Diagnostics of lithium-ion intercalation rate-determining step: Distinguishing between slow desolvation and slow charge transfer

• Published in: Electrochimica acta Vol. 302; pp. 316 - 326
• Main Authors: Vassiliev, Sergey Yu, Sentyurin, Vyacheslav V., Levin, Eduard E., Nikitina, Victoria A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 10.04.2019; Elsevier BV
• Subjects: Acetonitrile; Charge transfer; Dimethyl sulfoxide; Electrochemical impedance spectroscopy; Electrode materials; Intercalation; Intercalation kinetics; Ion desolvation; Limiting factors; Lithium; Lithium ions; Lithium manganese oxides; Lithium-ion battery; Mathematical models; Organic chemistry; Propylene; Rate-determining step; Reaction kinetics; Surface layers; Voltammetry; Lithium-ion battery; Ion desolvation; Rate-determining step; Intercalation kinetics; Electrochemical impedance spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.02.043

The elucidation of the reaction rate-determining step nature in intercalation processes is essential for the development of approaches for the precise control of rate-limiting factors. In this work, we explore the kinetic patterns of lithium-ion intercalation into two model cathode materials (LiCoO2 and LiMn2O4) and develop criteria for distinguishing between Butler-Volmer slow charge transfer and slow chemical steps. A numerical model for the rate-limiting ion desolvation step is developed and the predictions of the model are compared with the experimental voltammetric and electrochemical impedance spectroscopy data. We show that slow desolvation step results in essential changes in the shape of both cyclic voltammetry and impedance responses with the kinetic resistance vs. potential dependencies being highly informative for the reaction rate control diagnostics. The consideration of the intercalation kinetics in four solvents (water, propylene carbonate, acetonitrile and dimethyl sulfoxide) allows concluding on the influence of the resistivity of surface layer/electrode material interface on the reaction slow step nature. •Charge transfer rate vs. potential dependence is defined by the slow step nature.•Charge transfer rates depend sharply on the presence of SEI layers.•In SEI-free systems charge transfer rates are exceedingly fast.•Desolvation step results in a weak charge transfer rate vs. potential dependence.•Ion desolvation limiting step induces asymmetry in voltammetric responses.