Sponge-Inspired Pressing Approach to Facilitate Electrolyte Wetting in Li-Ion Pouch Cells

Abstract In lithium-ion battery manufacturing, following electrode preparation and cell assembly, electrolyte filling and wetting is a critical and throughput-determining step that often takes tens of hours due to the slow electrolyte infiltration of porous electrodes. This prolonged wetting process significantly limits production efficiency and increases manufacturing costs, highlighting the need for more effective electrolyte injection strategies. In this study, we investigated the electrolyte wetting behavior of 2 Ah LiFePO4 (LFP)–graphite (Gr) pouch cells using ultrasonic transmission imaging and electrochemical impedance spectroscopy. Although elevated temperature can moderately accelerate electrolyte wetting, the improvement remains insufficient for practical production. Inspired by the sponge-like absorption behavior in the densely packed, highly tortuous, and irregular porous structures, we developed a pulsed pressurizing strategy that applies intermittent mechanical pressure to promote electrolyte penetration, successfully reducing the impregnation time to within 1 hour. Electrochemical cycling tests further confirm that applying pressure during wetting does not compromise battery performance. This work offers a practical and scalable solution to significantly shorten electrolyte wetting time and accelerate the overall production process of lithium-ion batteries.