Combined High Catalytic Activity and Efficient Polar Tubular Nanostructure in Urchin‐Like Metallic NiCo₂Se₄ for High‐Performance Lithium–Sulfur Batteries

Abstract

Urchin-shaped NiCo 2 Se 4 (u-NCSe) nanostructures as efficient sulfur hosts are synthesized to overcome the limitations of lithium-sulfur batteries (LSBs). u-NCSe provides a beneficial hollow structure to relieve volumetric expansion, a superior electrical conductivity to improve electron transfer, a high polarity to promote absorption of lithium polysulfides (LiPS), and outstanding electrocatalytic activity to accelerate LiPS conversion kinetics. Owing to these excellent qualities as cathode for LSBs, S@u-NCSe delivers outstanding initial capacities up to 1403 mAh g −1 at 0.1 C and retains 626 mAh g −1 at 5 C with exceptional rate performance. More significantly, a very low capacity decay rate of only 0.016% per cycle is obtained after 2000 cycles at 3 C. Even at high sulfur loading (3.2 mg cm −2 ), a reversible capacity of 557 mAh g −1 is delivered after 600 cycles at 1 C. Density functional theory calculations further confirm the strong interaction between NCSe and LiPS, and cytotoxicity measurements prove the biocompatibility of NCSe. This work not only demonstrates that transition metal selenides can be promising candidates as sulfur host materials, but also provides a strategy for the rational design and the development of LSBs with long-life and high-rate electrochemical performance.

Enhanced Chemisorption and Catalytic Effects toward Polysulfides by Modulating Hollow Nanoarchitectures for Long‐Life Lithium–Sulfur Batteries

“…The average capacity fading rate per cycle is as low as 0.011%, and the coulombic efficiency is nearly 100%. The cycling stability is comparable with those in the reported long‐life Li–S batteries (Table S1, Supporting Information) . The postmortem analyses of Co‐NC@Co 9 S 8 /NPC‐S were performed in the discharge state after 2000 cycles at 2 C. Both the cathode and lithium anode pieces are intact, there are no yellow lithium polysulfides on the surface of lithium anode (Figure S11a,b, Supporting Information), indicating no serious parasitic reaction between dissolved polysulfides and lithium metal of the anode surface.…”

Nitrogen‐Doped Hollow Carbon Polyhedrons with Carbon Nanotubes Surface Layers as Effective Sulfur Hosts for High‐Rate, Long‐Lifespan Lithium–Sulfur Batteries

“…The observation of higher D Li + for S@CNTs/HNC‐800 than S@HNC‐800 suggests a faster reaction kinetics for the S@CNTs/HNC‐800 based electrode, probably due to the presence of abundant pores and tunnels in CNTs/HNC as well as the catalysis of N‐doped carbon matrix towards the reversible conversion of sulfur and lithium polysulfides. As for the electrochemical impedance spectra recorded with in the frequency range of 0.01 Hz to 100 kHz(Figure 4f), the Nyquist plots of all the three investigated samples display a semicircle that corresponds to charge‐transfer resistance (R 1 ) [49–51] in the high frequency region. Based on the corresponding equivalent circuit model (insetto the upper right of Figure 4f), the R 1 of electrolyte‐electrode interface is determined to be 22.72 Ω for S@CNTs/HNC‐800 electrode (Figure 4f), which is much smaller than that of S@HNC‐800 (57.02 Ω) and S@CNTs (75.50 Ω) electrodes, signifying a faster reaction kinetics for lithium polysulfides conversion and lower interfacial resistance for charge transfer in the S@CNTs/HNC‐800 electrode, most likely due to the effective catalysis of N‐doped carbon towards lithium polysulfides conversion and sufficient infiltration of electrolyte intothe abundant mesopores of S@CNTs/HNC‐800 electrode.…”

Catalytic and Dual‐Conductive Matrix Regulating the Kinetic Behaviors of Polysulfides in Flexible Li–S Batteries

“…Additionally, the g‐C 3 N 4 @CC exhibits a higher current density than that of pristine CC, implying the significantly enhanced redox kinetics between liquid phase LiPSs. [ 23,24 ] To gain more insight into the underlying reasons for the superb charge‐transfer capability of S@CP/g‐C 3 N 4 @CC across the liquid–solid interface, electrochemical impedance spectroscopy (EIS) measurements of S@CP/g‐C 3 N 4 @CC and S@CC interface versus the lithium counter electrode were also provided (Figure 5c). The charge‐transfer impedance of S@CP/g‐C 3 N 4 @CC (120.1 Ω) is much lower in comparison with that of S@CC (210.5 Ω) due to its improved electroconductivity of CP.…”