- Chitin and its derivatives from chitosan are natural polymers found in crustaceans and elsewhere in nature.
- Engineers at the University of Maryland have devised a way to make zinc-based batteries more durable by incorporating chitosan.
- This could pave the way for alternatives to lithium-ion batteries, which are becoming increasingly expensive, as well as the environmental issues associated with lithium mining.
Crab meat is delicious – this is an irreplaceable buttery fact. But here’s something you might not know about your penchant for boiled crustaceans: Every year, roughly six to eight million tons of crab, shrimp, and lobster shells waste It is produced all over the worldMost are dumped directly into the ocean or landfills, depending on the country.
The issue is not so much the massive waste dumped at the dinner table as the missed opportunity. The tough exoskeletons of crabs and their marine ilk are rich in beneficial and versatile chemicals such as calcium carbonate, which has medicinal and industrial uses, and chitin, the second most abundant natural polymer on Earth.
Over the years, scientists have extracted chitin from crustacean shells for everything tissue engineering to make biodegradable plastic. Because it and its brother, the chitosan polymer, are considered environmentally friendly and non-toxic, there has been much interest in incorporating these chemical compounds into batteries of all things.
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in paper Posted earlier this month in the magazine issueIn fact, a group of engineers at the University of Maryland did just that, making an impressive chitin-zinc battery that was biodegradable, but still had a great deal of electrical power. As the world heads toward a more sustainable future, the hope is that the rechargeable, crab-derived battery will be a viable alternative or even an alternative to lithium-ion batteries, which are in high demand (hello EVs!). At the same time, lithium itself has become a scarce resource.
“This is a really exciting application for chitin, taking advantage of its renewable and zinc-binding potential to make new electrode materials,” Mark MacLachlansays a professor of supramolecular materials at the University of British Columbia, who was not involved in the study popular mechanics in a letter.
All you need are electrons (and some conductive metals)
The reason behind the spark on your phone is that some chemistry is happening deep inside the battery.
Chemical reactions called redox reactions produce steady drumbeats of electric current in the form of moving electrons. These travel through a circuit made up of the battery’s electrodes (made of two different conductive metals), its chemical electrolyte (a gel or liquid that contains charged particles called ions), and any device or device connected to the battery.
There are many minerals and electrolytes used in a battery. For example, in a common household alkaline battery, the positive electrode (cathode) is made of manganese oxide and the negative electrode (or anode) is made of zinc metal. The electrolyte between them is potassium hydroxide. In lithium-ion batteries, lithium usually accumulates with another metal such as cobalt at the cathode and carbon at the anode, and also forms the electrolyte.
Lithium-ion batteries are the rising star in the energy world for being lightweight yet packing a great deal of power (and they’re rechargeable to boot). Not surprisingly, these batteries have found their way into almost all electronic devices and electric car Over the past few decades, however, lithium mining has had a major and devastating impact on the environment. Not only that, lithium-ion batteries aren’t easily biodegradable or recyclable, which doesn’t make them fully sustainable—at least in their current form.
“Rechargeable batteries as green energy sources are essential to reduce our dependence on fossil fuels and reduce greenhouse gas emissions. However, with the increase in demand for electric vehicles in recent years, huge amounts of batteries are being produced and consumed, increasing the potential for environmental problems,” Meiling Wufirst author of the new study and a postdoctoral fellow at the University of Maryland, in an email to popular mechanics. “For example, polypropylene and polycarbonate separators, which are widely used in Li-ion batteries, take hundreds or thousands of years to degrade and add a burden to the environment.”
Crabs to the rescue
Scientists have been using chitin for years, looking for ways to incorporate organic matter — which is structurally similar to cellulose in plants — in batteries. in 2016MacLachlan and his lab at the University of British Columbia discovered that when chitin was cooked with nitrogen at temperatures up to 1,652 degrees Fahrenheit, it converted the former crab shells into a carbon-nitrogen material suitable for electrodes.
