Pacific Northwest National Laboratory (PNNL) researchers have developed a nickel-based metal organic framework to hold onto polysulfide molecules in the cathodes of lithium-sulfur batteries and extend the batteries’ life spans.
A promising new battery chemistry is the lithium-sulfur battery, which can hold as much as four times more energy in a given mass than typical lithium-ion batteries. Lithium sulfur chemistry would enable far more available energy from a single charge, as well as help store more renewable energy. The down side of lithium-sulfur batteries, however, is they have a much shorter lifespan because they can’t currently be charged as many times as lithium-ion batteries.
The PNNL researchers added the nickel based powder, a kind of nanomaterial called a metal organic framework, to the battery’s cathode to capture problematic polysulfides that usually cause lithium-sulfur batteries to fail after a few charges. A paper describing the material and its performance was published online April 4 in the American Chemical Society journal Nano Letters.
Materials chemist Jie Xiao of the Department of Energy’s Pacific Northwest National Laboratory said, “Lithium-sulfur batteries have the potential to power tomorrow’s electric vehicles, but they need to last longer after each charge and be able to be repeatedly recharged. Our metal organic framework may offer a new way to make that happen.”
Of particular interest is today’s electric vehicles that are typically powered by lithium-ion batteries. But the native chemistry of lithium-ion batteries limits how much energy they can store. As a result, electric vehicle drivers are often anxious about how far they can go before needing to recharge. Metal organic frameworks in the cathodes would enable electric vehicles to drive farther on a single charge, as well as help store more renewable energy.
How the metal frameworks would improve lithium sulfur comes from how batteries work. Most batteries have two electrodes: one is positively charged and called a cathode, while the second is negative and called an anode. Electricity is generated when electrons flow through a wire that connects the two. At the same time controlling the electrons, positively charged atoms shuffle from one electrode to the other through another path inside the battery: the electrolyte solution in which the electrodes are mounted.
The lithium-sulfur battery’s main problem comes from unwanted side reactions that cut the battery’s life short. The side reactions start on the battery’s sulfur-containing cathode, which slowly disintegrates and forms molecules, called polysulfides, that dissolve into the liquid electrolyte. Some of the sulfur – an essential part of the battery’s chemical reactions – never returns to the cathode. As a result, the cathode has less material to keep the reactions going and the battery quickly dies.
Researchers worldwide are trying to improve materials for each battery component to increase the lifespan and mainstream the use of lithium-sulfur batteries. For this research, Xiao and her colleagues honed in on the cathode to stop polysulfides from moving through the electrolyte.
Many materials with tiny holes have been examined to physically trap polysulfides inside the cathode. Metal organic frameworks are porous, but the added strength of PNNL’s material is its ability to strongly attract the polysulfide molecules.
The framework’s positively charged nickel center tightly binds the polysulfide molecules to the cathodes. The result is a coordinate covalent bond that, when combined with the framework’s porous structure, causes the polysulfides to stay put.
PNNL electrochemist Jianming Zheng explains, “The metal organic framework’s highly porous structure is a plus that further holds the polysulfide tight and makes it stay within the cathode.”
Metal organic frameworks nanomaterial- also called MOFs – are crystal-like compounds made of metal clusters connected to organic molecules, or linkers. Together, the clusters and linkers assemble into porous 3-D structures. The MOFs can contain a number of different elements. PNNL researchers chose the transition metal nickel as the central element for this particular MOF because of its strong ability to interact with sulfur.
During lab tests, a lithium-sulfur battery with PNNL’s MOF cathode maintained 89% of its initial power capacity after 100 charge-and discharge cycles. Having shown the effectiveness of their MOF cathode, PNNL researchers now plan to further improve the cathode’s mixture of materials so it can hold more energy. The team also needs to develop a larger prototype and test it for longer periods of time to evaluate the cathode’s performance for real-world, large-scale applications.
“MOFs are probably best known for capturing gases such as carbon dioxide,” Xiao said. “This study opens up lithium-sulfur batteries as a new and promising field for the nanomaterial.”
Eighty nine percent at 100 cycles is a huge improvement even though not being a truly marketable solution. But the PNNL team may be closer than we know for now. Back in January, a Nature Communications paper by Xiao and some of her PNNL colleagues described another possible solution for lithium-sulfur batteries other side: developing a hybrid anode that uses a graphite shield to block the polysulfides.
More research sure to come.
