A versatile nano-TiO2 decorated gel separator with derived multi-scale nanofibers towards dendrite-blocking and polysulfide-inhibiting lithium-metal batteries

In this study, a versatile fluorine-bearing gel membrane with multi-scale nanofibers was rationally designed and synthesized via facile one-step blend electrospinning of nano-titanium dioxide (TiO2) particles and fluorinated poly-m-phenyleneisophthalamide (PMIA) polymer solution. The prepared multi-scale TiO2-assisted gel separator presented relatively high porosity, small aperture, giving rise to superior affinity to electrolyte and sufficient active sites to accelerate lithium ions migration. Meanwhile, the as-fabricated multifunctional GPE also rendered outstanding heat-resistance and well-distributed lithium-ions flux, and the mutual overlaps between the coarse fibers and the fine fibers within the multi-scale nanofiber membrane provided a strong skeleton support, which in turn laid a solid footing stone for high-security and dendrite-proof batteries. Particularly, the nano-TiO2 particles within PMIA membrane acted as “gatekeepers”, which can not only resist the growth of lithium dendrites, but also intercept the dissolved polysulfide on cathode side. Based on these merits, the gel PMIA-based lithium cobalt (LCO)/lithium battery obtained the remarkably improved rate capability and cycle performances on account of superior ionic conductivity, steady anodic stability window and weakened polarization behavior. Meanwhile, the resultant lithium-sulfur cell also delivered the outstanding cycling stability with the aid of the greatly prevented “shuttle effect” of dissolved lithium polysulfides based on the physical trapping and chemical binding of the prepared GPE to polysulfides species. This work proved that the addition of functional inorganic nanoparticles similar with TiO2 in multi-scale gel PMIA membrane can enhance the lithium ions transport capability, resist the growth of lithium dendrites as well as inhibit the shuttle effect of polysulfides, which would prompt a great development for dendrite-blocking and polysulfide-inhibiting lithium-metal cells.