Highly Stable Lithium–Sulfur Batteries Achieved by a SnS/Porous Carbon Nanosheet Architecture Modified Celgard Separator

Abstract

Lithium-sulfur batteries (LSB) are one of the potential candidates for the next generation of electrochemical energy storage technology, due to their advantages of high theoretical capacity and high energy density. However, sluggish redox kinetics and the shuttle effect of polysulfides in the cyclic process lead to low sulfur utilization, severe polarization and poor cyclic stability. Herein, an SnS modified porous carbon nanosheet (SnS/PCNS) hybrid material is synthesized by a simple hydrothermal method and used to modify the separator of the LSB for the first time. Specifically, SnS/PCNS can not only adsorb polysulfides, but also enhance the redox reaction of polysulfides. In addition, SnS/PCNS are shown to promote rapid nucleation and uniform deposition of Li 2 S, and to improve the discharge capacity and heighten cyclic stability. The initial capacity is 1270 mAh g −1 at 0.5 C, the slow decay rate of each cycle is 0.039% at 1 C. When the sulfur loading is improved to 6 mg cm −2 , the high reversible capacity is 955.3 mAh g −1 at 0.5 C. As a new polysulfides adsorbent, SnS provides a potential route for the commercialization of LSBs.

Engineering Functional Interface with Built‐in Catalytic and Self‐Oxidation Sites for Highly Stable Lithium–Sulfur Batteries

“…In view of the reversible electrochemical process, the G@MC‐based battery exhibits a high specific capacity of 1498.6 mAh g −1 at 0.1 C, which is much higher than the battery with pristine separator (889.2 mAh g −1 , Figure S11), the commercial MnCO 3 modified separator (1249.8 mAh g −1 , Figure S12), or the graphene modified separator (956.1 mAh g −1 , Figure S13). Moreover, it could also harvest a high specific capacity of 320.0 mAh g −1 with the distinct voltage platforms even at a high C rate of 8.0, which is comparable to many reported literatures (Figure 2d and Table S1) [51–60] . This superior rate performance is ascribed to the accelerated kinetic conversion of intermediates and the strong affinity with LiPS due to the G@MC modified layer in a working Li−S battery (Figure S14).…”

“… The electrochemical performance of Li−S batteries with the G@MC modified separator. a) CV curves; b) Charge‐discharge profiles; c) Cycling performance; d) Comparison with reported literatures [51–59] …”

“…Moreover, it could also harvest a high specific capacity of 320.0 mAh g À 1 with the distinct voltage platforms even at a high C rate of 8.0, which is comparable to many reported literatures (Figure and Table S1). [51][52][53][54][55][56][57][58][59][60] This superior rate performance is ascribed to the accelerated kinetic conversion of intermediates and the strong affinity with LiPS due to the G@MC modified layer in a working LiÀ S battery (Figure S14). The specific capacity of the battery could also be recovered to 1106.6 mAh g À 1 , when the C rate switched backed to low current of 0.1 C. Its capacity retention is much higher in comparison with the cased of the batteries with pristine and commercial MnCO 3 modified separator, respectively (Figure S11 and S12).…”

“…With the chemical deposition of LiPS, the corresponding Li element is also detected on the surface of G@MC layer due to the chemically redox reaction of intermediates (Figure 3d). Meanwhile, the positive Li + ions would simultaneously bond with the negative CO 3 2À ions because of the electrostatic interaction, providing the extra traps for anchoring polysulfides [51][52][53][54][55][56][57][58][59] and mitigating their shuttle in electrolyte. Moreover, it is worth noting that the additional characteristic peaks located at 162.5 and 163.5 eV of S element correspond to the conversion reaction from long-chain to short-chain LiPS on the active surface of G@MC layer (Figure 3e).…”

Porosity Engineering of MXene Membrane towards Polysulfide Inhibition and Fast Lithium Ion Transportation for Lithium–Sulfur Batteries

“…To further explore the effect of PM on Li ion diffusion in Li-S cells, CV measurements at various scanning rates were carried out to verify the kinetics enhancement of the Li-S cell with PM membrane. [57] As shown in Figure 5a-c, the peaks (cathodic and anodic peaks) for the cell with a PM (0.4 m)-CNT interlayer are higher than those for cells with pristine PP separator and Ti 3 C 2 T x -CNT interlayer, respectively, confirming LiPS conversion was promoted by the PM (0.4 m)-CNT interlayer. In the S redox processes, the Li ion diffusion properties were estimated by using the classical Randles-Sevcik equation: I p = (2.65 × 10 5 ) n 1.5 S D Li+ 0.5 ΔC Li v 0.5 , which states that the square root of the Li ion diffusion coefficient is positively correlated to the slope of the curve fitting the peak current (I p ) versus the square root of the scanning rate (ν 0.5 ).…”