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[Display omitted] • Fe 2 O 3 /MoC@NG shows excellent rate performance and large-current long-cycle stability. • Pseudocapacitance control is the major charge–discharge mechanism. • Fe 2 O 3 /MoC@NG shows 21-time enhanced Li+ ion diffusion kinetics compared with Fe 2 O 3 @NG. • Stabilization of Li-DIBs anode structure by heterointerface bonding of Fe 2 O 3 /MoC@NG. • The transport paths of PF 6 − and Li+ ions in dual-ion batteries are studied. Lithium dual-ion batteries (Li-DIBs) technology is expected to become a leader in replacing lithium-ion batteries (LIBs) to carry out high energy/power density energy storage devices. Unfortunately, the sluggish electrochemical reaction kinetics of anode materials critically restricts their practical development. Here, a Li-DIBs is proposed by using a three-dimensional (3D) structure composed of Fe 2 O 3 /MoC heterostructure nanoparticals embedded in a hierarchical mesoporous nitrogen-doped reduction graphene oxide (Fe 2 O 3 /MoC@NG) as the anode, which has low Li+ ion diffusion barrier (0.098 eV), high Li+ ion diffusion coefficient (4.99 × 10−11 cm2 s−1) and remarkable rate property (879.2 mA h g−1 at 10 A g−1), and choosing nano-graphite as the cathode. Originating from the respective strengths of Fe 2 O 3 /MoC@NG anode and the nano-graphite cathode, the as-constructed Li-DIBs full battery displays high reversible capacity and prominent rate property (103.9 mA h g−1 at 0.05 A g−1 and 48.9 mA h g−1 at 2 A g−1). Specifically, taking advantage of density functional theory (DFT) calculations, the exact paths of PF 6 − ion intercalation into graphite cathode and Li+ ion diffusion into Fe 2 O 3 /MoC@NG anode is obtained, namely PF 6 − ion transmits along the (0 0 2) face of nano-graphite and Li+ ion diffuses along the heterointerface of Fe 2 O 3 /MoC@NG. [ABSTRACT FROM AUTHOR]

• Rationally designed structure prevent the aggregation of Mn-doped MoS 2 nanosheets. • Mn-doping enhance the intrinsic electronic conductivity and Li+ diffusion rate. • The as-synthesized electrode shows high rate capacity of 659 mAh g−1 at 5 A g−1. Developing anode materials for lithium-ion batteries with excellent electrochemical performance is crucial to satisfy the requirement for energy storage. Molybdenum disulfide is recognized as a prospective anode material due to its high theoretical capacity and two-dimensional layered structure. However, its further application is mainly hindered by its poor electronic conductivity. Herein, we report Mn-doped MoS 2 nanosheets anchored on hierarchical carbon skeleton (MMSC) acting as an anode material. The as-synthesized electrode exhibits a high initial discharge capacity of 1280 mAh g−1 at a current density of 0.1 A g−1, high rate capacity (920 mAh g−1 at 2 A g−1), and long-time cycling stability (71% capacity retention after 1000 cycle). Compared to that of pristine MoS 2 electrode, the improved performance of MMSC anode can be attributed to the synergetic effects of optimized composite structure and Mn doping. The hierarchical carbon skeleton provides a larger surface area, allowing effective electrolyte penetration and preventing aggregation of MoS 2 nanosheets in charge/discharge cycles. To further understand the mechanism of the improved rate capability, calculation of corresponding atomic models according to experimental results and first-principles calculation are conducted. The calculated results prove that the Mn-doped MoS 2 (MMS) has a lower diffusion barrier of Li+ than that in pristine MoS 2. Moreover, the as-synthesized MMSC electrode also demonstrates better electronic conductivity because of the electronic injection by Mn atoms. [ABSTRACT FROM AUTHOR]

