Thiophene Based Self‐Doped Conducting Polymers as Cathode for Aqueous Zinc‐Ion Battery

Abstract

Self-doping strategy is well-known for enhanced ion transport in electrode materials. Herein we report self-doped thiophenebased conducting polymer (SDTP), where the dopant SO 3 À groups function as the hanging ion carrier mimicking a 'pendulum hand'. It synergistically improves the battery performance, ideally mitigating the dissolution and the enhance ion diffusion kinetics. The diffusion coefficient was determined by three different techniques, i. e., electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration technique (GITT), and cyclic voltammetry at different sweep rates. The calculated diffusion coefficient for the SDTP was found to be much better than the neat thiophene polymer (NTP). The material was evaluated as a cathode for an aqueous zinc-ion battery. The specific capacitance of the NTP was found to be 178 mAh g À 1 at 50 mA g À 1 current density. It was drastically reduced to 167, 118.2, and 83 mAh g À 1 after the 5 th , 10 th , and 30 th respective cycles. The polymer SDTP outperformed with a specific capacity of 274, 208, 159, 127, 108 mAh g À 1 at current densities of 50, 100, 200, 300, 400 mA g À 1 . It exhibited good rate reversibility, and excellent rate stability with ~99 % Coulombic efficiency in an over 4000 continuous cycles at 50 mA g À 1 suggesting wise molecular engineering is necessary to improve battery performance.

In Situ Electrochemical Activation of Hydroxyl Polymer Cathode for High‐Performance Aqueous Zinc–Organic Batteries

“…First of all, the hydroxyl group can increase the activity of carbonyl to accelerate the enolization process [41] . Secondly, since the deprotonation of polymers in the low pH electrolyte tends to lead to polymer deactivation, [34] the hydroxyl group as a proton carrier can ensure that the polymer does not lose activity in the weak acid electrolyte and improve the stability of PTFHQ. Finally, the hydroxyl group as a hydrophilic group can increase the compatibility between the polymer and the aqueous electrolyte and then accelerates the ion diffusion rate.…”

“…Polymer organic materials are ideal electrode materials due to their inherent insolubility and flexible polymer chains, which can provide stable skeletons and tunable internal space for highly reversible electrochemical reactions. However, the hydrophobicity of the polymer backbone usually leads to slow ion transport, while the deprotonation of the polymer would result in severe deactivation in the weakly acidic electrolytes [34] . These problems restrict the full performance liberation of organic polymer electrodes in AZIBs.…”

“…However, the hydrophobicity of the polymer backbone usually leads to slow ion transport, while the deprotonation of the polymer would result in severe deactivation in the weakly acidic electrolytes. [34] These problems restrict the full performance liberation of organic polymer electrodes in AZIBs. Besides, the existing research on polymer electrodes mainly focuses on the synthesis of new repeating units containing traditional active groups (such as carbonyl, amine, or thioether), whereas there are few studies on hydrophilic non-intrinsic electrochemically active functional groups.…”

“SPEEK-COF” Composite Cation Exchange Membrane for Zn-I2 Redox Flow Battery

“…18 Zinc based batteries are previously reported from our group addressing the dendrite growth suppression, 47,48 enhancement of electrode stability and self-doped conducting polymer to expedite the ion diffusion kinetics. 49 There are many additives like Methane sulfonic acid, polyethylene glycol, non-ionic dimethyl sulfoxide, thiourea, polyethyleneimine, polyvinyl alcohol, Triton X-100, polyacrylamide, Pluronic F-127, Alkyl halide salts etc are used for dendrite growth suppression. [50][51][52][53][54][55][56][57] The work in our laboratory is in progress in this direction to suppress the dendrite growth.…”

Non‐metallic Cation Storage using Poly(3,4‐ethylenedioxythiophene) Shells

“…[24] Naturally, organic materials, especially those with aromatic ring, are prone to interacting with non-metallic charge carriers through covalent bonds, hydrogen bonds or Van der Waals interactions that follow the donor-acceptor principle by delocalizing electrons between electrode materials and charge carriers. [25][26][27][28] PEDOT has been used in supercapacitor since the very beginning of its discovery, and its electrochemical performance is highly dependent upon its morphology and chemical/physical structure. [29][30][31] Inspired by these, we prepared flower-like PEDOT shells for aqueous NH 4 + storage.…”