CoSe2 Nanoparticles Encapsulated by N-Doped Carbon Framework Intertwined with Carbon Nanotubes: High-Performance Dual-Role Anode Materials for Both Li- and Na-Ion Batteries.

Jun Yang,Zhang Lin,Hongcheng Gao,Shuang Men,Shaowei Chen,Xiongwu Kang,Zhenqing Shi

doi:10.1002/advs.201800763

Abstract

It is of fundamental and technological significance to develop dual‐role anode materials for both lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) with high performance. Here, a composite material based on CoSe2 nanoparticles encapsulated in N‐doped carbon framework intertwined with carbon nanotubes (CoSe2@N‐CF/CNTs) is prepared successfully from cobalt‐based zeolitic imidazolate framework (ZIF‐67). As anode materials for LIBs, CoSe2@N‐CF/CNTs composites deliver a reversible capacity of 428 mAh g−1 even after 500 cycles at a current density of 1 A g−1 with almost 100% Coulombic efficiency. The charge and discharge mechanisms of CoSe2 are characterized using ex situ X‐ray diffraction and Raman analysis, from which the lithiation products of CoSe2 are found to be LixCoSe2 and Li2Se, which are further converted to CoSe2 upon delithiation. The CoSe2@N‐CF/CNTs composites also demonstrate excellent electrochemical performance as anode materials for SIBs with a carbonate‐based electrolyte, with specific capacities of 606 and 501 mAh g−1 at 0.1 and 1 A g−1 in the 100th cycle. The electrochemical performance of the anode materials is further studied by pseudocapacitance and galvanostatic intermittent titration technique (GITT) measurements. This work may be exploited for the rational design and development of dual‐role anode materials for both Li‐ and Na‐ion batteries.

Highlights

It is of fundamental and technological significance to develop dual-role anode are believed to be a viable alternative for lithium-ion batteries (LIBs), especially in the materials for both lithium-ion batteries (LIBs) and sodium-ion batteries field of large-scale energy storage.[1]
The scanning electron microscopy (SEM) images of the prepared polyhedral ZIF-67 template were shown in Figure S1 (Supporting Information), which showed a smooth surface
The growth of interconnected CNTs on the external surface of the carbon framework was attributed to the catalytic effect of Co nanoparticles under the reducing gas streams,[2b,8,9] which provided an interlaced conductive network to facilitate electrolyte penetration and charge transportation, and effectively mitigated the volume expansion and maintained the structural integrity of the carbon matrix.[2b,8,9] Figure 1b,c shows the SEM and transmission electron microscopy (TEM)

Summary

Structural Analysis

The scanning electron microscopy (SEM) images of the prepared polyhedral ZIF-67 template were shown in Figure S1 (Supporting Information), which showed a smooth surface. N2 adsorption–desorption isotherms of CoSe2@N-CF/CNTs and CoSe2@CF/CNTs were shown in Figure S5 (Supporting Information), which are characteristic of type IV isotherms with hysteresis loops at high relative pressures, indicating the formation of a mesoporous configuration.[5d,19] The specific surface areas of Co@N-CF/CNTs and Co@CF/CNTs derived from the isotherms were 277.59 and 237.96 m2 g−1, respectively, with the Weight loss (%). The slightly smaller specific surface area of Co@CF/CNTs than Co@N-CF/CNTs was likely due to the aggregation of cobalt nanoparticles at higher temperatures.[5d,20] Selenization of Co@N-CF/CNTs and Co@CF/CNTs remarkably reduced the specific surface area and total pore volume of the composites (Table S1, Supporting Information) due to the formation of CoSe2 nanoparticles.

Electrochemical Characterization

Conclusion

Experimental Section

Conflict of Interest