Isolated Fe-Co heteronuclear diatomic sites as efficient bifunctional catalysts for high-performance lithium-sulfur batteries

Abstract

The slow redox kinetics of polysulfides and the difficulties in decomposition of Li2S during the charge and discharge processes are two serious obstacles to the practical application of lithium-sulfur batteries. Herein, we construct the Fe-Co diatomic catalytic materials supported by hollow carbon spheres to achieve high-efficiency catalysis for the conversion of polysulfides and the decomposition of Li2S simultaneously. The Fe atom center is beneficial to accelerate the discharge reaction process, and the Co atom center is favorable for charging process. Theoretical calculations combined with experiments reveal that this excellent bifunctional catalytic activity originates from the diatomic synergy between Fe and Co atom. As a result, the assembled cells exhibit the high rate performance (the discharge specific capacity achieves 688 mAh g−1 at 5 C) and the excellent cycle stability (the capacity decay rate is 0.018% for 1000 cycles at 1 C).

Selenium-Doped Sulfurized Poly(acrylonitrile) Composites as Ultrastable and High-Volumetric-Capacity Cathodes for Lithium–Sulfur Batteries

“…All Nyquist curves consist of one depressed semicircle in the high-frequency region (HF) and a slope line in the low-frequency (LF) region. The semicircle reflects the charge-transfer impedance ( R ct ), and the line is related to the Warburg diffusion process ( W 0 ) . In addition, an equivalent circuit composed of R e , R ct , CPE , and W 0 was applied to calculate the specific value of each component (Figure S5).…”

“…The semicircle reflects the charge-transfer impedance (R ct ), and the line is related to the Warburg diffusion process (W 0 ). 50 In addition, an equivalent circuit composed of R e , R ct , CPE, and W 0 was applied to calculate the specific value of each component (Figure S5). According to the fitting results (Table S5), the R ct and W 0 for the Se 0.4 SPAN cathode are 108.2 and 61.5 Ω, respectively, which are much smaller than those of 159.1 and 72.9 Ω for SPAN.…”

Atomically Dispersed Fe–N4 and Ni–N4 Independent Sites Enable Bidirectional Sulfur Redox Electrocatalysis

“…After cycling at 0.5 C, all the electrodes show decreased charge transfer resistance (R ct ) owing to the redistribution of the sulfur species. 8 Compared with Ni−NC/S (13.67 Ω) and Fe−NC/S (13.81 Ω), Ni−Fe− NC/S (5.96 Ω) has the lowest R ct . After cycling, the Ni−Fe− NC/S electrode kept a porous surface, and the contour of nanocages was well retained (Figure S25a−-c), whereas clear passivation was found on both Ni−NC/S and Fe−NC/S.…”

“…Li–S batteries (LSBs) are regarded as promising energy storage technologies owing to their high theoretical energy density (∼2600 Wh kg –1 ) and specific capacity (1675 mAh g –1 ). − However, the commercial implementation of LSBs is impeded by the following challenges: the insulating nature of elemental sulfur (5 × 10 –30 S cm –1 ) and Li 2 S 2 /Li 2 S (∼10 –9 S cm –1 ), the volume expansion (76%) during cycling, the shuttle effect of the soluble lithium-polysulfides (LiPSs, Li 2 S x , 4 ≤ x ≤ 8), and the sluggish conversion kinetics. , These unfavorable factors lead to irreversible capacity decay, low sulfur utilization, and high polarization and ultimately a short cycling life of LSBs. An electrocatalytic effect in sulfur hosts can accelerate the redox kinetics of sulfur species and regulate the solid products. − These hosts range from doped carbon materials, metal compounds with cationic or anionic defects, and metal–organic frameworks to single atom catalysts (SACs). − In particular, SACs exert a higher activity than other conventional nanoparticle catalysts because of the theoretical 100% atom utilization. − …”

Fe3C Decorated Folic Acid-Derived Graphene-Like Carbon as Polysulfide Catalyst for High-Performance Lithium-Sulfur Battery

“…The development of modern energy storage systems is undoubtedly a consequential part of the implementation of carbon-neutral strategies in response to the current environmental situation. Lithium-sulfur (Li-S) batteries are one of the most promising expected candidates due to their high energy density (2600 Wh kg -1 ) and high theoretical capacity (1675 mAh g -1 ) [1,2]. Additionally, sulfur is extremely rich in the earth, nonpoisonous, and eco-friendly [3].…”