Fabricating Multifunctional Coatings Using Layer-By-Layer Langmuir-Blodgett Processes
Kim, Mun Sek
This thesis reports two new coating methods, Langmuir-Blodgett-Scooping (LBS) and Langmuir-Blodgett-Sequential-Dip-Coating (LBSDC), which allows one to efficiently create self-assembled, organized thin films of nanomaterials at the surface of water and to transfer these films onto nonreactive-supports in a layer-by-layer. The methods are used to create sophisticated coating configurations in clip-like and laminated/stripped configurations to impart explicit, desired functionality to membranes. LBS and LBSDC methods are used to integrate various forms of carbons, polymers and ceramics in specific configurations on conventional separators to enhance electrochemical performances of state-of-the-art lithium-sulfur cells. In essence, the coating methods utilize a self-assembly mechanism induced by spreading and mixing of water miscible solvents that create surface-tension-gradients caused by two different fluids known as the Marangoni effect. Utilizing this mechanism in a sequential fashion allows stacks of thin films composed of carbon/ceramic/polymer are successfully coated onto the porous polyolefin separator used in advanced energy storage devices, without the need for binders. It is shown that when the carbon/ceramic/polymer films are configured in the clip and laminated configurations, the resultant membranes are able to efficiently regulate mass and ion transport between the sulfur cathode and reactive lithium anode of a lithium-sulfur battery. Direct consequences of these improvements include enhanced capacity retention and Coulombic efficiency of rechargeable lithium-sulfur cells over a range of operating conditions.
Lithium sulfur; Separator; Langmuir-Blodgett
M.S., Chemical Engineering
Master of Science
dissertation or thesis