Microbes can be highly efficient, versatile and sophisticated manufacturing tools, and have the potential to form the basis of a vibrant economic sector. The report is based on the deliberations of experts who were gathered by the American Academy of Microbiology to discuss the potential contributions of a microbe-powered industry and the human elements needed for this emerging sector to thrive. It can be found online at: http://academy.asm.org/images/stories/documents/MicrobePoweredJobs.pdf. However the contents of the report reflect the discussions of the colloquium and are not intended to reflect official positions of the American Academy of Microbiology or the American Society for Microbiology.
In making a basis for the report Doran-Peterson said, “Industrial microbiology is experiencing a Renaissance; microorganisms make products ranging from the tightly regulated pharmaceuticals industry to large-scale production of commodity chemicals and biofuels. Educating and training the next generation of employees for these rapidly expanding industries is critically important to their survival.”
For thousands of years humans have harnessed the power of microbes to make products such as bread, cheese, beer and wine. In the early 20th century scientists discovered how to use mold to produce antibiotics. It has only been in the past few decades, with the advent of DNA-based technologies, that our understanding of the vast diversity of microbial capabilities has exploded.
“If there is a chemical you want to break down, there is probably a microbe that can do it. If there is a compound you wish to synthesize, a microbe can probably help,” says the report, entitled Microbe-Powered Jobs: How Microbiologists Can Help Build the Bioeconomy. The report provides a litany of examples of potential biological products including bioenergy, biofuels, environmentally friendly industrial chemicals, and bioenzymes (the production of which already fuels a nearly $4 billion market).
To take full advantage of the potential the bioeconomy offers, the report suggests academia needs to re-think and take a broader approach to teaching microbiology at the undergraduate level. According to the report, the future growth of a microbial-based industry sector depends on two crucial elements: expansion of the fundamental understanding of microbiology and translation of that understanding into viable products.
Current microbiology education primarily trains scientists with an eye toward academic research, which is what is needed to continue the expansion of knowledge. Most undergraduates that take microbiology, though, have an eye on a medical career, so many undergraduate microbiology curricula focus on the biomedical aspects of microbiology, according to the report.
Here is the point that could raise cheers among employers and entrepreneurs. The report said, “One can imagine that instead of the current situation where pre-medicine is virtually the only undergraduate program with a microbiology component, there could be a series of majors with microbiology at their cores.”
One specific major, which the report outlines, could be an industrial microbiology track, with a focus towards translation. Not only would it emphasize microbiology, but it would also include quantitative skills important for success in industry. This type of curriculum could also be made available to engineering students in the form of a bioengineering track.
In addition to the traditional degree programs, the report also recommends other formats be used to teach specialized skills or offer intensive introductions to new fields of study.
The report might seem to be an appeal to department chairs and curriculum designers to build out majors for students, and it is. But the report is much more, offering a wealth of information in narrative and graphics that make the case that we are overlooking an enormous opportunity.
The American Academy of Microbiology has a self interest, obviously. But for improving the future consumers, businesses and academics could do well to take notice of the points raised in the report.
For now the scientific understanding and technological capacity to put microbes to work continues to advance at an impressive pace. It will take a lot more well educated students and graduates to discover and produce the products of the future.
Purdue and Cornell University scientists found high levels of the greenhouse gas methane above shale gas wells at a pre-production point not thought to be an important emissions source. The findings could have implications for the design of gas well drilling sites and evaluation of the environmental impacts from natural gas production. Letting natural gas escape unsold is serious enough, but letting it escape into the atmosphere is not a good idea at all.
The study, which is one of only a few to use a so-called “top down” approach that measures methane gas levels in the air above wells, identified seven individual well pads with high emission levels during the drilling stage.
The high-emitting wells made up less than 1% of the total number of wells in the area and were all found to be in the drilling stage, a pre-production stage not previously associated with significant emissions.
Paul Shepson, a professor of chemistry and earth atmospheric and planetary sciences at Purdue who co-led the study with Jed Sparks, a professor of ecology and evolutionary biology at Cornell said, “These findings present a possible weakness in the current methods to inventory methane emissions and the top-down approach clearly represents an important complementary method that could be added to better define the impacts of shale gas development. This small fraction of the total number of wells was contributing a much larger large portion of the total emissions in the area, and the emissions for this stage were not represented in the current inventories.”
The researchers flew above the Marcellus shale formation in southwestern Pennsylvania in the Purdue Airborne Laboratory for Atmospheric Research, a specially equipped airplane. The aircraft-based approach allowed researchers to identify plumes of methane gas from single well pads, groups of well pads and larger regional scales and to examine the production state of the wells.
