Effects of cation substitution effects of dicarboxylic acid for energy storage applications

Organic materials (OMs) can accept alkali ions and function as energy storage systems, displaying several advantages such as low cost, ease of synthesis, and utilization of recyclable materials. Owing to their higher theoretical capacity, OMs exhibit a higher energy density, cheaper price, and easy recover than those of inorganic materials such as graphite, silicon, and metal oxides, respectively. This study reports the use of potassium 4-oxo4H-pyran-2,6-dicarboxylic acid (K2CDA) and potassium 4-oxo-4H-pyran-2,6-dicarboxylic acid (K2CDO) as anode materials for potassium-ion batteries (KIBs) and lithium-ion batteries (LIBs). Although they share similar lightweight, carbonyl, and carboxylate functional groups, both materials display distinct reaction behaviors owing to differences in electronegative heteroatoms N and O. In this study, two alkaline salts (KFSI and LiFSI) have been discussed on the substitution effect of doping/ de-doping processes. K2CDA and K2CDO. Consequently, after 200 cycles, the K2CDA anodes deliver capacities of 310 (KFSI) and 485 (LiFSI) mAh g- 1 , respectively, at 0.1 C. The larger size of K+ compared with Li+ negatively impacts the performance of K2CDA. A similar trend is observed in the case of K2CDO in capacities of 220 (KFSI) and 405 mAh g -1 (LiFSI), with 1.5 and 2.86 K+ ions participated in the corresponding redox reactions on the Fourier-transfer infrared spectroscopy analysis. The presence of N-H in the K2CDA structure contributes to its superior performance and rate capability compared with K2CDO. In addition to the cation effect, the structural differences between K2CDA and K2CDO also influence their electrochemical activity.