The 2019 Nobel Prize in Chemistry for lithium‐ion batteries is a powerful confirmation of the importance of portable energy storage devices, which will further promote collaborative innovation in the field of new energy storage. Non‐lithium rechargeable energy storage technologies are attracting attention due to their low cost and high energy densities. However, electrochemical performance depends upon the inherent properties of the electrodes. In recent decades, 2D materials have been extensively investigated owing to their unique physical and chemical properties. One of the typical representatives is the MXenes with good electrochemical properties, which have become popular material in the field of energy storage in recent years. The discovery of MXene with metal solution, expanded interlayer‐spacing and tamperable surface termination offers a valuable strategy to discover MXenes with new structures. These flexible properties of MXene allow the tuning of properties for energy storage technologies. Here, the synthesis, structure, properties and applications of MXenes in non‐lithium energy storage technologies are reviewed, and a comprehensive outlook and personal perspective on the future development of MXene in the energy storage system are also presented.

Sodium sulfur batteries require efficient sulfur hosts that can capture soluble polysulfides and enable fast reduction kinetics. Herein, we design hollow, polar and catalytic bipyramid prisms of cobalt sulfide as efficient sulfur host for sodium sulfur batteries. Cobalt sulfide has interwoven surfaces with wide internal spaces that can accommodate sodium polysulfides and withstand volumetric expansion. Furthermore, results from in/ex-situ characterization techniques and density functional theory calculations support the significance of the polar and catalytic properties of cobalt sulfide as hosts for soluble sodium polysulfides that reduce the shuttle effect and display excellent electrochemical performance. The polar catalytic bipyramid prisms sulfur@cobalt sulfide composite exhibits a high capacity of 755 mAh g⁻¹ in the second discharge and 675 mAh g⁻¹ after 800 charge/discharge cycles, with an ultralow capacity decay rate of 0.0126 % at a high current density of 0.5 C. Additionally, at a high mass loading of 9.1 mg cm⁻², sulfur@cobalt sulfide shows high capacity of 545 mAh g⁻¹ at a current density of 0.5 C. This study demonstrates a hollow, polar, and catalytic sulfur host with a unique structure that can capture sodium polysulfides and speed up the reduction reaction of long chain sodium polysulfides to solid small chain polysulfides, which results in excellent electrochemical performance for sodium-sulfur batteries.

MXenes, as a new type of two-dimensional layered structure material, have attracted much attention. MXenes have high electronic conductivity, a large specific area, excellent mechanical properties and a unique layered structure and have been extensively used in energy storage, adsorption, catalysis and other fields. In recent years, Mxenes and their composite materials have been widely used in the field of secondary batteries. Although oxides, sulfides and other materials have high capacity, there are problems such as low conductivity, volume expansion in the reaction process, poor cycling stability, etc. Therefore, building composite materials with MXenes can not only improve the capacity but also enhance the electronic conductivity of the materials, effectively alleviate volume expansion in the reaction process, and achieve better electrochemical performance. This article reviews the latest research status of MXenes, the synthesis methods, properties and application of MXenes and their composite materials in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), briefly introduces the research background of SIBs, PIBs and MXenes, and focuses on the application research of MXene composite materials in SIBs and PIBs, including classification according to sulfide, oxide and carbon materials. Finally, the development and application prospects of MXenes and their composite materials are summarized.

Room‐temperature Na–S batteries are facing one of the most serious challenges of charge/discharge with long cycling stability due to the severe shuttle effect and volume expansion. Herein, a sodium polysulfides defense system is presented by designing and constructing the cathode‐separator double barriers. In this strategy, the hollow carbon spheres are decorated with MoS₂ (HCS/MoS₂) as the S carrier (S@HCS/MoS₂). Meanwhile, the HCS/MoS₂ composite is uniformly coated on the surface of the glass fiber as the separator. During the discharge process, the MoS₂ can adsorb soluble polysulfides (NaPSs) intermediates and the hollow carbon spheres can improve the conductivity of S as well as act as the reservoir for electrolyte and NaPSs, inhibiting them from entering the anode to make Na deteriorate. As a result, the cathode‐separator group applied to room‐temperature Na–S battery can enable a capacity of ≈1309 mAh g⁻¹ at 0.1 C and long cycling life up to 1000 cycles at 1 C. This study provides a novel and effective way to develop durable room‐temperature Na–S batteries.