Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Imaging the inner workings of a sodium-metal sulfide battery for first time: Understanding how the structural and chemical makeup of the material changes during the charge/discharge process could help scientists advance battery design for future energy storage needs

Jun Wang (sitting), Christopher Eng (standing), Jiajun Wang (left, laptop screen), and Liguang Wang of Brookhaven National Laboratory used transmission x-ray microscopy combined with spectroscopy to produce the colored maps shown on the large screen. These maps reveal the structural expansion (and the resulting cracks/fractures) and chemical composition changes that occur as sodium ions (Fe, green) are added to and removed from iron sulfide (FeS, red) during the battery's first discharge/charge cycle. The pristine iron sulfide (box in upper left) does not return to its original state after this cycle, as some sodium ions remain trapped in the core (box in lower right). As a result, there is an initial loss in battery capacity.
CREDIT
Brookhaven National Laboratory
Jun Wang (sitting), Christopher Eng (standing), Jiajun Wang (left, laptop screen), and Liguang Wang of Brookhaven National Laboratory used transmission x-ray microscopy combined with spectroscopy to produce the colored maps shown on the large screen. These maps reveal the structural expansion (and the resulting cracks/fractures) and chemical composition changes that occur as sodium ions (Fe, green) are added to and removed from iron sulfide (FeS, red) during the battery's first discharge/charge cycle. The pristine iron sulfide (box in upper left) does not return to its original state after this cycle, as some sodium ions remain trapped in the core (box in lower right). As a result, there is an initial loss in battery capacity. CREDIT Brookhaven National Laboratory

Abstract:
Sometimes understanding how a problem arises in the first place is key to finding its solution. For a team of scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, taking this approach led them to the cause of degraded performance in an operating sodium-ion battery.

Imaging the inner workings of a sodium-metal sulfide battery for first time: Understanding how the structural and chemical makeup of the material changes during the charge/discharge process could help scientists advance battery design for future energy storage needs

Upton, NY | Posted on March 9th, 2017

"We discovered that the loss in battery capacity is largely the result of sodium ions entering and leaving iron sulfide--the battery electrode material we studied--during the first charge/discharge cycle," explained Brookhaven physicist Jun Wang, who led the research. "The electrochemical reactions involved cause irreversible changes in the microstructure and chemical composition of iron sulfide, which has a high theoretical energy density. By identifying the underlying mechanism limiting its performance, we seek to improve its real energy density."

The team's findings, published online in Advanced Energy Materials on March 3, could inform the design of future batteries capable of storing the amount of energy and surviving the many cycles required for large-scale energy applications, such as electric vehicles.

Identifying the problem

Most portable electronics today are powered by rechargeable lithium-ion batteries. But lithium is expensive and limited in supply, so scientists have been looking for alternatives. Sodium has recently emerged as a prime candidate because it is less expensive, more abundant, and has similar chemical properties.

Unfortunately, sodium-ion batteries, like their lithium counterparts, undergo changes during charge and discharge cycles that degrade their performance. While lithium-ion batteries have been extensively studied, little is known about the degradation mechanisms in sodium-ion batteries.

Wang's team set out to change that. Using a full-field transmission x-ray microscope (TXM) at Brookhaven's former National Synchrotron Light Source (NSLS) and later the Advanced Photon Source (APS) at DOE's Argonne National Laboratory (the instrument was temporarily relocated there when NSLS closed in 2015 and will return to Brookhaven when the new TXM beamline at the replacement facility, NSLS-II, is ready)--both DOE Office of Science User Facilities--the scientists imaged what happened as sodium ions were inserted into (sodiation) and extracted from (desodiation) an iron sulfide electrode over 10 cycles.

This study represents the first time that researchers have captured the structural and chemical evolution of a sodium-metal sulfide battery during its electrochemical reactions.

"Our full-field hard x-ray transmission microscope was critical because it provided nanoscale spatial resolution and a large field of view. Other microscopes typically provide one or the other but not both," said Wang.

