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William Brant

22 Jun, 12 tweets, 7 min read

@StructuralChem1

Ok lets take a look through the @StructuralChem1 lab! Development of new technologies begins with synthesis of new materials. This synthesis is carried out in many of the fumehoods that we have available

For synthesis of many ceramic materials we share a number of high temperature furnaces with other groups. Including tube furnaces for synthesis under various inert or reactive gases.

Additionally, a lot of synthetic work takes place inside our gloveboxes which are filled with Argon. Many chemicals we use for battery research (like Li metal) are air or moisture sensitive and so well maintained gloveboxes are a must!

Another two Ar boxes, one for sodium work and the PUB box (aka, Polymers Used in Batteries). These are also the boxes where we build our batteries before we test them. Speaking of testing batteries..

We have 100's of channels for connecting batteries. Most commonly we cycle pouch cells (shown in my schematic earlier and in the photo) but also coin (or button) cells and swagelok cells.

We also have high precision battery cycling equipment as well as ovens for testing batteries at elevated temperatures.

You may have noticed the radioactive box in the previous image :). This is where Fe-57 sources are kept after use in our Mössbauer spectrometer. This one was constructed in house many years ago. It could almost go into a museum if it wasn't so useful for us to this day.

Speaking of instruments, we have access to multiple characterisation methods for understanding the materials we make. Here we have our (old) XPS instrument, used for characterising surfaces and a TGA-MS for studying thermal behaviour.

Last but not least we have our diffractometers, including my personal favourite the Stoe diffractometer (shown with the green light) where I do all my diffraction experiments on batteries.

One thing that I always enjoy about visiting other labs are the personal touches that PhD students or postdocs add to the lab. Especially when they are in charge of running the gloveboxes :)

And finally, the most important piece of equipment of all. The coffee machine. Here we modified this one to show short clips from Futurama while your coffee is being made 🙃

So thats a brief run down of the main lab facilities! There is much more equipment that we have access to which is not directly a part of the Structural Chemistry group but we have access to (SEM, TEM etc)

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More from @RealSci_Nano

William Brant

@RealSci_Nano

23 Jun

@Altris_ab

The story of how @Altris_ab came to be and my involvement in PBA research is also a nice one. It was really a combination of the right people meeting at the right time and at the right place.

It began with Ronnie Mogensen, who was working on polymer electrolytes at the time and just needed a reliable positive electrode that was easy to make. He tried NaFePO4 which didn't always function. Then he turned to NaxFe[Fe(CN)6]. This always worked to a reasonable degree

He then stumbled upon a paper where the group of John Goodenough (Nobel laureate in chemistry for Li-ion #batteries) made rhombohedral Prussian white. pubs.acs.org/doi/10.1021/ja…

Read 22 tweets

William Brant

@RealSci_Nano

23 Jun

@Altris_ab

So how about Prussian blue analogues (PBAs) in batteries? In addition to @Altris_ab there are a number of other companies developing this class of compounds for energy storage applications. What makes them so attractive?

PBAs are commonly used as the positive electrode in beyond Li-ion batteries (sodium, potassium). They have an open structure leading to fast cation insertion. Additionally, due to the strong bonding of the cyanide ligand transition metals like iron have a decent voltage output.

Indeed, the performance metrics of PBAs, in particular the iron-based Na2Fe[Fe(CN)6], are quite similar to those of LiFePO4 (LFP). However, PBAs have the additional advantage of a simple and low cost synthesis making them very interesting to develop cheap sustainable batteries

Read 5 tweets

William Brant

@RealSci_Nano

23 Jun

Now to talk about Prussian blue analogues! To begin I have to tell the story behind them because it is one of my favourite pieces of chemical history. It is a tale of alchemists, theologians, famous paintings and about 200 years of wondering what Prussian blue was.

It all began in Berlin in 1704 with an enterprising dye maker by the name of Heinrich Diesbach. He was most interested in producing a red dye by the name of Cochineal red lake. The ingredients were iron sulphate, potash and crushed up beetles #alchemy

But Diesbach was running low on potash. Enter the scene one Johann Conrad Dippel. Master theologian, physician, alchemist. Dippel was captured by the allure of alchemy and like any good alchemist began his attempts at transmuting gold.

Read 13 tweets

William Brant

@RealSci_Nano

23 Jun

After our initial work on Li2MnO3, we discovered that there was a debate in the literature for a related compound. The more promising Li1.2Mn0.54Ni0.13Co0.13O2. It is the Li and Mn rich analogue to the Li[NiMnCo]O2 oxides used in commercial batteries.

What was this debate? It was whether the material existed as a solid solution or if it was an intergrowth or mix of Li2MnO3 and Li[NiMnCo]O2. Ie, if the composition crystallised as one or two phases. Here is an excerpt highlighting the debate pubs.acs.org/doi/10.1021/cm…

And here is what the two proposed models are. In the multi-phase model the hexagonal ordering occurs exclusively for Li and Mn whereas in the single phase Li in the transition metal layer can also have Ni and Co as nearest neighbours.

Read 10 tweets

William Brant

@RealSci_Nano

22 Jun

@ashok_menon12

We just got back from a group lunch/farewell to @ashok_menon12. I will use this opportunity to talk a little bit about what Ashok has done during his PhD. Ashok has worked with what is known as Li and Mn-rich layered oxides.

The Li and Mn rich oxide materials are interesting as they have the potential to store a lot more energy compared to regular battery cathodes.

The reason is due to the excess lithium which sits in the transition metal layer. The presence of Li in this layer creates local Li-O-Li bonding environments allowing of anionic redox due to unhybridised O orbitals. Below I show the regular LiCoO2 (yellow) and Li2MnO3 (purple).

Read 8 tweets

William Brant

@RealSci_Nano

22 Jun

But first, I think it is good to generally introduce what a Li or Na-ion #battery is built up from. While I am not an electrochemist by any stretch, I do work a lot with batteries and will mention them often.

A battery is comprised of four key components. Two electrodes connected to an external circuit: a positive (high potential) and a negative (lower potential) electrode. These are electrically isolated from each other by a separator soaked in electrolyte allowing ions to pass.

The electrons pass via an external circuit where they perform work during battery use. Both the positive and negative electrode materials need to accept both electrons and ions (such as Li+) reversibly. Designing materials which can do this is quite challenging.

Read 7 tweets

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