Honeycomb‐Like Spherical Cathode Host Constructed from Hollow Metallic and Polar Co<sub>9</sub>S<sub>8</sub> Tubules for Advanced Lithium–Sulfur Batteries

Biendicho

et al. 2019

Adv Funct Materials

185

150

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.

Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

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

Biendicho

et al. 2019

Adv Funct Materials

185

150

“…[ 21–24 ] However, the weak physical interaction between nonpolar carbon materials and LiPS is not comparable with the strong chemical affinity. [ 25–30 ] Therefore, a series of active materials (such as metal oxides/sulfides) with chemically polar sites were also fabricated to anchor the LiPS via the formation of the chemical bonding. [ 31–37 ] In addition to the effective immobilization of the LiPS, the rapid conversion of the intermediates on the surface of active materials with catalytic activity is also conducive to enhance the performance of Li‐S batteries.…”

Section: Introductionmentioning

confidence: 99%

Integration of Binary Active Sites: Co₃V₂O₈ as Polysulfide Traps and Catalysts for Lithium‐Sulfur Battery with Superior Cycling Stability

Wan

Cao

et al. 2020

Small

Lithium‐sulfur (Li‐S) batteries as a promising energy storage candidate have attracted attention due to their high energy density (2600 Wh kg−1). However, the serious shuttle effect caused by the dissolution of the lithium polysulfides (LiPS) in electrolyte significantly degrades their cycling life and rate performance. Herein, the “binary active sites” concept in a Li‐S battery system via the design of a cobalt vanadium oxide (CVO) modified multifunctional separator is designed. In the case of CVO, active vanadium sites simultaneously anchor the LiPS through the chemical affinity and active cobalt sites can dominate a rapid kinetic conversion. Such a synergistic effect contributes to improving the utilization of sulfur in the electrochemical process for the enhanced electrochemical performance. As a result, the Li‐S battery with the CVO modified separator possesses a high reversible capacity of 1585.5 mAh g−1 at 0.1 C and superior cycling stability with 0.012% capacity decay cycle−1 after 3000 cycles. More impressively, the assembled soft‐packaged Li‐S devices can exhibit the excellent stability under bending states. This binary active sites strategy provides a route to design the functional materials for modifying separators of Li‐S batteries to improve the performance.

“…The interconnected structure could provide efficient direct routes for ion and electron transport and then ensure each nanosheet for the HER process . High resolution transmission electron microscope (HRTEM) images and fast Fourier transform (FFT) images exhibit the characteristic groups of parallel fringes with the interlayer distances of 0.62, 0.56, and 0.30 nm (Figure d and e), which were assigned to the (002) plane of MoS 2 and (111) and (311) planes of Co 9 S 8 , respectively . Interestingly, the interfaces constituted by MoS 2 (002) and Co 9 S 8 (111) and (311) can be clearly identified, demonstrating the successful formation of Co‐Mo‐S heteronanosheets with a moderate degree of disorder .…”

mentioning

confidence: 99%

Co‐Modified MoS₂ Hybrids as Superior Bifunctional Electrocatalysts for Water Splitting Reactions: Integrating Multiple Active Components in One

Zhao

Shao

et al. 2019

Adv Materials Inter

that can significantly improve the sluggish kinetic process and reduce overpotentials in both HER and OER. Currently, noble metals (e.g., Pt) and noble metal oxides (e.g., IrO 2 and RuO 2 ) have been proven to be the most effective and catalytically stable electrocatalysts for HER and OER, respectively. [10][11][12] However, the high cost and scarcity of these noble metal-based electrocatalysts severely limit the largescale application. Thus, the development of cost-effective, earth-abundant electrocatalysts for efficient and durable water electrolysis is very imperative and significant. Most recent efforts have been focused on transition metal sulfides, [13,14] nitrides, [15,16] phosphides, [17,18] and selenides [19] for HER and transition metal oxide, [20,21] hydroxide, [22][23][24] and carbides [25] for OER.Molybdenum disulfide (MoS 2 ) has been considered as a promise non-noble metal catalyst for HER due to the uncoordinated Mo-S sites at the edge of MoS 2 with a near-optimal hydrogen adsorption free energy, which has been proved by both experimental and theoretical studies. [26][27][28] Motivated by this fundamental understanding, great efforts have been made to improve the electrocatalytic performance of MoS 2 , which shows the promising performance in acidic media but poor activity in both alkaline and neutral media. [29][30][31] It has been reported that the introduction of a metal element into metal sulfide can make electron transfer from the introduced metal to metal sulfide, [12] promoting water adsorption and activation to improve the HER performance. [32] Moreover, the merger of two or more metal species supplies more active sites and improves the electronic conductivity, which is beneficial for electrocatalytic application. [33] Meanwhile, compared to the HER, the OER is more challenging for MoS 2 because of the thermodynamical and kinetical limitation, involving four proton-coupled electron transfers and oxygen-oxygen bond formation. In order to use MoS 2 for overall water splitting, the effective way is to hybridize OER-efficient materials with MoS 2 to fulfill the synergetic effect of different components. [34][35][36] The Co-based sulfides, [37] oxides, [38] and hydroxides [39] are commonly used as OER-efficient materials due to their excellent adsorption of OH − and oxygen-containing intermediates. Therefore, the controllable integration of HER and OER materials in a designed manner to build novel heterostructures is a key innovation for both HER and OER.The development of highly active, stable, low-cost, and earth-abundant electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a great challenge. Herein, the cobalt (Co)-modified MoS 2 hybrid catalysts grown on nickel foam (NF) are successfully synthesized by a facile solvothermal method. The optimized catalyst (denoted as Co-Mo-S-2/NF) shows excellent HER activity with low overpotentials of 77 and 96 mV at a current density of 10 mA cm −2 , as well as excellent stability with negligible loss of t...