X-ray tomography as a powerful method for zinc-air battery research

Abstract X-ray tomography is used to investigate material redistribution and effects of electrochemical reactions in a zinc-air battery in-situ. For this, a special battery set-up is developed which meets tomographic and electrochemical requirements. The prepared batteries are discharged and some of them have partially been charged. To analyse the three-dimensional structure of the zinc and air electrode a tomographic measurement is made in charge and discharge condition without disassembling the battery. X-ray tomography gives the opportunity to detect and analyse three different effects within the cell operation: tracking the morphology and transformation of zinc and air electrode, monitoring electrolyte decomposition and movement, finding electrical misbehaviour by parasitic reactions. Therefore, it is possible to identify the loss of capacity and major problems of cyclability. The electrolyte strongly reacts with the pure zinc that leads to gassing and a loss of electrolyte. The loss prevents a charge carrier exchange between the anode and the cathode and reduces the theoretical capacity. One of the chemical reaction produces hydroxylated zinc, namely zincate. The most crucial problems with cyclability are affected by zincate movement into the catalyst layer. This assumption is confirmed by finding pure zinc areas within the catalyst layer.