Adjusting the Electrolyte Polarity to Address the Dissolution Issue of Organic Electrode

Abstract

Small organic molecules with carbonyl active site are a prominent member in the family of organic electrode material, due to the reversible reaction and more tunable electrochemical property. However, the dissolution loss is the biggest obstacle in its application. In this work, we tried to address the dissolution issue of 5,7,12,14-pentacenetetrone (PT), a typical quinone-based organic electrode. Highly concentrated electrolyte of 5 M LiTFSI DME was used and it significantly reduced the dissolution and well maintained the capacity after 500 cycles.Besides, through the investigation of the relationship between solvent/electrolyte property and dissolution, and the interaction between electrode and electrolyte, a guiding rule of the dependence of dissolution on polarity was proposed. With the rule, non-polar solvent of hexane was further added as cosolvent and its-adding decreased the polarity and substantially eliminated the dissolution loss. The work supplies a common electrolyte strategy to address the dissolution issue of small organic molecules.

Bipolar-Type Organic Electrode Material Composed of a Viologen–Naphthalene Diimide–Viologen Triad for Li-Organic Batteries

“…To circumvent the dissolution problem, we employed a highly concentrated electrolyte. In a high-salt-concentration electrolyte solution, fewer solvent molecules are capable of interacting with the active materials in the electrode, thus reducing its dissolution . Indeed, when we immersed the NDI-2Vi electrode in a DOL/DME (1:1) electrolyte solution containing 6 M LiTFSI, it was observed that the dissolution of NDI-2Vi was significantly retarded.…”

“…The initial discharge capacity delivered by the NDI-2Vi cathode in the 6 M LiTFSI electrolyte was measured to be 110.7 mA h g –1 , corresponding to 70% of the theoretical capacity (Figure b). The lower capacity utilization in the highly concentrated electrolyte is due to the low ion conductivity caused by high viscosity of the electrolyte . Then, the discharge capacity suddenly dropped to 92.2 mA h g –1 at the second cycle; however, the NDI-2Vi electrode exhibited stable cycle stability thereafter.…”

“…The lower capacity utilization in the highly concentrated electrolyte is due to the low ion conductivity caused by high viscosity of the electrolyte. 46 Then, the discharge capacity suddenly dropped to 92.2 mA h g −1 at the second cycle; however, the NDI-2Vi electrode exhibited stable cycle stability thereafter. It is noteworthy that the capacity retention of the NDI-2Vi electrode after 100 cycles was markedly improved to 68.0% related to the specific capacity at the second cycle (Figure 3c).…”

“…In a high-salt-concentration electrolyte solution, fewer solvent molecules are capable of interacting with the active materials in the electrode, thus reducing its dissolution. 46 Indeed, when we immersed the NDI-2Vi electrode in a DOL/DME (1:1) electrolyte solution containing 6 M LiTFSI, it was observed that the dissolution of NDI-2Vi was significantly retarded. As shown in Figure S5b, although an increase in the UV−vis absorption spectrum was detected for the 6 M electrolyte solution during the first 12 h after immersion, the absorbance value was considerably lower than that of the 2 M electrolyte solution.…”

Triquinoxalinediol as organic cathode material for rechargeable aqueous zinc-ion batteries

“…A similar effect has already been observed in lithium organic batteries, where the use of concentrated electrolytes suppressed the dissolution of small organic cathode materials. 28,29 The cycling stability of small organic cathode materials is inuenced by the depth of discharge, which inuences the This journal is © The Royal Society of Chemistry 2023 amount of active material dissolution. 22 To improve the cycling stability different cutoff voltages of 0.8 V, 0.6 V, 0.4 V, and 0.25 V were tested.…”