Interface ion-exchange strategy of MXene@FeIn2S4 hetero-structure for super sodium ion half/full batteries.

Herein, a well-designed hierarchical architecture of bimetallic transition sulfide FeIn2S4 nanoparticles anchoring on the Ti3C2 MXene flakes has been prepared by cation exchange and subsequent high-temperature sulfidation processes. The introduction of MXene substrate with excellent conductivity not only accelerates the migration rate of Na+ to achieve fast reaction dynamics but provides abundant deposition sites for the FeIn2S4 nanoparticles. In addition, this hierarchical structure of MXene@FeIn2S4 can effectively restrain the accumulation of MXene to guarantee the maximized exposure of redox active sites into the electrolyte, and simultaneously relieve the volume expansion in the repeated discharging/charging processes. The MXene@FeIn2S4 displays outstanding rate capability (448.2 mAh g-1 at 5 A g-1) and stable long cycling performance (428.1 mAh g-1 at 2 A g-1 after 200 cycles). Moreover, the Nay-In6S7 phase detected by ex-situ XRD and XPS characterization may be regarded as a "buffer" to maintain the stability of the Fe-based components and enhance the reversibility of the electrochemical reaction. This work confirms the practicability of constructing the hierarchical structure bimetallic sulfides with the promising electrochemical performance.

Hetero-structural and hetero-interfacial engineering of MXene@Bi2S3/Mo7S8 hybrid for advanced sodium/potassium-ion batteries.

Herein, heterogeneous bimetallic sulfides Bi2S3/Mo7S8 nanoparticles anchored on MXene (Ti3C2Tx) nanosheets (MXene@Bi2S3/Mo7S8) were prepared through a solvothermal process and subsequent chemical vapor deposition process. Benefiting from the heterogeneous structure between Bi2S3 and Mo7S8 and the high conductivity of the Ti3C2Tx nanosheets, the Na+ diffusion barrier and charge transfer resistance of this electrode are effectively decreased. Simultaneously, the hierarchical architectures of Bi2S3/Mo7S8 and Ti3C2Tx not only effectively inhibit the re-stacking of MXene and the agglomeration of bimetallic sulfides nanoparticles, but also dramatically relieve the volume expansion during the periodic charge/discharge processes. As a result, the MXene@Bi2S3/Mo7S8 heterostructure demonstrated remarkable rate capability (474.9 mAh/g at 5.0 A/g) and outstanding cycling stability (427.3 mAh/g after 1400 cycles at 1.0 A/g) for sodium ion battery. The Na+ storage mechanism and the multiple-step phase transition in the heterostructures are further clarified by the ex-situ XRD and XPS characterizations. This study paves a new way to design and exploit conversion/alloying type anodes of sodium ion batteries with hierarchical heterogeneous architecture and high-performance electrochemical properties.

Heterostructure and doping dual strategies engineering of MoS1.5Se0.5@VS2 nanosheets aggregated nano-roses for super sodium-ion batteries.

Herein, selenium (Se)-doped MoS1.5Se0.5@VS2 nanosheets aggregated nano-roses were successfully prepared from a simple hydrothermal process and the subsequent selenium doping process. The hetero-interfaces between MoS1.5Se0.5 and VS2 phase can effectively promote the charge transfer. Meanwhile, the different redox potentials of MoS1.5Se0.5 and VS2 alleviate volume expansion during the repeated sodiation/desodiation processes, which improves the electrochemical reaction kinetics and structural stability of electrode material. Besides, Se doping can induce charge reconstruction and improve the conductivity of electrode materials, resulting in improved diffusion reaction kinetics by expanding interlayer spacing and exposing more active sites. When used as anode material for sodium ion batteries (SIBs), the MoS1.5Se0.5@VS2 heterostructure exhibits excellent rate capability and long-term cycling stability with the capacity of 533.9 mAh g-1 at 0.5 A g-1 and a reversible capacity of 424.5 mAh g-1 after 1000 cycles at 5 A g-1, demonstrating potential application as anode material for SIBs.

Rational design of heterostructured bimetallic sulfides (CoS2/NC@VS4) with VS4 nanodots decorated on CoS2 dodecahedron for high-performance sodium and potassium ion batteries.

Developing electrode materials with desirable electrochemical properties for sodium and potassium ion batteries remains a tremendous challenge. Herein, hetero-structured hybrids with VS4 nanodots decorated on CoS2/NC dodecahedron (CoS2/NC@VS4) have been successfully synthesized through employing a cobalt-based imidazolate framework (ZIF-67) as a template to prepare CoS2/NC inner core. Then VS4 nanodots was then grown on the surface of CoS2/NC by hydrothermal method to construct a heterostructure. This heterogeneous structure facilitates full contact with the electrolytes and shortens electrons and ions diffusion distance. Besides, the nitrogen-doped carbon framework derived from ZIF-67 promotes electron transport and gives a reliable shield to buffer the volume swelling during discharge and charge processes. Driving by the synergistic effect of bimetallic sulfides and the multiple valence states vanadium sulfide, CoS2/NC@VS4 exhibits outstanding rate capability and stable cycle performance as the anode for SIBs and PIBs, including a specific capacity of 307 mAh g-1 at the current density of 1.0 A g-1 after 700 cycles for SIBs and a capacity of 291.54 mAh g-1 at the current density of 1.0 A g-1 after 430 cycles in PIBs.