Tag Archive for: Materials

My Topic of the Month – Sodium Ion Batteries (SIB)

These days, almost every child knows about lithium ion batteries (LIB). Many modern technologies that we are so dependent on today – smartphones, notebooks, etc. – would be unthinkable without these batteries. And they are thought to be indispensable for electro-powered mobility in the future. A vision that I do not share, but that is another issue…

Lithium has the lowest density among metals under standard conditions; thus, it is very light. Additionally, its ions are small, and it has an extremely negative redox potential, or in other words, it is extremely base. The latter enables high cell voltages of approximately 3 V (cf. nickel accumulators with a voltage of 1.2 to 1.5 V). The first results in high energy densities, i.e. a lot of energy per unit weight (Li-ion: 120-210 Wh/kg, Ni-batteries: 40-110 Wh/kg). These are the characteristics that enabled the realization of the small and durable batteries for smartphones and notebooks. Unfortunately, the base behavior also causes some problems, because lithium is extremely reactive, as some spectacular fires of electric cars of an American manufacturer demonstrate. Moreover, it does not occur in infinite quantities (it is less common than, e. g., copper, but more abundant than, e. g., lead), and its production is rather expensive.

Exchanging Lithium with Sodium

Should the development of electromobility develop as envisioned by ignorant dreamers, bottlenecks in the supply of lithium are possible. Therefore, more abundant and cheaper metals would be attractive. One metal being discussed as a substitute is sodium. This metal is chemically quite similar to lithium, but its ions are slightly larger, which increases problems associated with volume changes of the battery components in the course of charging and discharging. In addition, it is of course also heavier, which has a negative effect on the energy density. On the other hand, it occurs much more frequently than lithium (e. g. in the form of table salt) and is therefore cheaper to have. A review in Angewandte Chemie now addresses the chemical / physical / technical implications of replacing lithium with sodium. It has been shown that the battery chemistry often becomes more complex and some require solutions for well-resolved problems of lithium-ion batteries, but sodium ion batteries do not per se perform worse. SIB probably will not provide solutions for vehicle technology, but possibly for stationary energy storage, e. g. in connection with photovoltaics or wind turbines, where the weight of the battery is irrelevant. But even though research on SIB has achieved great progress in recent years, it is still in its infancy and a technical realization will take time.

Said paper, whose translation into Geman was done by me, by the way, can be found at:

German: http://onlinelibrary.wiley.com/doi/10.1002/ange.201703772/abstract

English: http://onlinelibrary.wiley.com/doi/10.1002/anie.201703772/abstract


Materials Chemistry 2017 in Liverpool

Every second year, the advances of materials chemistry are discussed in a fantastic conference of the Royal Chemical Society (RSC). Material is a broad term, and most issues in modern life need materials, be it clothes, mobile phones, energy devices or medicine. No big surprise therefore, that so many researchers of so many fields come together. 5 parallel sessions were offered each day, surrounded by plenary lectures and poster sessions. It was most difficult to make the right choices.
Whereas thermoelectric materials may seem completely uninteresting to the layman (who is probably wondering what I am talking about), novel materials for solar cells seem much important for our future energy supply. In fact, both techniques are interesting to solve our energy problems in future. Solar cells are self-explaining, but thermoelectrica convert thermal energy into electricy which is very interesting for process heat or exhaust gas heat in a car. And both have been the central point of multiple talks. The progresses made for perovskite and dye-sensitized solar cells are very interesting and one concept was presented that enables an indoor application. This means, you can produce energy while reading a book in lamp light!
Another interesting field are applications in the medical area, namely drug delivery, contrast agents, etc. A most inspiring method is the use of “bioink” which includes biomaterials such as cells or enzymes in a printable matrix. This can then be used for concepts like organ-on-a-chip, and, eventually, organ printing.
In the end, I have learned a lot, met very nice people and experienced a most exciting city – Liverpool – celebrating its musical and shiping heritage.