Graphene Liquid Cell Electron Microscopy of Initial Lithiation in Co₃O₄ Nanoparticles

As it governs the overall performance of lithium-ion batteries, understanding the reaction pathway of lithiation is highly desired. For Co₃O₄ nanoparticles as anode material, here, we report an initial conversion reaction pathway during lithiation. Using graphene liquid cell electron microscopy (GLC-EM), we reveal a CoO phase of the initial conversion product as well as morphological dynamics during Co₃O₄ lithiation. In accordance with the in situ TEM observation, we confirmed that the Co₃O₄ to CoO conversion is a thermodynamically favorable process by calculating the theoretical average voltage based on density functional theory. Our observation will provide a useful insight into the oxide electrode that undergoes conversion reaction.