Probing and Understanding Performances of Conductive Organic Radical Salts as Positive Electrode Material for Ion-Batteries

Abstract

We report here our investigations to evaluate the potential use of conductive 2:1 (TMTTF) 2 X radical salts (TMTTF = Tetramethyltetrathiafulvalene, X = PF 6 -, ClO 4 -, BF 4 -, AsF 6 -) as positive organic electrode material for energy storage applications. To do so, a scaled-up electrocrystallization method as well as a large-scale chemical oxidation process were developed to obtain these salts in large quantities (> 0.5 g/batch) needed for such applications.In the following, a new polymorph of the neutral TMTTF and a new 1:1 bromide phase isolated from large-scale chemical oxidation were also described. These crystalline 2:1 radical salts exhibit a high electronic conductivity (0.25-4.60 S.cm -1 ) originating from π-electron delocalization within the organic molecular stacks formed by mixed-valence TMTTF salts.Galvanostatic cycling experiments, conducted with or without carbon additive were associated with X-ray diffraction measurements and Fourier-transformed infrared spectroscopy, allowing for highlighting and monitoring the structural and redox changes occurring during cycling. This study demonstrates that, beyond the need for electronic conductivity, other parameters and properties need to be combined to obtain high-performance organic materials, paving the way toward more efficient organic electrode materials.Conductive intermediate radical salt(TMTTF) 2 PF