Multifunctional Lithium-Ion-Exchanged Zeolite-Coated Separator for Lithium-Ion Batteries

Positive electrodes utilizing more manganese are the primary choices for lithium-ion battery applications in electric vehicles and other large-scale energy storage systems because of the high price of cobalt. However, manganese deposition on negative electrode after its dissolution to electrolyte can cause capacity decay. To address this challenge, in this work, a multifunctional polymeric separator with lithium-ion-exchanged zeolite (Li-zeolite) coating has been developed using a simplified process to exchange undesirable cations in zeolite with lithium ions. The coin cell with Li-zeolite coated separator exhibits an average Coulombic efficiency of 99.89% and achieves a capacity retention rate of 78.3% after 500 cycles at 25 °C. From elevated temperature test, we find out that a lower amount of manganese is present on the cycled graphite electrode when Li-zeolite coated separator is used, suggesting less side reactions resulted from Mn. We propose that Li-zeolite can provide multiple functions to improve the cycle performance of manganese containing positive electrodes: (1) absorb trace water to reduce the formation of HF, (2) act as HF scavenger to mitigate its attack on the positive electrode, and (3) trap transition metal ions. Furthermore, the wettability and thermal stability of separator can be enhanced when Li-zeolite coating is applied.