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Summer 2012 Blog - Sergio Hidalgo

Sergio Hidalgo is spending twelve weeks at the National University of Singapore.

August 10, 2012

Before a final meeting with Professor Balaya, an explosion prevents anyone from entering the engineering building. And thus, the internship ends in a blazing glory!

July 21, 2012

hidalgo_2The difference in performance between the sample containing a rutile titanium dioxide impurity and the pure sample are somewhat puzzling. Although it was not surprising that the impure sodium titanate would result with imperfect performance, the charge/discharge capacity was twice that of the pure sample. However, the results for the pure sample for cycling were better than what were expecting. We achieved very stable charging and discharging. With only 20 cycles in the testing, we hold experience about a 1% drop in capacity. However, there remains an issue with both the impure and the pure sample: the large capacity drop after the first cycle. This normal happens because of the formation of the solid electrolyte interface, which only occurs in the first cycle. The formation is absolutely necessary for stable performance of the battery, and a drop in capacity is always expected, as part of the anode is no longer capable of storing charge. However, this brings us to the open-ended part of the research: minimizing the initial capacity drop.

This week ended with a tea session with the students brought in from the International Relations Office to give feedback on the programs that we are respectively in, and a discussion amongst all of us and our respective professors/supervisors.


June 27, 2012

hidalgo_1Researching sodium titanate as an anode material has gone surprisingly well! On the first attempt at synthesizing this material with the new techniques that they have developed for other materials here, we easily acquire a batch that is in phase, meaning it has a negligible amount of impurities within the material. The only difficulty arose in determining the temperature in which we had to sinter the precursors. The x-ray diffraction measurements helped determined what temperature gave us the lowest amount of impurities. The next step will be to use this material in a half-cell to characterize its performance, which should take some weeks. In addition to using the sample that was in phase, we will be comparing the performance to the other samples sintered at lower temperatures, which contain significant levels of the impurity rutile titanium dioxide. The reason for this is to understand the effects of the impurity on the anode material. Impurities do not necessarily hinder the performance of a substance: it can help with maintaining the stability of the material as it undergoes structural changes during charging and discharging. Moreover, titanium dioxide is itself a suitable candidate as an anode material. The reason for creating alternative methods for synthesizing sodium titanates is to increase the surface of the pores. By making the material mesoporous, we increase the number of sites that sodium ions can intercalate to, increasing battery capacity.

Moreover, during this time, Professor Balaya has worked hard to get press for the work that his group does, and I glad to be participating in the research done.

In additional to all the work that Akshay and I have been doing in the Alternative Energy Sources Laboratory at the National University of Singapore, we have met a large number of students from the University of Toronto. Their group arrived earlier than us at NUS, and they have adopted us as one of their own.

June 1, 2012

Never having traveled on my own, I had no idea what to expect. The only place outside of the US I have been is Guatemala; however, that was with my parents, so I never had to deal with any of the planning. Everything went well in LAX, as my family sent me on my way to Singapore.

As I attempted to sleep on the plane, I go over the reactions of friends and family who have heard about my internship in Singapore. Most are surprised to hear hat I’ll be so far away for the summer. The biggest surprise was the reaction from my mother, who could only ask, “Aren’t there jobs here in the United States?” Laughing at the rhetorical question, I reply, “It’s only three months! I’ll be back before you know it!”

A few moments after landing, I couldn’t help but wonder, almost paradoxically, why doesn’t it feel different being here in Singapore? Even now, having been here for two weeks, the only thing that strikes me are the similarities between the US and Singapore. The small differences in culture aren’t enough to raise an eyebrow. Perhaps, it is because of my experience growing up in Koreatown, a melting pot of Los Angeles. Or perhaps, it is because how modern the country of Singapore is. Maybe there is no difference at all.

The week beings with introductions with those I’ll be working with. I finally meet Dr. Palani Balaya, the professor “well convinced that [I] could take up some of the challenging projects that [the group carries] out in the field of energy storage at the moment.” I also meet with Ashish Rudola, the graduate student that I’ll be working with during this summer.

The anode material that I’ll be working with hasn’t been fully decided upon yet, but the other UC Berkeley student, Akshay Shrivastava, and I begin to learn about the processes used in their laboratory for battery fabrication.

But why sodium-ion batteries? Isn’t everyone usually talking about lithium-ion batteries? The purpose of researching materials for sodium-ion batteries lies in the fact that there is a much more limited amount of usable lithium for battery applications compared to sodium. Moreover, the use of sodium-ion batteries allows for higher power density compared to lithium-ion batteries, which makes it ideal for storing renewable energy, as energy density is not as much a concern when space can be allocated for increasing energy storage.

The internship has only begun. I am eager to see what the remaining ten weeks bring!

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