Complex Growth Behavior of Li Dendrites in Al2O3 Nanoparticles-Driven Viscoelastic Electrolytes for Lithium Metal Batteries: Dynamic versus Quasistatic Rheology

Abstract

Viscoelastic electrolytes have been focused as innovative electrolytes for Li metal batteries because of their unique mechanical and electrochemical properties compared to conventional Newtonian liquid electrolytes. However, the role of the mechanochemical properties of viscoelastic electrolytes in the electrochemical performance of Li metal has not been fully understood yet. In particular, dynamic rheology of viscoelastic electrolytes has not been considered one of significant factors accelerating Li dendrites growth. Herein, Al2O3 nanoparticles-driven viscoelastic electrolytes are introduced to improve the electrochemical performance of Li metal. In contrast to conventional Newtonian liquid electrolytes, viscoelastic electrolytes significantly suppress Li dendrites growth during cycling, resulting in excellent electrochemical performance, such as stable capacity retention over 400 cycles. Moreover, the complex growth mechanism of Li dendrites in viscoelastic electrolytes is demonstrated in terms of dynamic versus quasistatic rheology. Dynamic rheology prevails over quasistatic rheology as Al2O3 weight fraction and current density is increased in viscoelastic electrolytes. Dynamic rheology gives rise to spatial non-uniformity in the mechanical and rheological properties of viscoelastic electrolytes, leading to promoting Li dendrites growth due to the uneven distribution of local current density on the Li metal surface. These findings provide fundamental insights into strategies to design advanced electrolytes for Li metal batteries.