Aluminum-Lithium Alloy Fillers Enhancing the Room Temperature Performances of Polymer Electrolytes for...

Poly(ethylene oxide) (PEO) electrolytes usually suffer from low room temperature (RT) ionic conductivity and a narrow voltage window, which limits the improvement of energy density and practical applications in all-solid-state batteries. Composite polymer electrolytes (CPEs) are regarded as the common method to reduce the crystallinity of polymers and increase the lithium ion conductivity. Compared with active or inert ceramic material fillers in previous studies, aluminum-lithium alloy fillers are used to prepare composite electrolytes in this study, showing excellent performance at room temperature. The conductivity of the PEO-based electrolytes increases by a factor of 3.62-3.62× 10^-4 S cm^-1 at RT with 5 wt % Al-Li alloy. The transference number of Li⁺ is increased to 0.524. The characteristics of the Al-Li alloy and higher conductivity enable the composite electrolyte to stabilize the interface with the electrodes, reducing the polarization of solid-state batteries. The all-solid-state Li/PEO-5%/LiFePO₄ cells show the highest initial discharge capacity of 153 mAh g^-1 and the highest stable discharge capacity of 147 mAh g^-1 with the initial Coulombic efficiency of more than 100%. It also exhibits the best rate capacity and cycle performance (90% capacity retention rate after 100 cycles).