Distinction of impedance responses of Li-ion batteries for individual electrodes using symmetric cells

•Impedance of lithium ion battery and symmetric cells were analyzed.•Anode symmetric cells and cathode one were prepared with ca. 7 × 7 cm2 electrodes.•Except for Rct in cathode, electrochemical parameters did not change by reassembling.•Fitting data for symmetric cell were found to be useful for full cell analysis.•Electrochemical parameters of battery were traced during cycling degradation.

Symmetric cells were prepared with a newly designed separable cell module, which enabled ca. 70 mm by 70 mm electrode sheets to be used for a pouch type 5 Ah class Li-ion battery (LIB). Impedance analysis of the LIB as a full cell state was successfully performed with electrochemical parameters obtained by an impedance analysis of symmetric cells of anodes and cathodes obtained from the operated Li-ion batteries. While the charge transfer resistance of the cathode was found to increase after reassembling the cells symmetrically, other electrochemical parameters were found not to change when comparing the values obtained for full cells with symmetric cells. Eelectrodes degraded by charge/discharge cycling of the battery were also investigated, and the parameter change caused by the degradation was confirmed.

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