Polyethylene oxide-Li₇La₃Zr₂O₁₂ composite solid-state electrolyte for advanced Li-ion batteries (LIBs)

Recently, conformal solid-state polymer-based electrolytes have been considered as promising alternatives for liquid electrolytes in LIBs because of their fire safety and ease of fabrication in thin film form with desirable mechanical, thermal and high electrochemical stability. Several researchers have investigated polyethylene oxide (PEO) based films complexed with Li-salts, such as LiClO₄, as polymer electrolytes. However, these electrolytes exhibit low ionic conductivity (~10^-6 - 10^-7 S cm^-1) at room temperature due to high degree of crystallinity. This issue has been addressed by adding plasticizers such as ethylene carbonate (EC) or using inorganic fillers. We have studied PEO based polymer electrolyte with Li₇La₃Zr₂O₁₂ (LLZO) as an inorganic filler, which is also a Li-ion conductor. We show that the addition of LLZO (20 wt%) and EC (20 wt%) increases the ionic conductivity of PEO-LLZO composite electrolyte by an order of magnitude, lowers the activation energy from 0.6 eV to 0.5 eV, and maintains a high voltage stability (5 V). The results of electrochemical impedance spectroscopy, linear sweep voltammetry, and chronoamperometry measurements will be presented.