Nanoconfined solid polymer electrolytes as novel solid-state electrolytes for Li-ion batteries

Abstract

Solid-state electrolytes are crucial to the development of safe and high energy density rechargeable batteries. We have developed a new method to prepare nanoconfined solid polymer electrolyte composites and studied the effect of nanoconfinement on the electrolyte properties. Nanoconfined solid polymer electrolyte composite materials were successfully prepared from LiBF4, PEO and a mesoporous silica support (SBA-15 or MCM-41) using methods based on melt infiltration. This new technique led to greatly reduced total synthesis time and elimination of toxic wastes associated with the preparation of solid- polymer electrolytes. The resulting samples exhibit an impressive ionic conductivity on the order of 10−3 S/cm at 50 ◦C post-heating, which is higher than for solid polymer electrolyte composites prepared using conventional technique. Confinement of the solid polymer electrolytes in silica matrix led to a significant increase in the ionic conductivity and mechanical stability of liquid electrolyte. The ionic con- ductivity is found to depend on the pore sizes of the silica, the amount of the silica pores that are filled, and the Li-concentration. The most conductive elec- trolyte in this experiment is realized with 12 to 1 molar ratio PEO-monomer to LiBF4 in MCM-41 (2.8 nm pores) with polymer electrolyte in a volumetric amount that equates to 125% of silica pore volume.