Surface Morphology Control of Gel‐Polymer Electrolyte on Ceramic‐Coated Separator for Enhanced Electrochemical Performance of Lithium‐Ion Batteries

ABSTRACT Gel polymer electrolytes (GPE) and/or ceramic particles are generally coated on the lithium‐ion battery (LIB) separators. The morphology of the GPE highly affects the electrochemical performance of LIB, but its mechanism has not been clearly understood. In this study, porous GPE is applied to ceramic‐coated separators by using a controlled phase‐separation method. We controlled the morphology of GPE well by adjusting the concentration of the GPE and the phase separation kinetics. As the surface coverage area of GPE on the ceramic‐coated separators was increased, the thermal shrinkage of the separators was decreased further. The high discharge C‐rate capacity of the pouch‐type cells (~300 mAh) assembled with the GPE on ceramic‐coated separators was increased by minimizing the surface coverage area of the GPE. However, after hot pressing and laminating the cells, the high C‐rate discharge capacity of the laminated cells with the separator having a GPE coverage area of 85% was dramatically enhanced by hot pressing and laminating the cells. We can control the morphology of GPE on the ceramic‐coated separators, and we conclude that the optimally controlled morphology of the GPE can maximize the electrochemical performance of a lithium‐ion battery in the high C‐rate discharge conditions by considering the cell design and manufacturing processes.