A Sustainable Chitosan-Zinc Electrolyte for High-Rate Zinc-Metal Batteries
David Huang
ArticleDevelopment of new, sustainable renewable energy sources to reduce carbon emissions has been a hot topic for the past decade. Equally important has been developing rechargeable batteries that can store this energy. Zn-metal batteries have been an attractive candidate because of their inherent safety, fast charging/discharging capabilities, low cost, and environmental friendliness. However, these batteries have not yet been commercialized in large part because of issues involving the Zn-metal anode. Research has been conducted to deal with these issues, however solving one issue has led to others, such as compromising the safety of the battery, or hindering performance.
The research paper I chose focuses on using chitosan-zinc electrolytes for zinc metal batteries. Chitosan is an eco-friendly and biodegradable biopolymer derived from chitin, a naturally abundant polymer that is widely available in crustacean shells. The paper talks extensively on the battery’s performance, but did not ignore the safety and environmental impact the battery has as well. Even with the new electrolyte, performance was not lost, as the battery had a 99.7% Coulombic efficiency for 500 cycles when cycled at 10 mA cm-2. Even at a higher (50 mA cm-2) current density, the chitosan-Zn electrolyte could still enable stable cycling with a capacity of 10 mAh cm-2 and depth of discharge at 17.1% for 1000 cycles. This contrast with other aqueous electrolytes, in which the cell suffered from irreversible voltage increase and eventually failed after the 350th cycle. Aside from the battery’s high rate and high capacity performance, the paper discussed how the chitosan-Zn gel electrolyte is not flammable and only shrinks when placed in a flame. This is due to the non-flammable characteristic of the chitosan polymer, which ensures the high safety of the batteries. In addition, the chitosan-Zn electrolyte is biodegradable, and this was tested by burying the membrane in soil. The study found that the electrolyte became moldy after just 2 months and was totally degraded after 5 months. This is important because current battery disposal includes tossing them in landfills, which take many years to degrade, or incineration, which cause mercury, lead, and other dioxin emissions to the environment. The chitosan-Zn electrolyte derived from natural biomaterial releases the constitutes back to the environment in a natural way, while the other components are either also biodegradable (PQBS cathode), environmentally friendly (aqueous solution), or recyclable (Zn-metal). Lastly, due to the natural abundance of chitosan and the facile fabrication process, the chitosan-Zn material has a much lower manufacturing cost compared to other commercial separators. With a high-rate and high-capacity performance, coupled with the high safety, biodegradability, and low cost, make chitosan-based Zn-metal batteries promising for practical large-scale energy-storage applications.
The first thing the news article discussed was the sustainability and environmental impact of the new battery. One of the things that I really liked about the article was they went into a bit more detail as to what the current safety/environmental issues with batteries were, as they brought up how current batteries have caught on fire in aircraft and in waste sites. In addition, the article mentions how conventional batteries can take hundreds or thousands of years to break down, an important fact that adds to why a more environmentally friendly battery is needed. The article also briefly mentioned the composition of chitin and its applications in the biomedical engineering field.
After discussing the safety and sustainability of the battery, the article goes on to discuss the performance of the battery, such as mentioning its 99.7% energy efficiency after 1000 cycles (this info wasn't entirely correct, as I'll explain later). This is important because it means the battery can be quickly charged and discharged without affecting its performance. The article only talks about performance briefly before going back to the environmental impact of the battery. The article did a good job highlighting how most of the battery material was biodegradable and could degrade in just 5 months, which contrasts sharply with the hundreds and thousands of years that current batteries take.
Overall, I felt the article did an excellent job of picking out the most important elements of the paper and conveying it to the reader in an easy to understand manner. I did notice that the article spent much more time (over half the article) discussing the safety and environmental impact, and not as much into the performance of the battery, while the paper did the complete opposite. The article did leave out some of the testing done of the electrolyte, such as the morphology and characterization of the electrolyte, ionic conductivity, and electrodeposition behavior. I didn’t have much of a problem with that because to the general reader, those details weren’t as important as the performance and safety of the battery. What I didn’t like, however, was that the article didn’t really discuss how the electrolyte was synthesized, and instead described it as “Through chemical processing and adding acetic acid aqueous solution, chitin can ultimately be synthesized…” Using chitosan in batteries was a novel idea and I think the reader would’ve appreciated a brief paragraph on the actual synthesis process. In addition, the article discussed the chitin battery’s high efficiency and performance with the chitosan-Zinc electrolyte, but didn’t mention how in the paper, they also tested with other commonly used electrolytes (like zinc sulfate) and that the zinc sulfate electrolyte performed worse (the cell suffered from irreversible voltage increase and eventually failed after the 350th cycle). The article also had a slight error in data interpretation - the 99.7% efficiency was after 500, not 1000 cycles. The 1000 cycles was when the battery was ran at a higher (50 mA cm-2) current density. It was a small error that I noted, but doesn't change the bottom-line that the chitosan-Zn battery performed at a high efficiency. Nonetheless, the article did a great job, especially with the environmental impacts, that I would give it a 8/10.
