It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Saturday, January 27, 2024
Scientists design a two-legged robot powered by muscle tissue
Compared to robots, human bodies are flexible, capable of fine movements, and can convert energy efficiently into movement. Drawing inspiration from human gait, researchers from Japan crafted a two-legged biohybrid robot by combining muscle tissues and artificial materials. Publishing on January 26 in the journal Matter, this method allows the robot to walk and pivot.
“Research on biohybrid robots, which are a fusion of biology and mechanics, is recently attracting attention as a new field of robotics featuring biological function,” says corresponding author Shoji Takeuchi of the University of Tokyo, Japan. “Using muscle as actuators allows us to build a compact robot and achieve efficient, silent movements with a soft touch.”
The research team's two-legged robot, an innovative bipedal design, builds on the legacy of biohybrid robots that take advantage of muscles. Muscle tissues have driven biohybrid robots to crawl and swim straight forward and make turns—but not sharp ones. Yet, being able to pivot and make sharp turns is an essential feature for robots to avoid obstacles.
To build a nimbler robot with fine and delicate movements, the researchers designed a biohybrid robot that mimics human gait and operates in water. The robot has a foam buoy top and weighted legs to help it stand straight underwater. The skeleton of the robot is mainly made from silicone rubber that can bend and flex to conform to muscle movements. The researchers then attached strips of lab-grown skeletal muscle tissues to the silicone rubber and each leg.
When the researchers zapped the muscle tissue with electricity, the muscle contracted, lifting the leg up. The heel of the leg then landed forward when the electricity dissipated. By alternating the electric stimulation between the left and right leg every 5 seconds, the biohybrid robot successfully “walked” at the speed of 5.4 mm/min (0.002 mph). To turn, researchers repeatedly zapped the right leg every 5 seconds while the left leg served as an anchor. The robot made a 90-degree left turn in 62 seconds. The findings showed that the muscle-driven bipedal robot can walk, stop, and make fine-tuned turning motions.
“Currently, we are manually moving a pair of electrodes to apply an electric field individually to the legs, which takes time,” says Takeuchi. “In the future, by integrating the electrodes into the robot, we expect to increase the speed more efficiently.”
The team also plans to give joints and thicker muscle tissues to the bipedal robot to enable more sophisticated and powerful movements. But before upgrading the robot with more biological components, Takeuchi says the team will have to integrate a nutrient supply system to sustain the living tissues and device structures that allow the robot to operate in the air.
“A cheer broke out during our regular lab meeting when we saw the robot successfully walk on the video,” says Takeuchi. “Though they might seem like small steps, they are, in fact, giant leaps forward for the biohybrid robots.”
This work was supported by JST-Mirai Program, JST Fusion Oriented Research for disruptive Science and Technology, and the Japan Society for the Promotion of Science.
Matter (@Matter_CP), published by Cell Press, is a new journal for multi-disciplinary, transformative materials sciences research. Papers explore scientific advancements across the spectrum of materials development—from fundamentals to application, from nano to macro. Visit: https://www.cell.com/matter. To receive Cell Press media alerts, please contact press@cell.com.
Cellular agriculture – the production of meat from cells grown in bioreactors rather than harvested from farm animals – is taking leaps in technology that are making it a more viable option for the food industry. One such leap has now been made at the Tufts University Center for Cellular Agriculture (TUCCA), led by David Kaplan, Stern Family Professor of Engineering, in which researchers have created bovine (beef) muscle cells that produce their own growth factors, a step that can significantly cut costs of production.
Growth factors, whether used in laboratory experiments or for cultivated meat, bind to receptors on the cell surface and provide a signal for cells to grow and differentiate into mature cells of different types. In this study published in the journal Cell Reports Sustainability, researchers modified stem cells to produce their own fibroblast growth factor (FGF) which triggers growth of skeletal muscle cells – the kind one finds in a steak or hamburger.
“FGF is not exactly a nutrient,” said Andrew Stout, then lead researcher on the project and now Director of Science at Tufts Cellular Agriculture Commercialization Lab. “It’s more like an instruction for the cells to behave in a certain way. What we did was engineer bovine muscle stem cells to produce these growth factors and turn on the signaling pathways themselves.”
