Preparation of a Self‐Supported SiO₂ Membrane as a Separator for Lithium‐Ion Batteries

Abstract For the first time, electrophoretic deposition (EPD) has been employed to prepare a self‐supported, inorganic membrane consisting of SiO₂ nano‐fibers, as a separator for lithium‐ion batteries. The SiO₂ nano‐fibers that were fabricated by a low‐cost force spinning technique were deposited by EPD directly onto LiNi_0.8Co_0.15Al_0.05O₂ cathode material. Citric acid charging agent and anhydrous acetone solvent were used. The resulting porosity and tortuosity of the EPD SiO₂ separator were 71.42 %, and 1.70, respectively. The slightly higher tortuosity of the EPD‐SiO₂‐fiber separator (60 μm) led to a lower rate capability in comparison to commercial GF/A glass fiber separator (260 μm). On the other hand, the latter exhibited lower self‐discharge than the former in full‐cells with a graphite anode; this is proposed to be related to the different purities of the two materials that impart different electronic properties or the presence of 20 wt % PVDF in the EPD‐SiO₂ separator. Indeed, the deposited membrane has good characteristics as a battery separator and the EPD process is extremely feasible for the fabrication of miniaturized lithium‐ion batteries on wafer level.