Methods for Preparing Porous Separators for Electrochemical Cells


Porous separators are applied to battery electrodes through roll-to-roll processing. The current industry-standard for polymer separators (Celgard) for lithium-ion batteries (LIB’s) involves relatively involved manufacturing. These materials, fabricated separately from LIB’s, are produced from commodity polyolefin plastics derived from gases such as ethylene and propene. Therefore, these reactions require special catalysts and equipment. The polymers are then extruded into sheets and finally mechanically stressed, forming pores. Due to the chemical inertness of polyolefins and their limited solubility in common processing solvents, the pore formation step is complex and adds significant cost to the material. Another method for separator generation is polymerization-induced phase separation (PIPS), where pores are constructed in parallel to the synthesis of the separator material. Previous attempts at using PIPS to fabricate LIB separators were limited by the fact that the porogen—porosity inducer—must be removed from the matrix after polymerization.

Technology Overview

Researchers invented a facile PIPS-based method to allow LIB separators to be fabricated directly on a battery electrode. By using an essential component in LIB electrolytes, this reaction can take place in-situ, (i.e. without the need to remove the porogen compound) and eliminate the need for extrusion, mechanical formation of pores, roll-to-roll separator application, etc. Separator synthesis proceeds through rapid, low cost photopolymerization, which is readily scalable to high throughput manufacturing. Owing to the simplicity of the separator fabrication, to modify physical properties or add functionality to the material, the components to the PIPS reaction need only be modified, while still employing the same methods and set up. Electrochemical cycling of experimental lithium-ion cells demonstrates that the electrochemical performance of the PIPS separators is comparable to Celgard. Reducing the separator thickness is also shown to improve capacity retention at higher rates.


By eliminating processing steps in the manufacturing of batteries, this method promises to significantly reduce the cost of high-performance polymer separators, which currently account for approximately 15% of the cost of lithium-ion batteries. Since the PIPS separator will not be tensioned during roll-to-roll processing, the PIPS separator can be made much thinner than conventional separators (<20 mm), leading to battery cells with less volume and mass, as well as lower ohmic resistances, resulting in larger overall energy and power densities. The separators also undergo negligible thermal shrinkage at elevated temperatures, improving the thermal safety of the cell.


Lithium-ion battery manufacturing for electric vehicles, mobile devices, etc.

URV Reference Number: 2-21083
Patent Information:
For Information, Contact:
McKenna Geiger
Licensing Manager
University of Rochester
Wyatt Tenhaeff
Alexander Manly