(625g) In-Situ Atomic Force Microscopy Study on Solid-Electrolyte Interphase Formation of Li-Ion Batteries

Solid-electrolyte interphase (SEI) forms on the electrode during the first several charge-discharge cycles.  This thin layer on Li-ion electrode is believed to provide a voltage slop at the interface of the electrode and the electrolyte to prevent further electrolyte decomposition, while still provide significant ionic conductivity for Li ions insertion and extraction during cycling.  The SEI grows during cycling and develops into a thicker insulate layer to Li ions at the end.  Many groups have reported the composition, evolution and thickness of the SEI layer on the electrodes of Li ion batteries.  With the application of in-situ AFM, more precise scanning of the morphology can be achieved without the interference of the electrolyte residues and the effects of the oxidation in atmosphere.  However, the effect of decomposition products on lithium ion insertion, the thickness changes of the SEI layer and the compositions of the SEI during cycling have not been fully elucidated.  A better understanding of the formation and evolution of SEI will provide valuable data to explain the performance, self-discharge and failure mechanism of Li-ion batteries.  In this report, the SEI formation was investigated a step-by-step by in-situ AFM. A dynamic competition mechanism of the SEI formation process is proposed based on the experimental results.