Configurational-Entropy-Engineered Prussian Blue Analogue Cathodes for Low-Temperature Semi-solid-state H2 Batteries

Abstract Low-temperature proton transport kinetics remains a key limitation for rechargeable H2 batteries. Herein, we report a configurational-entropy-engineered K1.36Mn0.6Fe0.1Co0.1Ni0.1Cu0.1[Fe(CN)6]0.61·□0.39·1.2H2O (CEM0.6-PBA) cathode for semi-solid-state H2 batteries. Density functional theory calculations reveal that configurational entropy tailors the electronic structure, optimizes proton adsorption energetics, and lowers the proton migration barrier, thereby improving both the thermodynamics and kinetics of proton storage. In addition, an interconnected hydrogen-bonding network facilitates rapid proton transport under subzero conditions. As a result, the full cell delivers 155.9 mA h g–1 and 125.2 W h kg–1, with 71.9% capacity retention after 10,000 cycles. Notably, it exhibits outstanding low-temperature performance, delivering 157.9, 128.3, and 80.0 mA h g–1 at –10, –30, and –40 °C, respectively, operating down to –60 °C, and retaining 85.7 mA h g–1 after 2900 cycles at 0.3 A g–1 under –30 °C. This work establishes configurational-entropy engineering as an effective strategy for regulating proton-storage thermodynamics and kinetics in H2 batteries under extreme conditions.