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 LiNi1/3Mn1/3Co1/3O2) 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.