Hi David,
ReplyDeleteThanks for sharing these articles and your thoughts. One tool that researchers can use when evaluating the environmental impacts of a new technology or process is life cycle assessment (LCA) model. Essentially, this creates a basis comparison for one to evaluate the environmental toll that a new process creates in relation to existing technologies. I think a LCA of this group's new electrolyte would be beneficial, as it accounts for the GWP and ecotoxicity, among other impact factors, that would ground the work in relation to what is available. Additionally, I think that this model can inform the group about where, in the cradle-to-grave process, they can optimize to reduce emissions and if they should attempt to scale the electrolyte production. Without this comparison, I found it challenging to truly "buy in" to this new development. Do you feel that the authors should attempt to better illustrate the environmental effects of their technology and the process to produce it before claiming it is sustainable?
Hi Madeline,
DeleteFor as much data and experiments that the research did on the electrochemical performance of the battery, I agree that the research could've done more on the environmental side. I did think the part where they showed how the chitosan-Zn electrolyte would fully degrade within 5 months was impressive, but still felt a bit "incomplete". They mentioned that every component of their battery was either biodegradable, environmentally friendly, or recyclable, but I think going through the entire battery making process, battery cycling, and end of life battery disposal and showing how each step is environmentally friendly, would go a long way towards giving their battery more legitimacy.
Hi David! I really enjoyed reading through the article and paper that you chose. Like Madeline, I had some trouble "buying into" this new development as it seems almost too good to be true. The Guardian article begins to discuss this point towards the end of the article when they quote Graham Newton saying, "There are still quite a few challenges to be met in the development of zinc ion batteries, but fundamental studies such as this are hugely important." These 'challenges' don't seem to be elaborated on very much in the Guardian article or the research study, so I was wondering if you had found anything on what those might be, or what the future directions of this research study are.
ReplyDeleteHi Veronica,
DeleteSo I actually had to find the professor's own website and get a copy of their paper there because the paper was originally behind a paywall. Here is his website: http://yaoyangroup.com/
Unfortunately, it seems like the group studies a broad range of materials, and they don't give any specifics as to what they are researching now. Their paper was published less than 2 months ago, so it's uncertain if and what they are doing with this specific research. Nonetheless, it's certainly at least a good basis that hopefully inspires others that read their paper to advance their research.
As far as the other challenges, I mentioned this in Madeline's comment that I think the group should consider going through the entire process (cell assembly, to cell cycling, to cell end-of-life disposal), and showing how each step is environmentally friendly. The research is also very young, so one of the bigger challenges to making this idea into reality is scaling up, both in terms of production and perhaps more importantly, how to recycle the batteries. The paper showed how one of the chitosan-Zn electrolyte could decompose in soil, but how will millions of these batteries be recycled? And of course, it's not as simple as just tossing the battery into a patch of dirt when the battery is dead because not all of it (such as the Zn) is biodegradable, so it has to be recycled somehow. To me, this is the biggest question that has to be answered if this battery is to be a legitimate solution.
Hi Mike,
ReplyDeleteIt is true that dendrites have been one of the biggest challenges with battery design, and not just in Zn batteries. I didn't discuss this as much as I could have since I wanted to focus more on the environmental aspects, but the paper did discuss extensively as to how their chitosin-zinc separator could inhibit dendrite formation. On page 5 of the article (page 6 in the PDF) the paper talks about how "while water plays an important role in the ion conduction of electrolytes, excess water causes side reactions and dendrite formation on the Zn-metal anode". One of the experiments this research did was using differing water content on the chitosan-Zn membrane (by either soaking in water or evaporating), and they hypothesized that due to the hydrophilic hydroxyl and amine group of chitosan, the membrane would be able to better confine water, thus reducing the ratio of free water in the membrane. On page 8 of the PDF, they found that a water content of 57% gave the best results in terms of conductivity and prohibiting dendrite formation.
