Rheology as promising tool to determine ion-transport and electrochemical performance of block copolymer electrolytes

Nanostructured poly(styrene- b -ethylene oxide) block copolymers (BCPs) doped with lithium salt as solid-state electrolytes are of considerable interest for next-generation lithium-metal batteries. However, the advancement of nanostructured solid block copolymer electrolytes requires a deep understanding of the interconnection of electrochemical performance, ion transport, and mechanical properties. In this study, we investigated the electrochemical and rheological/mechanical behavior of several poly(styrene- b -ethylene oxide) (PS- b -PEO) block copolymers doped with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt ( r = 0.08), varying in PEO volume fraction within a consistent nanomorphology. Electrochemical and rheological measurements highlight diffusion correlations between both techniques. The implementation of theoretical equations based on the Stokes-Einstein, Nernst-Einstein, and Sand equations allows to predict ion-transport properties (ionic conductivity and salt diffusion), and electrochemical performance (limiting current) through viscoelastic mechanical characteristics, i.e. , rubbery plateau modulus ( G N 0 ). The calculated values from this novel methodology are in good agreement with experimental ones obtained by electrochemical measurements. This approach thus offers a new perspective on the interconnection between electrochemical performance, ionic transport, and the mechanical response of nanostructured block copolymer electrolytes. • G N 0 is a key mechanical property in block copolymer electrolytes. • Diffusion coefficient correlation from rheological and electrochemical measurements. • A novel approach was developed for determining electrochemical properties from G N 0