“It is particularly noteworthy that large emissions were measured for wells in the drilling phase, in some cases 100 to 1,000 times greater than the inventory estimates,” Shepson said. “This indicates that there are processes occurring – e.g. emissions from coal seams during the drilling process – that are not captured in the inventory development process. This is another example pointing to the idea that a large fraction of the total emissions is coming from a small fraction of shale gas production components that are in an anomalous condition.”
The estimated bottom-up inventories have been produced from industry measurements of emissions from individual production, transmission and distribution components and then scaling up to create an estimate of emissions for the region. However, with thousands of wells, and a complex processing and transmission system associated with each shale basin, obtaining a representative data set is difficult, he explained.
A paper detailing the results has been published in the Proceedings of the National Academy of Sciences. The David R. Atkinson Center for a Sustainable Future at Cornell University funded this research.
“We need to develop a way to objectively measure emissions from shale gas development that includes the full range of operator types, equipment states and engineering approaches,” Shepson said. “A whole-systems approach to measurement is needed to understand exactly what is occurring.”
Shepson concluded the study results fairly. But the press release leaves a lot to be desired in accurately describing the issue. Production from completed wells looks to be quite well contained, which is where almost all the natural gas flows, much to the relief of production companies, consumers and environmentalists.
Drilling a well borehole is going to release some natural gas. Drilling rig operators could do better in capturing the gas. And its a certainty that drilling operators are using “gas sniffers” to identify gas finds. But the natural gas has been forming and creeping through the ground for millions of years and while drilling on the way down there is always a chance a bit of gas trapped out of place is going to get dinged and flow.
The Marcellus formation is a huge, old and already fractured rock structure that’s been leaking the entire time since its formation. In some places a water well will release a bit of natural gas as famously seen in attempts to frighten folks.
One way or another, eventually most of the natural gas underground is going to get into the atmosphere someday. It might be best to use it with the CO2 allowed back into the natural carbon cycle.
For now the scientists have IDed a noticeable source of natural gas emissions and the well owners are sure to bring pressure on drilling rig operators to hold the gas in for sale instead of escaping.
Thanks are sent to the Purdue and Cornell University scientists and the David R. Atkinson Center for the financial backing. We know a lot more now than before the team ran the research.
April 12, 2014 | Leave a Comment
According to Penn State mechanical engineers porous silicon manufactured in a bottom up procedure using solar energy can be used to generate hydrogen from water. The team also sees applications for batteries, biosensors and optical electronics as outlets for the new material.
Donghai Wang, assistant professor of mechanical engineering said, The surface area of this porous silicon is high. It is widely used and has a lot of applications.”
The standard method for manufacturing porous silicon is a subtraction method, similar to making a sculpture. “Silicon is an important material because it is a semiconductor,” said Wang. “Typically, porous silicon is produced by etching, a process in which lots of material is lost.”
Wang’s team comes at production from the opposite perspective. They use a chemically based method that builds up the material rather than removing it. The researchers start with silicon tetrachloride, a very inexpensive source of silicon. They then treat the material with a sodium potassium alloy.
“The bonds between silicon and chlorine in silicon tetrachloride are very strong and require a highly reducing agent,” said Wang. “Sodium potassium alloy is such an agent.”
Once the bonds break, the chlorine binds with the sodium, potassium and silicon, potassium chloride and sodium chloride – table salt – become solid, forming a material composed of crystals of salt embedded in silicon. The material is then heat-treated and washed in water to dissolve the salt, leaving pores that range from 5 to 15 nanometers.
Simple and quite clever.
Because sodium potassium alloy is highly reactive, the entire procedure must be done away from the oxygen in the air, so the researchers carry out their reaction in an argon atmosphere.
“I believe that the process can be scaled up to manufacturing size,” said Wang. “There are some processes that use sodium potassium alloy at industrial levels. So we can adapt their approaches to make this new type of porositic silicon.”
Because these silicon particles have lots of pores, they have a large surface area and act as an effective catalyst when sunlight shines on this porous silicon and water. The energy in sunlight can excite an electron that then reduces water, generating hydrogen gas. This process is aided by the material’s larger-than-normal band gap, which comes from the nanoscale size of the silicon crystallites.
“This porous silicon can generate a good amount of hydrogen just from sunlight,” said Wang.
The researchers are also looking into using this porous silicon as the anode in a lithium ion battery.
The Penn State team looks to have a really interesting material. Its a long way from a product, but the seeming simplicity common chemicals and low energy inputs looks very attractive.
