RESUMO
The shuttle effect and sluggish redox kinetics of polysulfides have hindered the development of lithium-sulfur batteries (LSBs) as premier energy storage devices. To address these issues, a high-entropy metal phosphide (NiCoMnFeCrP) was synthesized using the sol-gel method. NiCoMnFeCrP, with its rich metal species, exhibits strong synergistic effects and provides numerous catalytic active sites for the conversion of polysulfides. These active sites, possessing significant polarity, can bond with polysulfides. In situ ultraviolet-visible were conducted to monitor the dynamic changes in species and concentrations of polysulfides, validating the ability of NiCoMnFeCrP to facilitate the conversion of polysulfides. The batteries with the NiCoMnFeCrP catalyst as functional separators exhibited minimal capacity decay rates of 0.04 % and 0.23 % after 100 cycles at 0 °C and 60 °C, respectively. This indicates that the NiCoMnFeCrP catalyst possesses good thermal stability. Meanwhile, its area capacity can reach 4.78 mAh cm-2 at a high sulfur load of 4.54 mg cm-2. In conclusion, NiCoMnFeCrP achieves the objective of mitigating the shuttle effect and accelerating the kinetics of the redox reaction, thereby facilitating the commercialization of LSBs.
RESUMO
Li-S batteries have drawn a lot of attention for their high theoretical specific capacity and significant economic benefits. However, the shuttle effect of polysulfides prevents them from being used widely. To tackle this difficulty, a heterogeneous structure based on tubular carbon nitride with evenly dispersed molybdenum dioxide nanoparticles (MoO2/t-C3N4) as the S host is constructed in this work. As a polar material with a large specific surface area, MoO2/t-C3N4 has a strong anchoring effect on polysulfide. Additionally, the heterogeneous material has excellent bidirectional catalytic ability for the redox process of S species based on the action of the built-in electric field formed by electron directional transfer. Not only does it improve the reaction kinetics of the redox process of the polysulfides but it also prevents polysulfides from accumulating on the surface of the modified material and deactivating it, further improving the utilization of the active material. Thus, MoO2/t-C3N4/S shows the high initial-discharge specific capacity of 812.7 mAh g-1 at the current density of 5C, and the Coulombic efficiency is maintained at more than 95% after 400 charge/discharge cycles. Moreover, MoO2/t-C3N4/S achieved a capacity retention of 89% after 100 cycles at the current density of 0.1C under the high S loading. Therefore, the research results of this work provide a trustworthy reference for the future commercial application of Li-S batteries.
