ZIF-67@Cellulose nanofiber hybrid membrane with controlled porosity for use as Li-ion battery separator

ZIF-67@CNF membranes were prepared and used as Li-ion battery separator to address the inhomogeneous pore distribution problem in CNF membranes. The hybrid membrane exhibited better cycling performance and rate capability. Zeolitic imidazolate framework-67 (ZIF-67) was synthesized on the surface of cellulose nanofibers (CNFs) in methonal to address the problems of unhomogeneous pore size and pore distribution of pure CNF membrane. A combination of Energy Dispersive X-Ray Spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) patterns were used to determine the successful synthesis of ZIF-67@CNFs. The size of the ZIF-67 particles and pore size of the ZIF-67@CNF membrane were 50–200 nm and 150–350 nm, respectively. The prepared ZIF-67@CNF membrane exhibited excellent thermal stability, lower thermal shrinkage and high surface wettability. The discharge capacity retention of the Li-ion batteries (LIBs) made with ZIF-67@CNF, glass fiber (GF), CNF and commercial polymer membranes after 100th cycle at 0.5C rate were 88.41%, 86.22%, 83.27%, and 81.03%, respectively. LIBs with ZIF-67@CNF membrane exhibited a better rate capability than these with other membranes. No damage of porous structure or peel-off of ZIF-67 was observed in the SEM images of ZIF-67@CNF membrane after 100th cycle. The improved cycling performance, rate capability, and good electrochemical stability implied that ZIF-67@CNFs membrane can be considered as a good alternative LIB separator.