Finding the root of the problem

The TXM images reveal significant fractures and cracks in the battery material after the first cycle. These microstructural defects, which originate at the surface of the iron sulfide particles and then proceed inward toward their core, are the result of the particles expanding in volume upon initial sodiation during the discharge process. Although these expanded particles subsequently shrink during the first desodiation (charging) process, they are unable to reverse back to their original pristine condition--a phenomenon called irreversibility.

To further support that this irreversibility was mainly due to the initial insertion and removal of sodium ions, the scientists tracked and mapped the corresponding chemical changes in real time. They used TXM in combination with a spectroscopy technique called x-ray absorption near edge structure, in which x-rays are fine-tuned to the energy at which there is a sharp decrease in the amount of x-rays that a chemical element absorbs. Because this energy is unique to each element, the resulting absorption spectra can be used to identify chemical composition.

The team's spectra show that the iron sulfide particles undergo a chemical transformation following the same surface-to-core mechanism as seen with the microstructural defects. In the early stage of sodiation, only the surface of the particles reacts with the sodium ions and converts to pure iron; as more sodium ions are inserted, this conversion reaction spreads to the core. By the end of the first discharge, nearly all the iron sulfide particles are converted to iron. During desodiation, most areas of the particles transform back to their original iron sulfide phase except for a few regions in the core, where some sodium ions remain "trapped."

"We know that the movement of metal ions is largely restricted by the interface between two coexisting phases," said Wang. "Sodium ions have a larger ionic radius compared to other metal ions, so they encounter even more resistance when trying to cross the interface between the iron sulfide core and the iron surface phases."

To quantify the diffusion of sodium ions, the team measured the changes in voltage of the battery material during cycling. From these voltage measurements, they were able to calculate the rate at which the sodium ions were moving in and out of the iron sulfide particles.

They found that in the beginning of the first discharge, sodium ions diffuse very slowly. But at some voltage, the diffusivity increases significantly. The opposite occurs during the first charge: sodium ions diffuse quickly at first, and then at a certain voltage, the diffusivity suddenly drops. These results are consistent with the structural and chemical changes observed through TXM.

"It appears that on the one hand, the cracks and fractures created by volume expansion of the iron sulfide particles during discharge destroy the particles' structure," said Wang. "But on the other hand, these defects provide a path for sodium ions to get to the particles' core. When the volume shrinks during charging, some of these paths are blocked, restricting the movement of sodium ions and trapping some in the core."

After this volume expansion and shrinkage in the first cycle, the battery material seems to achieve microstructural and chemical "equilibrium." Using the same TXM techniques, the team found that microstructure and chemical composition of the particles show robust reversibility as early as the second cycle and continuing through the tenth cycle. In other words, the battery material does not undergo significant subsequent changes in volume and is readily converted back to its original chemical form. They further confirmed their findings by performing real-time x-ray nanotomography to create 3D images of the battery material and measuring the percent volume change.

Coming up with a solution

Now that the scientists know why the structural and chemical irreversibility occurs, they can start working on ways to improve battery capacity after the first cycle. For example, one possible solution to the problem of sodium ion mobility may be decreasing the size of the iron sulfide particles so that a one-phase reaction occurs, making it much easier for sodium to react. Wang's team also plans to work with collaborators on modeling and simulations that will help inform the design of battery materials.

This work was supported by DOE's Laboratory Directed Research and Development program.

####

About Brookhaven National Laboratory
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, please visit science.energy.gov.

