Insight into the activation energy for the interfacial stability evaluation in all-solid-state Li-ion batteries

Abstract

While all-solid-state Li-ion batteries (ASSLIBs) by using non-flammable and superionic solid electrolytes (SEs) exhibit improved safety and higher energy density, a major challenge that remains to be overcome is the dissatisfactory rate performance and capacity retention due to the undesirable reaction at electrode/SE interfaces. Reaction energy is generally taken as the indicator of interfacial reactivity, i.e. reaction degree and reaction rate, although it only represents whether the reaction is thermodynamically favorable. In the physical origin, activation energy (reaction barrier) instead of reaction energy should be the determinant of reaction rate. Here, first principles calculations with the Arrhenius relationship show a difference of several orders of magnitude in reaction rates due to the distinct activation energies although the reaction energies are similar. Then, by combining the activation energy with the reaction energy and conductive ability of products, which representing kinetic feasibility, thermodynamic favorability, and continuity of a reaction respectively, we propose an evaluation strategy for interfacial stability and correspondingly classify the interfaces. This study manifests that the usually unheeded activation energy can provide a kinematic perspective for the interfacial reactions.