Incorporating Ethylene Oxide Functionalized Inorganic Particles to Solid Polymer Electrolytes for Enhanced Mechanical Stability and Electrochemical Performance

Abstract

Solid‐state batteries based on polymer electrolytes attract increasing interest owing to their high feasibility of roll‐to‐roll mass production. However, the mechanical strength of polymer electrolytes is not sufficient to suppress the formation of lithium dendrites, leading to early capacity fading. Many researchers have attempted to reinforce polymer electrolytes by adding inorganic particles, but insufficient compatibility between the particles and electrolytes can cause particles to agglomerate, deteriorating the mechanical stability of the resulting hybrid electrolytes. Herein, surface‐functionalized inorganic particles are used to prepare hybrid polymer electrolytes (HPEs). The surface of aluminum oxide (Al2O3) nanoparticles is chemically modified by an organic material containing an ethylene oxide (EO) group. The EO group on the functionalized Al2O3 (F‐Al2O3) enables uniform dispersion of the nanoparticles in the EO polymer electrolytes and improves the ionic conductivity and electrochemical stability. The nanoindentation measurements show that the hybrid polymer electrolytes with F‐Al2O3 (HPE‐F‐Al2O3) have enhanced stiffness. The electrochemical stability and ionic conductivity of the polymer electrolytes also benefit from incorporating F‐Al2O3. As a result, a lithium polymer battery with Li anode, LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, and HPE‐F‐Al2O3 electrolyte demonstrates stable long‐term cycling with a capacity retention of up to 87% over 100 cycles.