An Argonne National Laboratory team of researchers has identified one of the major culprits in capacity fade of high-energy lithium-ion batteries. Scientists refer to a battery becoming old is its diminished performance as “capacity fade,” as the amount of charge a battery can supply decreases with repeated use.
Capacity fade is the reason why a cell phone battery that used to last a whole day will, after a couple of years, last perhaps only a few hours.
Researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory identified one of the major culprits in capacity fade of high-energy lithium-ion batteries in a paper published in The Journal of the Electrochemical Society.
But what if scientists could reduce this capacity fade, allowing batteries to age more gracefully?
For a lithium-ion battery – the kind that we use in laptops, smartphones, and plug-in hybrid electric vehicles – the capacity of the battery is tied directly to the amount of lithium ions that can be shuttled back and forth between the two terminals of the battery as it is charged and discharged.
This shuttling is enabled by certain transition metal ions, which change oxidation states as lithium ions move in and out of the cathode. However, as the battery is cycled, some of these ions – most notably manganese – get stripped out of the cathode material and end up at the battery’s anode.
Once near the anode, these metal ions interact with a region of the battery called the solid-electrolyte interphase, which forms because of reactions between the highly reactive anode and the liquid electrolyte that carries the lithium ions back and forth. For every electrolyte molecule that reacts and becomes decomposed in a process called reduction, a lithium ion becomes trapped in the interphase. As more and more lithium gets trapped, the capacity of the battery diminishes.
Some molecules in this interphase are incompletely reduced, meaning that they can accept more electrons and tie up even more lithium ions. These molecules are like tinder, awaiting a spark.
When the manganese ions become deposited into this interphase they act like a spark igniting the tinder: these ions are efficient at catalyzing reactions with the incompletely reduced molecules, trapping more lithium ions in the process.
Study coauthor and Argonne scientist Daniel Abraham said, “There’s a strict correlation between the amount of manganese that makes its way to the anode and the amount of lithium that gets trapped. Now that we know the mechanisms behind the trapping of lithium ions and the capacity fade, we can find methods to solve the problem.”
It won’t be a very long spell until the chemistry issues are worked out in battery production. These is more to do in research, but the big clue is in hand. Meanwhile, we’ll just keep on buying, replacing and recycling those batteries.
University of Southern California researchers have devised a way to produce and store hydrogen from methanol, without concurrent production of either carbon monoxide or carbon dioxide, by trapping it in organic derivatives of ammonia called amines.
1994 Nobel Prize in Chemistry winner the late George Olah in his last major paper, G. K. Surya Prakash, and their team at the USC Dornsife College of Letters, Arts and Sciences have had their research paper published in the Journal of the American Chemical Society where they outlined the carbon-neutral method with a little help from the simplest alcohol known to man: methanol.
The well-known steam reforming process usually used to extract hydrogen from methanol, called the methanol reformer, traditionally produces carbon monoxide and carbon dioxide as part of this extraction process.
The research of Prakash, Olah and their team has been focused on finding a way to extract hydrogen fuel from methanol in ways that are not only carbon-neutral, but can even be carbon-positive.
Methanol, sometimes called “wood alcohol,” is the simplest alcohol that can be produced, requiring only water, carbon dioxide and energy. While methanol stores half the energy of traditional petroleum-based gasoline, the light that burns half as bright also burns more cleanly, with no soot, particulates or other residue.
Methanol quickly biodegrades. It has traditionally been produced from natural gas and can be corrosive to older automobile tubing and casing, though much less so to newer generations of automobiles. Methanol is a more efficient fuel to replace gasoline or diesel, but it provides fewer miles to the gallon because of its lower energy density.
Methanol has also long been prized by race car drivers for its higher octane on shorter tracks and because it produces clearer smoke, preventing pileups. Also, unlike typical petroleum-based gasoline, water is effective in fighting methanol-based fires, though those clean-burning fires often appear invisible in daylight. However, additives can also easily be added to methanol to increase visibility.
Methanol is also already employed in the raw chemical production of all petroleum-based chemicals and products.
In a testament to its elegance, simplicity and ubiquity, methanol naturally occurs in small amounts in Earth’s atmosphere, and there are even huge clouds of it floating in the star-forming regions of space. Olah, Prakash and colleagues published research last year examining the differences between the formation of methanol both terrestrially and extraterrestrially.
Prakash, who worked with Olah for more than 40 years, said “Olah was a giant of a chemist and a great visionary who had a prophetic approach to solve tough problems. He had remarkable memory and was quite intuitive. He was very well-read, he knew history and philosophy and appreciated music and the arts. He was a voracious reader. He can be described as a Renaissance man.”
The research demonstrates just one more way carbon has been freed from the cycle of creating and storing fuels via methanol, supporting Olah and Prakash’s long-standing vision of a completely renewable “methanol economy.”
