New NMR technique could lead to better batteries

First, some background

Batteries have three essential parts: two electrodes (an anode and a cathode) and between them an electrolyte. Ions (charged particles) travel between the electrodes, generating electricity. Scientists are always trying to develop better batteries for energy storage out of materials like lithium.

Most lithium batteries today use liquid electrolytes, and that approach has its problems: Metallic bridges can form between the electrodes that short the battery. That's why scientists are trying to develop solid electrolytes that could be safer and yield more capacity.

What did scientists discover?

MagLab scientists have developed a new way, using nuclear magnetic resonance (NMR), to study the way lithium ions travel through solids. That journey is actually fairly complex, involving two variants, or isotopes, of lithium. As lithium-6 crosses the electrolyte, it swaps out for lithium-7. The MagLab experiments revealed that those pathways vary significantly, depending on the composition and structure of the solid electrolytes. Using a technique called operando NMR, the scientists could charge and discharge the batteries inside the instrument and observe changes in real time.

Why is this important?

The development of safe, high-energy-capacity batteries is of critical and growing importance. Replacing flammable liquid electrolytes with solid electrolytes in rechargeable Li-ion batteries will increase both performance and safety. This requires a fundamental understanding of lithium transport pathways. This study provides a novel and convenient tool for this type of research and contribute to better battery designs.

Who did the research?

Jin Zheng¹, Mingxue Tang¹, Po-Hsiu Chien¹, Kevin Huang², Hailong Chen³, Yan-Yan Hu¹

¹Florida State University; ²University of South Carolina; ³Georgia Institute of Technology

Why did they need the MagLab?

Lithium-6 NMR is a challenging measurement technique, due to the isotope's low natural abundance and low resonance frequency. High magnetic fields and fast sample spinning instrumentation available at the MagLab achieve the required sensitivity and resolution for this work. The MagLab's in-house development of an "in operando" NMR probe for battery studies has made it possible to probe lithium ion transport in real time.

Details for scientists

• View or download the expert-level Science Highlight, Tracking Lithium Transport Pathways in Solid Electrolytes for Batteries
• Read the full-length publication, Composite Polymer Electrolytes with Li₇La₃Zr₂O₁₂ Garnet-Type Nanowires as Ceramic Fillers: Mechanism of Conductivity Enhancement and Role of Doping and Morphology, in ACS Appl. Mater. Interfaces.
• Read the full-length publication, Li-ion transport in a representative ceramic-polymer-plasticizer composite electrolyte: Li₇La₃ r₂O₁₂—polyethylene oxide—tetraethylene glycol dimethyl ether, in Journal of Materials Chemistry A

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490); Y.-Y. Hu (NSF DMR 1508404)

For more information, contact Tim Cross.