A team of scientists led by a professor from Duke University discovered a way to help make batteries safer, charge faster and last longer. They relied on neutrons at the Department of Energy's Oak Ridge National Laboratory to understand at the atomic scale how lithium moves in lithium phosphorus sulfur chloride (Li6PS5Cl), a promising new type of solid-state battery material known as a superionic compound.
Using neutrons at ORNL's Spallation Neutron Source (SNS), and machine-learned molecular dynamics simulations at the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory, they found that lithium ions easily diffused in the solid material, as they do in liquid electrolytes, allowing faster, safer charging. The results, published in Nature Physics , could bring the best of both worlds for solid-state electrolytes (SSEs) enabling next-generation batteries.
"Our research was about figuring out what is going on inside these materials using the power of neutron scattering and large-scale computer simulations," said Olivier Delaire, associate professor of mechanical engineering, materials science, chemistry and physics at Duke University. Delaire arrived at ORNL in 2008 as a Clifford G. Shull Fellow and won DOE's Office of Science Early Career Award in 2014. Today, he leads a research group at Duke dedicated to investigating the atomic structure and dynamics of energy materials.
"The two big challenges, but also opportunities, we face are understanding how these materials work and how to design the next generation of batteries," Delaire said. "Neutron scattering is necessary in designing these."
While SSEs have known advantages over liquid electrolytes, such as improved energy density, increased safety and reduced combustibility, liquid electrolytes are more prevalent in battery materials because SSE materials are more challenging to create. Similarly, ions move more freely through liquid electrolytes than they do SSEs, and for batteries, ion mobility is crucial. Electrolytes allow ions to move from one end of a battery to the other, a process necessary for charging and discharging. The team used neutrons to study the lithium behavior in the superionic compound because neutrons see lighter elements, such as lithium, allowing them to gain new insights into solid-state superionic material for future energy storage and conversion technologies.
"Neutrons provide information about where things are happening that we wouldn't be able to see otherwise," said Doug Abernathy, SNS's Direct Geometry Spectroscopy group leader.
The team applied a neutron scattering technique known as neutron spectroscopy. This technique measures molecular and atomic motions with lattice vibrations and magnetic excitations in materials. Using the Wide Angular-Range Chopper Spectrometer (ARCS) and the Backscattering Spectrometer (BASIS) at SNS, the scientists measured and modeled lithium diffusion in the solid material, finding that lithium easily diffused.
With its intense, brighter source of neutrons and world-class instrument suite, SNS offers one of the world's most powerful sources of neutrons for discovery research.
"Our findings are impactful because they open the door to optimizing conductivity of the ions inside the material, therefore unlocking a path to increasing battery performance," said Naresh Osti, a neutron scattering scientist at ORNL.
The National Science Foundation funded this work through the Designing Materials to Revolutionize and Engineer our Future program. This research used resources at SNS and the National Energy Research Scientific Computing Center, DOE Office of Science user facilities at Oak Ridge and Lawrence Berkeley national laboratories, respectively.
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science . - Kaeli Dickert and Sumner Brown Gibbs
