Elucidation of Separator Effect on Energy Density of Li-Ion Batteries

Fast charging of batteries is the key to increase the adoption of electric vehicles. All the components of a battery: anode, cathode, electrolyte and separator, contribute to the limiting factors of fast charging. While majority efforts are focused on novel electrode architecture and electrolyte formulation for high rate capabilities, studies on separators are mostly pertaining to their mechanical and physical properties and little attention has been paid to their effect on rate performance. In this study, we report a comprehensive analysis of the physical properties, electrochemical performance and high rate capabilities of the widely used battery separator Celgard 2325 and Celgard 2500. It is demonstrated that the Celgard 2500 has better electrolyte wettability and ∼2 × in electrolyte uptake, and 2.23 Ω/cm 2 less in resistance. Consequently, 57% and 47% improvement in capacity is obtained when charged at 2C and 3C, respectively. This indicates that separator can also play an important role in enabling fast charging for lithium-ion batteries.