Enhanced Li‐Ion‐Storage Performance of MoS₂ through Multistage Structural Design

Abstract

Inspired by a folded protein, multistage structural MoS 2 is designed as an advanced anode material for lithium-ion batteries (LIBs). Density functional theory (DFT) calculations are initially performed, demonstrating that the ideal primary structure (PÀ MoS 2 ) has saw-tooth-like edges terminated by Mo atoms and the desired secondary structure (CÀ MoS 2 ) may form via crumpling. For the latter, more exposed (002) planes exist within the wrinkled parts, creating more active sites and promoting isotropic Li + insertion. Importantly, the rate capability and capacity of a MoS 2 anode are enhanced after such a PÀ MoS 2 to CÀ MoS 2 transition: a superb specific capacity of 1490 mAh/g for CÀ MoS 2 at 0.1 A/g (vs. 1083 mAh/g for PÀ MoS 2 ), an excellent cycling stability (858 mAh/g after 450 cycles at 0.5 A/ g), and an improved rate capability of 591 mAh/g at 1 A/g (vs. 465 mAh/g) are documented. The curving effects and mechanical properties of a single CÀ MoS 2 particle are further visualized by in situ TEM. Drastically enlarged spacing changes upon Liinsertion and high elasticity are confirmed, which lead to enhanced LIB performances and the excellent mechanical strength of CÀ MoS 2 . The present multistage design of a MoS 2 structure should pave the way toward high-energy MoS 2 anode materials for future LIBs.

Synthesis of Porous Nanostructured MoS2 Materials in Thermal Shock Conditions and Their Performance in Lithium-Ion Batteries

“…The EIS data for the ATM700 material revealed a high diffusion rate of lithium ions and a low contact resistance of charge transfer (Figure e). The first factor can be associated with uniform distribution of sulfur over the volume of the composite, and the second can be determined by the presence of molybdenum clusters and Mo-terminated MoS 2 nanolayers, which ensure the electrical conductivity of the material. , Such a porous structure remained stable for at least 70 repeating cycles at a current density 0.5 A g –1 (Figure c).…”

“…The higher electrical conductivity of the material can be provided by Moterminated MoS 2 layers (Figure 3d), as quantum-chemical calculations predict. 18,59 The largest slope angles of the straight lines equal to 61.9 and 57.9°were determined from the spectra of ATM400 and ATM700, respectively (Figure 4e). The high rate of ion diffusion in these samples could be because of a very small size of MoS 2 layers in ATM400 and a high degree of MoS 2 ordering in ATM700.…”

“…It has been shown that the reversible capacity of nanostructured MoS 2 materials can reach 800–1200 mA h g –1 , − significantly exceeding the value of the theoretical capacity of the hexagonal MoS 2 . Ex situ and in situ studies of electrode materials after extraction of lithium find sulfur instead of the MoS 2 phase. , This observation indicates that the conversion reaction of MoS 2 is irreversible.…”

Environmental and Thermal Stability of Chemically Exfoliated LixMoS2 for Lithium–Sulfur Batteries

“…An endothermic peak starting from 175 °C in the MDSC curve suggests that the change in the Raman spectrum originates from Li deintercalation. 25 The exothermic dip with an onset at 282 °C in the MDSC curve is attributed to the formation of other chemical species, likely lithium sulfide (Li 2 S) from deintercalated Li and partially sublimated sulfur. The sudden change in material heat capacity and the intense endothermic nonreversing heat peak (Figure S2) provide evidence of sulfur sublimation and Li 2 S formation starting at 282 °C.…”

Core–Sheath Structured MoO3@MoS2 Composite for High-Performance Lithium-Ion Battery Anodes

“…Seen as the feasible choice to take the place of graphite anode material, transition metal oxides (TMOs) are widely investigated by researchers. , Among various TMOs, α-MoO 3 is considered as a potential replacement of graphite because of its high theoretical specific capacity of 1117 mAh/g and high thermal stability . Meanwhile, the graphite-like-layered structure of α-MoO 3 makes it can undergo reversible Li + insertion/extraction during the cycling process. − Resembling TMOs, transition metal dichalcogenides (TMDs) have also attracted great attention due to their high energy density and special structural characteristics. − As a typical representative of TMDs, molybdenum disulfide (MoS 2 ) possesses a complex Li + insertion/extraction mechanism, which makes MoS 2 reveal a more enhanced capacity than its theoretical capacity. ,− Benefitting from those merits, MoO 3 and MoS 2 seem to be promising electrode materials if some intrinsic defects of both can be solved. Pure MoO 3 and MoS 2 have the disadvantages of poor cycling stability and inferior rate capability, which can be attributed to the low electric conductivity and large volume variation during the discharge/charge process. − Besides, MoS 2 nanoflakes also suffer from serious self-stacking and severe agglomeration that bury the Li + conversion active sites. − …”