Low-Cost Nanoporous Sol Gel Separators for Lithium-Based Batteries

70566S02-II Lithium-based batteries for vehicles need to be longer lasting, faster recharging, able to deliver high power pulses, safer, lower in cost, and have higher energy density. However, the commercial microporous plastic polymer separators used in these batteries are too expensive and are very limited in their ability to provide these needed performance improvements. This project will develop nanoporous sol gel coatings as a new type of separator that can be coated from a water-based solution at less than one-half the cost per square meter of commercial plastic separators. The non-flammable, ionic, and ultra-thin properties of the sol gel separators would allow major improvements in the safety, recharging and discharging speeds, lifetime, and energy density of lithium-based batteries. In Phase I, tough but very flexible 8-micron-thick sol gel separators were made and showed porosities of 45%. A manufacturing process, which involved sol gel coating on a smooth substrate and then delaminating the coating from the substrate to form a free standing sol gel separator, was demonstrated. In Phase II, the mechanical properties of the 8-micron-thick sol gel separators will be optimized by determining the amount and type of crosslinked polymers to add. The interfacial surfaces between the sol gel separator and the anode and cathode layers will be designed and tested, first in lithium-ion batteries and then in lithium-sulfur batteries. 8-micron-thick sol gel separators will be made on machine coating equipment using a low cost coating/delamination process. Commercial Applications and Other Benefits as described by awardee: Besides providing separators for lithium-based batteries for vehicles, sol gel separators could be used for other battery applications such as mobile computers and cell phones, as separator membranes for fuel cells, as ultrafiltration membranes for purifying water, as dye-sensitized sol gel coatings for solar splitting of water or methanol to produce hydrogen fuel, and as photo-quality ink jet digital printing materials.