Rapid SECM probing of dissolution of LiCoO₂ battery materials in an ionic liquid
2012
Snook, Graeme A. | Huynh, Thuy D. | Hollenkamp, Anthony F. | Best, Adam S.
Attempts to utilise LiCoO₂ as the cathode when the electrolyte is based on an ionic liquid, e.g. 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, have been severely limited by significant capacity fade. Given that some form of instability of this material in ionic liquids is widely suspected as the principal cause, the aim of the current work is to determine the efficacy of using the scanning electrochemical microscope (SECM), to detect solubilisation of species leaving the LiCoO₂ electrode during charging and/or discharging. The SECM microelectrode probe tip was lowered to within 10–20μm of the platinum substrate electrode, onto which solid LiCoO₂ had been coated. This substrate material was charged and discharged to different voltages, whilst probing any solubilised species at the microelectrode tip. The detection of solubilised Co²⁺ and oxygen during over-charge and more so under deep discharge was observed. Possible mechanisms for degradation of the electrode are proposed. From these preliminary results, strategies are suggested for mitigating the degradation of LiCoO₂ when used in a room temperature ionic liquid electrolyte.
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