N‐doped carbon‐coated CoSe ₂ nanocrystals anchored on two‐dimensional MXene nanosheets for efficient electrochemical sodium‐ and potassium‐ion storage

Abstract

Sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have received much attention as next-generation energy storage systems owing to the abundance. Nevertheless, they face great challenges in the design of optimum electrode materials for practical applications. Herein, we prepared a unique twodimensional structured composite consisting of N-doped carbon-coated CoSe 2 nanocrystals and MXene nanosheets (CoSe 2 @NC/MX) for efficient electrochemical Na-and K-ion storage. In this strategy, a Co-based zeolitic imidazole framework (ZIF-67) was deposited on the surface of MXene nanosheets, and the subsequent selenization process resulted in the transformation of the ZIF-67 into CoSe 2 @NCs. The unique structure can shorten the transport pathways for electrons/ions and provide sufficient space to accommodate the volume change of the active materials. Furthermore, the N-doped carbon matrix and MXene can enhance the robustness of the electrode materials. Accordingly, the composites exhibited enhanced electrochemical performance in terms of cycle stability (317 mA h g À1 after 200 cycles at 0.5 A g À1 ) and rate capability (343 mA h g À1 at 7.0 A g À1 ) for SIBs. For KIBs, they exhibited a high reversible capacity of 358 mA h g À1 at 0.5 A g À1 after 100 cycles and 276 mA h g À1 at a high rate of 2.0 A g À1 .

Porous nanofibers comprising hollow Co 3 O 4 / Fe 3 O 4 nanospheres and nitrogen‐doped carbon derived by Fe@ ZIF ‐67 as anode materials for lithium‐ion batteries

“…The presence of graphitic carbon in A300NF is confirmed by the highest intensity of CC peak among those peaks (Figure 4D). In the N 1s XPS spectrum (Figure 4E), the pyrrolic‐N at 400 eV, graphitic‐N at 400.9 eV, and oxidized‐N species at 401.9 eV are detected 26,39 . These peaks confirm N‐doping into carbon.…”

Metal–organic framework-derived nitrogen-doped carbon-confined CoSe2 anchored on multiwalled carbon nanotube networks as an anode for high-rate sodium-ion batteries

“…Obviously, the trend of the GCD curves for the CoSe 2 @NC/MWCNTs electrode is always well maintained along with increasing current rates, suggesting the superior dynamic electrochemical stability. Meanwhile, the excellent rate performance of the prepared CoSe 2 @NC/MWCNTs surpasses many of the CoSe 2 -based anodes of the SIBs in the literature 18,25,27–29,56,57,59–61 (Fig. 4f and Table S2†).…”

“…3h), the spectra of both the samples consist of two deconvoluted peaks, corresponding to Se 3d 5/2 and Se 3d 3/2 , respectively, while the other three peaks are assigned to Co 3p 3/2 , Co 3p 1/2 , and Se–O bonding, respectively. 20,25,57 The appearance of Se–O bonding might be related to the oxidation of the material surface. Notably, the Se 3d and Co 3p peaks in the CoSe 2 @NC/MWCNTs sample migrate to a higher binding energy compared with that of the CoSe 2 @NC composite, demonstrating that the interaction of CoSe 2 with MWCNTs weakens the electron density of Co and Se, leading to accelerated charge transfer kinetics.…”

Spaced-Confined Janus Engineering Enables Controlled Ion Transport Channels and Accelerated Kinetics for Secondary Ion Batteries

“…Herein, carbon nanotubes and carbon shell not only provide stable structure and enough space to alleviate the volume expansion effect but also enhance the electrical conductivity. 29,30 To confirm the crystal structure of Janus Co/Co 2 P@CNT-CS refined urchin-like architecture, XRD pattern is shown in S6 and Table S1. In addition, the specific surface area and the pore size distribution of Janus Co/Co 2 P@ CNT-CS, Co, and Co 2 P are shown in Figure S7 and Table S2.…”