Until now, growth factors had to be added to the surrounding liquid, or media. Made from recombinant protein and sold by industrial suppliers, growth factors contribute to a majority of the cost of production for cultivated meat (up to or above 90%). Since the growth factors don’t last long in the cell culture media, they also have to be replenished every few days. This limits the ability to provide an affordable product to consumers. Taking that ingredient out of the growth media leads to an enormous cost savings.
Stout is leading several research projects at Tufts University Cellular Agriculture Commercialization Lab —a technology incubator space which is set up to take innovations at the university and develop them to the point at which they can be applied at an industrial scale in a commercial setting.
“While we significantly cut the cost of media, there is still some optimization that needs to be done to make it industry-ready,” said Stout. “We did see slower growth with the engineered cells, but I think we can overcome that.” Strategies may include changing the level and timing of expression of FGF in the cell or altering other cell growth pathways. “In this strategy, we’re not adding foreign genes to the cell, just editing and expressing genes that are already there” to see if they can improve growth of the muscle cells for meat production. That approach could also lead to simpler regulatory approval of the ultimate food product, since regulation is more stringent for addition of foreign genes vs editing of native genes.
Will the strategy work for other types of meat, like chicken, pork, or fish? Stout thinks so. “All muscle cells and many other cell types typically rely on FGF to grow,” said Stout. He envisions the approach will be applied to other meats, although there may be variability for the best growth factors to express in different species.
“Work is continuing at TUCCA and elsewhere to improve cultivated meat technology,” said Kaplan, “including exploring ways to reduce the cost of nutrients in the growth media, and improving the texture, taste, and nutritional content of the meat. Products have already been awarded regulatory approval for consumption in the U.S. and globally, although costs and availability remain limiting. I think advances like this will bring us much closer to seeing affordable cultivated meat in our local supermarkets within the next few years.”
JOURNAL
Cell Reports Sustainability
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Cells
ARTICLE TITLE
Engineered autocrine signaling eliminates muscle cell FGF2 requirements for cultured meat production
ARTICLE PUBLICATION DATE
26-Jan-2024
U$A
Emergency contraception related ER visits dropped significantly over 14 year period
U.S. emergency departments see 96 % fewer visits, $7.6 million less in medical costs after FDA approval of over the counter emergency contraception in 2006
Following federal approval for over the counter emergency contraception in 2006, emergency departments across the U.S. saw dramatic decreases in related visits and medical charges, a new study suggests.
Emergency room visits related to emergency contraception fell by 96 %, from 17,019 to 659, while total related hospital expenses decreased by $7.2 million – from $7.6 million to $385,946 – between 2006 and 2020. The most notable decrease was between 2006-2007 for people primarily seen for emergency contraception.
The Michigan Medicine led findings appear in JAMA Network Open.
“Emergency departments are important sites for accessing emergency contraception given their 24-hour access and high acuity care,” said senior author Erica Marsh, M.D., professor of obstetrics and gynecology at the University of Michigan Medical School and chief of the division of reproductive endocrinology and infertility at U-M Health Von Voigtlander Women's Hospital, of Michigan Medicine.
“We believe this is the first study to specifically examine the association between relevant policy changes and disparities and trends in emergency department visits related to emergency contraception utilization.”
A disproportionate rate of younger, low income, Black, Hispanic and Medicaid insured patients were also seen for emergency contraception related visits compared to other emergency department services, researchers found.
“We found an overrepresentation of certain demographic groups utilizing emergency departments for emergency contraception,” Marsh said. “This aligns with previous outpatient research suggesting ongoing barriers to over the counter emergency contraception access and or increased emergency department utilization for other reasons, including sexual assault.”
Emergency contraception traditionally includes contraceptive methods used to prevent pregnancy in the first few days after unprotected intercourse, sexual assault, or contraceptive failure.
Although the FDA approved the first dedicated product for emergency contraception in 1998, over the counter approval didn’t come until 2006 for adults, followed by minors in 2013. The Patient Protection and Affordable Care Act also mandated emergency contraception insurance coverage in 2012.
While decreases in emergency contraception ER visits may have started before 2006, the steep decline between 2006-2007 suggests an association, authors say.
Barriers still persist
Researchers analyzed national data of more than 2 million emergency department visits among female-identifying patients aged 15-44 during the 14 year period.
Northeast hospitals comprised 44 to 59 % of emergency contraception related emergency room visits despite comprising only 17-19 %t of other ER visits.
