Revisiting the Relation Between the Stability of the LUMO of the Electrolytes and the Kinetics of Solid Electrolyte Interface Formation in Lithium- and Post-Lithium-ion Batteries

Despite their high theoretical capacity, the practical application of Li-ion batteries (LIBs) and post-LIBs with metal anodes are limited due to their poor safety and electrochemical performance. Solid electrolyte interface (SEI) was found to have an important role in this. It was found that SEI on metal anodes is overgrown and non-uniform owing to their high reactivity, which in turn affects the performance of metal anode-based batteries. Recent studies indicate that modulating the properties of the SEI is a good strategy to improve the electrochemical performance of batteries. In this regard, identifying the critical reactivity descriptors that can provide insights into the SEI formation kinetics is of large importance. Herein, we performed computational studies involving 53 selected ion-solvent complexes that represent 53 commonly used electrolytes and 12 salt molecules in LIBs and post-LIBs. Unlike previous studies which considered the LUMO energy of the electrolyte as the suitable chemical reactivity descriptor, this study shows that electron affinity and electrophilicity of the individual ions and solvents that constitute the electrolytes are more suitable and general chemical reactivity descriptors for predicting the SEI formation kinetics. In addition to suggesting suitable approaches to modulate the SEI formation kinetics, this study also brings light to the critical role of the ion-solvent combination in determining the SEI formation kinetics.