![]() ![]() Figure 2b depicts the scanning electron microscopy (SEM) image of NiCo 2O 4. Meanwhile, combined with the thermogravimetric analysis (TGA) results in Figure S2, it can be inferred that the carbon template is basically removed after a long time of heat treatment in air. The absence of other peaks meant that the sample was pure. All patterns matched those of spinel NiCo 2O 4 (JCPDS No. The phase and purity of the as-obtained samples were first determined by X-ray powder diffraction (XRD) in Figure 2a. Even with a high loading of 3.16 mg cm −2, the battery with a modified separator could still achieve a ~3.2 mAh cm −2 area capacity, which greatly increased its potential to meet the actual requirements. When the current density was increased to 4 C, the capacity was still as high as 505 mAh g −1 and remained about 80.6% after 300 cycles. A high reversibility of 1386 mAh g −1 could be obtained at 0.2 C. Unlike the conventional PP separator cell ( Figure 1b), the battery based on such a NiCo 2O 4 coated separator (defined as NiCo 2O obtained an excellent electrochemical performance ( Figure 1c). In addition, the rich Ni–Co sites provided a good catalytic path for the rapid LiPS conversion. The high surface area adsorbed more sulfur species and closed them in the inner cavity of NiCo 2O 4, further inhibiting the migration of soluble LiPSs. The structure consisted of lots of ultra-thin NiCo 2O 4 nanosheets, which showed a specific surface area of up to 281 m 2 g −1, meaning that it has a more active area as a separator modification material. Herein, the edelweiss shaped nickel cobaltate (NiCo 2O 4) hollow nanospheres were prepared by a simple template method ( Figure 1a). It can be seen that the correct design of transition metal oxide as a modified material for a Li–S separator still faces many challenges and is worth exploring. Unfortunately, the low surface area and heavy block are not conducive to the energy density. Among these oxides, the ternary metal oxide composed of two different metal cations shows higher electronic conductivity and electrochemical activity than mono-metal oxides due to its complex chemical composition and the synergistic action. Combined with the anchoring effect of MnO 2 on LiPSs and the stability of carbon materials, the modified electrode can effectively inhibit the diffusion of LiPSs. coated a functional MnO 2/graphene oxide/carbon nanotube composite interlayer on a PP separator in Li–S batteries. Different oxides including MnO 2, Fe 2O 3, and NiO are used in Li–S batteries. More importantly, some metal oxides have a certain catalytic effect, which can promote the LiPS reaction. ![]() It has a good affinity with LiPSs and can effectively anchor the latter. Therefore, transition metal oxides with a “polar surface” are increasingly being studied. In addition, carbon materials cannot effectively solve the problem of slow LiPS conversion kinetics. The soluble LiPSs will still be shed from the carbon substance during long or high load electrochemical cycles. ![]() The carbon coating with a high specific area on separator is only a barrier layer in the physical sense. However, the “non-polar” carbon has a limited effect on the shuttle of LiPSs, because its interaction with the latter is in the category of van der Waals forces. ![]() Carbon based materials (carbon nanofibers, mesporous carbon, etc.) were first used to modify the Li–S separator. In recent years, many studies have shown that the initial PP separator can be modified (separator engineering) to obtain different inhibition abilities of LiPS diffusion. Even at 4 C, a high capacity of 505 mAh g −1 was obtained, and about 80.6% could be retained after 300 cycles. As a result, the sulfur cathode based on this composite separator showed significantly enhanced electrochemical performance. Therefore, the modified separator realized multiple physical constraints and strong chemical anchoring on sulfur species. The hollow structure also provided a physical barrier to mitigate the sulfur species diffusion. On the other hand, mesoporous NiCo 2O 4 nanomaterials provided many strong chemical binding sites for loading sulfur species. On one hand, the good electrolyte wettability of NiCo 2O 4 promoted the migration of Li-ions and greatly improved the dynamics. Herein, edelweiss shaped NiCo 2O 4 hollow nanospheres with a high surface area were prepared by a simple template method to modify the separator to realize multiple physical constraints and strong chemical anchoring on the polysulfides. Inhibiting the shuttle effect of soluble polysulfides and improving slow reaction kinetics are key factors for the future development of Li–S batteries. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |