Peng Bai

 

Math, Science & History

EES paper published online and attracted media reports

Our lithium dendrite paper appears online on 9/1 with an MIT News story. For the general audience, there two most important discoveries/implications: 1) The "dendrite" (quotation denotes previous understanding) we saw in battery is different from the existing concept of metal dendrite derived from copper/zinc dendrite, which only occur beyond diffusion limitation. Batteries are designed to work under the limiting current, so that the "dendrites" should be called whiskers, as they indeed grow like human whiskers from the root. Only if the applied current is larger than the intrinsic limiting current, would the real fractal lithium dendrites, similar to copper dendrites, start to form at Sand's time and grow at the tips. 2) The root-growing lithium whiskers can be blocked by nanoporous ceramic separators, which therefore should be used more widely than they are right now. Battery management systems should monitor and analyze the transport proerties of the battery to avoid dendritic growth by avoiding currents larger than the decreasing intrinsic limiting current due to battery degradation.

My first paper on Lithium dendrites was accepted by Energy and Environmental Science

The results are very surprising and interesting. My best work. More details will be posted soon.

A co-authored paper was published in Science

The amazing in situ liquid TEM cell reveals the lithium intercalation dynamics at nanoscale, which verified the predictions we made 5 years ago.

Paper on energy-dense Li-Bromine system was finally accepted

In this paper we discussed the possible ways to fully exploit the very high specific energy of Li-Br chemistry. We found that the commercially available water-stable solid electrolyte degrades fairly rapidly in highly concentrated bromine-bromide catholytes, which necessitates system level design to circumvent this problem. The full story is published in Electrochimica Acta.

Received the ISE 2014 Young Author Prize in Taipei

The striking beauty, Taipei 101, witnessed the opening ceremony of the 66th Annual Meeting of the International Society of Electrochemistry (ISE), where I received my first international prize for my original and independent scientific contribution.

Paper on dual-mode Li-Bromine flow battery was just accepted

My paper on the experimental work of developing a hybrid lithium metal flow battery was just accepted by Journal of Materials Chemistry A.

Delivered my first keynote speech on charge transfer kinetics

I attened the International Symposium of Electrocatalysis in Whistler last week, and gave a keynote talk in the power sources session. This trip reinforced my understanding on the electrochemical interfaces.

Two co-authored papers were accepted last month

Congratulations to Yi, for his paper on the approximation of Marcus-Hush-Chidsey kinetics was accepted by Journal of Electroanalytical Chemistry; and Jihyung, for her paper on Cu electrodeposition in AAO membranes was accepted by Scientific Reports.

Oronzio and Niccolò De Nora Foundation Young Author Prize

"It is my great pleasure to inform you that you have been selected as the winner of the Oronzio and Niccolò De Nora Foundation Young Author Prize, as author of the article "Statistical kinetics of phase-transforming nanoparticles in LiFePO4 porous electrodes", Electrochimica Acta 89 (2013) 644-651. Please accept my warmest congratulations." - Excerpt of the letter from Dr. Hasuck Kim, the president of the International Society of Electrochemistry.

Presented at several meetings during this summer

I presented at the 225th ECS meeting in Orlando, 17th National Congress of Theoretical and Applied Mechanics in East Lansing and 2014 Electrochemistry Workshop in Monterey on electrochemical kinetics of lithium ions and electrons transfer in battery electrodes.

MIT PDA Summer 2014 Travel Award

"Out of the 92 applications, the evaluation team from the MIT Post-doc Association (PDA) professional development committee has selected seven outstanding applicants as recipients of the award, based exclusively on the scientific merits and originality of the submitted works." - Excerpt of the formal announcement from MIT PDA.

Paper was published in Nature Communications

My postdoc work on Marcus kinetics was published today. In this paper, I used my simple statistical model to extract the reaction rates of porous electrodes from chronoamperometry experiments, which enable consistent Tafel analysis of ln(k), instead of ln(I), versus the overpotentials. Surprisingly, the obtained Tafel plot contradicts the Butler-Volmer prediction, but fit the Marcus-Hush-Chidsey model very well without any empirical fitting, at overpoetnals larger than 100mV. The immediate implication of this work for battery design is that carefully engineering the solid-solid interface would improve the performance of the battery. Independent comments from Prof. Chidsey and Prof. Marcus can be found in the news reports by MIT News and ClimateWire, respectively.

MRS slides were uploaded

I gave a talk on the interpretation of chronoamperometry of porous electrodes in the MRS meeting this fall. The slides can be found here, by which you will be convinced that population dynamics has been fooling us for a long time. Let's get rid of it before drawing conclusions from experiments of porous electrodes.

SES 50th Annual Meeting at Brown University

The 50th Annual Meeting of the Society of Engineering Sciences is being held at Brown University. I met with several Chinese professors, and saw even more Chinese names in the program of this "mechanics" meeting. I guess one major reason that we have so many Chinese students and scholars studying mechanics is that most universities in China have a separate and quite large department for mechanics, in addition to the department of Mechanical Engineering.

Paper was accepted by Electrochimica Acta

My paper, with Prof. Guangyu Tian, was just accepted for publication by the journal Electrochimica Acta. In this paper, we carefully evaluated the analogy between the phase transformation in porous electrodes and that in metal/alloy recrystalization. Our simple mathematical model revealed that population dynamics of phase-transforming nanoparticles in porous electrode can produce non-monotonic transient currents, which could be misinterpreted as the nucleation and growth mechanism by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. We stressed that, only under certain circumstances, electrochemical responses of a porous electrode are equivalent to the microscopic behavior of a single composing particle. So, better to be becareful when interpreting your curves!

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