As far as other possible ways to reduce dendrite formation, there's actually a professor at U of M that has done research on it, and they found that using a piezoelectric material could help prevent dendrite growth. Here's a link to their paper: https://pubs.acs.org/doi/10.1021/acsmaterialslett.9b00289
Hi Seth,
ReplyDeleteDendrites are metallic microstructures that form on the anode during the charging process. This is because sometimes the metallic ions that reach the surface don't get absorbed in time into the anode, and you begin to have what is essentially a "pile-up". These dendrites can get quite sharp and pierce through your separator, which will cause your battery to have lower performance. If it gets so bad that the dendrites reach from the anode to the cathode, then the battery is now short circuited. It's also the reason why batteries have caught on fire.
As far as performance comparison, the paper claims that their battery has better capacity, rate performance, and cycling life than other batteries, so my assumption is they compared their numbers with other batteries. Unfortunately, I don't know what those numbers are.
Hi David! Thanks for sharing. I really enjoyed these papers. After our discussion in class, I was thinking that an experiment that really would've added to the paper would be like a proof-of-concept showing that you can go from the unprocessed chitosan material (ethically sources of course) to the battery material. This would make the article's claims less misleading.
ReplyDeleteHi, David! This is late due to not having a presenter today (Thursday) in class. Regardless, really good job presenting in class. I wanted to reiterate kind of what you were discussing in class that because this is such a new idea and topic of development, the title of this article almost seemed unreal. A way the article authors could have made it seem a little more viable is like we discussed in class of including a step by step mechanism for making the battery. This would not only clear skepticism but also confusion in general that may be the first thing that comes to mind when seeing that crab and lobster shells could be used for renewable batteries. Great work.
ReplyDeleteNice work, David! This is another late comment coming due to the fact that there was no presenter today, but I wanted to comment on the potential implications of using this on a large-scale. Someone mentioned the environmental concerns of using this type of material in the batteries (ecological, biodiversity concerns). If it became scaled up to the point where these types of batteries were storing energy for entire electrical grids, it seems to me that those concerns are very valid. What do you see as the threshold for these types of batteries?
ReplyDeleteGreat job presenting! I'm wondering how the degradation timeline will be changed when the membrane is inside of a battery casing, and what kind of challenges there are in creating something which can be easily degraded at end-of-life, but will not break down during normal use.
ReplyDeleteGreat evaluation of the article and the paper! I'm glad the article broke down the scientific details of the paper for the general public to understand, and I appreciate how you went more in depth for us to better understand it from the paper's perspective
ReplyDeleteGreat evaluation and presentation! I think what would be good to include in the article is the fabrication of the Zn membrane. There are plenty of ways to make a size selective/ion membrane for batteries. There have been other studies on batteries that have applications for renewable energy storage that have done something similar. It would be nice to to know what makes the paper's membrane so unique other than it being biodegradable? Does it have multiple uses? Can it be scaled up for industry use?
ReplyDeleteI thought that your presentation on Tuesday was great! One thing I was wondering about is if we will see this kind of technology trickling down to consumer-level batteries, such as in phones, or even EVs. A lot of people are still searching for the holy grail of battery tech particularly for electric vehicles as we are seeing them take off recently, and I was curious what the future of this particle battery technology looks like.
ReplyDeleteHi David, I was thinking about the environmental aspect of this concept. I don't recall seeing how much of the chitosan was needed for each battery and how that relates back to the crustacean shells. Do you know how much is needed for each battery and how the scaling of that would affect the crustacean population, considering we also use crustaceans for other purposes such as food? Or will they synthesize their own to avoid using crustacean populations?
ReplyDeleteHi David, really interesting article!! I think it's interesting to think about using crustacean-sourced chitin for renewable energy applications from an animal rights/ecology standpoint, and I would be interested to hear what an ecologist or animal rights activist would think about this. Especially now that veganism is becoming more of a lifestyle than just a diet, relying on other living creatures for energy creates a sticky situation. For those who consider themselves environmentalists and support the development of renewable energy technology, but simultaneously don't want to rely on the exploitation of other animals, chitin batteries become a bit controversial.
ReplyDeleteHey David! Thanks for a great paper and article. I found it interesting how the scientific paper spent a lot of time talking about dendrite formation but the article avoids this topic. From the paper, I got the sense that dendrite formation is one of the major problems battery manufacturers face, and the researchers have found a way to possibly minimize its effect on batteries. I get that the article is mostly focused on the environmental impact of batteries, but this finding could result in longer lasting batteries and therefore less batteries that need to be thrown away in general. Do you think that including a paragraph on dendrite formation would add to or take away from the overall theme of the article?
ReplyDeleteThis was a really interesting read! With the ever increasing focus on switching to sustainable technologies made from natural materials, I am curious to see how the development of new batteries will progress in the future. I thought it was great that the article included information on why a new more sustainable battery was needed, and you did a great job at highlighting the importance of this background information to readers.
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