Structure of Ionic Liquids Under Nanoconfinement in Energy Applications

Eric Meshot | 18-LW-064


Ionic liquids (ILs) are a promising next-generation electrolyte for use in energy storage technologies. However, their structure, which dictates a device’s ability to store an electrical charge, is poorly understood. There is little experimental data available regarding the structure of ILs confined inside nanopores.

The goal of this project was to improve upon prior characterization studies by (a) turning to carbon nanotubes (CNTs) as model pores with inherently smooth atomic surfaces and well-defined cylindrical geometry and size distribution; and (b) probing the IL nanostructure with chemical specificity by combining spectroscopy with small-angle x-ray scattering techniques. We leveraged our team’s expertise in CNT synthesis, nanofabrication, and nanofluidic integration to design and build a new scientific tool to enable in situ probing of a confined IL. We simultaneously employed synchrotron x-ray scattering and molecular dynamics simulations to resolve ion coordination and the nanostructure of ILs confined within nanopores.

Impact on Mission

This research is relevant to important science and technology areas at Lawrence Livermore National Laboratory including CO 2 capture, catalysis, electrodeposition of metals, and energy storage. The project's findings indicate future opportunities related to energy harvesting and storage involving nanoporous materials and solid–liquid interfaces, a focus area for Laboratory of Energy Applications for the Future (LEAF). Our research supports the Laboratory's core competencies in high-performance computing (HPC), simulation, and data science as well as advanced materials and manufacturing, especially considering the theme of in situ materials characterization. Our research is strongly aligned with Livermore's mission research challenge of energy and resource security—materials for energy applications and HPC applied to energy innovation. Additionally, the scientific tools and methods developed to probe confined ions potentially benefit the Laboratory's existing efforts at the multi-lab Hydrogen Materials Advanced Research Consortium and the Vehicle Technology Office programs. This work addresses DOE basic research needs and overlaps with DOE Basic Energy Sciences programs, which are "pursuing a molecular-level understanding of chemical, physical…processes in liquids and at interfaces."

Publications, Presentations, Etc.

Meshot, E., et al. 2018. "Designing Single-Wall Carbon Nanotube Forest Growth for Nanofluidic Applications." 233rd Electrochemical Society (ECS) Meeting, Seattle, WA, May 2018. LLNL-PRES-751027.

Pham, T., et al. 2018. "Structure of Room Temperature Ionic Liquids from X-ray Scattering and ab-initio Molecular Dynamics. Simulations." Materials Research Society (MRS) Fall Meeting, Boston, MA, November 2018. LLNL-PRES-763446.

Shi, W., et al. 2018. "High-Performance Capacitive Deionization via Manganese Oxide-Coated, Vertically Aligned Carbon Nanotubes." Environmental Science & Technology Letters 5 (11):692-700. doi: 10.1021/acs.estlett.8b00397. LLNL-JRNL-755914.