Outstanding Catalytic Effects of 1T′-MoTe₂ Quantum Dots@3D Graphene in Shuttle-Free Li–S Batteries

Abstract

It is still challenging to develop sulfur electrodes for Li−S batteries with high electrical conductivity and fast kinetics, as well as efficient suppression of the shuttling effect of lithium polysulfides. To address such issues, herein, polar MoTe 2 with different phases (2H, 1T, and 1T′) were deeply investigated by density functional theory calculations, suggesting that the 1T′-MoTe 2 displays concentrated density of states (DOS) near the Fermi level with high conductivity. By optimization of the synthesis, 1T′-MoTe 2 quantum dots decorated threedimensional graphene (MTQ@3DG) was prepared to overcome these issues, and it accomplished exceptional performance in Li−S batteries. Owing to the chemisorption and high catalytic effect of 1T′-MoTe 2 quantum dots, MTQ@3DG/S exhibits highly reversible discharge capacity of 1310.1 mAh g −1 at 0.2 C with 0.026% capacity fade rate per cycle over 600 cycles. The adsorption calculation demonstrates that the conversion of Li 2 S 2 to Li 2 S is the rate-limiting step where the Gibbs free energies are 1.07 eV for graphene and 0.97 eV for 1T′-MoTe 2 , revealing the importance of 1T′-MoTe 2 . Furthermore, in situ Raman spectroscopy investigation proved the suppression of the shuttle effect of LiPSs in MTQ@3DG/S cells during the cycle.

Nickel–Platinum Alloy Nanocrystallites with High‐Index Facets as Highly Effective Core Catalyst for Lithium–Sulfur Batteries

“…Different from G, LiPS can be anchored on Ni–Pt {100} and Ni–Pt {410} facets by chemical interaction, and the structure of LiPS is distorted to some extent. [ 59 ] Compared with Ni–Pt {410}, Ni–Pt {100} facets possess more binding sites toward LiPS, thus delivering a stronger adsorption capacity. Additionally, Gibbs free energies are estimated for the conversion of LiPS on three substrates.…”

“…Although the {410} facets deliver a lower anchor capacity toward LiPS, the abundant low‐coordinated atoms on Ni–Pt {410} can facilitate the charge transfer between adsorbates and catalyst, thus delivering the lowest energy barriers on the formation of Li 2 S 6 , Li 2 S 4 , Li 2 S 2 , and Li 2 S. From the Gibbs free energy profiles, the last step (from Li 2 S 2 to Li 2 S) is the rate‐determining step on Ni–Pt {411}, Ni–Pt {100} facets, and G surface with energy barriers of 0.69, 1.41, and 0.86 eV, respectively, indicating that the Li 2 S deposition on Ni–Pt {410} facets is the most thermodynamically favorable. [ 59–61 ] Although the Li 2 S 8 /Ni–Pt {100} system shows the lowest free energy, the conversion of Li 2 S 8 to Li 2 S on the Ni–Pt {100} facets is arduous owing to the excessive affinity toward LiPS. Furthermore, dissociation energy barriers of Li 2 S 6 on different substrates are studied.…”

“…Additionally, Gibbs free energies are estimated for the conversion of LiPS on three substrates. As shown in Figure 4e, the first reduction step is a spontaneous reaction, whereas the subsequent four steps from [59][60][61] Although the Li 2 S 8 /Ni-Pt {100} system shows the lowest free energy, the conversion of Li 2 S 8 to Li 2 S on the Ni-Pt {100} facets is arduous owing to the excessive affinity toward LiPS. Furthermore, dissociation energy barriers of Li 2 S 6 on different substrates are studied.…”

NbN nanodot decorated N-doped graphene as a multifunctional interlayer for high-performance lithium–sulfur batteries

“…Graphene oxide (GO) was obtained by using a modified Hummers method according to our earlier report. 8 At first, GO (30 mg, 1 mg mL −1 ) and C 6 H 12 N 4 (700 mg) were dispersed in deionized (DI) water (30 mL) under constant ultrasonication for 1 h. NbCl 5 (50 mg) was dissolved in ethanol (30 mL) by continuous stirring at ambient temperature, and then transferred to the GO suspension followed by vigorous stirring for an additional 20 min. Afterwards, the homogeneously dispersed suspension was transferred to a three-neck flask for microwave treatment at 80 °C for 30 min (800 W power).…”

“…Additionally, uncontrollable lithium polysulde (LiPSs) intermediate dissolution into the organic electrolytes is the root of the shuttle effect, which triggers irreversible capacity decay and inferior coulombic efficiency (CE). [7][8][9][10][11] Consequently, it is urgent to develop efficient strategies to achieve advanced cathodes and anodes for accelerating industrial application of Li-S batteries.…”