Lithium-ion batteries power our modern way of life. Using ionic battery technology, they store electrical energy, allowing our devices to come with us wherever we go. They can also store electricity from renewable sources, making them a viable alternative to fossil fuels.
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Professor John B. Goodenough from the Cockrell School of Engineering at The University of Texas at Austin, along with M. Stanley Whittingham and Akira Yoshino, was awarded the 2019 Nobel Prize in Chemistry for his pioneering work on lithium-ion batteries. In the late 1970s, he developed the Li cathode that could allow charge to be stored more safely, and at a higher density, within the cell. Professor Goodenough has continued to work in this field, with a paper using Bruker’s PeakForce QNM technology published last year bringing further improvements to battery research1.
The Importance of Batteries
Batteries play an important role in technologies including consumer electronics, transportation, and renewable energy. Mobile phones, laptop computers, tablets, and electric cars are all designed to be used whenever and wherever they are needed, and therefore require efficient, high density, rechargeable batteries.
Renewable energy also relies on batteries. Wind and solar power are often inconsistent due to changing weather conditions. Fully exploiting their capabilities means that power must be stored at times when the supply outpaces the demand so that it is readily available when usage increases.
There is a constant drive for smaller, lighter batteries that store more energy and recharge faster. Designing better batteries requires a detailed understanding of how they work, the role of each material within a battery, and how they can be improved.
Research has shown that the interfaces between battery materials are crucial to battery function. Fully understanding these interfaces requires reliable and accurate nanoscale techniques. Atomic force microscopy is the leading technique for analyzing battery materials, thanks to its unique ability to provide a quantitative characterization of nanoscale interfaces.
Early Devices
Storing energy was the issue that John B. Goodenough was tasked with solving when he was working for the Ford motor company during the oil crisis of 19722. US motorists were queuing at petrol pumps, and Ford wanted alternative materials that they could use in the battery of a mass-produced electric car. At the time Goodenough was focused on sodium ion conductivity and energy storage, but he would soon identify a more promising candidate.
After leaving Ford, he took up a position as the lead at the University of Oxford’s inorganic chemistry lab. His interest was piqued by a paper written by Stanley Whittingham and published in Nature that described a battery composed of a lithium anode and a titanium disulfide cathode.
Although it had a high energy density and was rechargeable, there was a major drawback due to the formation of lithium dendrites across the electrolyte when the battery had experienced a few charge cycles3. The dendrites shorted the cell and caused the entire setup to explode.
Goodenough’s Battery Solution
Goodenough's great discovery was to use lithium cobalt oxide as the cathode instead of Li metal. This meant that the battery was still rechargeable with a high density of stored energy, but avoided the explosive results that had plagued the previous version.
Along with Stanley Whittingham who laid the initial groundwork, and Akira Yoshino who created the first commercially viable lithium-ion battery, in 2019 Goodenough was awarded the Nobel Prize in Chemistry. This is the highest scientific honor one can be presented with and reflects how important this technology has proven to be.
Ongoing Research & Development
Battery research and development has come a long way. Goodenough’s early accomplishments designing lithium-ion batteries with improved lifetime and energy density compared to their predecessors paved the way for a flood of improvements in battery materials and technologies, but there is still a lot to do. There is an ever-increasing global demand for better batteries, with better storage capabilities, increased lifetime, improved energy density, and lower cost.
At 97 years of age, Goodenough continues to research multiple strands of materials science, as well as advancing the field of lithium-ion battery storage. As recently as last year he co-authored a paper that characterized and compared the solid-electrolyte interphase (SEI) layer on a composite Li anode that contained a protective layer of lithium fluoride (LiF) and graphite fluoride (GF)1. This work used Atomic Force Microscopy, specifically Bruker’s PeakForce QNM (Quantitative Nanoscale Mechanical) mode to conduct high-resolution, quantitative characterization of the topographical and nanomechanical properties of the battery anode.
Peakforce QNM utilizes PeakForce Tapping technology to map and distinguish mechanical properties of a material, such as elastic modulus4, with nanoscale resolution. The technique has been successfully used to study a wide range of other delicate materials with nanoscale characteristics including polymers, nanoparticles, living mammalian cells, and tissues.
Goodenough and his colleagues used Peakforce QNM to visualize how the GF–LiF–Li anodes inhibited the growth of the Li dendrites. High-resolution topography images of a GF–LiF–Li and a bare Li anode were collected, and comparison showed the GF–LiF–Li surface to be smooth with a uniform coating, compared to the rough and pitted surface of the bare Li anode.
Correlating elastic modulus maps showed how the modulus varies between the two anodes, with the decreased modulus of the GF-LiF layer suggesting that it is more flexible and not easily broken as the SEI layer that develops on bare Li metal.
Through the use of PeakForce QNM, researchers gained valuable insight into the mechanism by which the GF-LiF layer is able to stabilize the interface of the working Li anode and prevent dendrite formation. This development of a dendrite-free lithium anode is a critical step towards the production of a new battery that could be lower in cost, charge faster, have a longer life cycle and a greater density of stored electric power. It also demonstrates how fundamentally important the research carried out by Professor Goodenough is, as he continues to influence and guide a technology that he created over 40 years ago.
References and Further Reading
- Shen, X. et al. Lithium anode stable in air for low-cost fabrication of a dendrite-free lithium battery. Nat. Commun. 10, (2019).
- Perks, B. Goodenough Rules. Chemistry World Available at: https://www.chemistryworld.com/features/goodenough-rules/8099.article.
- Masaki Yoshio, H. N. Lithium-Ion Batteries, Chapter 2. Lithium-Ion Batteries (2009). doi:10.1007/978-0-387-34445-4
- Bruker. PeakForce QNM. Available at: https://www.bruker.com/products/surface-and-dimensional-analysis/atomic-force-microscopes/modes/modes/imaging-modes/peakforce-qnm.html