“The Methanol Economy” is a concept that the Olah-Prakash team first began refining in the mid-1990s, right after the time Olah became USC’s first Nobel laureate for his contributions to carbocations, the name that Olah himself coined for ions that have a positively charged carbon atom.
According to Olah and Prakash, the goal of a methanol-based economy would be to develop renewable sources of energy, led by methanol, that could mitigate the problem of climate change caused by carbon emissions, as well as the U.S. dependence on other countries for energy, particularly oil.
The need to offset crude oil consumption has only grown in the intervening decades since Olah and Prakash began their research. At that time, global consumption of oil was around 70 million barrels; that number is expected to be about 100 million as early as next year.
Countries like China have already begun the transition away from petroleum. At the beginning of the century, methanol use there was negligible but now accounts for more than 500,000 barrels each day, though much of it is coal-based, which can create its own problematic carbon runoff.
The USC news story leaves a lot about methanol out. Its already being used in Asia as a fuel cell fuel. There is also a lot of excess content involving greenhouse gases and such. And as usual, little or nothing is said about the reality of what 80 to 100 million barrels of crude oil represents as energy.
The science is welcome, though. For now methanol and its use is too small of a market to attract either devices needing fuel or the production capacity to keep a niche system going. But never say never, if a team can put together a 75 kilowatt power unit and an economical methanol fuel supply it could trigger the methanol economy’s startup.
University of California – Riverside researchers have used waste glass bottles and a low-cost chemical process to create nanosilicon anodes for high-performance lithium-ion batteries. The batteries will extend the range of electric vehicles and plug-in hybrid electric vehicles, and provide more power with fewer charges to personal electronics like cell phones and laptops.
The group’s research paper describing the research has been published in the Nature journal Scientific Reports. At this writing the paper is not behind a paywall. Cengiz Ozkan, professor of mechanical engineering, and Mihri Ozkan, professor of electrical engineering, led the project.
Even with today’s recycling programs, billions of glass bottles end up in landfills every year, prompting the researchers to ask whether silicon dioxide in waste beverage bottles could provide high purity silicon nanoparticles for lithium-ion batteries.
Silicon anodes can store up to 10 times more energy than conventional graphite anodes, but expansion and shrinkage during charge and discharge make them unstable. Downsizing silicon to the nanoscale has been shown to reduce this problem, and by combining an abundant and relatively pure form of silicon dioxide and a low-cost chemical reaction, the researchers created lithium-ion half-cell batteries that store almost four times more energy than conventional graphite anodes.
To create the anodes, the team used a three-step process that involved crushing and grinding the glass bottles into a fine white power, a magnesiothermic reduction to transform the silicon dioxide into nanostructured silicon, and coating the silicon nanoparticles with carbon to improve their stability and energy storage properties.
As expected, coin cell batteries made using the glass bottle-based silicon anodes greatly outperformed traditional batteries in laboratory tests. Carbon-coated glass derived-silicon (gSi@C) electrodes demonstrated excellent electrochemical performance with a discharge capacity of 2936 mAh g−1 and a capacity of ~1420 mAh/g after 400 cycles.
Changling Li, a graduate student in materials science and engineering and lead author on the paper, said one glass bottle provides enough nanosilicon for hundreds of coin cell batteries or three-five pouch cell batteries.
Li said, “We started with a waste product that was headed for the landfill and created batteries that stored more energy, charged faster, and were more stable than commercial coin cell batteries. Hence, we have a very promising candidates for next-generation lithium-ion batteries.”
This research is the latest in a series of projects led by Mihri and Cengiz Ozkan to create lithium-ion battery anodes from environmentally friendly materials. Previous research has focused on developing and testing anodes from portabella mushrooms, sand, and diatomaceous (fossil-rich) earth.
Along with Mihri and Cengiz Ozkan and Li, contributors include graduate students Chueh Liu, Wei Wang, Zafer Mutlu, Jeffrey Bell, Kazi Ahmed and Rachel Ye. Financial support for this work was provided by the UC-Riverside and UC Faculty Climate Champion initiative.
The UCR Office of Technology Commercialization has filed a patent application for the inventions above.
The first build of this concept is quite an accomplishment. The new material in its battery holds about half of its capacity over 400 charge / discharge cycles without self destructing. This is progress on the breakthrough level.
April 20, 2017 | 2 Comments
Kobe University researchers have found the mechanism behind oil synthesis within microalgae cells. The team believes the discovery could contribute to the development of biofuels. It has been a very long time since we’ve seen any news on the algae front. The improvement the team shows looks like an addition to algae competitiveness.
The team’s findings have been published in Scientific Reports. The research was carried out by a group led by Professor Hasunuma Tomohisa and Academic Researcher Kato Yuichi, both from the Kobe University Graduate School of Science, Technology and Innovation.
During the 20th century the petrochemical industry developed rapidly. The researcher’s press release said that in order realize a sustainable and environmentally-conscious society, we must make use of renewable biomass such as plants and algae.
