Investigating the Electrochemical Behavior of Cobalt(II) Terephthalate (CoC₈H₄O₄) as the Organic Anode in K-ion Battery

Highlights: •Cobalt terephthalate as the organic anode was studied in K-ion cell •Nearly 100% Coulombic efficiencies could be maintained •The average capacities of 146 mAh g⁻¹ for 200 cycles were realized -- Abstract: The electrochemical behavior of cobalt terephthalate (CoTP) as the organic anode was initially carried out in K-ion battery, with the main intention to test whether the abnormal capacity enhancement of CoTP previously occurring in Li-ion battery could continuously happen in the different K-ion battery system. However, as confirmed by the cyclic voltammetry and X-ray photoelectron spectroscopy (XPS), the Co element of CoTP was irreversibly reduced from Co²⁺ cation to Co⁰ atom in the 1st discharge process, thus converting CoTP into K₂TP in the following electrochemical cycles. Despite of that, the satisfactory specific and rate capacities could be realized for CoTP after a small amount of conductive Super P was added, with the average capacities of 146 mAh g⁻¹ for 200 cycles under the current density of 60 mA g⁻¹, which were comparable or even superior to some inorganic anodes recently reported for K-ion battery.