For more information, please click here

Contacts:
Ariana Tantillo

631-344-2347

Copyright © Brookhaven National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

RELATED JOURNAL ARTICLE:

Related News Press

News and information

Biophysics -- lighting up DNA-based nanostructures April 25th, 2018

Getting electrons to move in a semiconductor: Gallium oxide shows high electron mobility, making it promising for better and cheaper devices April 24th, 2018

JPK reports on research of the Mestroni Lab at the University of Colorado Denver which use the JPK NanoWizard® AFM to help in the characterization of cardiomyopathies April 24th, 2018

Organic solar cells reach record efficiency, benchmark for commercialization April 23rd, 2018

Laboratories

Psst! A whispering gallery for light boosts solar cells April 14th, 2018

Artificial intelligence accelerates discovery of metallic glass: Machine learning algorithms pinpoint new materials 200 times faster than previously possible April 13th, 2018

Doing the nano-shimmy: New device modulates light and amplifies tiny signals April 12th, 2018

Light 'relaxes' crystal to boost solar cell efficiency: Rice, Los Alamos discovery advances case for perovskite-based solar cells April 6th, 2018

Govt.-Legislation/Regulation/Funding/Policy

Organic solar cells reach record efficiency, benchmark for commercialization April 23rd, 2018

Remote-control shoots laser at nano-gold to turn on cancer-killing immune cells April 20th, 2018

Salt boosts creation of 2-D materials: Rice University scientists show how salt lowers reaction temperatures to make novel materials April 18th, 2018

Quantum shift shows itself in coupled light and matter: Rice University scientists corral, quantify subtle movement in condensed matter system April 16th, 2018

Possible Futures

Biophysics -- lighting up DNA-based nanostructures April 25th, 2018

Getting electrons to move in a semiconductor: Gallium oxide shows high electron mobility, making it promising for better and cheaper devices April 24th, 2018

JPK reports on research of the Mestroni Lab at the University of Colorado Denver which use the JPK NanoWizard® AFM to help in the characterization of cardiomyopathies April 24th, 2018

Organic solar cells reach record efficiency, benchmark for commercialization April 23rd, 2018

Discoveries

Biophysics -- lighting up DNA-based nanostructures April 25th, 2018

Getting electrons to move in a semiconductor: Gallium oxide shows high electron mobility, making it promising for better and cheaper devices April 24th, 2018

JPK reports on research of the Mestroni Lab at the University of Colorado Denver which use the JPK NanoWizard® AFM to help in the characterization of cardiomyopathies April 24th, 2018

Organic solar cells reach record efficiency, benchmark for commercialization April 23rd, 2018

Announcements

Biophysics -- lighting up DNA-based nanostructures April 25th, 2018

Getting electrons to move in a semiconductor: Gallium oxide shows high electron mobility, making it promising for better and cheaper devices April 24th, 2018

JPK reports on research of the Mestroni Lab at the University of Colorado Denver which use the JPK NanoWizard® AFM to help in the characterization of cardiomyopathies April 24th, 2018

Organic solar cells reach record efficiency, benchmark for commercialization April 23rd, 2018

Industrial

Leti and Inac Show Path to Creating Building Blocks of Quantum Processors With 28Si isotope in a CMOS Line: Fabrication of Isotopically Enriched, Industry-Compatible Wafers Points Way To Realizing Silicon Spin Quantum Bits with Enhanced Fidelity March 20th, 2018

Glass matters: UCSB researchers find that the chemical topology of silica can influence the effectiveness of many chemical processes that use it March 14th, 2018

Big steps toward control of production of tiny building blocks March 9th, 2018

GLOBALFOUNDRIES Strengthens 22FDX® eMRAM Platform with eVaderis’ Ultra-low Power MCU Reference Design: Co-developed technology solution enables significant power and die size reductions for IoT and wearable products February 27th, 2018

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Ultra-powerful batteries made safer, more efficient: Team aims to curb formation of harmful crystal-like masses in lithium metal batteries April 12th, 2018

CAP-XX Develops Industry’s First 3 Volt Thin Prismatic Supercapacitors: Provides peak power support to 3V coin cell batteries and eliminates need for 2.7V LDO regulator for less expensive, smaller, more energy-efficient designs with extended battery life April 11th, 2018

A new way to find better battery materials: Design principles could point to better electrolytes for next-generation lithium batteries March 29th, 2018

Graphene oxide nanosheets could help bring lithium-metal batteries to market March 23rd, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project