Tailoring silk fibroin separator membranes pore size for improving performance of lithium ion batteries

The search of natural materials for their application in energy storage systems in general and batteries in particular is growing due to their promising properties and the need of environmental sustainability. Silk fibroin (SF) is one of those materials due to their mechanical and thermal properties, non-toxicity and biocompatibility. Further, SF exhibits excellent cycling performance as separator for lithium-ion battery applications. This work reports on SF membranes with different pore sizes (within the rages: 38-22, 106-38 and 250-106 mu m) prepared for separators in lithium-ion batteries. The morphology, structure and thermal properties were evaluated. It is shown that the beta-sheet conformation percentage increases with increasing pore size, which also leads to higher electrolyte uptake, reaching 350% for SF membranes with pore size of 250-106 mu m. With respect to battery performance, a high discharge capacity (131.3 mAh g(-1), for C/8) is obtained for this membrane.