Porous PEO-Silica Hybrid Solid Electrolyte for All-Solid-State Lithium Ion Batteries

Dry polymer electrolytes based on poly (ethylene oxide), PEO, and Li-salt complexes are one of the most cheapest, environmentally friendly and promising materials for developing safe, cheap and durable all-solid-state Li-ion batteries. The rigid structures that are interesting from the point of view of application in all-solid-state battery cells are characterized by low conductivity at ambient temperatures. Dispersion of oxide nanoparticles inside the PEO-matrix greatly improves the physicochemical properties of the complex due to the physical interaction between the grains and the polymer matrix. Unfortunately, such a great effect drops at high loading-content, mostly above 10 wt%, owing to agglomeration of the nanoparticles and the consequence Li-ion blocking effect. In our work, we have proposed a novel approach that leads to a porous composite electrolyte consisted of higher weight fraction of nanoporous silica than PEO polymer. Here, the polymer-salt complex is being entirely soaked inside the mesoporous silica matrix that offers the mechanical support for the electrolyte. To do this, the walls of silica pores are tailored in the controlled manner with low molecular weight PEO polymer chains. The studied system that contained 70 to 80 wt% of SiO2 showed high conductivity, excellent mechanical strength and wide electrochemical potential window. Textural and structural properties of the starting materials and the hybrid electrolytes will be presented. Furthermore, the electrochemical properties of the porous electrolytes will be discussed to demonstrate the feasibility of our materials as solid electrolytes in all-solid-state Li-ion battery cells.