Synthesis and electrochemical performance of poly(vinylidene fluoride)/SiO2 hybrid membrane for lithium-ion batteries

In this work, a series of rationally designed hybrid membranes composed of poly(vinylidene fluoride) (PVDF) as polymer matrix and silica nanoparticles (SiO2) as inorganic fillers are prepared by combining slurry coating method and phase inversion method. The effects of the added SiO2 nanoparticles on the porosity, electrolyte wettability, thermal stability, and ionic conductivity of PVDF/SiO2 hybrid membranes are investigated systematically. Compared to the commercial polypropylene (PP) membrane, PVDF/SiO2 hybrid membranes present enhanced physical and electrochemical performance. Particularly, the incorporation of 5wt.% SiO2 to PVDF polymer matrix (PVDF5 hybrid membrane) shows the highest ionic conductivity of 1x10(-3)Scm(-1) at 25 degrees C among all the samples. The electrochemical tests demonstrate that the LiNi0.8Co0.1Mn0.1O2/Li coin cell assembled with PVDF5 hybrid membrane exhibits high reversible discharge capacity (179mAhg(-1) at 0.05 C), excellent cyclic stability (169mAhg(-1) after 100cycles at 0.1 C), and superior rate performance, which are much better than other counterparts and PP separator. Moreover, as for the large capacity battery application, 1.1Ah LiNi0.8Co0.1Mn0.1O2/graphite pouch cell with PVDF5 hybrid membrane can deliver a high discharge capacity of 992mAh and good Coulombic efficiency of 99.5%. Evidently, the optimized PVDF/SiO2 hybrid membrane will be a very promising alternative to the commercial PP separator for advanced lithium-ion batteries.