High-capacity, reversible hydrogen storage using H – -conducting solid electrolytes

Hydrogen absorption and desorption in solids are pivotal reactions involved in batteries and hydrogen storage devices. However, conventional thermodynamic and electrochemical hydrogen storage using high-capacity materials suffers from high hydrogen-desorption temperatures and instability of electrolytes. In this work, we explored electrochemical hydride ion (H – )–driven hydrogen storage and developed a solid electrolyte, anti–α-AgI–type Ba 0.5 Ca 0.35 Na 0.15 H 1.85 , which exhibits excellent H – conductivity and electrochemical stability. This electrolyte is compatible with several metal-hydrogen electrodes, such as titanim hydride and magnesium hydride (MgH 2 ), allowing for high-capacity, reversible hydrogen storage at low temperatures. Specifically, Mg–H 2 cells operating as hydrogen storage devices (Mg + H 2 ⇄ MgH 2 ) achieved a reversible capacity of 2030 milliampere hours per gram at 90°C, offering safe and efficient hydrogen-electricity conversion and hydrogen storage devices.