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Submicro-sized vanadium carbide (V2C) with orthorhombic structure prepared by the molten salt disproportionation method was firstly applied as an anode in lithium-ion batteries. The V2C has delivered a reversible discharge capacity of ~ 223.6 mAh·g−1 at 0.1 A·g−1 in the continuous 300 cycles without capacity attenuation and ~ 107 mAh·g−1 at 0.5 A·g−1 after 600 cycles with the capacity retention of 83.6%, respectively. Meanwhile, Li-ion storage mechanism of V2C is pseudocapacitive, accompanied with the redox reaction of V-ions during the Li-ions insertion/extraction process. The exploration of orthorhombic V2C may extend the selection of anode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Nanosized vanadium nitride (VN) wrapped onto carbon fibers was synthesized by a molten salt disproportionation synthesis method at 800–1,000 ºC, using V and melamine as raw materials in molten (Li,K)Cl salts. Molten salts could accelerate the formation of nanosized VN at a lower temperature, which is possibly associated with the disproportionation reaction of V-ions on g-C 3 N 4 surface. VN displays remarkable application prospects as an anode material for lithium-ion batteries (LIBs), delivering a reversible discharge capacity of 320.1 mAh·g−1 at 1.0 A·g−1 after 500 cycles and 669.4 mAh·g−1 at 0.1 A·g−1 after 230 cycles without capacity attenuation. Such a remarkable cyclability of VN is attributed to the increased surface area and superior structural stability, induced by the dispersion of VN nanoparticles onto high-conductive carbon fibrous network. Li-ions storage mechanism of VN is pseudocapacitive, accompanied with the conversion-type electrochemcial reaction of VN with Li-ions during the de-/lithiation process. • Nanosized VN wrapped onto carbon fibers was firstly prepared by a molten salt disproportionation synthesis method. • Formation of nanosized VN may be associated with the disproportionation reaction of V-ions on g-C 3 N 4 surface. • VN exhibits impressive electrochemical performances as an anode for LIBs. [ABSTRACT FROM AUTHOR]

Herein, the 3D flower-like V 2 Al 1- x CT z with an estimated petaloid nanosheet thickness of 10–20 nm were firstly obtained by etching the submicro-sized V 2 AlC precursors, which were synthesized at 1000 °C holding for 5 h in (Na,K)Cl melt by a facile molten salt method, in 40 wt% HF at room temperature. The synthesis mechanism of V 2 AlC is possibly related to the disproportionation reaction of V-ions on carbon surface in molten salts to form V 2 C, followed by the intercalation of Al into V 2 C. Subsequently, the 3D flower-like V 2 Al 1- x CT z was applied as an anode in lithium-ion batteries, releasing ~215.2 mA h g−1 in the continuous 500 cycles at 0.5 A g−1, which exhibits the superiority in the reversible capacity in contrast with some reported micro-sized layered V 2 CT z MXenes. Such excellent electrochemical characteristics of V 2 Al 1- x CT z could be mainly ascribed to its unique submicro-sized flower-like morphology with high specific surface areas and abundant electrochemical sites for accommodating the reversible insertion/extraction of Li-ions. [Display omitted] • 3D flower-like V 2 Al 1- x CT z was firstly obtained by etching the submicro-sized V 2 AlC precursors. • Thickness of the nanosheets on V 2 Al 1- x CT z with a lot of defects was estimated as 10–20 nm. • The V 2 Al 1- x CT z exhibits desirable electrochemical performances as an anode in LIBs. • It may be extended to the synthesis of MXenes with diverse morphologies as anodes for LIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core-shell structured vanadium oxide@vanadium carbide composites were firstly constructed via an in-situ oxidation method. • Phase compositions of vanadium oxide@vanadium carbide composites could be regulated by temperature. • The V 2 O 5 @VO 2 @V 2 C@VC exhibits the most impressive cyclability as an anode in LIBs. • It may be extended to the development and design of other V x O y @V x C composites as alternative anode materials for LIBs. Vanadium oxide@vanadium carbide (V x O y @V x C) composites with a core–shell structure was constructed via a simple in-situ oxidation method, i.e. by oxidizing V 2 C precursor at 350–400 °C for 1 h under air atmosphere. As-obtained V x O y @V x C composites are in the submicro-sized particle distribution. These V x O y @V x C composites have displayed remarkable electrochemical performances as anodes in lithium-ion batteries (LIBs), thereinto V 2 O 5 @VO 2 @V 2 C@VC composite exhibits the most impressive cycling stability, releasing ∼252.1 mAh g−1 after 200 cycles at 0.5 A g−1 with capacity retention of 89.5% and ∼492 mAh g−1 in the continuous 120 cycles at 0.1 A g−1. Such an outstanding electrochemical performance could benefit from the unique core–shell heterostructure of V x C encapsulated by V x O y , with an excellent structural stability. It is favorable to provide the excellent charge transfer field and effectively restrain the aggregation and structural deformation during the electrochemical reaction process. This design of V 2 O 5 @VO 2 @V 2 C@VC composite is promising for motivating the development of anode materials in LIBs. [ABSTRACT FROM AUTHOR]