High-capacity, reversible hydrogen storage using H <sup>–</sup> -conducting solid electrolytes
Takashi Hirose, Naoki Matsui, Takashi Itoh, Yoyo Hinuma, Kazutaka Ikeda, Kazuma Gotoh, Guangzhong Jiang, Kota Suzuki, Masaaki Hirayama, Ryoji Kanno
Abstract
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>⇄</mml:mo> </mml:math> 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.