Meanwhile, southern hospitals made up 4.5 to 17 % of emergency contraception related visits despite consistently averaging more than 40% of other types of emergency department visits in 2006.
“Our analysis suggests ongoing barriers in over the counter emergency contraception and disparities in utilization for certain populations,” Marsh said.
“Future policies should reduce barriers to make emergency contraception safe and affordable to all.”
JOURNAL
JAMA Network Open
ARTICLE TITLE
JAMA Trends in Encounters for Emergency Contraception in US Emergency Departments
ARTICLE PUBLICATION DATE
26-Jan-2024
The science behind mindfulness: How one University of Ottawa professor embraced it for the benefit of her students
Tapping into mindfulness to understand the neuroscience and physiological basis of the brain and training its networks to combat anxiety and life’s stressors
Understanding the neuroscience and physiological basis of the brain and training its networks to combat anxiety and life’s stressors
Professor Andra Smith, from the School of Psychology at the Faculty of Social Sciences, has combined her research and her personal experience with mindfulness to teach the course Neuroscience of Mindfulness: Neurons to Wellness. Her interest in neuroscience explores how to optimize cognitive processes behind decision-making, organizing behaviour, setting goals while taking the necessary steps to accomplish them without distractions. Mindfulness has allowed her students to achieve these skills while keeping stress at bay.
Question: What inspired you to explore the use of mindfulness to attack the stress you saw in your students?
Andra Smith: “During Covid, I didn’t have the usual hands-on connection with students and noticed they were battling high stress levels and anxiety was impacting their performance. I wanted to give them tools to handle some of these stressors and their fear of the future. I had gained so much from my own mindfulness training that I knew they would benefit from learning why and how it works.”
Q: Scientifically speaking, what kind of research did you lead to find evidence behind the effectiveness of mindfulness?
AS: “I performed two fMRI studies with mindfulness as an intervention, studying breast cancer patients with neuropathic pain and musicians suffering from performance anxiety. In both studies, we found significant changes in brain structure and function. Currently, we are working on an imaging study with pediatric concussion, and we hypothesize that mindfulness can help with emotion regulation and quality of life issues post-injury.”
Q: Mindfulness comes with skepticism for many; how did you view it as you moved forward in using it?
AS: “This required understanding the brain and how mindfulness worked from a neuroscience lens. I was skeptical until I learned why and how mindfulness worked in the brain: the stress response; the evolution of our brains; the attention networks; the nervous systems and their interactions; the way in which stress hijacks our prefrontal cortex and how to counter that. Those were the academic and scientific features, but personal life experiences also solidified my passion for mindfulness training. I used my mindfulness training during my mother’s illness and final passing, being with it despite how sad it was. It was a lightbulb moment that brought the science and experience together, confirming its power. I wanted to give this to my students. They embraced it, used it, and loved how it changed their day-to-day lives.”
Q: How did your students respond and what was ultimately achieved by introducing mindfulness to their curriculum/routine?
AS: “I provided mindfulness practices at the start and end of class plus suggested homework exercises. They did the homework and enjoyed it! One exercise was to have a mindful conversation, listening to listen, not to respond. This was eye-opening for students because they realized that they don’t really listen in a conversation without thinking about what their answer will be. It is a gift to give someone your full attention, and they felt it with this exercise and appreciated their relationships more afterwards. The consensus from the course was that the students had tools to deal with stress and learned that the stress did not have to control them; they could be in the driver’s seat and this made them more productive. For a professor it doesn’t get any better than hearing a student say that they implemented what they learned in class and that it enriched their lives.”
Q: How do you suggest people take a first step towards engaging in the practice of mindfulness for their benefit?
AS: “Gradually putting together several short practices that feel good is a good way to start. Mindfulness is a variety of practices so you can pick and choose what you like. It is really about attention and training those networks in the brain that allow us to stay focused and out of the pre-living and re-living narratives that we run so often. My book walks the reader through the whole course we did so that is a great place to start. I would be happy to help anyone who wants to try it. I would add that I do not recommend learning on your own if you have had trauma or suffer with significant mental health issues. It is not a replacement for treatment or therapy. It is a supplement.”
