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The diffusion of lithium ions and sodium ions in the anode materials is the main factor limiting the fast-charging performance of lithium and sodium-ion batteries. Due to the slow diffusion kinetics, taking lithium-ion batteries as an example, lithium ions and electrons accumulate locally in and on the surface of anode materials, especially in the process of fast-charging, resulting in uneven lithiation reaction and enormous transient stress, which leads to poor fast-charging performance. In this work, from the aspect of solving the ion diffusion rate, a capacitive type of energy storage is introduced by designing MoS 2 /rGO composite materials with pinned structures as fast-charging and stable anode materials for lithium-ion batteries and sodium-ion batteries. Combining the high ion conductivity and structural rigidity of the rGO conductive network with a few-layer MoS 2 provides a high ion diffusion rate and capacity. As expected, it can charge to 69 % in 25 min and 44 % in 3.2 min, respectively, providing a high capacity of 214.2 mAh g−1 at 10 A g−1 and a high-capacity retention of 85.31 % after 1, 000 cycles at the current density of 3 A g−1 in sodium-ion batteries. Similarly, the high reversible capacity of 910.5 mAh g−1 is achieved in the lithium-ion batteries, and there is almost no capacity loss after 1, 000 cycles at a high current density of 2 A g−1. This work may provide a reference for designing more fast-charging anode materials with high capacity. [Display omitted] • A stable structure in which MoS 2 with an interlayer spacing of 6.75 Å is uniformly dispersed on graphene. • By amino modification of MoS 2 stripped by lithium ion intercalation and the action of oxygen-containing functional groups of graphene. • MoS 2 /rGO composite materials can charge to 69 % in 25 min and 44 % in 3.2 min. • A high fast-charging capacity of 214 mAh g−1 at 10 A g−1 in SIBs, and 910 mAh g−1 in LIBs. [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]

Vanadium-based MXenes are prospective as anode materials in energy-storage devices including lithium-ion batteries (LIBs) but limited by their charge-discharge capacities. Herein, partially-etched V 2 Al x CT z with the average particle size of ~400 nm was synthesized using 40 wt% HF or mixed NaF+HCl solutions as etchants, respectively. V 2 Al x CT z etched by 40 wt% HF for 96 h at room temperature (RT) has more exceptional charge-discharge performances against mixed NaF+HCl solutions, with an average reversible capacity of ~450 mAh g−1 at 0.1 A g−1 in the 120 cycles and ~301.2 mAh g−1 at 0.5 A g−1 after 200 cycles in LIBs. The effect of etchants on electrochemical performances and lithium-ion (Li-ion) storage mechanism of V 2 Al x CT z was discussed comprehensively. Additionally, a Li-ion full cell using LiFePO 4 as cathode has exhibited excellent electrochemical performance (150.4 mAh g−1 at 0.1 C). This work illustrates that partially-etched V 2 Al x CT z with the submicro-sized distribution is also a promising anode material for LIBs. • Partially etched V 2 Al x CT z with ~400 nm was synthesized by etching submicro-sized V 2 AlC with 40 wt% HF and mixed NaF+HCl solutions, respectively. • V 2 Al x CT z etched by HF solution has more prominent electrochemical performances against NaF+HCl solutions. • Increased capacity contribution of V 2 Al x CT z etched by HF solutions may come from its defects and Al-Li alloying effect. [ABSTRACT FROM AUTHOR]