New material allows for better hydrogen-based batteries and fuel cells

This article reports the development of a room-temperature hydride ion (H⁻)-conducting solid electrolyte, representing a significant advance toward practical hydrogen-based solid-state batteries and fuel cells. The work addresses a central limitation of current proton-conducting polymer electrolyte membranes, which require continuous hydration, adding complexity, cost, and reliability constraints to hydrogen energy systems. The researchers focused on lanthanum hydrides (LaH₃₋δ), which exhibit intrinsically high hydride ion conductivity and favorable operating temperatures but suffer from hydrogen non-stoichiometry at room temperature, preventing efficient ion transport. By partially substituting lanthanum with electropositive strontium and introducing controlled oxygen content to form La₁₋ₓSrₓH₃₋ₓ₋₂yOᵧ, they stabilized the hydride composition and realized effective H⁻ conduction under ambient conditions. Crystalline samples prepared by ball-milling and annealing demonstrated high hydride ion conductivity, which was validated in a solid-state fuel cell configuration employing titanium electrodes. For Sr contents of x ≥ 0.2, galvanostatic discharge measurements showed complete conversion of Ti to TiH₂, indicating nearly lossless hydride ion utilization. These results establish the first demonstration of a room-temperature hydride ion-conducting solid electrolyte and provide concrete materials design guidelines for next-generation hydrogen-based electrochemical devices. The study outlines future directions, including performance optimization and the development of reversible hydrogen-absorbing electrodes, as key steps toward rechargeable hydrogen batteries and efficient hydrogen storage systems.