Morphology Engineering of VS₄ Microspheres as High-Performance Cathodes for Hybrid Mg²⁺/Li⁺ Batteries

Abstract

V-based sulfides are considered as potential cathode materials for Mg2+/Li+ hybrid ion batteries (MLIBs) due to their high theoretical specific capacities, unique crystal structure, and flexible valence adjustability. However, the formation of irreversible polysulfides, poor cycling performance, and severe structural collapse at high current densities impede their further development. Herein, VS4 microspheres with various controllable nanoarchitectures were successfully constructed via a facile solvothermal method by adjusting the amount of hydrochloric acid and were used as cathode materials for MLIBs. The VS4 microsphere self-assembled by bundles of paralleled-nanorods and some intersected-nanorods (VS4@NC-5) exhibits an outstanding initial discharge capacity of 805.4 mAh g–1 at 50 mA g–1 that is maintained at 259.1 mAh g–1 after 70 cycles. Moreover, the VS4@NC-5 cathode can deliver a superior rate capability (146.1 mAh g–1 at 2000 mA g–1) and ultralong cycling life (134.5 mAh g–1 at 2000 mA g–1 after 2000 cycles). The extraordinary electrochemical performance of VS4@NC-5 could be attributed to its special multi-hierarchical microsphere structure and the formation of N-doped carbon layers and V–C bonds, resulting in unobstructed ion diffusion channels, multidimensional electron transfer pathways, and enhancements of electrical conductivity and structure stability. Furthermore, the electrochemical reaction mechanism and phase conversion behavior of the VS4@NC-5 cathode at various states are investigated by a series of ex situ characterization methods. The VS4 well-designed through morphological engineering in this work can pave a way to explore more sulfides with high-rate performance and long cycling stability for energy storage devices.

Synergistic Effect of the Hydrogen Pump and Heterostructure Enables Superior Hydrogen Storage Performance of MgH2

“…The chemical composition and surface valence states of the VS 2 /NiS 2 sample were characterized by X-ray photoelectron spectroscopy (XPS). The strong peaks at about 516.4 and 523.9 eV in Figure S2b are attributed to V 4+ in V 2p 3/2 and V 2p 1/2 , respectively. − It is worth noting that no other valence states of V were detected. In the Ni 2p spectrum (Figure S2c), the distinct peaks situated at 854.2 and 871.4 eV are ascribed to Ni 2+ 2p 3/2 and Ni 2+ 2p 1/2 , respectively.…”

Dual Strategy of Morphology Optimization and Interlayer Expansion in VS2 Cathode Toward High-Performance Mg–Li Hybrid Ion Batteries

“…Impressively, the diffraction peaks of the as-prepared VS 2 @C are distinctly different from those of 2H-VS 2 (JCPDS 89–1640). , Two obviously formed sharp peaks at 2θ = 9.0° and 17.9° corresponding to the interlayer spacing of 0.98 and 0.50 nm can be observed, which can be indexed to the expanded (001) and (002) planes of VS 2 , respectively. , Notably, three diffraction peaks at 35.7°, 45.2°, and 57.1° can be well assigned to (011), (012), and (110) planes of 2H-VS 2 , suggesting that for the three samples the atomic arrangement along above basal planes are the same as 2H-VS 2 . Moreover, it has been reported that the carbonization of carbon source (such as AA and glucose) results in the formation of amorphous carbon layers in the solvothermal process, which can be in situ coated on the surface of the VS 2 nanosheets to enhance the interaction between VS 2 and carbon. − However, the characteristic peaks of carbon are not obvious in the XRD patterns, which probably is amorphous and deserves further discussion. When AA is not added in the solvothermal process, the E-VS 2 -200 shows the same XRD pattern as the above three samples, indicating that AA has no influence on the phase structure of VS 2 .…”

“…Previous articles have reported that the formation of amorphous carbon layers is due to the carbonization of carbon source (such as AA and glucose) in the solvothermal reaction. 45,46 The higher relative intensity ratio value of D and G bands in amorphous carbon can be calculated to be 0.72, which is beneficial for improving the ion storage properties. 32 TG analysis in air atmosphere was performed to quantify the content of amorphous carbon in the E-VS 2 @C-200 (Figure 1d).…”

Novel Electrospun Sn-Based Composite Cathodes Exhibiting Extended Cycle Life for Hybrid Magnesium–Lithium Batteries

“…The cycling stability of MLIBs is an important indication of the effectiveness of cathode material modification, which is also an important criterion for practical application in production. The cycling performance of MLIBs was compared with that reported in ref ,,– . The relevant comparison results are listed in Table .…”

“…Subsequently, it was dissolved in N -methyl pyrrolidone as a binder and uniformly coated onto pure copper foil (99.9%, Goodfellow), achieving a loading of approximately 0.8 mg per cathode. The anode was composed of meticulously polished magnesium foil, while the electrolyte for MILBs consisted of a mixed solvent containing 0.4 M Alkylpyrrolidinium chloride and 0.4 M lithium chloride (LiCl) dissolved in tetrahydrofuran. − The MLIBs were assembled under ultrahigh purity conditions within a glovebox where water and oxygen levels were maintained below 0.1 ppm. The galvanostatic cycling and rate capability assessments were systematically carried out on a multichannel battery testing platform.…”