By summerstudent Alice Rodgers>
The annual global carbon dioxide emissions have increased by over three times since the 1960s, and in 2023 they were an estimated 36.8 billion tonnes.1 This is primarily due to the use of fossil fuels as an energy source and therefore in recent years it has become important to find renewable sources of energy. Since the 1990s lithium-ion batteries (LIBs) have become one of the most important ways of storing energy and have applications in everything from mobile phones to cars. However, lithium is a limited resource making the supply chain of LIBs at risk. Furthermore, there are ethical and environmental concerns surrounding the mining practices of cobalt and nickel. This is where sodium ion batteries (SIBs) come in.
Lithium and Sodium are both group 1 metals, and therefore they have very similar chemistries. Sodium is also the sixth most abundant element in the world and is found in the earth’s crust as well as in sea water. In addition to this, SIBs do not require cobalt and nickel.
My project:
In LIBs, graphite is commonly used for the anode as it can reversibly insert lithium ions between its layers. However, normally this intercalation is not possible for sodium ions, and this has been a major challenge for the development of SIBs. Nevertheless, when certain electrolytes, called glymes are used in the battery, it co-intercalates with the ions between the graphite layers, solving this issue.
During my project, I have been investigating whether changing the composition of the graphite electrode or calendaring (pressing the material at high temperatures) affects the co-intercalation process.
My project has involved fabricating electrode materials and then turning these into battery cells to cycle. When I started the project, I had never made a battery cell before or cycled one, and so I am very grateful to my supervisor who has taken a lot of time to show me how to do everything and explain the theory. It at least a week to gather all of the cycling data I need for each cell and so one of the main challenges of my project has been planning my time carefully in order to be as efficient as possible. During my labs at university, we are quite time restricted and only have sufficient time to collect a small quantity of data. However, cycling produces huge datasets and so it has been really important to learn how to handle it, what all the data actually means and which parts of it are important for my project.
I have really enjoyed my time at HZB and have learnt so much about batteries and different techniques to study them. It has been really exciting to have the opportunity to apply what I have been learning during my degree to practical applications
About the author: Alice is a third year MSci Chemistry student at Imperial College London. She is doing her project in Philipp Adelhelm’s group.
Reference 1: Fossil CO2 emissions at record high in 2023 (accessed 15 June 2024)