“Being aware of how stress impacts our physiology can give us a jump start on countering its potential negative effects. If we can be in tune with our physiology, it gives us all kinds of information and cues that we then have control over. Knowledge is power. We need to know our brain, as it controls everything we do, good and bad. Mindfulness can help us with this.
UT awarded $2.8 million DOE Grant to modernize the nation’s electric power grid
Validating its status as a leader in power electronics for grid and aviation applications, the University of Tennessee has been awarded a grant from the Advanced Research Projects Agency-Energy (ARPA-E) of the US Department of Energy (DOE) to help modernize the nation’s power grid.
ARPA-E is distributing $42 million for 15 projects across 11 states to improve the reliability, resiliency, and flexibility of the domestic power grid through the development of next-generation semiconductor technologies.
Funded through ARPA-E’s Unlocking Lasting Transformative Resiliency Advances by Faster Actuation of power Semiconductor Technologies (ULTRAFAST) program, the technologies being developed would enable more effective control of grid power flow and better protection of critical infrastructure assets.
UT is receiving $2,759,821 to develop scalable, light-triggered semiconductor switch modules with integrated optical sensing for the protection of the grid and aviation power systems. Dubbed as a UNIVERSAL (Ultrafast, Noise-Immune, Versatile, Efficient, Reliable, Scalable, and Accurate Light-controlled) Switch module, it seeks to achieve cost savings, fast switching speeds, and built-in redundancy by using sub-modules featuring lower-voltage and lower-current silicon carbide semiconductor devices for desired higher application voltage and current levels. In this project, a 25 kilo-volt switch module capable of switching off 2.5 kilo-amp current will be developed and demonstrated.
“This keeps UT at the forefront of power electronics technologies for grid and aviation applications,” Wang said. “Future electric grid will be dominated by power electronics interfaced energy sources like wind and solar and loads like EV chargers and data centers. The new grid will have much faster dynamics than today’s rotating machinery-based grid and will require much faster control and protection. Our proposed UNIVERSAL Switch module can interrupt a fault current in micro-second range, several orders of magnitude faster than the mechanical switch used today. It is also designed to have comparable efficiency and lifetime with the mechanical switches and can definitely help to enable the future power electronics dominated grid. The same technology can also be applied to future aircraft with electrified propulsion, which requires fast, efficient, and light-weight protection devices. DOE recognized the need for this kind of technology and that is why they fund this project.”
UT is working in collaboration with seven partners on this project, including long-time CURENT Industry Consortium members Dominion Energy and Boeing. As a leading US utility company, Dominion Energy will provide guidance on grid application design, while the global aerospace industry leader Boeing will provide guidance on aviation application design. Eaton, a leading US electrical equipment manufacturer, will provide support on the UNIVERSAL Switch module design and testing, while leading the technology-to-market activities. This project also involves several academic partners, with Clemson University focusing on optical sensing, Rensselaer Polytechnic Institute (RPI) on optical controller, Drexel University on wireless power control and sensing, and the University of Houston on application use case study. UT will be responsible for overall switch module design, integration, build and testing.
Wang anticipates the three-year project beginning in the spring of 2024. All of UT’s work will be done on campus.
“It is pretty challenging to work with so many organizations and people with different specialties. In this case, the optical part is totally new to us,” Wang said. “It will be beneficial to work on it, especially for our students. It will open their eyes to other ideas and possibilities. This will be very good for their education and training, which is always the most important part of our work at UT.”
UT’s UNIVERSAL Switch modules are controlled by light instead of electrical signals to minimize the electromagnetic interference and to simplify electrical isolation and insulation design. The light control will also be extremely fast and accurate, making them easy to be used in series and in parallel to achieve higher desired voltage and current for different applications. The modular structure will help to reduce cost and increase reliability, according to Wang.
“In the past decade, UT has led several DOE sponsored multi-million dollar projects developing power electronics technologies for distribution grids, which are usually around 10 to 15 kV voltage level. This will be the first project targeting transmission grid, which can be at tens to hundreds of kV voltage levels,” Wang said. “Although each of our modules will be only at 25 kV, it can be relatively easily stacked up to higher voltages with its modular structure and optical isolation design. It can be used for future high voltage direct current (HVDC) transmission, offshore wind transmission, and many other scenarios that require fast protection. We are extremely excited about its potentials.”
