I tested the EIS of layered oxide materials for sodium batteries (coin cell). EIS data shows that the ohmic impedance and charge transfer impedance decrease after 200 cycles, compared with the EIS data tested after 1 cycle. The capacity decreases after cycles. How to analyse this phenomenon?
Hi Jinpin, I'm not sure if you're still looking for an answer to this question but I might be able to help. If there is a decrease of impedance in a system after cycling, my first suspicion would be that there is degradation of material allowing a leakage current to form. Without some description of your experimental setup (equipment? connections? coin or beaker cell?) it's difficult to start a diagnosis.
Anne Sawhney We tested coin cells in the voltage range of 2.0-4.3 V. The cathode material is sodium layered oxide. The decrease in ohmic resistance may be attributed to the decomposition of surface carbonates, while the decrease in charge transfer resistance could result from the deep activation of the material after cycling. And the ohmic resistance and charge transfer resistance increase for further cycling.
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