For the last two weeks, I have learned a variety of techniques, such as NMR spectroscopy and analysis, synthesis of PIM-1, PIM membrane casting, PEIS (potentiometric electrochemical impedance), CP (chronopotentiometry), GCPL (galvanostatic cycling with potential limitation), and EC Lab.
I self-studied about the NMR through watching Khan Academy videos and perusing the “Spectrometric Identification of Organic Components” textbook, and realized it is important that I take the next Organic Chemistry class to further my understanding of chemistry. I am starting to envision my plan for the years ahead, whereby I apply for a Master’s program in chemistry to solidify my understanding of Chemistry and work in a job that entails interacting with people in the meanwhile, as I have realized I need to learn how to be socialize with people. I was also exposed to the career paths available post-grad. For example, instead of directly entering graduate school, one could apply for a SULI or ARE fellowship at LBNL, which allows undergraduates who have matriculated for a year to work in a startup. Two of my coworkers obtained work from the ARE fellowship. The last coworker applied for 2 SULI experiences after graduation and was hired by the startup from his second SULI experience.
Recently, I created a 60 g batch of polymer with intrinsic microporosity. This required mixing chemicals in the right amounts, purification twice to remove salt impurities, and drying in the vacuum oven to remove solvents. A small sample of the polymer was then solvated and cast into Teflon wells to create ion-selective membrane films for both full cells and symmetric cells. The thicknesses of the films were measured using a digital microcaliper which was so fun to use! This is because all one had to do was rotate a rough gauge and then a fine gauge until the microcaliper clicked, meaning the thickness of the film had been reached.
Before performing chemical synthesis with Max, I was taught about material integration by both Jon and Kira. The company’s focus is on creating ion-selective membranes. Kira taught me about the two methods they used to test the membrane. The first involved using a symmetric cell where the anode and cathode were the same. This cell tests the membrane for their resistance and how well they cycle. The second involved a full cell where the anode and cathode material differed. For example, for a lithium ion battery, the anode would be graphite and the cathode would be LiCOO2. They would run the cell on either the Biologic or the Neware cycling devices. The PEIS test and the CP test are applied on the symmetric cells. The GCPL test is applied on the full cells. The PEIS involves applying a sinusoidal potential or current of various frequencies and measuring the resistance of the system. The imaginary part of the resistance is plotted on the y axis, and the real part of the resistance is plotted on the x axis. The relevant impedance value is the real part. One would see semi circles. The diameter of the semicircle represents the interfacial impedance, meaning surface area of support (such as Celgard) and PIM. The left-most point of the semicircle represents the bulk resistance, meaning the resistance of the electrolyte and overall cell. The CP test involves applying an increasing current magnitude at certain time intervals with an alternate bias and measuring the emitted voltages as the cell is charged and discharged. One can calculate the ASR (area specific resistance) by multiplying the surface area by the resistance to obtain a value that gives a more spatially accurate value of resistance. GCPL involves setting a potential boundary that depends on the electrode of choice. This potential boundary is obtained by looking for the potential difference relative to the standard hydrogen electrode (SHE) or another reference electrode that is safe from side reactions. The current is specified and the potential is measured. The cycle time is determined by specified, applied current. For example, a capacity C/10 represents 10 hours to charge and 10 hours to discharge.
Thereafter, Kira taught me how to use the EC Lab to manipulate the data from these tests. It was definitely tedious to obtain the impedance, current, voltage, and resistance values, but they all help to inform the team on the progress of the membranes, which is our product of importance.
We have weekly meetings where we present our important results from the week. It is a time to troubleshoot challenges, obtain feedback, and enlighten team members about each other’s work.
Now, putting all business/professional language aside, I shall talk about the fun things I have done with my group! I am still trying to get along with my coworkers, as in trying to strike the balance between staying true to myself, while being open to their interests and conversations. I am trying to strike the conversation first, offer the hand to shake first, and being optimistic and well-rested for work. We have eaten at Thai Noodle and Platanos together! Salvadoran food with their plantains are muy rico!