With the explosive growth of the electric vehicles market, the demand for high-powered batteries with desirable properties such as high-energy density, long term capacity retention and low self-discharge rate have grown significantly. The separator assumes a pivotal function in avoiding direct interfacial contact between the cathode and anode, thereby mitigating internal short circuits, preserving the liquid electrolyte, and facilitating the transport of ions within the system. Though, long been thought of as inert membranes, they should be considered as functional membranes whose properties and structure impact the batteries cycle life, safety, energy density and capacity.In this thesis, composite separators made from electrospun polybenzimidazole (PBI)/ ceramic hybrid coatings on ultrathin PE separator are successful fabricated. These coatings considerably improved the tensile strength, electrochemical properties like wettability, ionic conductivity and uptake, and battery performance at high C-rates compared to the pristine PE separator, enabling the LIBs to not only be high rate capable but also reliable. The novelty of the work lies in optimizing the electrospinning parameter, post processing and type of ceramic and then coat the polymer/ceramic blend on the ultrathin PE separator by tailoring their morphology and thickness that lead to gains in mechanical properties, electrochemical properties, and cell performance. Additionally, free-standing non-woven hybrid PBI/Ceramic separators were fabricated successfully. These separators offer a combination of desirable attributes such as exceptional dimensional thermostability, flexibility, and nonflammability. Furthermore, the PBI membranes demonstrate synergistic advantages including high ionic conductivity enabled by high porosity and uniform pore sizes, a large electrochemical stability window and attractive battery performance at high C-rates. The comprehensive comparison is done to reach a conclusion on the best set of properties achieved by both coated and free-standing separators that act as a guide on the best way forward for usage in next generation LIBs.