Lithium hydride for advanced technologies

A group of materials scientists at Lawrence Livermore National Laboratory (LLNL) have made significant progress in developing a scalable and efficient method to produce dense lithium hydride (LiH), a material with immense potential for use in nuclear fusion, long-term human space travel, and thermal energy storage.

In nuclear fusion, LiH has the potential to serve as a source of deuterium–tritium (DT) fuel, which is essential for achieving plasma ignition and net energy gain. Unlike tritium gas, which is hazardous to handle, solid-state LiH offers a safer and more practical alternative for DT fuel production. Owing to its high hydrogen content, LiH has also demonstrated greater radiation dose reduction compared to other lightweight radiation shielding options such as polyethylene, making it a promising option for radiation shielding in space missions.

However, to unlock its full potential, scientists need to fabricate LiH in dense, customizable shapes and sizes while minimizing impurities that form during processing. To do this, the research team turned to a technique called pressureless sintering, a cost-effective and scalable method for fabricating dense, customizable materials without applying external pressure. This approach allows for the creation of complex geometries by selectively controlling the maximum temperature, heating rate, and hold time throughout the process.

For their study, the team pressed LiH powder into compact pellets and heated them at controlled rates (ranging from 2.5°C to 20°C per minute) to a maximum temperature of 650°C, systematically investigating how LiH behaves when heated in an inert argon environment—used to prevent LiH from reacting with atmospheric components like oxygen, water vapor, nitrogen, and carbon dioxide, which can cause corrosion and the formation of undesirable impurities. They then used advanced tools like x-ray diffraction, scanning electron microscopy, and computed tomography to analyze the resulting material's density, microstructure, and chemical stability.

The team’s analyses revealed the LiH pellets had densities as high as 96%. This percentage is a measure of how close the sintered LiH pellets are to their theoretical maximum density. As the temperature increases, the LiH grains were found to grow larger and bond together, reducing the empty spaces (pores) and increasing the material's density.

During heating, it was also found that LiH reacts with trace amounts of water and oxygen in the environment, forming impurities like lithium oxide and lithium hydroxide. The researchers identified the temperature ranges where these reactions occur, allowing for better control of the process to minimize impurities.

One of the key outcomes of this work was the development of a Master Sintering Curve (MSC) for lithium hydride. This curve provides a predictive model for how LiH densifies under different heating conditions, enabling scientists to optimize the sintering process for specific applications.

While this research represents a significant milestone in the journey toward harnessing the full potential of lithium hydride for energy, space, and beyond, future studies are needed to further elucidate the complex sintering mechanisms of LiH and ceramics in general.

[P.W.F. Evans, C.G. Bustillos, H. Charalambous, A.E. Wilson-Heid, J. Shittu, A.J. Swift, J. Root, and W.L. Du Frane, Pressureless sintering of lithium hydride, Journal of the European Ceramic Society (2025), doi: 10.1016/j.jeurceramsoc.2024.117152.

–Physical and Life Sciences Communications Team