Harry Hoster, Director and Co-Founder at Altelium, Director of Energy Lancaster and Professor of Physical Chemistry at Lancaster University explains how lithium ion battery inventors transported us to the modern age.
Lithium ion batteries (LIB) have had a huge impact on our society. They enabled modern portable electronics such as laptops and mobile phones. And they are now enabling clean and low-carbon transport, be it via electric cars or even flying taxis, and grid-scale storage of renewable energy.
Last year’s Nobel Prize in Chemistry was shared by Michael Stanley Whittingham, John Bannister Goodenough and Akira Yoshino. These three world-leading scientists deserve enormous credit for their contributions to LIB technology – and the decision to award more than one person reflects the fact that this technology is not the work of an individual genius, but rather is a history of systematic problem solving.
The way in which the batteries work explains the success of LIBs. A battery cell releases the energy from a chemical reaction in the form of electricity. If the internal reaction is a powerful one, which yields a high voltage. And if the materials in the cell don’t claim too much space and are not too heavy either, this gives it a high-energy density in terms of volume and weight.
Lithium is a very reactive element and the lightest metal on the periodic table, so it ticks both these boxes. This is why LIBs rapidly became a crucial part of electronics after their commercialisation in the early 1990s. Using lithium for electrochemical energy storage is a no-brainer on the back of an envelope. But that very reactivity that boosts the energy content also makes it very difficult to build a cell that can be safely kept in charged state, drained of its energy via electric current, and then returned to charged state just by feeding back that current.
In the 1970s Whittingham developed and later commercialised (via Exxon) the first lithium-based rechargeable battery. It relied on the compound titanium disulfide (TiS₂), which not only conducts electricity but can also host lithium in its crystal lattice, allowing us to draw a current from the battery.
However, one of the peculiarities of lithium is its tendency to form needles and dendrites (long branching structures) during the recharging process, causing internal short circuits, and this making the first generation of rechargeable lithium batteries inherently unsafe.
Goodenough discovered in the 1980s that lithium cobalt oxide was a better alternative to TiS₂ in a LIB. This material contains lithium but is less reactive with its environment and so easier to handle in the manufacturing process. Lithium cobalt oxide became the “father” material of most modern commercial LIBs and powered the first generations of cell phones.
Today, even cutting-edge high-energy electrodes – such as NMC 811 – that boost the range of the next generation of electric vehicles are essentially made from lithium cobalt oxide with the cobalt largely replaced by nickel and manganese in an otherwise similar crystal structure. Cobalt mines are rare and often associated with poor working conditions, so there’s an added advantage in being able to avoid using this metal.
In the late 1980s, Yoshino built the first commercially viable rechargeable lithium battery that used graphite instead of metallic lithium as the negative electrode. In this architecture, also used in modern cells, lithium travels between two different host structures: lithium cobalt oxide and graphite. This (in principle) eliminates metallic lithium and so you don’t get dendrite formation.
The latest challenge is to scale LIB mass-production from portable electronics to the automotive and energy markets, and this requires concerted global efforts.
The three deserving Nobel laureates must surely be happy to see the fruits of their work inspire research projects such as “JCESR”, “Batteries 2030+” and the Faraday Institution. This work has just begun.
As we look to the future beyond Covid-19 and a return to full economic activity, we must redouble our efforts to ensure that the potential of electric vehicles and renewable energy storage is delivered.
This article originally appeared in The Conversation.