Influences of Cations’ Solvation on Charge Storage Performance in Polyimide Anodes for Aqueous Multivalent Ion Batteries

Abstract

Among the examined organic electrodes for aqueous mono and multivalent ions batteries, polyimide is considered a promising candidate because of its high capacity and good cyclability in different electrolyte solutions. While most of the studies so far were focused on the energetic performance of polyimide anodes, much less is known about their charge storage mechanism and particularly how such electrodes are affected by the solvation properties of the inserted cations. Using in situ EQCM-D, a direct assessment of the cationic fluxes and their hydration shells inserted/extracted to/from PI electrodes upon potential application was performed for a large variety of mono and multivalent cations. Our observations demonstrated a pronounced withdrawal of water molecules from the polymeric electrodes during insertion of chaotropic cations and significantly less water withdrawal upon insertion of kosmotropic cations. These findings are well correlated with the capacity and the rate capability of the polyimide electrodes in the examined systems and shed light on their charge storage mechanism.

A Sub‐Square‐Millimeter Microbattery with Milliampere‐Hour‐Level Footprint Capacity

“…A low charge transfer resistance ( R p , 530 Ω) shows the cation transferability of the PI. [ 12 ] The additional charge transfer process due to the formation of the PI layer will impede ion diffusion in the electrode. Therefore, the solid diffusion coefficient (D) obtained from the galvanostatic intermittent titration technique (Figure S3, Supporting Information) shows that the D value of MnO 2 ‐PVDF is higher than that of MnO 2 ‐PI (Figure 2c).…”

Unique Mechanisms of Ion Storage in Polyaniline Electrodes for Pseudocapacitive Energy Storage Devices Unraveled by EQCM-D Analysis

“…In order to separate the involvement of anions and the proton-dominated charge transfer in the charge-compensation process, the EQCM-D responses were measured only across the first and the second peaks (i.e., formation of ES + ·(A ins – ) and PPhz + ·(A ins – ), see Figure c,e). Similarly, EQCM-D measurements were performed separately across the third CV peak (shift of potential from 0.45 to 0.75 V) in which the deprotonation/protonation process of the PANI takes place, see Figure d,f …”

“…Similarly, EQCM-D measurements were performed separately across the third CV peak (shift of potential from 0.45 to 0.75 V) in which the deprotonation/protonation process of the PANI takes place, see Figure 3d,f. 23 Considering the amount of transferred charge, the theoretical frequency changes can be calculated by the following formula…”

“…The conclusion that ions with higher chaotropic nature replace a larger number of water molecules agrees well with our previous report on the electrochemical insertion of cations into polyimide anodes. 23 As in various inorganic electrodes that comprise nanofluidic channels, 23 extraction of a sufficient amount of water molecules allows better electrostatic screening of the redox centers in the PANI macromolecule by the inserted anions, resulting in higher capacity values.…”

Fundamentals and Scientific Challenges in Structural Design of Cathode Materials for Zinc‐Ion Hybrid Supercapacitors

“…Stagnation diffusion of massive and strongly bonded divalent charges such as Zn 2+ within MXene-based electrodes causes an issue in building high-performance ZHSC because of greater sizes and stronger electrostatic interactions of the divalent charges in comparison to the smaller, faster-moving, and smaller univalent charges. [229] A new design was proposed by Wu et al [230] which integrates well-behaved nanoscale spacers into a many-layered substrate via the homogenous intercalation of bacterial cellulose fiber (BCF) was created to overcome this issue to extend the interlayer spacing between restacked MXene sheets (MXene/BCF). Further, molecular dynamics simulation (MDS) and electrochemical testing found that by increasing the ion-transport channels of few-layered MXene sheets, Zn 2+ diffusion can be enhanced, thereby lowering the diffusion barrier for the MXene/BCF host electrodes.…”