In-Situ Characterization of Si-Based Electrodes By Dilatometry and Acoustic Emission

The replacement of carbon by silicon as active material in negative electrodes of Li-ion batteries is very attractive since the gravimetric and volumetric capacities of silicon are much higher than those of carbon. However, silicon suffers from huge volume variation (up to ~300% versus 10% for C) upon cycling. This leads to the electrode pulverization inducing electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and coulombic efficiency. A precise evaluation of the volume variation and cracking processes is thus crucial to develop more efficient Si-based electrodes. For that purpose, in the present study, the volume change of Si-based anodes during cycling is monitored by in situ dilatometry. In addition, in situ acoustic emission (AE) measurements are performed to study the electrode pulverization process with cycling. For a better identification of the origin of the different populations of detected AE signals, a detailed study of their energetic and temporal characteristics (amplitude, rise time, frequency...) is conducted. The influence of the cycling conditions (discharge capacity, cycle number, C-rate), electrode formulation (Si particle size…) and processing (calendar pressure) and electrolyte composition on the electrode volume variation and cracking is highlighted and correlated to its electrochemical performance.