Not much fanfare here, but a lot of the long haul products start out just like this – simple and practical. Now if it can scale stay cheap and be effective.
Navy researchers at the U.S. Naval Research Laboratory (NRL), Materials Science and Technology Division have demonstrated a proof-of-concept of a novel technology developed for the recovery of carbon dioxide (CO2) and hydrogen (H2) from seawater and converting it to a liquid hydrocarbon fuel.
The Navy’s research team demonstrated sustained flight of a radio-controlled (RC) P-51 replica of the legendary Red Tail Squadron, powered by an off-the-shelf and unmodified two-stroke internal combustion engine. The replica, a high end hobbyist’s model was fueled by a liquid hydrocarbon – a component of NRL’s novel gas-to-liquid (GTL) process that uses CO2 and H2 as feedstock.
The fuel production technology uses an innovative and proprietary NRL electrolytic cation exchange module (E-CEM) of both dissolved and bound CO2 removed from seawater at 92% efficiency. The process re-equilibrates carbonate and bicarbonate to CO2 and simultaneously produces H2. The gases are then converted to liquid hydrocarbons by a metal catalyst in a reactor system.
Dr. Heather Willauer, NRL research chemist said, “In close collaboration with the Office of Naval Research P38 Naval Reserve program, NRL has developed a game changing technology for extracting, simultaneously, CO2 and H2 from seawater. This is the first time technology of this nature has been demonstrated with the potential for transition, from the laboratory, to full-scale commercial implementation.”
Here is the important data point. CO2 in the air and in seawater is an abundant carbon resource, but the concentration in the ocean (100 milligrams per liter [mg/L]) is about 140 times greater than that in air, and 1/3 the concentration of CO2 from a “stack” gas (296 mg/L). Two to three percent of the CO2 in seawater is dissolved CO2 gas in the form of carbonic acid, one percent is carbonate, and the remaining 96 to 97% is bound in bicarbonate.
The NRL effort has made significant advances in the development of a gas-to-liquids (GTL) synthesis process to convert CO2 and H2 from seawater to a fuel-like fraction of C9-C16 molecules. In the first patented step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60% and decrease unwanted methane production in favor of longer-chain unsaturated hydrocarbons (olefins). These value-added hydrocarbons from this process serve as building blocks for the production of industrial chemicals and designer fuels.
In the second step these olefins can be converted to compounds of a higher molecular using controlled polymerization. The resulting liquid contains hydrocarbon molecules in the carbon range, C9-C16, suitable for use a possible renewable replacement for petroleum based jet fuel.
Today’s predicted cost of jet fuel using these technologies is in the range of $3-$6 per gallon With sufficient funding and partnerships, the approach could be commercially viable within the next seven to ten years. Pursuing remote land-based options would be the first step towards a future sea-based solution.
The minimum modular carbon capture and fuel synthesis unit is envisioned to be scaled-up by the addition individual E-CEM modules and reactor tubes to meet fuel demands.
The NRL operates a lab-scale fixed-bed catalytic reactor system and the outputs of this prototype unit have confirmed the presence of the required C9-C16 molecules in the liquid. This lab-scale system is the first step towards transitioning the NRL technology into commercial modular reactor units that may be scaled-up by increasing the length and number of reactors.
The process efficiencies and the capability to simultaneously produce large quantities of H2, and process the seawater without the need for additional chemicals or pollutants, has made these technologies far superior to previously developed and tested membrane and ion exchange technologies for recovery of CO2 from seawater or air.
There are a couple very interesting things in this news. First is the natural carbon cycle process where the CO2 is already concentrated in the seawater setting up an obvious point for carbon recapture. Second, the fuels produced would be “carbon neutral” inasmuch as no new fossil fuels would be used.
What is left out so far is the capital costs per produced unit – something that industry would be far better at driving to a low cost than a military effort. Three dollar diesel isn’t so very far from today’s wholesale price.
Perhaps the best part of the news comes a nearly “free resource” as in the seawater. The energy needed to drive the process is reported to be directed at producing the hydrogen with the CO2 product nearly free. Processed together the team reports recovering CO2 and concurrently producing H2 gas eliminates the need for additional large and expensive electrolysis units.
According to the team the process efficiencies and the capability to simultaneously produce large quantities of H2, and process the seawater without the need for additional chemicals or pollutants, has made these technologies far superior to previously developed and tested membrane and ion exchange technologies for recovery of CO2 from seawater or the atmosphere.
Next up is a military scale up. Its also time for some private industry interest to take hold.