Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe₇S₈/FeS₂/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe₇S₈/FeS₂/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g⁻¹ up to 100 cycles at 1.0 A g⁻¹ and superior rate capability (273.4 mAh g⁻¹ at 20.0 A g⁻¹) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g⁻¹ after 1,000 cycles at 5.0 A g⁻¹) and outstanding rate capability (536.5 mAh g⁻¹ at 20.0 A g⁻¹) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte.

Rapid capacity degradation caused by poor structural stability and slow reaction kinetics is the main obstacle faced by the cathode materials of current aqueous magnesium ion hybrid supercapacitors (MHSs). Herein, we propose and evaluate Co-doped MnO₂ (Co-MnO₂) with abundant oxygen vacancies as the cathode material for MHSs. Comprehensive studies show that the decrease in the combined valence of Mn caused by Co doping leads to more oxygen vacancies, which improves the electronic conductivity, exposes more active sites, and promotes the adsorption/desorption behavior of Mg²⁺. In addition, Co intercalating between the MnO₂ layers improves the stability of the electrode material by enhancing the strength of the interlayer framework. Consequently, an MHS based on the Co-MnO₂ cathode and AC anode exhibits an excellent energy density of 79.6 W h kg⁻¹ at a power density of 360 W kg⁻¹ and amazing long-term cycling life with 94.8% capacity retention after 15 000 cycles. This work demonstrates that the Co doping strategy can enhance the electrochemical performance of MnO₂ and opens up a new horizon for developing high-performance candidate cathodes in aqueous MHSs.

Compared with the extensively used ester‐based electrolyte, the hard carbon (HC) electrode is more compatible with the ether‐based counterpart in sodium‐ion batteries, which can lead to improved cycling stability and robust rate capability. However, the impact of salt anion on the electrochemical performance of HC electrodes has yet to be fully understood. In this study, the anionic chemistry in regulating the stability of electrolytes and the performance of sodium‐ion batteries have been systematically investigated. This work shows discrepancies in the reductive stability of the anionic group, redox kinetics, and component/structure of solid electrolyte interface (SEI) with different salts (NaBF_4, NaPF₆, and NaSO₃CF₃) in the typical ether solvent (diglyme). Particularly, the density functional theory calculation manifests the preferred decomposition of PF₆⁻ due to the reduced reductive stability of anions in the solvation structure, thus leading to the formation of NaF‐rich SEI. Further investigation on redox kinetics reveals that the NaPF₆/diglyme can induce the fast ionic diffusion dynamic and low charge transfer barrier for HC electrode, thus resulting in superior sodium storage performance in terms of rate capability and cycling life, which outperforms those of NaBF₄/diglyme and NaSO₃CF₃/diglyme. Importantly, this work offers valuable insights for optimizing the electrochemical behaviors of electrode materials by regulating the anionic group in the electrolyte.

The VSe ₂ –ZrO ₂ /C/MXene composite derived from a MXene-MOF hybrid with excellent cycling stability and high reversible capacity exhibited satisfying lithium-ion storage performancedde.