In a new paper in WIREs Computational Molecular Science, researchers from clinical stage artificial intelligence (AI)-driven drug discovery company Insilico Medicine (“Insilico”) demonstrate how quantum computing can be integrated into the study of living organisms in order to provide greater insight into biological processes like aging and disease.
In May 2023, Insilico, University of Toronto’s Acceleration Consortium, and Foxconn Research Institute published research that successfully demonstrated the potential advantages of quantum generative adversarial networks in generative chemistry. Those findings were published in the American Chemical Society’s Journal of Chemical Information and Modeling.
In this latest paper, Insilico researchers present a broad picture of how combining methods from AI, quantum computing, and the physics of complex systems can help researchers advance new understandings of human health – and detail the latest breakthroughs in physics-guided AI.
While AI has been an invaluable tool in helping researchers process and analyze large, complex biological datasets in order to find new disease pathways and connect aging and disease at the cellular level, they write, it still faces challenges in applying those insights to more complex interactions within the body.
In order to fully understand the inner workings of living organisms, the researchers note, scientists need multimodal modeling methods that can manage three key areas of complexity: the complexity of scale, the complexity of the algorithms, and the increasing complexity of datasets.
“While we are not a quantum company, it is important to utilize capabilities to take advantage of the speed provided by the new hybrid computing solutions and hyperscalers. As this computing goes mainstream, it may be possible to perform very complex biological simulations and discover personalized interventions with desired properties for a broad range of diseases and age-associated processes. We are very happy to see our research center in the UAE producing valuable insights in this area,” says co-author Alex Zhavoronkov, PhD, founder and co-CEO of Insilico Medicine.
Biological processes within living systems scale from cells to organs to the whole body with lots of complex interactions between systems. Interpreting these processes needs to work on multiple scales simultaneously. And access to biological data has reached previously unimaginable levels. There’s the 1000 Genomes Project – a catalog of human genetic variation which has identified over 9 million single nucleotide variants (SNVs) – and the UK Biobank which contains full sequences from 500,000 genomes of British volunteers, to name just a couple. We need massive computing power to analyze and process it.
Quantum computing, the researchers write, is uniquely positioned to augment AI approaches – allowing researchers to interpret across multiple levels of the biological system simultaneously. Because qubits hold values of 0 and 1 simultaneously, whereas classical bits hold only values of 0 or 1, qubits have massively greater computing speed and capability.
The authors note that major advances in quantum computing are already underway, including IBM’s recent debut of both a utility-scale quantum processor and the company’s first modular quantum computer, which has already begun operations.
Ultimately, the authors call for a physics-guided AI approach to better understand human biology – a new field that combines physics-based and neural network models, which they write is already underway.
By combining methods from AI, quantum computing, and the physics of complex systems, scientists can better understand how, as the authors write, “the collective interactions of smaller-scale elements within a cell, organism, or society generate emergent characteristics that can be observed at larger scales and levels of reality.”
Hierarchical complexity of living organisms
About Insilico Medicine
Insilico Medicine, a global clinical stage biotechnology company powered by generative AI, is connecting biology, chemistry, and clinical trials analysis using next-generation AI systems. The company has developed AI platforms that utilize deep generative models, reinforcement learning, transformers, and other modern machine learning techniques for novel target discovery and the generation of novel molecular structures with desired properties. Insilico Medicine is developing breakthrough solutions to discover and develop innovative drugs for cancer, fibrosis, immunity, central nervous system diseases, infectious diseases, autoimmune diseases, and aging-related diseases. www.insilico.com
Could quantum physics be the key that unlocks the secrets of human behavior?
Human behavior is an enigma that fascinates many scientists. And there has been much discussion over the role of probability in explaining how our minds work.
Probability is a mathematical framework designed to tell us how likely an event is to occur – and works well for many everyday situations. For example, it describes the outcome of a coin toss as ½ – or 50% – because throwing either heads or tails is equally probable.
Yet research has shown that human behavior can’t be fully captured by these traditional or “classical” laws of probability. Could it instead be explained by the way probability works in the more mysterious world of quantum mechanics?
Mathematical probability is also a vital component of quantum mechanics, the branch of physics that describes how nature behaves at the scale of atoms or sub-atomic particles. However, as we’ll see, in the quantum world, probabilities follow very different rules.
