Scientists at Rice University (Houston) have found that high-performance electrodes for lithium-ion batteries can be improved by paying closer attention to their defects, and then capitalizing on them.
Research by Rice materials scientist Ming Tang and chemists Song Jin at the University of Wisconsin-Madison and Linsen Li at Wisconsin and the Massachusetts Institute of Technology led a study that combined in situ X-ray microscopy and modeling to gain insight into lithium transport in battery cathodes. The scientists found that a common cathode material for lithium-ion batteries, olivine lithium iron phosphate, releases or takes in lithium ions through a much larger surface area than previously thought.
“We know this material works very well but there’s still much debate about why,” Tang said. “In many aspects, this material isn’t supposed to be so good, but somehow it exceeds people’s expectations.” Part of the reason, Tang said, comes from point defects—atoms misplaced in the crystal lattice—that are known as antisite defects. These defects are impossible to completely eliminate in the fabrication process, and as it turns out, Tang said, they make real-world electrode materials behave very differently from perfect crystals.
That and other revelations in a Nature Communications paper, which is now available online at https://www.nature.com/articles/s41467-017-01315-8, could potentially help manufacturers develop better lithium-ion batteries that power electronic devices worldwide.
The lead authors of the study, Liang Hong of Rice and Li of Wisconsin and MIT, and their colleagues collaborated with Department of Energy scientists at Brookhaven National Laboratory to use its powerful synchrotron light sources and observe in real time what happens inside the battery material when it is being charged. The scientists also employed computer simulations to explain their observations. One revelation, Tang said, was that microscopic defects in electrodes are a feature, not a bug.
“People usually think defects are a bad thing for battery materials, that they destroy properties and performance,” Tang said. “With the increasing amount of evidence, we realized that having a suitable amount of point defects can actually be a good thing.”
Inside a defect-free, perfect crystal lattice of a lithium iron phosphate cathode, lithium can only move in one direction, Tang said. Because of this, it is believed the lithium intercalation reaction can happen over only a fraction of the particle’s surface area. But the team made a surprising discovery when analyzing Li’s X-ray microscopic images: The surface reaction takes place on the large side of his imperfect, synthesized microrods, which counters theoretical predictions that the sides would be inactive because they are parallel to the perceived movement of lithium.
The researchers explained that particle defects fundamentally change the electrode’s lithium transport properties and enable lithium to hop inside the cathode along more than one direction. That increases the reactive surface area and allows for more efficient exchange of lithium ions between the cathode and electrolyte.
Because the cathode in this study was made by a typical synthesis method, Tang said, the finding is highly relevant to practical applications.
“What we learned changes the thinking on how the shape of lithium iron phosphate particles should be optimized,” he said. “Assuming one-dimensional lithium movement, people tend to believe the ideal particle shape should be a thin plate because it reduces the distance lithium needs to travel in that direction and maximizes the reactive surface area at the same time. But as we now know that lithium can move in multiple directions, thanks to defects, the design criteria to maximize performance will certainly look quite different.”
The paper’s co-authors are graduate student Fan Wang of Rice, Jun Wang, Yuchen-Karen Chen-Wiegart and Jiajun Wang of Brookhaven National Laboratory, Kai Xiang and Yet-Ming Chiang of MIT, and Liyang Gan, Wenjie Li and Fei Meng of the University of Wisconsin-Madison. Tang is an assistant professor of materials science and nanoengineering at Rice.
The research was supported by the US Department of Energy (DOE) Office of Basic Energy Science, the National Science Foundation (NSF), a University of Wisconsin-Madison WEI Seed Grant and the Vilas Research Travel Awards. Research was also conducted at the Department of Energy’s Brookhaven and Argonne national laboratories. The Texas Advanced Computing Center at the University of Texas at Austin and the National Energy Research Scientific Computing Center funded by the DOE and the Big-Data Private-Cloud Research Cyberinfrastructure funded by the NSF and Rice also provided computing resources.
Study Says US Power Supply Can
Be More Adaptable to Climate Change
A new report from scientists at City University of New York (CUNY) contends that climate change, while disrupting weather, sea levels, and loss of biodiversity, will ultimately have a negative effect on power generation in the United States, but that the infrastructure may be more adaptable to future climate than previously thought.
