SBIR-STTR Award

There exists an urgent need for advanced ion-selective membranes to enable new energy storage chemistries and architectures (beyond lithium ion batteries, for example, sodium ion batteries) Some novel liquid electrolytes, such as highly concentrated ionic liquids and water-in-salt electrolytes, have shown great potential to improve safety, rate performance and cycling stability of rechargeable batteries with different chemistries; however, due to the varying hydrophobic / hydrophilic nature and rapidly changing viscosity (as a function of temperature) of highly concentrated electrolytes, the choice of a suitable separator for these novel liquid electrolytes is extremely challenging The incompatibility or poor wettability with commercial separators is a primary barrier to apply novel liquid electrolytes into practical batteries For novel electrolytes to reach their full potential in practical batteries, a new type of separator is needed Our proposed separator aims to fulfill this need In this project, TalosTech LLC (Talos) and California Institute of Technology (Caltech) propose to develop a flexible and multi-functional polymer/ceramic composite membrane with vertically aligned hierarchical pores as a new type of separators The new separator has excellent wettability with highly concentrated electrolytes and provides a short working-ion transportation path for high ionic conductance The novel multifunctional membrane will be fabricated by a facile bidirectional freeze-casting process and tailor-made for novel liquid electrolytes, with the following features: (1) vertically aligned submicron pores designed to minimize pore tortuosity, and therefore, increased ionic conductance, (2) polymer/ceramic composite designed to enhance separator wettability, and (3) a cost-effective and scalable roll-to-roll manufacturing process This composite membrane separator will be outperforming to other existing commercial separators for new battery chemistries using novel liquid electrolytes

It’s highly desired to develop safe, sustainable and low-cost battery technology beyond current lithium-ion batteries. However, there is still lack of suitable separators for future new battery chemistries. Some novel liquid electrolytes (such as ionic liquid and aqueous electrolytes) with enhanced safety and low cost features are also delayed to be applied in commercial batteries, due to no compatible separators. In this project, TalosTech LLC and California Institute of Technology developed a new class of separators to fill the market gap and facilitate the development and commercialization of new battery chemistries such as sodium-ion batteries with novel liquid electrolytes. Our novel separators are tailor-made by an innovative tape-freeze casting technology, with the features of vertically aligned pore structure, which has excellent wettability with various liquid electrolytes and provides a short working-ion transportation path for high ionic conductivity. In Phase I, we demonstrated the technical feasibility to use the laboratory-scale freeze casting process to make such kind of tunable separators. The developed separators showed much better wettability and ionic transport properties than commercial polyolefin-type separators, and delivered excellent cell performance for sodium ion batteries in both cyclic carbonate and ionic liquid electrolytes. In Phase II, we will optimize the freeze casting technology with deep understanding of the process parameters, develop separator prototypes for sodium ion batteries in various liquid electrolytes, and scale up the technology to a roll-to-roll continuous production process. Upon the success of this project, we will partner with large material companies and battery separator manufacturers to commercialize this technology, promoting the development and commercialization of more safe and sustainable battery technologies.