Efficient Regulation of Polysulfides by MoS₂/MoO₃ Heterostructures for High‐Performance Li‐S Batteries

Abstract

Li-S) batteries are considered as promising next-generation energy storage systems due to their high theoretical energy density (2600 Wh kg −1 ) and high specific capacity (1675 mAh g −1 ) that far exceed the state-of-the-art lithium-ion batteries. [3][4][5] In addition, the environmental friendliness and cost-effective nature of sulfur make Li-S batteries a strong competitive advantage in the market. [6] In spite of these advantages, the commercialization of Li-S batteries is still hindered by the rapid capacity decay, poor cycle stability and low coulombic efficiency due to the following problems. 1) The poor conductivity of sulfur (≈10 −30 S cm −1 ) and its discharge product Li 2 S (≈10 −13 S cm −1 ) lead to low utilization of active material. [6,7] 2) Due to the different densities of S (2.03 g cm −3 ) and Li 2 S (1.66 g cm −3 ), severe volume expansion/contraction (≈80%) leads to the collapse of the cathode structure. [8,9] 3) The notorious "shuttle effect" caused by the soluble lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8), that is, the intermediates generated during the discharge process easily dissolve in the ether-based electrolyte and diffuse to the lithium anode, leads to the corrosion of lithium metal and rapid fading of capacity. [8,10,11] 4) In the process of repeated lithium plating/stripping, uncontrollable lithium dendrites form on the anode, causing short circuit and safety problems. [1,12] In order to address these issues, great efforts have been devoted in the past decade to construct various multifunctional sulfur-based composite cathodes using diverse host materials, such as carbon materials, [13,14] polar materials, [15][16][17] conductive polymers, [18] etc.. Based on this strategy, great progress has been made in improving the performance of Li-S batteries. However, the low actual content of active material and the cumbersome preparation process of the composites usually sacrifice the energy density and increase the cost, which is very unfavorable to the actual requirements of industrial production. [19,20] In contrast to the sulfur cathode architectures, designing functional separators is a simple and effective approach to inhibit the shuttle effect and improve the electrochemical performance of Li-S batteries. In this regard, various carbonaceous materials, such as carbon nanotubes, [21] graphene, [22] and hierarchical porous carbon [23] have been widely used to functionalize separators. However, the weak van der Waals interaction between The notorious shuttle effect and sluggish conversion of polysulfides seriously hinder the practical application of Lithium-sulfur (Li-S) batteries. In this study, a novel architecture of MoS 2 /MoO 3 heterostructure uniformly distributed on carbon nanotubes (MoS 2 /MoO 3 @CNT) is designed and introduced into Li-S batteries via decorating commercial separator to regulate the redox reactions of polysulfides. Systematic experiments and theoretical calculations showed that the heterostructure not only provides sufficient surface affinity to capture polysulfi...

MoO2/t-C3N4 Heterogeneous Materials with Bidirectional Catalysis for the Rapid Conversion of S Species in Li–S Batteries

“…Lower ΔE means faster ion migration rates. 46,47 The ΔE of MoO 2 /t-C 3 N 4 /S (41.96 mV, 35.91 mV) is significantly lower than that of t- This also proves that LBSs with MoO 2 /t-C 3 N 4 /S as the cathode have a higher ion migration rate and faster redox kinetics.…”

“…The effect of different electrode materials on the ion migration rate inside the LSBs is investigated by the constant current intermittent titration technique (GITT) (Figure e,f). Lower Δ E means faster ion migration rates. , The Δ E of MoO 2 /t-C 3 N 4 /S (41.96 mV, 35.91 mV) is significantly lower than that of t-C 3 N 4 /S (45.43 mV, 43.84 mV) during the discharge and charging processes. The average lithium ion migration coefficients [log D Li+ (cm 2 s –1 )] of the two materials during charging and discharging are shown in the Figure d, which shows that the lithium ion migration coefficients of MoO 2 /t-C 3 N 4 /S (−11.361) is superior to that of t-C 3 N 4 /S (−11.599).…”

Dual‐Functional V2C MXene Assembly in Facilitating Sulfur Evolution Kinetics and Li‐Ion Sieving toward Practical Lithium–Sulfur Batteries

“…Additionally, the inset in Figure 5h shows a digital graph of powering a light-emitting diode (LED) by the VC-1/PP-enabled pouch cell. Thanks to the synchronously protective effect of the VC-1/PP separator on the sulfur cathode and lithium anode, both the high-sulfur-load cathode and pouch-cell demonstrate overwhelming electrochemical performance compared with those of the recent literature (Figure 5i and Table S2, Supporting Information, Figure 5j and Table S3, Supporting Information), [32][33][34][35][36][37][38][39][40][41][42] revealing the feasible scale control of VC spheres toward commercially viable Li-S batteries.…”

Vanadium Intercalation into Niobium Disulfide to Enhance the Catalytic Activity for Lithium–Sulfur Batteries

“…For example, conductive additives or scaffolds are used to construct continuous electron pathways. Strong adsorbents and/or porous structures are developed to capture or confine polysulfides inside cathodes. , A strong adsorbent also influences the deposition models of Li 2 S. , In addition, catalysts are studied to accelerate the conversion of polysulfides and suppress the shuttling effects. , Among various previously reported catalysts, − transition metal chalcogenides and pnictogenides receive intense interests. Chen and co-workers designed Co 3 O 4 nanopolyhedra with different dominant lattice planes to optimize the polysulfide adsorption and enhance catalytic conversion owing to varied oxidation states and coordination environments of the catalysts .…”

“…Two-dimensional transition metal disulfides (WS 2 , − MoS 2 , − TiS 2 , − and VS 2 − ) that have simple and comparable crystallographic structures were reported to exhibit interesting catalytic activities for polysulfide conversion. However, these 2D disulfides usually expose less active basal planes because of strong covalent in-plane bonding and weak van der Waals interactions between layers.…”