Pyrene Diimide Based π-Conjugated Copolymer and Single-Walled Carbon Nanotube Composites for Lithium-Ion Batteries

Abstract

A π-conjugated copolymer based on a pyrene diimide unit (P(PyDI-T2)) was synthesized using the Suzuki−Miyaura crosscoupling reaction between 4,5,9,10-pyrene diimide-2,7-diboronic ester and 2,2′-dibromo-5,5′-bithiophene for use as an active material in a Li-ion battery. Usually, diimide molecules are known to demonstrate reversible redox processes with a maximum of a two-electron insertion per unit. The unique structure of pyrene diimide, consisting of a pyrene core bearing two imide functions lying on formal double bonds, was anticipated to potentially demonstrate reversible redox processes involving four electrons per unit via aromatic stabilization. Also, the 2-and 7-positions are much less sterically hindered than similar relative positions in other diimides and hence should permit good electron mobility in the resulting polymer. Unfortunately, we were unable to observe any reduction phenomena in a half-cell (with a Li anode), likely due to negligible electronic conductivity. Subsequently, P(PyDI-T2) was blended with SWCNTs for dispersion in order to enhance both conductivity and surface area. High concentration dispersion was filtered to obtain a freestanding film of P(PyDI-T2)/SWCNT, with an intrinsic conductivity of 30 S/cm, which was used directly as a cathode in the half-cell. Reversible redox pointing to two one-electron phenomena was observed with 40.6 mA h/g at a galvanostatic slow rate of C/50 with a high mass loading of 3.2 mg/cm 2 . Density functional theory calculations were performed on pyrene diimide units to elucidate poor mobility and to compare Gibbs free energies for the second reduction of each site.

Large π-Conjugated Condensed Perylene-Based Aromatic Polyimide as Organic Cathode for Lithium-Ion Batteries

“…Summary plots for the comparison of the practical specific capacity of perylene-based aromatic polyimides (BA-PI and PI as control) and other organic cathode materials used in organic batteries (vs Li + /Li and Na + /Na) concerning the applied current densities. Data from refs , , , , and and this work.…”

“…These were seemingly higher, in terms of specific capacities and cycling stability, to previously reported state-of-the-art perylenediimide-based frameworks, small molecules, perylene-based aromatic polyimides, and pyrenediimide-based conjugated copolymer. 33,40,44,73,74 A detailed comparison of the battery performance of BA-PI-and PIbased cells in terms of initial discharge capacities and cyclic stabilities are provided in the Supporting Information (Table S1). As can be seen from Figure 5 and Table S1, the battery cell based on BA-PI showed not only higher practical specific capacity but also better cycling stability than a previously reported state-of-the-art perylenediimide-based small molecule (G 2 PDI) 73 and pyrenediimide-based conjugated copolymer (P(PyDI-T2)) in organic batteries (vs Li + /Li).…”

“…In parallel, several studies have reported the use of condensed/conjugated aromatic structure of pyrene (i.e., crystalline pyrene, noncrystalline oligopyrene, and polypyrene), pyrenediimide-based π-conjugated copolymer, pyrene-based derivatives, and its nanocomposites with carbon matrix. These are promising highly reversible and high-capacity electrode materials that can be used in various electrical energy-storage applications, such as organic LIBs and sodium-ion batteries, , electrochemical energy-storage devices, , lithium–sulfur (Li–S) batteries, and rechargeable aluminum batteries . Inspired by these results, we proposed utilizing only a few condensed aromatic rings/extended π-conjugated aromatic rings to emulate the cathodic behavior of greatly condensed polyaromatic graphite/graphene structures .…”

Weak Intermolecular Interactions for Strengthening Organic Batteries

“…In general, there are several methods to fabricate composite of graphene (or CNTs) as conductive additives with the active materials: 1) The most efficient way is the direct mixing of graphene or CNTs with active materials. [60,[97][98][99] Benefiting from p-p interactions between the graphene (or CNTs) and the active materials, [10] efficient mixing between them is possible even in molecular level through special process. Hence, the electrochemical performance can be enhanced significantly, where graphene or CNTs act as the conduction path.…”

Synthesis and Excimer Formation Properties of Electroactive Polyamides Incorporated with 4,5-Diphenoxypyrene Units

“…Therefore, many studies have introduced aromatic groups with π-stacking steric barriers into the molecular structure of pyrene, which can effectively improve the luminous efficiency of such compounds in the solid state [35,36]. However, there is not much research and literature on 4, 5, 9, 10tetra-substituted pyrene [37][38][39][40][41][42]. The main obstacle to the synthesis is that the electrophilic substitution of pyrene preferentially takes place at the 1, 3, 6, 8 positions (non-K-region), as accessing the 4, 5, 9, 10 positions (K-region) is much more difficult.…”