No abstract

This paper describes a general method to change the surface property of the oleic acid stabilized silver nanoparticles and successful tranferring of the silver nanoparticles from the organic phase into the aqueous phase. By vigorous shaking of a biphasic mixture of the silver organosol protected with oleic acid and p-sulfonated calix[4]arene (pSC4) aqueous solution, it is believed that an inclusion complex is formed between oleic acid molecules and pSC4, and the protective layer of the silver nanoparticles shifts from hydrophobic to hydrophilic in nature, which drives the transfer of silver nanoparticles from the organic phase into the aqueous phase. The efficiency of the phase transfer to the aqueous solution depends on the initial pSC4 concentration. The pSC4-oleic acid inclusion complex stabilized nanoparticles can be stable for long periods of time in aqueous phase under ambient atmospheric conditions. The procedure of phase transfer has been independently verified by UV-vis, transmission electron microscopy, Fourier transform infrared, and 1H nuclear magnetic resonance techniques.

Lithium–sulfur (Li–S) batteries have attracted considerable attention over the last two decades because of a high energy density and low cost. However, the wide application of Li–S batteries has been severely impeded due to the poor electrical conductivity of S, shuttling effect of soluble lithium polysulfides (LiPSs), and sluggish redox kinetics of S species, especially under high S loading. To address all these issues, a Ni–CeO2 heterostructure‐doped carbon nanofiber (Ni‐CeO2‐CNF) is developed as an S host that combines the strong adsorption with the high catalytic activity and the good electrical conductivity, where the LiPSs anchored on the heterostructure surface can directly gain electrons from the current collector and realize a fast conversion between S8 and Li2S. Therefore, Li–S batteries with S@Ni‐CeO2‐CNF cathodes exhibit superior long‐term cycling stability, with a capacity decay of 0.046% per cycle over 1000 cycles, even at 2 C. Noteworthy, under a sulfur loading up to 6 mg cm−2, a high reversible areal capacity of 5.3 mAh cm−2 can be achieved after 50 cycles at 0.1 C. The heterostructure‐modified S cathode effectively reconciles the thermodynamic and kinetic characteristics of LiPSs for adsorption and conversion, furthering the development of high‐performance Li–S batteries.

Covalent organic frameworks (COFs) with one-dimensional (1D) pores are capable of sulfur encapsulation; however, the physical absorption leads to an insufficient suppression on the shuttle of lithium polysulfides that ultimately cripples the performance of lithium–sulfur batteries (LSBs). Here, we prepared two vinylene-linked COFs bearing different pores, denoted as COF-1 and COF-2. Interestingly, COF-1 can only physically isolate sulfur to give S-COF-1, while the polysulfide chains can be covalently linked to the framework of COF-2 via inverse vulcanization to produce S-COF-2. S-COF-1 and S-COF-2 deliver superior capacities of 1179 and 1293 mAh g–1 at 0.2C, an outstanding rate performance (331 and 692 mA h g–1 at 3C), and a prolonged cycling life span (a low declining value of 0.09% per cycle at 1C for S-COF-2). Due to the synergistic effect of covalent linking and physical confinement of sulfur, S-COF-2 features a superior LSBs performance compared to S-COF-1. Our studies provide a strategy for improving the performances of LSBs by combining the chemical and physical installation of sulfur.