Decoupling of mechanical properties and ionic conductivity in a low molecular weight polymer nanocomposites with highly connected particle aggregates

Abstract

Hypothesis: High molecular weight polymer nanocomposites (PNCs) with good thermal stability and elevated mechanical strengths can serve as composite polymer electrolytes (CPEs) and thus have been considered as an alternative to conventional liquid electrolytes. However, resolving low ionic conductivity issues of CPEs arising from the low chain mobility derived from a long polymer chain remains challenging.Experiments: Here, we introduce PNCs for use in CPEs which show 1.4 x 10-4 S/cm of ionic conductivity at room temperature with a high shear modulus of 107 Pa using a low molecular weight poly(ethylene glycol) (PEG) matrix and dopamine-modified PEG brush polymer grafted-silica nanoparticles.Findings: We found that densely interconnected supramolecular particle networks can decouple the mechanical strength and ionic conductivity, as the Li-doped interfacial polymer layer supports a direct lithium-ion transport pathway. The extensive structural and rheological studies characterized by small-angle X-ray scattering and oscillatory rheometry experiments revealed that particle connections through interfacial polymer layers play an important role in supporting the elevated mechanical and electrochemical properties with a good thermal stability of PNCs.