Deconvolution of the electrochemical impedance of Na/NaCrO2 cells with ester- and ether-based electrolytes

Na-ion battery is regarded as the most promising battery chemistry for the post Li-ion battery generation. Unlike Li-ion batteries, Na-ion batteries, due to the intrinsic instabilities, are rarely studied using electrochemical impedance spectroscopy to inspect the electrode kinetics within. Here, we combine the electrolyte-dependent Na metal labeling and distribution function of relaxation time analysis to readily deconvolute the conventional Nyquist spectrum of Na/NaCrO2 cells into individual electrode processes. Utilizing the corresponding equivalent circuit model with physical implications, the performance-limiting kinetics of Na/NaCrO2 cells with the typical ester-based electrolyte, PC/FEC, and ether-based one, diglyme, are precisely identified. Given the sluggish interference generated at the Na metal counter electrode with PC/FEC electrolyte, proper ether-based electro-lytes are recommended to be adopted in the future validation of potential materials for Na-ion battery studies.