Encapsulated sulfur cathodes for rechargeable lithium batteries
A battery and cathode technology, applied in lithium batteries, battery electrodes, non-aqueous electrolyte battery electrodes, etc., can solve the problems of rupture of surrounding materials, less attention to sulfur treatment, and undesired problems.
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example 1
[0069] Sulfur encapsulated in hollow carbon nanofibers
[0070] This example illustrates the synthesis of a hollow carbon nanofiber-encapsulated sulfur electrode structure comprising a substantially vertical array of hollow carbon nanofibers filled with molten sulfur. AAO membranes were used as templates to fabricate hollow carbon nanofibers through a polystyrene carbonization process.
[0071] Scanning electron microscopy ("SEM") images of the designed structures of some embodiments at various stages of fabrication are shown in Figure 5 middle. After carbon coating at about 750 °C, substantially continuous hollow carbon nanofibers formed inside the AAO template ( Figure 5 a). The nanofibers have an outer diameter of about 200 nm to about 300 nm, corresponding to the pore size of the AAO template ( Figure 10 ). The weight gain after carbon coating was about 2% of the AAO template. Figure 5 b shows the image of hollow carbon nanofibers after sulfur infusion and AAO et...
example 2
[0089] Polymer-encapsulated hollow sulfur nanoparticles
[0090] This example illustrates the implementation of monodisperse polymer-encapsulated hollow sulfur nanoparticle cathodes by scalable one-step room temperature synthesis. The cathode incorporates several features to largely or completely address the various challenges of sulfur-based materials. The synthesis is based on the reaction of sodium thiosulfate with hydrochloric acid in aqueous solution in the presence of poly(vinylpyrrolidone) ("PVP"). The reaction can be represented as follows:
[0091] Na 2 S 2 o 3 +2HCl→S↓+SO 2 ↑+NaCl+H 2 O.(1)
[0092] The described fabrication of sulfur nanoparticles offers one or more of the following advantages over other possible sulfur cathode synthesis methods. 1) Neither time-consuming procedures nor high temperatures are involved. The synthesis is carried out in one step in about two hours at about room temperature. 2) The synthesis is low in cost, harmless to the envi...
example 3
[0132] Sulfur-TiO 2 Yolk-Shell Nanostructures
[0133] This example illustrates the implementation of sulfur-TiO in lithium-sulfur batteries 2 Yolk-shell nanofabrication for stable and extended cycling over 1,000 charge / discharge cycles. The advantage of the yolk-shell morphology is that there is an internal void space to accommodate the relatively large volume expansion of sulfur during lithiation, thereby preserving the structural integrity of the shell to mitigate polysulfide dissolution. with bare sulfur and sulfur-TiO 2 Compared with core-shell nanoparticles, yolk-shell nanostructures were found due to intact TiO 2 The effectiveness of the shell in limiting polysulfide dissolution can exhibit high capacity retention. An initial specific capacity of about 1,030 mAh / g at a 1 / 2C ratio and a Coulombic efficiency of about 98.4% during 1,000 cycles were achieved using the yolk-shell nanoarchitecture. Furthermore, at the end of 1,000 cycles, the capacity fade was found to b...
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