Incorporation ZnS quantum dots into carbon nanotubes for high-performance lithium–sulfur batteries

Abstract

Constructing sulfur hosts with high electronic conductivity, large void space, strong chemisorption, and rapid redox kinetics is critically important for their practical applications in lithium–sulfur batteries (LSBs). Herein, by coupling ZnS quantum dots (QDs) with carbon nanotubes (CNTs), one multifunctional sulfur host CNT/ZnS-QDs is designed via a facile one-step hydrothermal method. SEM and TEM analyses reveal that small ZnS-QDs (<5 nm) are uniformly anchored on the CNT surface as well as encapsulated into CNT channels. This special architecture ensures sulfur direct contacting with highly conductive CNTs; meanwhile, the catalytic effect of anchored ZnS-QDs improves the chemisorption and confinement to polysulfides. Benefiting from these merits, when used as sulfur hosts, this special architecture manifests a high specific capacity, superior rate capability, and long-term cycling stability. The ZnS-QDs dependent electrochemical performance is also evaluated by adjusting the mass ratio of ZnS-QDs, and the host of CNT/ZnS-QDs 27% owns the optimal cell performance. The specific capacity decreases from 1051 mAh g−1 at 0.2 C to 544 mAh g−1 at 2.0 C, showing rate capability much higher than CNT/S and other CNT/ZnS-QDs/S samples. After 150 cycles, the cyclic capacity at 0.5 C exhibits a slow reduction from 1051 mAh g−1 to 771 mAh g−1, showing a high retention of 73.4% with a coulombic efficiency of over 99%. The electrochemical impedance spectroscopy analyses demonstrate that this special architecture juggles high conductivity and excellent confinement of polysulfides, which can significantly suppress the notorious shuttle effect and accelerate the redox kinetics. The strategy in this study provides a feasible approach to design efficient sulfur hosts for realizing practically usable LSBs.

Novel bayberry-like functional separator coating as a physicochemical polysulfide barrier for advanced lithium–sulfur batteries

“…5(b)). 61 The lattice spacing of 3.12 Å corresponds to the d (111) plane of ZnS and 3.4 Å corresponds to the d (002) plane of the CNTs, confirming their existence in the composite, as identified in the XRD spectra.…”

In Situ Anchoring Ultrafine ZnS Nanodots on 2D MXene Nanosheets for Accelerating Polysulfide Redox and Regulating Li Plating

“…ZnS nanodots on MXene nanosheets belonged to cubic structure, with (111), (220), and (311) characteristic peaks located at around 28.9°, 48.5°, and 57.2°, respectively. [ 38 ] The fabricated ZnS/MXene composite films exhibited characteristic peaks of both MXene and ZnS, indicating ZnS nanodots were successfully anchored on MXene nanosheets. The characteristic peaks of ZnS were not obvious in ZM‐A and ZM‐B due to the low ZnS loading and the interlayer structure of the composite film.…”

“…Previous reports have proved that MXene and ZnS could effectively adsorb LiPSs and then suppress the shuttle effect of LiPSs in Li−S batteries. [26,38,51,52] So ZnS/MXene powders obtained by freeze drying in this research were used to modify the surface of separator in Li−S batteries. DFT theoretical calculation revealed the adsorption energy of -F, -OH, and -O on Ti 3 C 2 T x MXene with Li 2 S 6 was −0.83, −3.41, and −1.55 eV, respectively (Figure 6a).…”

Sandwich-type CoSe2-CNWs@rGO/S composites with efficient trapping and catalytic conversion of polysulfides in lithium–sulfur batteries

“…[3][4][5][6] Comparatively, LSBs have increased extensive focus on global-scale energy storage owing to their large theoretical capacity (1675 mA h g −1 ), high energy density (2600 W h kg −1 ) and advantages of low cost, earth abundance, and environmental friendliness. 7,8 However, there are several challenges toward the commercialization of LSBs: (i) S loss and the shuttle effect due to the dissolution of Li 2 S x (4 < x < 8) into electrolytes, 9 (ii) stability issues resulting from volume expansion/shrinkage during Li insertion/deletion in S, 10 and (iii) low electrical conductivity of sulfur and solid sulfur compounds. 11 These obstructions usually result in low sulfur utilization, sluggish redox kinetics, electrode crack, rapid capacity fading, anode passivation, poor coulombic efficiency, and even a series of safety concerns.…”

“…However, C scaffolds can only confine polysulfides physically because of the weak nonpolar interaction between polysulfides and C. 20 Many efforts have been devoted to exploring highly conductive S hosts combined with polarity. Recent research studies have demonstrated that coupling C scaffolds with metal oxides/sulfides, such as ZnO, 21 V 2 O 5 , 22 ZnS, 7 and CoS 2 , 23 can effectively chemisorb polysulfides and mitigate the shuttle effect. These approaches do improve the capacity and cycling stability of LSBs.…”