Abstract
We developed a new nanowire for enhancing the performance of lithium-sulfur batteries. In this study, we synthesized WO3 nanowires (WNWs) via a simple hydrothermal method. WNWs and one-dimensional materials are easily mixed with carbon nanotubes (CNTs) to form interlayers. The WNW interacts with lithium polysulfides through a thiosulfate mediator, retaining the lithium polysulfide near the cathode to increase the reaction kinetics. The lithium-sulfur cell achieves a very high initial discharge capacity of 1558 and 656 mAh g−1 at 0.1 and 3 C, respectively. Moreover, a cell with a high sulfur mass loading of 4.2 mg cm−2 still delivers a high capacity of 1136 mAh g−1 at a current density of 0.2 C and it showed a capacity of 939 mAh g−1 even after 100 cycles. The WNW/CNT interlayer maintains structural stability even after electrochemical testing. This excellent performance and structural stability are due to the chemical adsorption and catalytic effects of the thiosulfate mediator on WNW.
Highlights
Next-generation batteries have been in the spotlight to meet the demand for batteries with higher energy densities than commercial lithium-ion batteries [1,2,3,4,5,6]
During the fabrication of the WO3 nanowires (WNWs)/carbon nanotubes (CNTs) composite, a simple hydrothermal reaction occurred between Na2 WO4 ·2H2 O and HCl; namely, Na2 WO4 ·2H2 O + 2HCl → WO3 +
Images obtained through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicate that the synthesized WO3 has a long nanowire shape with a thickness of approximately 20 nm (Figure 1b,c), which is similar to the morphology of CNTs (Figure S1a)
Summary
Next-generation batteries have been in the spotlight to meet the demand for batteries with higher energy densities than commercial lithium-ion batteries [1,2,3,4,5,6]. Recent improvements in the performance of lithium-sulfur cells are attributed to filmtype interlayers between the separator and the cathode These interlayers facilitate electron transfer and prevent the migration of the produced lithium polysulfide toward the anode, thereby minimizing the loss of active materials to significantly improve capacity retention during cycling [16,17,18,19]. Yang et al demonstrated the ability of WO3 and carbon nanofibers, i.e., WO3 -decorated N, S co-doped carbon nanofibers, to trap polysulfides and form an electro-conducting network [27] These studies demonstrate the catalytic efficacy of WO3 in reducing high-order polysulfides to low-order Li2 S. WNW and lithium polysulfide interact to produce thiosulfate, which combines with high-order polysulfides to form low-order polysulfide and polythionate complexes This mediating reaction enhances the kinetics of Li2 S formation during discharge and S formation during charge. Owing to the thiosulfate mediation on the surface of the WNW/CNT interlayer, the sulfur electrode exhibits excellent electrochemical capacity and rate capability even at high sulfur mass loadings of 4.2 mg cm−2
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