and charged it with electrons, so that lithium ions were drawn toward it. Petroleum-coke charged with electrons allowed the intercalation of lithium ions. When the battery was turned on, the electrons and lithium ions flowed towards the cobalt oxide in the cathode. This battery not only produced four volts, but was also stable and lightweight.
It was the first commercially viable lithium-ion battery.
How the lithium-ion battery revolutionised the world
Since graphite was not used, the anode was not destroyed. Also, the intercalation capacity of petroleum-coke allowed electrons to flow back and forth between the electrodes when the battery was used or charged, for long periods. In this way, the lithium-ion battery allows the electrodes to remain stable because ions flow between the electrodes without reacting with the surroundings.
A major advantage of the lithium-ion battery is that it does not use pure lithium. Yoshino revolutionised the field of rechargeable batteries by developing a battery which does not use pure lithium, but lithium ions. In order to test the safety of the lithium-ion battery, he dropped a piece of iron on it. Since the battery is stable, it did not explode. However, when the experiment was repeated with a battery containing pure lithium, it exploded.
A major Japanese electronics company began selling the first lithium-ion batteries in 1991. This led to a revolution in electronics because mobile phones shrank, computers became portable, and tablets were developed.
Scientists have explored several other elements to build better batteries, but none succeeded in inventing a battery better than the lithium-ion battery.
In order to make the battery more environmentally friendly, Goodenough had replaced the cobalt oxide with iron phosphate.
Lithium-ion batteries have resulted in reduced emissions of greenhouse gases and particulates because they enable the development of cleaner and greener energy technologies and electric vehicles.
Therefore, Goodenough, Whittingham and Yoshino have benefited humanity in the best way imaginable by laying the foundation for a wireless and fossil fuel-free world.