The mystery of Li2O2 formation pathways in aprotic Li-O2 batteries

TM912; The solid-state discharge product Li2O2 is closely related to the performance of Li-O2 batteries,which exacer-bates the concentration polarization and charge transfer resistance,leading to sudden death and poor cyclability.Although previous theories of the Li2O2 formation pathway help to guide battery design,it is still difficult to explain the full ob-served Li2O2 behaviors,especially for those with unconventional morphologies.Thus,the pathways of Li2O2 formation re-main mysterious.Herein,the evolution of the understanding of Li2O2 formation over the past decades is traced,including the variable Li2O2 morphologies,the corresponding reaction pathways,and the reaction interfaces.This perspective pro-poses that some Li2O2 particles are strongly dependent on the electrode surface as a result of the dynamic coupling of solu-tion and surface pathways and emphasizes a possible mechanism based on previous experimental results and theories.Fur-ther methods are expected to be developed to reveal complex Li2O2 formation pathways and spearhead advanced Li-O2 batteries.