The amount of biomass on Earth is approximately 10 times the amount of energy we currently consume. Roughly half of this biomass grows in aquatic environments, and ocean-based biomass such as microalgae can produce oil without using up arable land and drinking water.
Microalgae can grow with light, water, carbon dioxide and a small amount of minerals, and their cells divide quickly, meaning that they can be harvested much faster than land-based biomasses. Algae can also be harvested all year round, potentially offering a more stable energy supply.
Many species of algae are capable of producing large amounts of oil (lipids), but this is the first time that researchers have captured the metabolic changes occurring on a molecular level when lipids are produced in algae cells.
Focusing on marine microalgae, Professor Hasunuma’s group found that Chlamydomonas sp. JSC4, a new species of green alga harvested from brackish water, combines a high growth rate with high levels of lipids. The research team developed an analysis method called “dynamic metabolic profiling” and used this to analyze JSC4 and discover how this species produces oil within its cells.
Professor Hasunuma’s team incubated JSC4 with carbon dioxide as the sole carbon source. Four days after the start of incubation, over 55% of cell weight consisted of carbohydrates (mainly starch). When saltwater comprised 1-2% of the incubation liquid, the team saw a decrease in carbohydrates and increase in oil, and 7 days after the start of incubation over 45% of cell weight had become oil.
That’s a “Eureka Moment”.
JSC4 has a high cell growth rate, and the lipid production rate in the culture solution achieved a speed that greatly surpassed previous experiments. At the start of the cultivation period starch particles were observed in the cells, but in saltwater these particles vanish and numerous oil droplets are seen.
Using dynamic metabolic profiling, the group found that the sugar biosynthesis pathway (activated when starch is produced) slows down, and the pathway is activated for synthesizing triacylglycerol, a constituent element of oil. In other words, the addition of seawater switched the pathway from starch to oil production. They also clarified that the activation of an enzyme that breaks down starch is increased in saltwater solution.
The discovery of this metabolic mechanism is not only an important biological finding, it could also be used to increase the production of biofuel by improving methods of algae cultivation. Based on these findings, the team will continue looking for ways to increase sustainable oil production by developing more efficient cultivation methods and through genetic engineering.
This is very encouraging news. An organism at 45% body weight in harvestable oils at 7 days is astonishing. It suggests that algae isn’t out of the future at all, just quiet in the face of incredibly low cost fossil fuels.
Using quantum dots (QD) and a process called Multiple Exciton Generation (MEG), the NREL researchers were able to push the peak external quantum efficiency for hydrogen generation to 114 percent. The advancement could significantly boost the production of hydrogen from sunlight by using the cell to split water at a higher efficiency and lower cost than current photoelectrochemical approaches.
Details of the research are outlined in the team’s Nature Energy paper titled “Multiple Exciton Generation for Photoelectrochemical Hydrogen Evolution Reactions With Quantum Yields Exceeding 100%”, co-authored by Matthew Beard, Yong Yan, Ryan Crisp, Jing Gu, Boris Chernomordik, Gregory Pach, Ashley Marshall, and John Turner. All are from NREL; Crisp also is affiliated with the Colorado School of Mines, and Pach and Marshall are affiliated with the University of Colorado, Boulder.
In 2011 Beard and other NREL scientists published a paper in Science that showed for the first time how MEG allowed a solar cell to exceed 100 percent quantum efficiency by producing more electrons in the electrical current than the amount of photons entering the solar cell.
Beard explained, “The major difference here is that we captured that MEG enhancement in a chemical bond rather than just in the electrical current. We demonstrated that the same process that produces extra current in a solar cell can also be applied to produce extra chemical reactions or stored energy in chemical bonds.”
The maximum theoretical efficiency of a solar cell is limited by how much photon energy can be converted into usable electrical energy, with photon energy in excess of the semiconductor absorption bandedge lost to heat. The MEG process takes advantages of the additional photon energy to generate more electrons and thus additional chemical or electrical potential, rather than generating heat. QDs, which are spherical semiconductor nanocrystals (2-10 nm in diameter), enhance the MEG process.
In current report, the multiple electrons, or charge carriers, that are generated through the MEG process within the QDs are captured and stored within the chemical bonds of a H2 molecule.
NREL researchers devised a cell based upon a lead sulfide (PbS) QD photoanode. The photoanode involves a layer of PbS quantum dots deposited on top of a titanium dioxide/fluorine-doped tin oxide dielectric stack. The chemical reaction driven by the extra electrons demonstrated a new direction in exploring high-efficiency approaches for solar fuels.
So far your humble writer is unaware of the 2011 work making it commercial products, which of so would have been, or should be, quite noticeable. This suggests there are some difficulties somewhere in the run up to products. Hopefully someone will advise of commercial applications.
These are huge improvements. But with natural gas so low cost for now, a lot of the energy in the drive to advanced products has cooled. One hopes that these massive improvements can overcome the low cost obstacle. But it takes quite some financial courage to get there.