Nav: Home

Neutrons offer guide to getting more out of solid-state lithium-ion batteries

December 21, 2015

Although they don't currently have as much conductivity, solid-state electrolytes designed for lithium-ion batteries (LIBs) are emerging as a safer alternative to their more prevalent--sometimes flammable--liquid-electrolyte counterparts.

However, a new study conducted at Oak Ridge National Laboratory's Spallation Neutron Source (SNS), a Department of Energy Office of Science user facility, has revealed promising results that could drastically boost the performance of solid-state electrolytes, and could potentially lead to a safer, even more efficient battery.

Using neutron diffraction techniques via the VULCAN instrument, SNS beam line 7, lead instrument scientist Ke An and his team recently concluded an in-depth study probing the entire structure evolution of doped garnet-type electrolytes during the synthesis process to unravel the mechanism that boosts the lithium-ionic conductivity. Their findings were recently published in the journals Chemistry of Materials and the Journal of Materials Chemistry A.

"The question we want to answer is how can we correlate the material's structure with its performance," An said. "Finding an answer to this will be very useful to the materials community, particularly in the field of electrochemical devices like batteries."

The problem with liquid electrolytes, says An, is that while they can produce high levels of conductivity--which is good--in some cases, they become flammable under high voltages or high temperatures, causing the battery to "explode"--which is obviously very bad.

In general, solid electrolyte-based LIBs consist of two electrodes, a positive and a negative, and an electrolyte in the middle, forming the battery's core, which facilitates the movement of ions traveling back and forth between the electrodes. In order to achieve a desired level of conductivity in the electrolyte, ions require vacancies in the crystal structure, or tunnels for the ions to "hop" to and from--kind of like connecting the dots.

Lithium lanthanum zirconates, or materials based on Li7La3Zr2O12 with a garnet structure, are favorable for application as electrolytes because they promote fast lithium transport. However, explained An, synthesized garnets often develop unwanted low-conductivity secondary phases, which in some cases can be detrimental to electrolytic performance. Essentially what that means is that useful vacancies for ions to "hop" don't always develop where designers want them to.

During synthesis, myriad chemical reactions take place as the material goes through several different phases, beginning with the mixing of chemicals or materials, then annealing, or heating the structure for desired performance and consistency, followed by a cool down period in which the structure is hardened. Analyzing what's going on during each phase would be next to impossible without the use of special instruments and techniques.

"Getting better performance out of the electrolyte can't be done without first understanding what's going on inside the structure. We need to understand what the mechanisms are that drive the synthesis process," said materials scientist and lead author Yan Chen, a postdoctoral research associate at SNS. "VULCAN enables us to perform in situ experiments, visualizing the structure's evolution in real time without disturbing the garnet synthesis process."

With VULCAN's help they monitored the low-conductivity phases' formation during the thermal process, and found that it could be mitigated by doping the material--adding trace amounts of various elements that have high valences, or an affinity to create bonds, to reduce the effect. Being able to both suppress the formation of those unwanted phases and increase the number of useful vacancies for ion transport proved to be the key to unlocking garnets with high electrolytic performance.

"By tracking the lithium vacancies as functions of temperature and dopants, we found a common rule that the different dopants obey, and how they redistribute the vacancies in the framework of the garnets," Chen said. "Furthermore, a comprehensive analysis of neutron diffraction results revealed how the dopants tune vacancy quantity, control vacancy distribution, and alter the charge carrier pathways in solid electrolytes."

Thanks to the experiments by An and his team, materials researchers now have a proven method for achieving the best results in garnet structures--results that are sure to lead to safer materials with much needed savings of time and money.

"Now when people look at our work they can be guided how to make high ionic conductivity by choosing the right element with the right valence rather than repeatedly doing trial and error experiments on every single additional element--work that takes you a lot of time," said An. "Now we can give you a simple formula to do it, and you should end up with a better material."
Chen's coauthors include Ezhiylmurugan Rangasamy, Chengdu Liang, Clarina R. dela Cruz, and Ke An. Related research of this material was conducted at the POWGEN instrument, SNS beam line 11A, using time of flight neutron diffraction data, and published in Advanced Energy Materials.

This work was sponsored by DOE's Office of Science.

UT-Battelle manages ORNL for the DOE's Office of Science. 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

DOE/Oak Ridge National Laboratory

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...