Facile Synthesis of a “Two-in-One” Sulfur Host Featuring Metallic-Cobalt-Embedded N-Doped Carbon Nanotubes for Efficient Lithium-Sulfur Batteries

Abstract

The exploration of efficient host materials of sulfur is significant for the practical lithium-sulfur (Li-S) batteries, and the hosts are expected to be highly conductive for high sulfur utilization and exhibit strong interaction toward polysulfides to suppress the shuttle effect for long-lasting cycle stability. Herein, we propose a simple synthesis of metallic cobalt-embedded N-doping carbon nanotubes (Co@NCNT) as a “two-in-one” host of sulfur for efficient Li-S batteries. In the binary host, the N-doped CNTs, cooperating with metallic Co nanoparticles, can serve as 3D conductive networks for fast electron transportation, while the synergetic effect of metallic Co and doping N heteroatoms helps to chemically confine polysulfides, acting as active sites to accelerate electrochemical kinetics. With these advantages, the S/Co@NCNT composite delivers an excellent cycling stability with a capacity decay of 0.08% per cycle averaged within 500 cycles at a current density of 1 A g–1 and a high rate performance of 530 mA h g–1 at 5 A g–1. Further, the superior electrochemical performance of the S/Co@NCNT electrode can be maintained under a high sulfur loading up to 4 mg cm–2. Our work demonstrates a feasible strategy to design promising host materials simultaneously featuring high conductivity and strong confinement toward polysulfides for high-performance Li-S batteries.

Tubular CoFeP@CN as a Mott–Schottky Catalyst with Multiple Adsorption Sites for Robust Lithium−Sulfur Batteries

“…This newly appearing loop was associated with the resistance of an insoluble Li 2 S 2 /Li 2 S passivation layer (R p in the equivalent circuit) grown during cycling. [60,67] After cycling, R ct notably decreased for the three types of electrode tested due to the activation process. After cycling, S@CoFeP@ CN electrodes were characterized by smaller R ct (9.56 Ω) and R p (20.14 Ω), when compared with S@CoFeP (R ct = 29.39 Ω and R p = 23.36 Ω) and S@CN electrodes (R ct = 52.67 Ω and R p = 120.91 Ω).…”

“…Figure 5g and Figure S27, Supporting Information display the Nyquist plot obtained from S@CoFeP@CN, S@CoFeP, and S@CN coin cells before and after cycling at 1 C. The fresh electrodes displayed a semicircle in the high-frequency region associated with the chargetransfer resistance (R ct ), followed by a linear dependence in the low-frequency region that is related to the diffusion of lithium ions. [43,67] Data were fitted considering the equivalent circuit displayed as an inset in Figure 5g. A moderate R ct was obtained for the S@CoFeP@CN electrode (62.99 Ω), when compared with that of S@CoFeP (80.36 Ω) and S@CN (125.5 Ω).…”

“…The small R p value obtained for CoFeP and especially CoFeP@CN hosts indicated a reduction of the deposition of insulting Li 2 S/Li 2 S 2 on the surface, associated with an accelerated LiPS conversion. [67] To thoroughly demonstrate that CoFeP@CN host could effectively capture soluble LiPS to confine the shuttle effect in the charging/discharging process, cycled coin cells were disassembled and analyzed after 200 cycles at 1 C. A striking contrast in the color of separators of the different cells can be observed in Figure 5h. The membrane disassembled from a S@CoFeP@CN cell (left one) showed a much lighter color than the dark brown membrane recovered from a S@Super P (right one).…”

Metal Atom-Decorated Carbon Nanomaterials for Enhancing Li-S/Se Batteries Performances: A Mini Review

“…Cobalt-nitrogen doped carbon materials as the sulfur/Li 2 S host are most frequently reported (He et al, 2016;Zhong et al, 2018;Hu et al, 2019;Li et al, 2019a;Li et al, 2019d;Wu et al, 2019;Yu et al, 2019;Liu et al, 2020a;Shao et al, 2020;Wang et al, 2020a;Wang et al, 2020c;Wang et al, 2020e;Yao et al, 2020). In 2017, Dong et al reported a honeycomb-like Co@ N−C composite that served as the sulfur host as shown in Figure 2A (Li et al, 2017).…”

Recyclable cobalt-molybdenum bimetallic carbide modified separator boosts the polysulfide adsorption-catalysis of lithium sulfur battery

“…pected to be favorably reduced or oxidized during subsequent cycles, which were impeded on the nonconductive substrate surface due to the sluggish interface redox kinetics [36,37]. Recently, as a new mechanistic understanding of the catalytic effect of polysulfide conversion emerged, researchers realized the great potential of applying various catalytic host materials [38][39][40][41][42] to boost the electrochemical kinetics of polysulfide redox reaction. Therefore, we expect that a desirable modified separator (Fig.…”