Fig 1

Schematic illustration of performance optimization strategies for the inorganic cathode materials in RMBs."

Fig 2

Cyclic voltammetry curves of the Mg||Cu cell at a scan rate of 0.1 mV s−1 in 0.001–2.2 V (a, b) or 10 mV s−1 in 0.001–2.5 V (c). Optical photograph of Cu electrode, separator and Mg electrode extracted from the Mg||Cu cell after 500 CV cycles at a scan rate of 10 mV s−1 (d). Galvanostatic charge-discharge profiles (e) and cycle performance (f) of the Mg||Cu cell at a current density of 0.1 mA cm–2 and in a voltage window of 0.01–2.2 V [39]. Copyright 2024, Wiley-VCH."

Fig 3

Schematic illustration of various concentration ratio of W and O vacancies in WO3 (a). Electron localization function of VO/WO3, VW-O/WO3–0.8, VW-O/WO3–1.0 and VW-O/WO3–1.2, respectively (b). Calculated Mg2+ diffusion coefficient in VW-O/WO3–1.0 (c). Cycling performance of VW-O/WO3–1.0 under 0.05 A g–1 (d) [46]. Copyright 2023, Elsevier."

Fig 4

Schematic illustration of the synthesis process of HMoOF (a). Crystalline structure of HMoOF for Mg2+ intercalation along the side and top direction (b). Schematic illustration of the Mg2+ intercalation chemistry for HMoOF (c). Mg2+ migration behaviors along the b-axis in MoO3 and HMoOF electrode (d). Cycling performances at 0.1 A g−1 (e) and 1 A g−1 (f) [51]. Copyright 2022, American Chemical Society."

Fig 5

Density of states of 2H and 1T MoS2 and SACu-MoS2 (a). Crystal structure and charge density difference of 1T MoS2 and SACu-MoS2 inserted one Mg2+ from side or top views (b). Crystal structure and charge density difference of 2H MoS2 and SACu-MoS2 inserted one Mg2+ from side views (c). Energy difference between 2H and 1T MoS2 and SACu-MoS2 with zero, one or eight Mg2+ inserted (d). The diffusion energy barriers of Mg2+ in MoS2 and SACu-MoS2, respectively (e) [63]. Copyright 2025, Wiley-VCH. Partial density of states (f), optimized structures of the Mg cation adsorbed (g), and the diffusion energy barriers in MoS2 and B-MoS2 (h) [64]. Copyright 2025, Wiley-VCH."

Fig 6

Cycling performance (a) and rate performance (b) of (NH4)2Mo3S13 and MoSx. Comparison of active material loading and rate performance with advanced RMB cathodes (c). Experimental Raman spectra of (NH4)2Mo3S13 and theoretical calculated Raman spectra of the [Mo3S13]2− cluster anion (d). Scheme for four typical vibration modes of [Mo3S13]2− (e). Ex situ Raman spectra of (NH4)2Mo3S13 cathodes (f). Theoretical calculated Raman activities of (S‒S)br and (S‒S)t in different magnesiation states of [Mo3S13]2− (g). Scheme for the Mg-storage reaction of (NH4)2Mo3S13 (h) [69]. Copyright 2024, American Chemical Society."

Fig 7

Energy diagram of transition metals, d band center, and S 3p top in transition metal sulfides (a). Schematic band structure of layered V1–xCrxS2 (0 ≤ x < 1) (b). Voltage profiles and corresponding maximum amount of Mg2+ intercalation in the 10th cycles at 0.05 A g−1 (c) [82]. Copyright 2025, Wiley-VCH."

Fig 8

Schematic illustration effect of C–S bonds on the phase conversion barrier of CuS (a) and CuS@G (b). Cycling performance and Coulombic efficiencies at current densities of 1 A g−1 (c). Comparison of electrochemical performance with previously reported cathode materials (d) [93]. Copyright 2024, Wiley-VCH. Structure of covellite CuS (e). Schematic diagram for the conversion of CuS (f) [95]. Copyright 2024, Elsevier."

Fig 9

Crystal structure (a), ELF of valence electron along the (011) and (001) planes (b), XRD pattern (c), cycling performance (d), rate performance (e), rate capabilities at different active material loadings (f), and scheme of the Mg-storage reaction mechanism for Cu3VS4 (g) [119]. Copyright 2024, American Chemical Society."

Fig 10

In situ XRD patterns of the Swagelok cell with a Cu2–xSe cathode during the first and second cycle (a). Ex situ XPS results of Se 3d and Mg 2p of Cu2–xSe cathodes in the various charge-discharge states (b). The x-ray absorption near-edge structure results of Cu2–xSe cathodes after discharging to 1.3 V, 0.9 V and 0.4 V in the first cycle (c). The schematic diagram of the Mg-storage mechanism of the Cu2−xSe@Mo6S8 (ICH) cathode (d). The long cycle performance of ICH and Cu2–xSe cathode at 0.1 A g–1 (e) [128]. Copyright 2022, Wiley-VCH."

Fig 11

Schematic illustrations of (a) Conventional (SIM) and (b) ISEA methods. In situ XRD patterns of CuSe cathode treated with (c) SIM and (d) ISEA methods. XPS depth profile for F 1s of CuSe cathode cycled with ISEA method (e). The surface energies σ of (001), (100), and (110) planes of CuSe (f). Cycling performance of CuSe at the ISEA and SIM methods in 0.1 A g–1 [132]. Copyright 2025, Springer Nature."

Fig 12

Crystal structure (a) and electron localization function of valence electron along the (011) plane (b) of Cu3VSe4. Ex situ Cu 2p, V 2p and Se 3d XPS spectra of Cu3VSe4 at the 50th cycle (c). Scheme of Mg-storage reaction mechanism for Cu3VSe4 (d). Cycling performance (e) and rate performance (f) of Cu3VSe4. Rate capabilities of Cu3VSe4 at 3.0 mg cm‒2 active material loadings (g) [145]. Copyright 2024, Wiley-VCH."