Heating is vital to the production of nearly all chemical products. It is not often thought about as extremely energy-intensive, but nearly 17% of all energy used in industry is used in heating processes. Additionally, energy costs for process heating can represent 2%-15% of a product's final cost.  There is a large variation between industries, and this is a very general statistic, but from this information, it is clear that reducing the amount of energy used to heat chemical products provides significant opportunity to reduce product cost as well as energy use. However, changing a process or material used in creating a chemical product can have far-reaching effects, and it is difficult to predict chemical compatibility without extensive experimentation. The following blog post is an extension of the experiment talked about in Blog #1, looking into solvent replacements to reduce the amount of heating needed to dry the electrolyte after printing.
Before making any mixtures, I did research on possible candidate chemicals that had the potential to be compatible with all of Imprints electrolyte compositions and be in the right boiling point range. From online research, I created a list of 66 chemicals with basic information like flashpoint, boiling point, compatibilities, and information from their safety sheets.
The whole list of 66 was unnecessary, but it was important due diligence to make sure suitable chemicals weren’t overlooked. Two already earmarked chemicals were then tested because they were by far the safest and had suitable boiling points.
Both of these chemicals were mixed with electrolyte binders to create “solubility curves”. The key information gathered in this step was the temperature at which the binder would mix, how long it would take the binder to mix, the range of binder wt.%s that could be mixed, and lastly the viscosities of the binder mixtures. Additional qualitative information was collected, like the ease and techniques of mixing, and how the smell may have changed throughout the mixing processes. There were 6 combinations of binders and solvents tested. Two had workable solubility curves.
Fig 1. Test Mixtures
One of these two mixtures seemed to show evidence of a side-reaction that caused discoloration and an extreme increase in viscosity and gelation.
Testing the different components individually, the discoloration and gelation happened due to one of the components and the amount of time heated. The far-left jar and far-right jar have roughly the same composition, but the far-right jar was held at a much lower temperature during mixing. The incompatible component is second from the furthest right. Time at high heat is part of the general mixing process, and the solution continued to discolor over the week following heat application. Since the gelation didn’t happen immediately after any part of the experiment, it was difficult to determine the cause for the reaction.
After addressing the discoloration issue, several different electrolyte iterations were made to tune the viscosity curve into a printable range. Where it wouldn’t stick in the printer, but its shape and thickness wouldn’t change much after printing. The other mechanical properties like stickiness and strength looked good after tuning the viscosity curve, so we moved onto printing. Below is a picture of the final mixture.
Fig 2. Pre-run mixture.
After checking and making sure the print onto the cathode was accurate, the drying was tested.
Fig 3. Drying test sheet
Fig 4. Drying Plot
The drying curve was much steeper and complete drying happened much faster for the new solvent system than the base solvent system! This means that significant energy is saved in the new electrolyte drying process.
I learned so much over the course of my summer internship at Imprint. The team was close-knit and flexible and allowed me to work on many different sorts of projects. I talked already about my 3 main projects. But I also helped write an SOP, performed a literature review of possible new UV-Curable electrolyte systems, and more. Each project had its own set of takeaways, like in the case of the SOP I learned how to use extremely precise language to describe different actions. The SOP was for a detailed and tedious procedure, so figuring out how to best describe it was a very interesting process. I learned most from my team members though.
In my time at Berkeley and LBNL, I’ve only seen one side of battery research. There are a lot of really interesting things studied in academia, but that's only one part of research in the battery industry. A lot of pragmatic research is being advanced by private companies. My manager Konstantin Tikhonov has had a lot of experience in this industry and I’ve enjoyed the opportunity to learn from him about the interesting ways the battery industry operates. One of the very unfortunate parts of this summer was that there was relatively less interaction with the other people at Imprint, but I am very grateful that I was able to work on-site for necessary R&D functions, and for the interactions I have had. The kindness of the Imprint team and their willingness to involve me in essential on-site ops gave me a unique internship experience to many people this summer.
Another big point of enjoyment was seeing how Christine, the company CEO, took tech she researched as a PhD student at Berkeley and turned it into a viable startup. Founding a company based on your PhD research is something I’ve heard a lot of grad students talk about being interested in. However, I’ve also heard a lot of grad students talk about how rare and difficult it is. Battery startups are unique and uniquely difficult in a lot of ways. They’re much more capital intensive than many other startups, and they also face really intense competition from the bigger players. It was really interesting to see how objectives were prioritized for a small and specialized team. I’ve already said it several times now, but at this point, I can’t help from gushing: I am truly so happy with my experience over the summer. I wasn’t given one single online project to work on the entire internship. I got the opportunity to do R&D lab research, data analysis and data science, battery testing, etc. I did all sorts of things I’ve been interested in learning.
This summer I was given the opportunity to develop unique research and work on my own projects. I’ve had wonderful guidance from the Imprint team and been able to learn and experience so much over the summer. I am extremely grateful to the Cal Energy Corps staff for giving me the opportunity to complete this internship, especially during the Covid-19 Shelter In Place when so many internships have been canceled.