But Wu and her colleagues at the University of Maryland took a different approach. Their focus was on zinc-based batteries, a commonly used, but non-rechargeable battery. Since the metal is more readily available compared to lithium (read: cheaper to produce and supply) and less toxic (zinc batteries use water as the electrolyte), there has been as much interest in zinc as our Silver White Energy Knight.
However, replacing lithium with zinc is not a smooth process. In batteries as an electrode, zinc has an unpleasant tendency to form irregularities on its surface. These irregularities form when electrons move around and turn into tiny snowball-shaped bumps that accumulate into larger and larger clumps called dendrites, disrupting the battery’s electrical current.
Because chitosan, a chemically processed derivative of chitin, reacts well with water and is able to hold it apart from floating in air, Wu and her colleagues thought they could use it to make a battery separator—a semi-permeable membrane that keeps oppositely charged electrodes apart—which is also amenable to to decompose.
So, how do they do that? The researchers took a coin-sized film of chitosan and washed it in a zinc-filled solution to make the metal adhere to the film. Next, they squeezed out a chitosan-zinc film, squeezing it tightly to pack it densely. In contrast to previous attempts to thicken chitosan films, this technique allowed for relatively large pores (up to five micrometers in size), allowing free movement of ions, Judy Lutkenhousea professor of chemical engineering at Texas A&M University, who was not involved in this study, says popular mechanics.
Says Lutkenhaus, who did Searching for organic derived batteries.
To complete the construction, a zinc anode was placed on top of a chitosan-zinc separator along with a cathode made of an organic compound called poly (benzoquinonyl sulfide), or PBQS. When Wu and her colleagues turned on the Krabby battery in the lab, they saw none of this dendrite formation on the zinc anode. Impressively, it produced an electric current of 50 mA per square centimeter for 400 hours (or 1,000 charge cycles), which is close to what small lithium batteries can do.
Next, they buried the chitosan-based electrolyte, not the entire battery, to see how long it would take to decompose. They found that the microorganisms that live in the dirt took about five months to feed on the electrolyte, which is what Wu says. Many Faster compared to traditional electrolytes found in landfills and definitely good for the environment.
“This does not mean that the battery device itself will degrade within five months,” she says. “In fact, the electrolyte is packaged in a closed cell, separated from air and living organisms. This type of device can work for much longer.”
The future of chitosan-based batteries
While you won’t see crab shell batteries any time soon, researchers hope their batteries will become commonplace, used in electronic devices like your cellphone to store dedicated renewable energy that trips to a commercial grid.
Considering chitosan only costs about $1.70 per gram and you don’t need much of it to make their prototype (only about 20 mcg for a 20mm coin-sized battery), which could give the chitosan-zinc battery a higher price advantage. Lithium-ion batteries, which suffer from high demand and attendant costs.
However, as climate change heats up harming marine life, there is a question about what will happen to the costs if chitosan batteries are taken off. It is also worth considering how green the environment will really be used in the future – we have to take into account the carbon footprint of activities associated with chitin recovery and conversion into chitosan.
“I think the next important step will be to do a technical economic analysis to examine global production of chitosan, and if we are going to apply it, for example, to grid-scale energy storage, do we have sufficient access to he-she?” Lutkenhaus says. “If we start using it, will the price change because of the demand… [Also] The life cycle analysis concludes… the carbon footprint of crustacean capture, shipment and processing.”
Fortunately, says Wu, we have other sources of chitin, such as insects and fungi cell walls, so it’s not completely useless if a marine source falls by the wayside. And while no one has yet attempted to synthesize chitin in the lab, who knows what the future may hold. For now, it seems our delicious seafood hangover could be a solution to our current energy problems.
Myriam Fawzia is a contributing writer for Popular Mechanics who is obsessed with all things energy. Her work has appeared in USA Today, The Daily Beast, and Inverse. When she’s not talking about the store, she writes science fiction, reads a lot of comics, and chases a lot of cats (her cat, thankfully).
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