Discoveries over the last two decades have shed light on a crucial role for “quantumness” in human cognition – how the human brain processes information to acquire knowledge or understanding. These findings also have potential implications for the development of artificial intelligence (AI).
Human ‘irrationality’
Nobel laureate Daniel Kahnemann and other cognitive scientists have carried out work on what they describe as the “irrationality” of human behavior. When behavioral patterns do not strictly follow the rules of classical probability theory from a mathematical perspective, they are deemed “irrational”.
For example, a study found that a majority of students who have passed an end-of-term exam favor going on holiday afterwards. Likewise, a majority of those who have failed also want to go for a holiday.
If a student doesn’t know their result, classical probability would predict that they would opt for the holiday because it is the preferred option whether they have passed or failed. Yet in the experiment, a majority of students preferred not to go on holiday if they didn’t know how they’d done.
Intuitively, it’s not hard to understand that students might not want to go on holiday if they are going to be worrying about their exam results the whole time. But classical probability does not accurately capture the behavior, so it is described as irrational. Many similar violations of classical probability rules have been observed in cognitive science.
Quantum brain?
In classical probability, when a sequence of questions is asked, then the answers do not depend on the order in which the questions are posed. By contrast, in quantum physics, the answers to a series of questions can depend crucially on the order in which they are asked.
One example is the measurement of the spin of an electron in two different directions. If you first measure the spin in the horizontal direction and then in the vertical direction, you will get one outcome.
The outcomes will generally be different when the order is reversed, because of a well known feature of quantum mechanics. Simply measuring a property of a quantum system can affect the thing that’s being measured (in this case an electron’s spin) and hence the outcome of any subsequent experiments.
They were then asked if his vice president, Al Gore, seemed honest.
When the questions were delivered in this order, a respective 50% and 60% of respondents answered that they were honest. But when the researchers asked respondents about Gore first and then Clinton, a respective 68% and 60% responded that they were honest.
On an everyday level, it might seem that human behavior is not consistent because it often violates the rules of classical probability theory. However, this behaviour does appear to fit with the way probability works in quantum mechanics.
Observations of this kind have led cognitive scientist Jerome Busemeyer and many others to recognize that quantum mechanics can, on the whole, explain human behavior in a more consistent way.
Based on this astonishing hypothesis, a new research field called “quantum cognition” has arisen within the area of cognitive sciences.
How it is possible that thought processes are dictated by quantum rules? Is our brain working like a quantum computer? No one yet knows the answers, but the empirical data strongly appears to suggest that our thoughts follow quantum rules.
Dynamic behaviour
In parallel to these exciting developments, over the past two decades my collaborators and I have developed a framework for modeling – or simulating – the dynamics of people’s cognitive behavior as they digest “noisy” (that is, imperfect) information from the outside world.
We again found that mathematical techniques developed for modelling the quantum world could be applied to modeling how the human brain processes noisy data.
These principles can be applied to other behavior in biology, beyond just the brain. Green plants, for example, have the remarkable ability to extract and analyse chemical and other information from their environments and to adapt to changes.
In this context, efficiency means that the plant is consistently able to reduce the uncertainty about its external environment to the greatest extent possible in its circumstances. This could, for example, encompass easily detecting the direction that light is coming from, so that the plant can grow towards it. The efficient processing of information by an organism is also linked to saving energy, which is important for its survival.
Similar rules may apply to the human brain, particularly to how our state of mind changes when detecting outside signals. All of this is important for the current trajectory of technological development. If our behavior is best described by the way probability works in quantum mechanics, then to accurately replicate human behavior in machines, AI systems should probably follow quantum rules, not classical ones.
I’ve called this idea artificial quantum intelligence (AQI). A great deal of research is needed to develop practical applications from such an idea.
But an AQI could help get us to the goal of AI systems that behave more like a real person.
UPTON, NY—On a mission to build better electric vehicle batteries, chemists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have used an electrolyte additive to improve the functionality of energy-dense lithium metal batteries. By adding a compound called cesium nitrate to the electrolyte that separates the battery’s anode and cathode, the research team has significantly improved the charging rate of lithium metal batteries while maintaining a long cycle life.
The team’s new work, recently published in Nature Communications, targets the interphase—a protective layer formed on the battery’s anode and cathode. This layer, which prevents degradation of battery electrodes, is the key to creating lithium metal batteries that can be charged and discharged as many times as lithium-ion batteries.
