Dual‐Functional NbN Ultrafine Nanocrystals Enabling Kinetically Boosted Lithium–Sulfur Batteries

Abstract

Herein, NbN nanocrystals immobilized on N-doped carbon nanosheets to functionalize a polypropylene (PP) membrane (NbN@NC/PP) with a thin coating of only 4 µm are designed and synthesized. The functional modifier layer allows for sulfur-involved transformations and also lithium plating behaviors. On the one hand, the sulfur cell with NbN@NC/PP separator exhibits excellent cycling stability and rate capacity. The good electrochemical performance partially results from the strong chemical interactions between NbN and lithium polysulfides via the formation of NbS and NLi bonds, which is proven by the first-principles calculations and X-ray photoelectron spectroscopy analyses. The formation of tiny nanoscrystals (<2 nm) and clusters tends to maximize the surface of NbN to interact with polysulfides and enable the effective catalysis over the sulfur-involved reactions. The higher exchange current density and Li + diffusion coefficient of NbN@NC/ PP cells experimentally verify that the introduction of NbN indeed catalytically accelerates the reaction kinetics. On the other hand, the performance of Li// Li symmetric cells demonstrates that the NbN@NC modifier layer can well induce homogeneous lithium deposition. This work confirms the application potential of NbN in lithium-sulfur batteries and encourages the exploration of prospective nitrides to engineer high performance next-generation batteries.

Mo2N Quantum Dots Decorated N‐Doped Graphene Nanosheets as Dual‐Functional Interlayer for Dendrite‐Free and Shuttle‐Free Lithium‐Sulfur Batteries

“…The Mo 2 N@NG electrode ( Figure b) depicts a larger peak area and higher peak current response in contrast to the NG electrode (Figure 6a), confirming the increased LiPSs redox kinetics. [ 25,39 ] The redox peaks of Mo 2 N@NG still maintain a stable shape with only a slight shift and narrow peak separation even at higher scan rates (Figure 6c), which shows the high electrochemical durability. On the contrary, the NG electrode exhibits the rectangle CV profiles without a pair of redox peaks under various scan rates, indicating the weak catalytic conversion ability toward LiPSs (Figure S26, Supporting Information).…”

“…[ 17–19 ] In particular, functional separators are regarded as the most promising and economical strategy to hamper the shuttle effect of LiPSs and inhibit lithium dendrite growth. [ 20–25 ] In 2012, for the first time, Manthiram and coworkers added carbon paper onto the separator facing the cathode to enhance the active materials utilization and cycling lifespan. [ 26 ] Since then, carbon‐based materials with high electrical conductivity have been employed to modify separators to block LiPSs migration via physical confinement, ranging from graphene to porous carbon and carbon nanofiber.…”

Regulated Li2S Deposition toward Rapid Kinetics Li‐S Batteries by a Separator Modified by CeO2‐Decorated Porous Carbon Nanostructure

“…Consequently, the cycling performance of the CeO 2 /KB/PP is more competitive compared with recently reported modified separator materials (Figure 7f and Table S1, Supporting Information). [22,29,[61][62][63]…”

“…[11][12][13][14] To date, researchers have made tremendous efforts to target the above problems. [15] The main strategies include using host materials to encapsulate sulfur, [16,17] regulating electrolyte components, [18,19] modifying separators, [20][21][22] and protecting lithium anode [23,24] to enhance cyclic stability for Li-S batteries. Furthermore, considering the convenient manipulation, separator modification for improving the kinetics of the conversion of Li-S batteries has been reported a promising approach due to the low cost.…”

Understanding the Catalytic Kinetics of Polysulfide Redox Reactions on Transition Metal Compounds in Li–S Batteries

“…Polar NbN with high electrical conductivity (1.28 × 10 6 S/m) and chemical stability has received much attention as the interlayer modification materials. Xiong et al 131 synthesized the NbN@CN nanocrystals and coated them on PP (4 μm thick), which promoted both the sulfur conversion and homogeneous deposition of metal Li. Theoretical calculations and XPS analysis proved a strong chemical interaction between NbN and polysulfides because of the formation of Nb−S and N−Li bonds.…”