MXene materials have great potential for energy storage applications, owing to their unique two-dimensional structure, exceptional electrical conductivity, and versatile surface chemistry. However, the practical utilization of pristine MXenes is hindered by several intrinsic limitations, such as interlayer restacking (which impedes ion diffusion), susceptibility to oxidation in aqueous and oxygen-rich environments, instability of surface functional groups, and suboptimal electrical conductivity. The structural engineering and surface modification strategies of MXenes were reviewed in this manuscript. The modification approaches include intercalation, surface functionalization, doping, and composite engineering. The insights presented herein aim to promote the development and practical application of MXene-based materials in next-generation energy storage devices.

Multicomponent alloys (MCAs) have garnered significant attention in electrocatalytic applications due to their tunable multielement composition, electronic structure, and excellent stability. However, the homogeneity of MCAs results in the potential lack of distinctive catalytic sites and surface sites. This work demonstrates an MCA's design strategy and structural evolution process combining heterophase and selective defect engineering. Preferential dealloying in the bcc phase with lower ORR activity is achieved by taking advantage of the atomic arrangement structural difference of the heterophase, thus obtaining an fcc/bcc with defects ( bcc‐d ) MCA encapsulated in the carbon nanotubes (HFeCoCuAl@CNTs). The formed vacancies in the bcc‐d generate the unsaturated coordination of adjacent Fe/Co active sites and optimize the electronic structure. The synergistic catalysis of the fcc / bcc‐d accelerates all steps of the 4e ⁻ ORR. Therefore, HFeCoCuAl@CNTs exhibits the excellent electrocatalytic activity and stability in ORR (half‐wave potential: 0.823 V) and OER ( E _j=10 : 344 mV) under alkaline conditions. Using the commercial Pt/C as a comparison, the HFeCoCuAl@CNTs‐based zinc–air batteries deliver the higher specific capacity of 814 mAh g _Zn ⁻¹ , power density of 144.8 mW cm ⁻² , and long‐term stability exceeding 780 h. These findings provide unique ideas for designing MCA electrocatalysts suitable for high‐performance zinc–air batteries.

Mg–air batteries have garnered substantial research attention owing to their high specific capacity, low electrode potential, environmental benignity, and abundant natural magnesium reserves. Nevertheless, sluggish oxygen reduction reaction (ORR) kinetics at the air cathode severely restrict their practical implementation, which necessitates the development of low-cost, high-activity non-precious metal electrocatalysts. Herein, modified Mo₂C@P electrocatalysts are successfully synthesized via phosphidation of Mo₂C mixed with sodium hypophosphite (NaH₂PO₂) under thermal treatment. Multiple characterization techniques are employed to systematically investigate the crystal structure, chemical bonding configuration, micromorphology, and ORR electrocatalytic performance of the as-prepared materials. Meanwhile, Mg–air battery evaluations are carried out in 3.5 wt.% aqueous NaCl electrolyte. The results reveal that the Mo₂C MXene backbone is well retained. Phosphorus doping is confined to surface modification and is accompanied by the formation of P–O and P–C bonds. The stacked lamellar architecture undergoes surface reconstruction, generating a uniform particulate morphology. The ORR electrocatalytic activity exhibits a volcano-type trend with phosphidation temperature, and Mo₂C@P-350 achieves the highest limiting diffusion current density of 2.87 mA cm⁻². The Mg–air battery assembled with Mo₂C@P-350 delivers outstanding and stable discharge voltages of 1.19 V at 5 mA cm⁻² and 1.13 V at 10 mA cm⁻², along with optimal rate capability. This work demonstrates that mild-temperature phosphidation represents a reliable surface-engineering strategy for constructing high-performance ORR electrocatalysts.

Designing cathode materials that can synergistically store ions with significantly different charge densities and ionic radii poses a critical challenge in the ongoing development of Mg ²⁺ /Li ⁺ hybrid batteries (MLHBs). MXene‐based materials with vacancy defects offer promise, yet conventional monovacancy strategies cannot balance capacity and reaction kinetics. Herein, an innovative dual‐anion (Se, O) vacancy engineering strategy is proposed and constructed a quantum dot (QD) Ti ₃ C ₂ MXene heterostructure (QD@V _Se,O ‐Ti ₃ C ₂ ). Benefiting from (i) the quantum confinement effect induced by QD TiO ₂ , which modifies the electronic band structure and improves interfacial charge transfer, (ii) dual‐anion vacancies that establish a complementary charge environment, providing electrostatic shielding to lower Mg ²⁺ diffusion barriers and facilitate charge compensation, and (iii) in situ formed TiSe ₂ layers combined with strong Se─C bonds, which ensure rapid ion/electron transport and maintain structural integrity. The QD@V _Se,O ‐Ti ₃ C ₂ cathode delivers an ultra‐high capacity (705 mAh g ⁻¹ at 50 mA g ⁻¹ ) and outstanding cycling stability with 70% capacity retention after 2300 cycles at 1000 mA g ⁻¹ . The synergy among quantum‐confined, charge compensation and shielding effects, and interfacial electronic structure achieved unprecedented Mg ²⁺ /Li ⁺ co‐adsorption stability and rapid kinetics. This work establishes a new paradigm of QD‐enhanced multi‐anion vacancy engineering for next‐generation multivalent‐ion batteries.