Amorphizing Iron Molybdate as a High‐Capacity Cathode for Lithium Metal Batteries Enabled by Multiple Insertion Reactions in the Metastable Structure

The rising energy demand for electric vehicles and energy storage has revived interest in lithium-metal batteries (LMBs). However, present LMBs still mainly rely on conventional lithium-ion batteries (LIBs) cathodes (e.g., LiFePO₄ and LiNi_1/3Mn_1/3Co_1/3O₂) with limited reversible capacity (≈150 to ≈190 mAh g^-1 _cathode), necessitating the paradigm to achieve a new host with abundant Li⁺ accommodation sites. Herein, it is proposed a high-capacity amorphizing iron molybdate cathode a-Fe₂(MoO₄)₃ (a-FMO), which can reversibly unlock Fe³⁺/Fe²⁺ and Mo⁶⁺/Mo⁴⁺ redox insertion reactions in the metastable structure. Different from its parent crystal and stoichiometric oxides mixtures, a-FMO, with its inherent metastable structure, can not only augment the lithium storage capacities with fully activated redox centers, but also attenuate the lattice confinements for Li⁺ ion migration. Consequently, the in-situ generated a-FMO electrode exhibited a notable reversible capacity of 254 mAh g^-1 with stable cycling over 500 cycles. It endowed a specific energy density of 597 Wh kg^-1 and all-climate adaptability over 60 to -40 °C benefited from the amorphizing nature, as well as negligible capacity degradation when cycling at -30 °C. The identification of local structure evolutions and multiple-redox activations in amorphizing materials broadens the scope for designing high-energy-density cathodes.