High-performance flexible sodium-ion batteries based on carbon sphere-supported hierarchical Nb2CTx MXene/MoS 2 composites, which excellent specific capacity, cycle stability and rate performance. It has a specific capacity of 196 mAh g-1 at a current density of 20 A g-1. In addition, this design scheme can also be extended to other application scenarios. [Display omitted] • Hollow carbon sphere could make electrode three-dimensional. • MXene-bonded 3D hierarchical structure could reduce the charge transfer path. • Nb 2 CT x /MoS 2 @CS anode have outstanding cycle stability for Na ion storage. • MXene-bonded electrode have certain flexibility. Hand-made Nb 2 CT x /MoS 2 @CS//NVP full battery could reach to 90° bending. Sodium-ion batteries, as a promising alternative to the lithium-ion battery, have attracted extensive attention. However, due to the larger ion radius and higher standard reduction potential, the sodium-ion batteries still face poor cycle stability and relatively low energy density problems. In this work, a carbon sphere-supported Nb 2 CT x MXene/MoS 2 hierarchical structure has been designed and synthesized through hydrothermal and electrostatic self-assembly methods. The design strategy successfully improves the utilization efficiency of the MoS 2 carbon sphere as a support skeleton and reducing the diffusion path length of Na ions, leading to an improved specific capacity and rate performance. Moreover, Nb 2 CT x sheets also effectively inhibit the capacity attenuation caused by MoS 2 shedding, thus achieving the long cycle life of the sodium-ion battery. As a result, the carbon-supported MXene/MoS 2 anode delivers an ultrahigh reversible capacity, long cycling stability, and superior capacity retention rate. Notably, the carbon-supported MXene/MoS 2 anode can also obtain a considerable capacity of 196 mAh g−1 at a current density of 20 A g−1. The full cell of SIBs was assembled, and the flexibility of the battery was tested. The density functional theory simulation results show that the sodium ion has a smaller diffusion barrier under this material design strategy. [ABSTRACT FROM AUTHOR]

• The potassium storage mechanisms of MXenes were briefly explained. • The applications of various modified MXenes in potassium ion batteries were comprehensively summarized. • The advantages and challenges of MXenes in potassium ion batteries were pointed out. • This review proposed several promising strategies to improve the potassium storage performances of MXenes. MXenes, a new kind of two-dimensional (2 D) materials derived from MAX phases, have shown wide application prospects in metal-ion batteries due to their unique structural and electronic properties. Particularly, the diffusion barrier of K+ on MXenes is very low, indicating that MXenes may have excellent rate performance when applied to potassium ion batterie (PIBs) as anodes. However, pristine MXenes are not suitable to be used as anodes for PIBs due to their low theoretical potassium storage capacity and rapid capacity decline. Here, the potassium storage mechanisms of MXenes are briefly introduced. Besides, this review summarizes the applications of various modified MXenes in PIBs, with emphasis on the relationship between structure and electrochemical performances. Through the analysis of various modification methods, it is hoped that the future development direction of MXenes in PIBs can be seen, so as to provide enlightenment for readers. [ABSTRACT FROM AUTHOR]

A facile structural refining for Sb film anode is firstly applied in SIBs by increasing the working pressure. Compared with Sb@0.2Pa and Sb@1Pa, the Sb@3Pa anode exhibits improved performance, stemming from its refined architecture. Surprisingly, the progressive in-situ electrochemically-driven Cu-Sb alloying can be probed upon cycling onward and further clarified by operando XRD, ex-situ SEM and DFT calculations. • A scalable structural refining for sputtered Sb film via altering working pressure. • The Sb@3Pa anode exhibits better performance owing to refined structure. • The (de)sodiation mechanism of Sb anodes was probed utilizing operando XRD. • In-situ electrochemically-driven Cu-Sb alloying is firstly observed in SIBs. Sb is a promising anode for sodium ion batteries (SIBs) but held back from practical application owing to its pulverization induced by dramatic volumetric variation. Herein, we propose a simple pressure-induced regulation strategy to efficiently refine nanoscale column-channel architecture of Sb layer by magnetron sputtering, which is easily manipulated and reproductive in practical conditions. The refining process under high working pressure can be ascribed to the synergistic effects from the shadow effect, the low kinetic energy of sputtered Sb atoms and high diffusion barrier on substrate. As benchmarked with Sb@0.2Pa and Sb@1Pa electrodes, the Sb@3Pa anode exhibits significantly enhanced electrochemical performance owing to structural refining effect generated by the elevated working pressure, effectively accelerating the ion/electron transfer and mitigating the volumetric variations. Notably, the progressive in-situ electrochemically-driven alloying in Sb layer on the Cu substrate to form Cu x Sb with the gradient Cu/Sb content is detected and further rationalized by operando XRD, ex-situ SEM and DFT calculations. Simultaneously, the formed Cu-Sb layer yields a novel (de)sodiation mechanism of Cu x Sb 1−x ↔ Na y Cu x Sb 1−x ↔ Na 3 Cu x Sb 1−x after the 1st discharge. [ABSTRACT FROM AUTHOR]