Semi-Interpenetrating Polymer Electrolyte as a Coating Layer Constructed on Polyphenylene Sulfide Nonwoven to Afford Superior Stability and Performance for Lithium-Ion Batteries

High power lithium-ion battery (LIB) puts forward higher requirements for separator. In this study, a new composite separator (SIPN/PPS) with superior stability and improved electrochemical performance was fabricated by the construction of semi-interpenetrating polymer network (SIPN) on polyphenylene sulfide (PPS) nonwoven substrate. In SIPN, branched polyethyleneimine (PEI) was selected as crosslinking points due to multiple reactive terminal groups -NH2. Meanwhile, PEI owned irregular topology structure, which would be beneficial to interrupt the crystallization of polymer matrix and increase electrolyte storage by swelling. Characterization results show that this designed composite separator can exhibit higher porosity, improved electrolyte wettability, enhanced electrolyte uptake and excellent electrochemical performance, thus endowing battery with superior discharge capacity even at 3 C. In addition, the introduction of SIPN is confirmed to increase mechanical strength more obviously than that of single cross-linked network reported in previous study. Meanwhile, anode current begins to be detected for SIPN/PPS composite separator under higher applied voltage (4.6 V vs Li+/Li), indicating its broader electrochemical window. Moreover, SIPN/PPS composite separator is displayed satisfactory cycling stability with higher discharge capacity retention ratio (85.3 %). Consequently, this contribution opens a new avenue for separator applied in high power LIB.