Schematic of a solid-state fuel cell made from the new material and titanium. The result of the galvanostatic discharge reaction showed that the Ti electrode was completely hydrogenated to TiH.2 for x ≥ 0.2. Credit: RIKEN
Researchers led by Genki Kobayashi of the RIKEN Cluster for Pioneering Research in Japan have developed a solid electrolyte to transport hydride ions (H−) at room temperature.
This advancement means that the benefits of solid-state batteries and hydrogen-based fuel cells are within reach, including improved safety, efficiency and energy density, which are essential for progress toward a practical energy economy based on hydrogen. The study was published in the journal Advanced energy materials.
For energy storage and hydrogen fuels to become widespread, they must be safe, highly efficient and as simple as possible. Hydrogen fuel cells currently used in electric cars work by allowing hydrogen protons to pass from one end of the fuel cell to the other through a polymer membrane when generating power .
Efficient and rapid movement of hydrogen in these fuel cells requires water, meaning the membrane must be continually hydrated so as not to dry out. This constraint adds a layer of complexity and cost to the design of batteries and fuel cells, thereby limiting the practicality of a next-generation hydrogen-based energy economy. To overcome this problem, scientists have struggled to find a way to conduct negative hydride ions through solid materials, especially at room temperature.
The wait is over. “We have reached a real milestone,” says Kobayashi. “Our result is the first demonstration of a solid electrolyte conducting hydride ions at room temperature.”
The team had experimented with lanthanum hydrides (LaH3-δ) for several reasons: hydrogen can be released and captured relatively easily, the conduction of hydride ions is very high, they can operate below 100°C and have a crystalline structure.
But, at room temperature, the number of hydrogens attached to lanthanum fluctuates between 2 and 3, making efficient conduction impossible. This problem is called hydrogen non-stoichiometry and is the biggest obstacle overcome in the new study. When researchers replaced part of the lanthanum with strontium (Sr) and added just a pinch of oxygen, to obtain a basic formula of La1 timeSrXH3-x-2aOhYesthey got the results they hoped for.
The team prepared crystalline samples of the material using a process called ball milling, followed by annealing. They studied the samples at room temperature and found that they could conduct hydride ions at a high rate. Next, they tested its performance in a solid-state fuel cell made from the new material and titanium, varying the amounts of strontium and oxygen in the formula. With an optimal value of at least 0.2 strontium, they observed 100% complete conversion of titanium to titanium hydride, or TiH.2. This means that almost no hydride ions were wasted.
“In the short term, our results provide guidelines for the design of materials for hydride ion-conducting solid electrolytes,” says Kobayashi. “In the long term, we believe this is an inflection point in the development of hydrogen-powered batteries, fuel cells and electrolytic cells.”
The next step will be to improve performance and create electrode materials that can reversibly absorb and release hydrogen. This would allow batteries to be recharged, as well as hydrogen to be stored and easily released when needed, which is a requirement for using hydrogen-based energy.
More information:
Yoshiki Izumi et al, Electropositive metal doping in lanthanum hydride for H− Carry out use of solid electrolyte at room temperature, Advanced Energy Materials (2023). DOI: 10.1002/aenm.202301993
Quote: New material enables better hydrogen-based batteries and fuel cells (December 22, 2023) retrieved December 22, 2023 from
This document is subject to copyright. Apart from fair use for private study or research purposes, no part may be reproduced without written permission. The content is provided for information only.
