Constructing Extended π-Conjugated Molecules with o-Quinone Groups as High-Energy Organic Cathode Materials

Abstract

Although organic cathode materials with sustainability and structural designability have great potential for rechargeable lithium batteries, the dissolution issue presents a huge challenge to meet the demands of cycling stability and energy density simultaneously. Herein, we have designed and successfully synthesized two novel small-molecule organic cathode materials (SMOCMs) by the same innovative route, namely 7,14-diazabenzo­[a]­tetracene-5,6,8,13-tetraone (DABTTO) and 7,9,16,18-tetraazadibenzo­[a,l]­pentacene-5,6,8,14,15,17-hexaone (TADBPHO). The integrated p-quinone, o-quinone, and pyrazine groups provide these SMOCMs with attractive theoretical capacities of 473 and 568 mAh g–1 based on 6- and 10-electron reactions, respectively, which were almost fully utilized within 0.8–3.8 V vs Li+/Li. The extended aromatic nucleus of TADBPHO makes it much less soluble than DABTTO and thus able to achieve the highest level of cycling stability (66% @ 500th cycle) for SMOCMs in addition to the exceptional energy density (364 mAh g–1 × 2.56 V = 932 Wh kg–1) within 1.5–3.8 V. In addition to the excellent electrochemical performance, the redox reaction and capacity fading mechanisms have been also investigated in detail. The novel approach to construct extended π-conjugated molecules with o-quinone groups is enlightening for the development of high-energy and stable OCMs for future efficient and sustainable energy storage devices.

Thionin as a Bipolar Organic Cathode Material for Aqueous Rechargeable Zinc Batteries

“…It suggested that the reaction kinetics of Thn-CH 3 COO was controlled by hybrid solid diffusion and pseudocapacitive behaviors. [22] Figure 2(c) shows the EIS data of the cell in charged state at different cycle numbers, which were fitted using a classic equivalent circuit (Table S2). The charge transfer resistance (R ct ) was 163 Ω at the pristine state, and significantly decreased to 73 Ω after the initial cycle, indicating that the Thn-CH 3 COO electrode structure was optimized after a discharge-charge cycle, probably caused by its dissolutionredeposition behavior.…”

“…The relation between peak current ( i p ) and scan rate ( v ) was analyzed by a linear fitting of lg( i p ) vs. lg( v ) (Figure 2b), resulting in b values (in the equation of i p =a × v b ) of 0.65 and 0.58 in the cathodic and anodic processes, respectively. It suggested that the reaction kinetics of Thn‐CH 3 COO was controlled by hybrid solid diffusion and pseudocapacitive behaviors [22] . Figure 2(c) shows the EIS data of the cell in charged state at different cycle numbers, which were fitted using a classic equivalent circuit (Table S2).…”

Bis-imidazole ring-containing bipolar organic small molecule cathodes for high-voltage and ultrastable lithium-ion batteries

“…When b approached 0.5, it meant a diffusion-controlled kinetic process, and a b value close to 1.0 suggested the domination of a capacitive process. 36 The b values obtained from the peaks 1 to 4 were 0.67, 0.72, 0.88, and 0.92, respectively, demonstrating that the kinetics process of BNBQ was predominantly controlled by the non-diffusion process. The contribution of a capacitive This journal is © The Royal Society of Chemistry 2023 process and a diffusion-limited redox process in overall capacity could be quantied through the equation i = k 1 n + k 2 n 1/2 , 58 where k 1 and k 2 were constants which could be conrmed by plotting n 1/2 versus i/n 1/2 at specic potentials.…”

“…Tetraamino-p-benzoquinone (TABQ) with high-density functional groups not only has a high theoretical specic capacity, but is also easily extended into larger molecules due to the presence of four side amino groups, which makes it a desirable building unit of organic electrode materials of LIBs. 21,35,36 Herein, we employed TABQ as the raw material to not only contribute the low-voltage capacity but also behave as a bridging agent, and aromatic aldehydes 4-(N,N-diphenylamino)benzaldehyde (NDP) as p-type redox-active units to offer high-voltage capacity. 37 Consequently, the NDP units were connected with TABQ through bis-imidazole rings, and smallmolecular 2,6-bis(4-(diphenylamino)phenyl)benzo [1,2-d:4,5-d ′ ] diimidazole-4,8(1H,5H)-dione (BNBQ), was synthesized.…”

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

“…Though the organic electrode material and insoluble matrix can be composite anchored, the complex processing as well as the limited number of energy species on the substrate cannot be ignored. In addition, enhancing the π-π intermolecular interaction between materials [17,18] or forming intramolecular hydrogen bond [19,20] by designing molecular structures are also effective strategies to achieve stable cycling of organic electrode materials.…”