Phenothiazine Molecules

Abstract

The molecules 10-methylphenothiazine, 10-ethylphenothiazine, 3-chloro-10-methylphenothiazine, 10-isopropylphenothiazine, and 10-acetylphenothiazine are shown to be stable redox shuttle additives in LiFePO 4 /graphite and LiFePO 4 /Li 4/3 Ti 5/3 O 4 Li-ion coin cells to protect against overcharge and overdischarge. The diffusion constant of 10-methylphenothiazine was measured using cyclic voltammetry to be 1.5 ϫ 10 −6 cm 2 /s, which translates to maximum shuttle-protected overcharge current densities near 2 mA/cm 2 in practical cells. Although the redox potentials of these molecules ͑near 3.5 V͒ are somewhat low for LiFePO 4 , their stability over repeated overcharge and overdischarge cycles is about equal to that of 2,5-di-tert-butyl-1,4-dimethoxybenzene that has been shown to provide protection for over 200 cycles of 100% overcharge at C/10. Given the stability of these oxidized molecules, we believe that phenothiazine represents an attractive core for ligand substitution to adjust the redox potential to more practical values.

Safer Electrolytes for Lithium‐Ion Batteries: State of the Art and Perspectives

“…[150,151] [152] In the following years, as eries of other potentialc andidates were reported, for instance, 10-methylphenothiazine (3.74 V), [153] 4-tert-butyl-1,2-dimethoxybenzene (4.18 V), [154] 2-(pentafluorophenyl)tetrafluoro-1,3,2-benzodioxaborole( 4.43 V), [155] 2,5-difluoro-1,4-dimethoxybenzene (4.4 V), [156] 1,4-di-tert-butyl-2,5-bis(2,2,2,-trifluoroethoxy)benzene, [157] or tetraethyl-2,5-di-tert-butyl-1,4-phenylened iphosphate. [158] Another approach for protecting lithium-ion cells from hazardous overcharge, which mayb eb riefly mentioned at this point,i st he utilization of shutdown-typee lectrolyte additives.…”

The electronic structure of TEMPO, its cation and anion

“…Thus, the recently emerged organic radical battery [6,7] is based on the reversible electrochemical oxidation-reduction of TEMPO and similar nitroxides [8,9]. Redox reactions of TEMPO and its derivatives may be useful in dye-sensitised solar cells [10] or for overchargeprotection of lithium ion batteries [11]. TEMPO-induced electron transfer quenching of fluorescence may lead to * Corresponding author.…”

Additives for Functional Electrolytes of Li-Ion Batteries

“…Other organic redox shuttles based on aromatic compounds with heteroatom substitutions include phenothiazine [18], triphenylamine [89], diarylamines with different substitutions [38], and 2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole [29,137]. Nitroxide radicals such as (2,2,6,6-Tetramethylpiperidin-1-yl) oxy (TEMPO) have been studied as a redox shuttle as well but showed inferior rate of charge transfer compared with DDB [90].…”