Molybdenum Atom Engineered Vanadium Disulfide for Boosted High-Capacity Li-Ion Storage

Synergetic Effect of Mo-Doped and Oxygen Vacancies Endows Vanadium Oxide with High-Rate and Long-Life for Aqueous Zinc Ion Battery

Vanadium (V)-based oxides have garnered significant attention as cathode materials for aqueous zinc-ion batteries (AZIBs) due to their multiple valences and high theoretical capacity. However, their sluggish kinetics and low conductivity remain major obstacles to practical applications. In this study, Mo-doped V2O3 with oxygen vacancies (OVs, Mo-V2O3-x@NC) is prepared from a Mo-doped V-metal organic framework. Ex situ characterizations reveal that the cathode undergoes an irreversible phase transformation from Mo-V2O3-x to Mo-V2O5-x·nH2O and serves as an active material exhibiting excellent Zn2+ storage in subsequent charge-discharge cycles. Mo-doped helps to further improve cycling stability and increases with increasing content. More importantly, the synergistic effect of Mo-doped and OVs not only effectively reduces the Zn2+ migration energy barrier, but also enhances reaction kinetics, and electrochemical performance. Consequently, the cathode demonstrates ultrafast electrochemical kinetics, showing a superior rate performance (190.9 mAh g-1 at 20 A g-1) and excellent long-term cycling stability (147.9 mAh g-1 at 20 A g-1 after 10000 cycles). Furthermore, the assembled pouch cell exhibits excellent cycling stability (313.6 mAh g-1 at 1 A g-1 after 1000 cycles), indicating promising application prospects. This work presents an effective strategy for designing and fabricating metal and OVs co-doped cathodes for high-performance AZIBs.

Enhancing the Lithium Storage Performance of the Nb2O5 Anode via Synergistic Engineering of Phase and Cu Doping

Nb2O5 has been viewed as a promising anode material for lithium-ion batteries by virtue of its appropriate redox potential and high theoretical capacity. However, it suffers from poor electric conductivity and low ion diffusivity. Herein, we demonstrate the controllable fabrication of Cu-doped Nb2O5 with orthorhombic (T-Nb2O5) and monoclinic (H-Nb2O5) phases through annealing the solvothermally presynthesized Nb2O5 precursor under different temperatures in air, and the Cu doping amount can be readily controlled by the concentration of the precursor solution, whose effect on the lithium storage behaviors of the Cu-doped Nb2O5 is thoroughly investigated. H-Nb2O5 shows obvious redox peaks (Nb5+/Nb4+ and Nb4+/Nb3+) with much higher capacity and better cycling stability than those for the widely investigated T-Nb2O5. When introducing appropriate Cu doping, the optimized H-Cu0.1-Nb2O5 electrode shows greatly enhanced conductivity and lower diffusion barrier as revealed by the theoretical calculations and electrochemical characterizations, delivering a high reversible capacity of 203.6 mAh g-1 and a high capacity retention of 140.8 mAh g-1 after 5000 cycles at 1 A g-1, with a high initial Coulombic efficiency of 91% and a high rate capacity of 144.2 mAh g-1 at 4 A g-1. As a demonstration for full-cell application, the H-Cu0.1-Nb2O5||LiFePO4 cell displays good cycling performance, exhibiting a reversible capacity of 135 mAh g-1 after 200 cycles at 0.2 A g-1. More importantly, this work offers a new synthesis protocol of the monoclinic Nb2O5 phase with high capacity retention and improved reaction kinetics.

Molecular modulation strategies for two-dimensional transition metal dichalcogenide-based high-performance electrodes for metal-ion batteries

In the past few decades, great efforts have been made to develop advanced transition metal dichalcogenide (TMD) materials as metal-ion battery electrodes. However, due to existing conversion reactions, they still suffer from structural aggregation and restacking, unsatisfactory cycling reversibility, and limited ion storage dynamics during electrochemical cycling. To address these issues, extensive research has focused on molecular modulation strategies to optimize the physical and chemical properties of TMDs, including phase engineering, defect engineering, interlayer spacing expansion, heteroatom doping, alloy engineering, and bond modulation. A timely summary of these strategies can help deepen the understanding of their basic mechanisms and serve as a reference for future research. This review provides a comprehensive summary of recent advances in molecular modulation strategies for TMDs. A series of challenges and opportunities in the research field are also outlined. The basic mechanisms of different modulation strategies and their specific influences on the electrochemical performance of TMDs are highlighted.

Regulation of the surface activity of carbon anodes for rationalization of potassium storage

The gradient temperature was manipulated to construct hollow irregular carbon spheres with regulated intrinsic defects and surface area targeting favorable potassium storage. An enlarged surface area, increased intrinsic defects, and superior conductivity induced more surface-active interfaces. These actions facilitated a high reversible capacity as well as excellent cycling stability.