In recent decades, capacity losses at United States power plants occurred infrequently, but the CUNY scientists warn that the warming climate may increase their regularity and magnitude. This instability could interrupt power supply to homes, hospitals, transportation systems, and other critical institutions and infrastructure at a potentially high financial cost. This new research, “Climate and Water Resource Change Impacts and Adaptation Potential for U.S. Power Supply,” is published in Nature Climate Change. The study found that climate change ultimately will have a negative effect on the reliability of electricity generation in the United States, but today’s infrastructure may be more adaptable. An abstract of the work is available online at https://www.nature.com/articles/nclimate3417.
The improvements in resiliency are largely the result of efforts driven by policy and economic opportunities that are making the US power supply cleaner and more efficient, noted the scientists with the Advanced Science Research Center (ASRC) at the Graduate Center, CUNY. The study notes that modern power plants use fewer natural resources, such as water, to produce electricity, making them more adaptable to warmer, drier conditions than older plants, and these power plants also are better able to maintain power supply reserves during peak demands. While some regions appear susceptible to climate-change-related constraints on electricity production, an excess of reserves in other less-affected regions can aid those with diminished reserves, said Ariel Miara, ASRC research associate and lead author of the paper.
“Almost all power plants will be affected by climate change, but we don’t require all plants to operate at full capacity 24/7,” said Miara, also a doctoral candidate at The City College of New York’s Grove School of Engineering. “Lower available capacity due to climate impacts at some plants may be insignificant because the collective available capacity remains sufficient for meeting electricity needs.”
Miara and other ASRC scientists worked with researchers from National Renewable Energy Laboratory and Sandia National Laboratories to conduct the study. The team analyzed 1080 thermoelectric plants across the contiguous United States under future climate conditions and evaluated both their individual and collective performance across 19 North American Electric Reliability Corporation (NERC) sub-regions. Previous studies projecting power supply capacity only considered individual plant capabilities.
“This study demonstrates how the traditional approach of studying individual power stations fails to assess our true level of vulnerability,” said Charles J. Vörösmarty, director of the Environmental Sciences Initiative at the ASRC and a contributing author. “A regional system-wide viewpoint is needed because it allows us to see all sorts of factors and synergies that cannot be articulated by focusing on individual plant behaviors. Our findings about the full system offer a promising result among the otherwise daunting challenges of climate change—that if you search in the correct manner, you can find opportunities to adapt to change.”
Although the study’s findings are encouraging, the paper’s authors said further understanding of the collective strengths and vulnerabilities of the US power grid in the face of climate change is essential. For example, lower reserve margins do not imply inevitable brownout or blackout events. The utilization of demand-response measures, gas turbines, renewable energy sources, and electricity imported from other regions may help ensure a steady supply of power that can meet demand.
Aerospace supplier Northrop Grumman Corp. (El Segundo, CA) on Nov. 2 in London launched this year’s CyberCenturion, the UK’s national youth cyber-defense competition for 12–18 year olds. A record 575 teams, made up of more 2500 students, including 116 all-female and 45 cadet teams from across the country have registered to participate, according to the company, marking a more than threefold increase over last year.
This is the fourth consecutive year the CyberCenturion competition has been held.
CyberCenturion is the UK version of the CyberPatriot competition, part of a major US national youth cyber-education program presented by the Northrop Grumman Foundation and created by the Air Force Association. It is a key element of the company’s commitment to promoting science, technology, engineering, and mathematics (STEM) education and is aimed at engaging students with an interest in cyber to encourage them to pursue academic and career opportunities in STEM to help close the skills gap.
The competition is played over three rounds, with the formal kickoff on Nov. 3, at the Air Force Association headquarters in Arlington, VA. The two rounds following take place on Dec. 8 and Jan. 19, and culminate in the National Finals held in London, March 8, 2018.
“This year we have seen truly amazing growth in the number and diversity of teams that have entered the competition showing the increasing interest that young people have in cyber security,” Andrew Tyler, chief executive, Northrop Grumman Europe, said in a statement. “CyberCenturion is an important and popular means of inspiring young people to take further studies and follow careers in cyber.” CyberCenturion is delivered in partnership with Cyber Security Challenge UK, a nationwide program focused on bringing more talented people into the cybersecurity profession and building a bigger UK cyber-talent pool for government, businesses and citizens.
The Air Force Association is a nonprofit, independent, professional military and aerospace education association. Its mission is to promote a dominant United States Air Force and a strong national defense, and to honor airmen and the Air Force Heritage.
Northrop Grumman is a provider of full-spectrum cyber solutions to the United States government and to allied nations around the world.
Tech Front is edited by Senior Editor Patrick Waurzyniak; email@example.com.