A simple mechanical damage testing method, combined with Acoustic Emission (AE) monitoring was developed in order to investigate the mechanical performance of solid state electrochemical devices under operating conditions. The damage testing method was applied to solid oxide fuel cells and lithium ion batteries. The damage process was shown to involve cracking in the electrode and electrolyte, and the fracture damage was most likely due to chemical expansion-induced stresses. It was demonstrated that the AE method enabled us to detect the above-mentioned damage process and to determine the condition for the onset of the damage in the newly electrochemical devices.
