Metal–selenium (M–Se) batteries are considered promising candidates for next‐generation battery technologies owing to their high energy density and high‐rate capability. However, Se cathode suffers from poor cycling performance and low Coulombic efficiency, owing to the shuttle effect of polyselenides. Herein, it is reported the incorporation of Ti3C2Tx MXene onto Se infiltrated porous N‐doped carbon nanofibers (PNCNFs) to construct free‐standing Janus PNCNFs/Se@MXene cathodes for high‐performance Na–Se and Li–Se batteries. The increase of pyrrolic‐N content and the porous structure of the PNCNFs is conducive to enhancing the adsorption of Na2Se and alleviating the shuttle effect. Meanwhile, density functional theory (DFT) calculations have proven that 2D Ti3C2Tx MXene with polar interfaces enables the effective chemical immobilization and physical blocking of polyselenides to suppress the shuttle effect. The unique architecture with Ti3C2Tx MXene built on top of interlinked nanofiber ensures the continuous electron transfer for redox reaction. As a result, the novel Janus PNCNFs/Se@MXene electrodes deliver robust rate capabilities and superior long‐term cycling stability in both Na–Se and Li–Se batteries. The incorporation of 2D MXene to construct Janus electrodes provides a competitive advantage for selenium‐based cathode materials and highlights a new strategy for developing high‐performance batteries.

As a promising energy-storage and conversion anode material for high-power sodium-ion batteries operated at room temperature, the practical application of layered molybdenum disulfide (MoS2) is hindered by volumetric expansion during cycling. To address this issue, a rational design of MoS2 with enlarged lattice spacing aligned vertically on hierarchically porous Ti3C2T x MXene nanosheets with partially oxidized rutile and anatase dual-phased TiO2 (MoS2@MXene@D-TiO2) composites via one-step hydrothermal method without following anneal process is reported. This unique “plane-to-surface” structure accomplishes hindering MoS2 from aggregating and restacking, enabling sufficient electrode/electrolyte interaction simultaneously. Meanwhile, the heterogeneous structure among dual-phased TiO2, MoS2, and MXene could constitute a built-in electric field, promoting high Na+ transportation. As a result, the as-constructed 3D MoS2@MXene@D-TiO2 heterostructure delivers admirable high-rate reversible capacity (359.6 mAh g–1 up to 5 A g–1) at room temperature, excellent cycling stability (about 200 mAh g–1) at a low temperature of −30 °C, and superior electrochemical performance in Na+ full batteries by coupling with a Na3V2(PO4)3 cathode. This ingenious design is clean and facile to inspire the potential of advanced low-dimensional heterogeneous structure electrode materials in the application of high-performance sodium-ion batteries.

Lithium sulfur (Li-S) battery has exhibited great application potential in next-generation high-density secondary battery systems due to their excellent energy density and high specific capacity. However, the practical industrialization of Li-S battery is still affected by the low conductivity of sulfur and its discharge product (Li2S2/Li2S), the shuttle effect of lithium polysulfide (Li2Sn, 4 ≤ n ≤ 8) during charging/discharging process and so on. Here, cobalt disulfide/reduced graphene oxide (CoS2/rGO) composites were easily and efficiently prepared through an energy-saving microwave-assisted hydrothermal method and employed as functional interlayer on commercial polypropylene separator to enhance the electrochemical performance of Li-S battery. As a physical barrier and second current collector, the porous conductive rGO can relieve the shuttle effect of polysulfides and ensure fast electron/ion transfer. Polar CoS2 nanoparticles uniformly distributed on rGO provide strong chemical adsorption to capture polysulfides. Benefitting from the synergy of physical and chemical constraints on polysulfides, the Li-S battery with CoS2/rGO functional separator exhibits enhanced conversion kinetics and excellent electrochemical performance with a high cycling initial capacity of 1,122.3 mAh g−1 at 0.2 C, good rate capabilities with 583.9 mAh g−1 at 2 C, and long-term cycle stability (decay rate of 0.08% per cycle at 0.5 C). This work provides an efficient and energy/time-saving microwave hydrothermal method for the synthesis of functional materials in stable Li-S battery.

Lithium–sulfur (Li–S) batteries have attracted increasing attention for next-generation energy storage systems with a high energy density and low cost. However, the practical applications have been plagued by the sluggish reaction kinetics and the shuttle effect of lithium polysulfides (LiPSs). Herein, core–shell SiO2@Ti3C2Tx MXene (SiO2@MX) hollow spheres are constructed as multifunctional catalysts to boost the performance of Li–S batteries. The dual-polar and dual-physical properties of SiO2 core and MXene shell provide multiple defense lines to the shuttle effect by chemical and physical confinement to LiPSs. Density functional theory calculations prove that Ti3C2Tx MXene and SiO2 enable the stronger trapping ability of LiPSs and the fast Li2S decomposition process. With this strategy, the robust SiO2@MX/S electrodes deliver superior electrochemical performances, including a high capacity of 1263 mAh g−1, and remarkable cycling stability with an ultralow capacity decay of 0.04% per cycle over 1000 cycles at 1 C. This work highlights the significance of core-shell dual-polar structural sulfur catalysts for practical application in advanced Li–S batteries.

The lithium-sulfur (Li-S) battery has been regarded as an important candidate for the next-generation energy storage system due to its high theoretical capacity (1675 mAh g−1) and high energy density (2600 Wh kg−1). However, the shuttle effect of polysulfide seriously affects the cycling stability of the Li-S battery. Here, a novel Fe3C-decorated folic acid-derived graphene-like N-doped carbon sheet (Fe3C@N-CS) was successfully prepared as the polysulfide catalyst to modify the separator of Li-S batteries. The porous layered structures can successfully capture polysulfide as a physical barrier and the encapsulated Fe3C catalyst can effectively trap and catalyze the conversion of polysulfide, thus accelerating the redox reaction kinetics. Together with the highly conductive networks, a cell with the Fe3C@N-CS-modified separator evinces superior cycling stability with 0.06% capacity decay per cycle at 1 C rate over 500 cycles and excellent specific capacity with an initial capacity of 1260 mAh g−1 at 0.2 C. Furthermore, at a high sulfur loading of 4.0 mg cm−2, the batteries also express superb cycle stability and rate performance.