Maxwell Marple | 20-FS-012
Solid-state batteries are a safer and higher-energy-density alternative to current liquid electrolyte batteries; however, their performance has been hindered by the solid-solid interface that forms between the solid electrolyte and electrodes. Mechanistic information regarding solid–solid interfaces in solid-state batteries remains elusive because a nondestructive operando technique is needed to observe it, but no such technique currently exists. Solid-state nuclear magnetic resonance (NMR) is uniquely suited to address this challenge because it is sensitive to chemistry, structure, and dynamics, and because it can measure buried interfaces. However, there are technical challenges because of the need to spin the sample at high speeds to obtain adequate resolution, and because a wireless means of charging is required for operando capabilities.
Our project addressed these challenges and demonstrated optical wireless charging. By limiting the size of the metallic components, we were able to spin a sample holder with electrical leads and a solid-state battery up to a few kilohertz, fast enough for high-resolution NMR. We achieved wireless charging by attaching a photovoltaic cell to the head of the NMR rotor and used a laser to transmit power to the photovoltaic cell. This novel capability is a transformative technique for investigating the mechanistic electrochemical processes in solid-state samples. We tested the feasibility of operando magic-angle-spinning NMR by (1) creating a rotor holder that can spin a battery while providing secure electrical contact, and then (2) testing whether the battery could be charged wirelessly using a coupled laser and photovoltaic cell. We also developed a better understanding of the solid electrolyte used for this study.
The operando magic-angle-spinning NMR capability is an entirely new characterization technique for investigating energy materials and is unique to Lawrence Livermore National Laboratory. The technique can be applied more broadly to investigate not only batteries, but any material under bias, such as performing operando electroplating, water splitting, electrochemical reduction, and oxidization of materials. Thus, this new capability supports the Laboratory's core competency in advanced materials and manufacturing and addresses Livermore's energy and resource security mission research challenge.