| Popis: |
Electrically and non-electrically conductive fibrous substrates have been investigated for the preparation of S cathodes. For nonconductive substrates such as wool and glass membranes, cathodes were prepared by spraying a mixture containing sulfur, carbon black and a polymer such as polyacrylic acid or PVDF. The preparation process is fast and well suited for large scale production of large cathodes with uniform coating and good adhesion. High sulfur loading of 55% or higher was possible by using this process. Cathodes prepared by spraying were assembled into 2032 coin cells with a Li anode, Solupor separator and an ionic liquid based electrolyte. Cycling of cells at the C/10 rate showed high initial discharge capacities, close to 1500 mAh g-1, with good stability. Sulfur cathodes were also prepared by electropolymerisation with electrically conductive substrates such as carbon fibre cloth and fine stainless steel mesh. For electropolymerisation, a solution containing sulfur, carbon black, Nafion, pyrrole monomer and a dopant like sulfate is prepared. Cathodes were readily prepared by applying a potential for a certain period of time while mixing the solution. The loading of sulfur can reach up to 30% based on the amount of sulfur in the starting solution. The prepared cathodes showed high initial discharge capacities of 1500 mAh/g along with a coulombic efficiency of 97%. The use of such fibrous substrates adds another dimension to sulfur cathode technology by providing more control over the content and nature of active functional groups, surface porosity, and morphology. Each of these factors can be employed to counter the problem of polysulfide shuttling by enhancing the retention of sulfur reduction products within the cathode. In addition substrates which are electrically non-conductive can act both as a cathode and separator at the same time, without the need for an additional physical separator, by simple re-arrangement of the cell’s active components. |
