Improvement of the Battery Performance of Indigo, an Organic Electrode Material, Using PEDOT/PSS with d-Sorbitol

Abstract

Rare-metal-free and high-performance secondary batteries are necessary for improving the efficiency of renewable energy systems. Organic compounds are attractive candidates for the active material of such batteries. Many studies have reported organic active materials that show high energy density per active material weight. However, organic active materials, most of which exhibit low conductivity and low specific density, typically require a large amount of a conductive additive (>50 wt %) to obtain a high utilization rate. Therefore, organic active materials rarely display high energy density per electrode weight. High energy densities per electrode weight can be obtained using high weight fractions of active materials and low weight fractions of conductive additives. Herein, we report that a low-conductivity organic active material, indigo, showed improved net discharge capacity density when even a small amount of a conductive polymer composite, poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT/PSS) with d -sorbitol, was used as both a binder and conductive additive. The cycle life was also improved by coating one side of the separator with the composite, which probably hindered the dissolution of the active material. A discharge capacity of 96% of the theoretical capacity of indigo and an improved cycle life were achieved with an electrode containing 80 wt % indigo and with a PEDOT/PSS-coated separator. The optimal fraction of the conductive binder was examined, and the mechanism of conductivity enhancement was discussed. The present scheme allows us to replace the dispersion solvent of the slurry, N -methylpyrrolidone, with water, which can reduce the environmental load during battery manufacturing processes.

Cross-Linked Naphthalene Diimide-Based Polymer as a Cathode Material for High-Performance Organic Batteries

“…On the other hand, the Nyquist plots of the Li||DP-NDI cell reveal that the charge transfer was significantly increased after 100 cycles, indicating that the cell with the non-cross-linked DP-NDI polymer exhibits poor cell performance. 49,51,52 To investigate the diffusion coefficient of Li + in the polymer matrix, CV profiles of the CL-DVP-NDI composite electrode at scan rates of 0.1, 0.2, 0.3, 0.4, and 0.5 mV s −1 were obtained (see Figure S11). Based on the results obtained from the CV curves, the anodic peak current is linearly proportional to the square root of the scan rates.…”

“…The results of charge-transfer impedance demonstrate that the excellent stability of the electrode material may be due to the formation of a three-dimensional network structure of the cross-linked polymer. On the other hand, the Nyquist plots of the Li||DP-NDI cell reveal that the charge transfer was significantly increased after 100 cycles, indicating that the cell with the non-cross-linked DP-NDI polymer exhibits poor cell performance. ,, …”

Electrochemical Assessment of Indigo Carmine Dye in Lithium Metal Polymer Technology

“…Note that IC is thermally stable at more than 200 °C [ 40 ], as it is commonly observed in the case of alkali salts of organic compounds [ 33 ]. Before presenting the as-obtained results in the LMP ® battery technology, we have thought useful to recall the typical electrochemical features of IC-based composite electrodes reported in the literature to date [ 38 , 39 , 40 , 41 ].…”

High Active Material Loading in Organic Electrodes Enabled by a Multifunctional Binder

“…Recently, increased research efforts have been directed toward developing functional polymeric binders with enhanced electronic conductivity to replace or reduce the amounts of inactive components in the cathode. − However, while much progress has been made to improve the electronic conductivity and mechanical properties of the cathode, there has been little attention on improving the ionic conductivity. Having enhanced ionic conductivity is essential to allow efficient Li-ion transport in the system during battery cycling, and may be achieved using organic mixed ionic-electronic conductors.…”