“We wanted to improve the charging rate of the current state-of-the-art lithium metal batteries,” explained Muhammad Mominur Rahman, a research associate in the Electrochemical Energy Storage Group of the Chemistry Division at Brookhaven and first author on the new paper. “But we also wanted to stabilize the batteries with a more protective interphase so they would last longer.”
In addition to successfully stabilizing the battery, Rahman’s electrolyte additive altered the battery chemistry in an unexpected way.
“Mominur’s findings challenge conventional beliefs about the components of an effective interphase,” said Enyuan Hu, Brookhaven chemist and principal investigator within the Electrochemical Energy Storage Group. “We’re excited to see how these findings contribute to the major DOE effort focused on lithium metal batteries.”
One step towards a larger goal
Hu and his team are working among other battery experts as part of the Battery500 Consortium, a collaboration of several national labs and universities. The Consortium, which is led by DOE’s Pacific Northwest National Laboratory, is striving to make batteries with an energy density of 500 watt-hours per kilogram—more than double the energy density of today’s state-of-the-art batteries.
This energy density cannot be achieved in the lithium-ion batteries powering most of today’s battery-operated devices—including phones, television remotes, and even electric vehicles. So, scientists needed to turn to lithium metal batteries to pursue their goals. These batteries possess a lithium metal anode, rather than the graphite anode present in lithium-ion batteries.
“The lithium metal battery is attractive because it can give twice the energy density of a battery with a graphite anode,” explained Rahman. “But there are lots of challenges to tackle.”
Brookhaven’s most recent research addresses one of these challenges—striking a balance between the charging speed and the cycle life.
The electrolyte that typically enables fast battery charging is also likely to be reactive with the lithium metal anode. If these chemical reactions proceed uncontrollably, the electrolyte decomposes and reduces the battery’s cycle life. To prevent this from happening, Brookhaven chemists set out to engineer the interphase.
Previous studies had indicated that the lithium metal anode could be stabilized with a cesium additive. But to increase the charging rate while maintaining the battery cycle life, the anode and cathode need to be stabilized simultaneously. The Brookhaven scientists believed cesium nitrate could serve this purpose for lithium metal batteries. As they had hypothesized, the positive cesium ion accumulated on the negatively charged lithium metal anode side of the battery, while the negative nitrate ion accumulated on the positively charged cathode.
To better understand how the cesium nitrate additive influenced the electrolyte composition and battery performance, the chemists brought the new batteries to the National Synchrotron Light Source II (NSLS-II), a DOE Office of Science user facility at Brookhaven Lab.
A gaze into the interphase
NSLS-II is one of the most advanced x-ray light sources in the world, producing light beams that are 10 billion times brighter than the sun. Of the 29 beamlines currently operating at NSLS-II, Rahman and Hu took advantage of the capabilities of four beamlines for their most recent research.
“NSLS-II is really a great facility for conducting battery research,” said Hu. “There is a breadth of techniques available, which enables us to conduct complete studies of complex materials.”
Among the four beamlines used by the chemists was the X-ray Powder Diffraction (XPD) beamline, a high energy diffraction beamline with photon beams that can contain more than three times the energy of conventional x-ray powder diffraction beamlines. For more than five years, Hu’s group has been leveraging these high energy beams for interphase studies that have led to a series of new understandings of battery chemistry.
The high-energy x-rays are capable of penetrating thick materials, like the anodes and cathodes within batteries. But they are also characterized by their high intensity, which enables the quick data collection necessary to take a “snapshot” of the elusive interphase.
“The XPD beamline is excellent because its x-rays have low absorption power and do not damage the interphase samples,” Hu elaborated. “One of the greatest challenges in characterizing interphase samples is their sensitivity to the x-ray beams, but we’ve characterized over 1,000 interphase samples at XPD without observing any damage to the samples.”
Some components of the interphase are crystalline, meaning that their atoms are neatly arranged. These components can typically be studied with conventional x-ray diffraction (XRD). But battery interphases also contain unorganized, amorphous components whose characterizations are beyond the capabilities of XRD. Instead, a technique called pair distribution function (PDF) analysis is needed. At the XPD beamline, led by Sanjit Ghose, scientists can conduct both techniques simultaneously. With these two techniques, the researchers can understand all the chemical species that evolve during the reactions that form the interphase components.
“We call this combined method total scattering,” explained Ghose, who is a co-author on the paper. “But these techniques are especially unique because they can characterize the structures of chemical species reliably—even if they are only present in trace amounts—which is needed for battery research.”
“Enyuan’s group is really becoming a champion of leveraging XPD’s total scattering techniques and its ability to not damage samples,” he added.
The scientists found that the cesium nitrate additive increased the presence of components known to make the interphase more protective. The XRD data, however, had a surprise in store. In addition to the typical crystalline components, a compound called cesium bis(fluorosulfonyl)imide was also identified.
“This component of the interphase had never been reported before,” said Rahman, emphasizing the novelty of the finding.
“But it’s not just about what we found,” added Hu. “It’s also what was missing from the interphase.”
Scientists studying batteries generally regard lithium fluoride as a necessary component of a good interphase. In fact, its presence and abundance are typically used to explain the impressive performance of lithium metal batteries. That’s why Rahman and Hu were especially surprised by its absence.
“We don’t know why it is not there,” Hu said. “But the fact that this lithium fluoride-free interphase enables a long cycle life and fast charging inspires us to revisit the current understanding of the interphase.”
Though the XPD beamline is adept at detecting trace amounts of interphase components, it is difficult to use the same x-ray beams to quantify these components—especially when some of them are present in such small amounts. So, the scientists brought their batteries to the Submicron Resolution X-ray Spectroscopy (SRX) beamline to quantitatively analyze how the different chemical elements collected on the battery electrodes and in their respective interphases after cycling.
To do this, the SRX beamline scientists used an ultra-sensitive technique called scanning x-ray fluorescence (XRF) microscopy. This technique, which is based on a known and calibrated standard, evaluates the chemical distribution of the interphase. The scanning XRF images confirmed that there was more cesium present in the anode interphase than the cathode interphase. With further scanning XRF analysis, the scientists revealed that the cesium nitrate additive prevented the breakdown of the transition metals that make up the cathode, contributing to the overall stabilization of the cathode and lithium metal battery.
The scientists also analyzed their samples at the Quick X-ray Absorption and Scattering (QAS) and the In situ and Operando Soft X-ray Spectroscopy (IOS) beamlines to verify that cesium accumulated on the lithium metal anode and nitrate accumulated on the cathode, respectively. Furthermore, the IOS beamline scientists confirmed that the cathode was stabilized with the cesium nitrate additive.
QAS beamline scientists take advantage of the beamline’s high energy x-rays, which can probe deep into the sample, to conduct hard x-ray absorption spectroscopy (XAS). Scientists at the IOS beamline, on the other hand, use low energy x-rays to directly probe atoms near the surface of the sample. Both techniques provide detailed analyses of the chemical and electronic states of the atoms present at the respective electrodes.
“Conducting complementary analyses at these additional beamlines helped us verify our design idea,” said Hu. The two XAS techniques were crucial for characterizing the anode and cathode as well as the interphase.
But the scientists’ analyses were not yet complete; they also had to check for stabilization of the lithium metal anode with the cesium nitrate additive. So, the scientists brought their batteries to the materials synthesis and characterization facility at the Center for Functional Nanomaterials (CFN), a DOE Office of Science user facility at Brookhaven Lab, to make use of the scanning electron microscope. The resulting microscope images showed that the lithium formed by electrochemical reactions deposits uniformly when the cesium nitrate is added to the electrolyte, thus contributing to the stabilization of the electrode and reinforcing the benefits of this additive.
"We really took advantage of all the resources available to us at Brookhaven Lab,” said Rahman.
By combining various techniques across two user facilities, the scientists were able to paint a full picture of how the lithium metal battery behaves with the cesium nitrate additive. This research contributes to a better understanding of interphase optimization and overall battery chemistry.
“Lithium metal batteries have come a long way, but they still have a long way to go. The interphase plays a key role in progress that still needs to be made,” Rahman said. “Our work has created new opportunities for interphase engineering, and I hope that this will inspire others to look at the interphase differently so that we can accelerate the development of lithium metal batteries.”
This work was supported by DOE’s Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office and DOE’s Office of Science. Operations at NSLS-II and CFN are supported by the Office of Science.
Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit science.energy.gov.