Hydrophilic Anthraquinone-Substituted Polymer: Its Environmentally Friendly Preparation and Efficient Charge/Proton-Storage Capability for Polymer–Air Secondary Batteries

Abstract

Organic redox-active materials have been extensively studied as electrode-active materials to enable innovative battery designs with low environmental burdens. Facile condensation of 4,5-dihydroxyanthraquinone-2-carboxylic acid and poly­(allylamine) in water produces hydrophilic 1,8-dihydroxyanthraquinone (DHA)-substituted poly­(allylamine) (PDHA). Its high hydrophilicity originates from the poly­(allylamine) main chain, and the distorted structure of the DHA inhibits intermolecular stacking of the polymer side chain. This made it possible to achieve a high electron and proton diffusion coefficient of 10–11 cm2/s, which is an order of magnitude higher than that of conventional redox polymers that have one-step, two-electron redox capability. The electrode, composed of appropriately synthesized PDHA, showed a full capacity of 140 mAh g–1 with excellent cyclability (>97% capacity maintenance after 500 cycles) and high rate capabilities (e.g., 120 C) in an acidic aqueous electrolyte under inert gas. These electrochemical properties were maintained even in air, making PDHA a promising candidate for a robust, electrode-active material. A polymer–air secondary battery was fabricated with PDHA, Pt/C, and a 0.5 M H2SO4 aqueous solution as the anode material, cathode material, and electrolyte, respectively, without any separator, inert gas, or strict sealing. This open-air battery displayed a discharge voltage of 1.05 V, with high cyclability greater than 500 cycles and high rate capabilities (e.g., 60 C), demonstrating a new battery concept and potential for large-scale applications.

Initiating a High‐Rate and Stable Aqueous Air Battery by Using Organic N‐Heterocycle Anode

“…Moreover, in various aqueous electrolytes, the maximum voltage of the NHCC‐air full battery (1.6 V) is higher than that reported for organic‐based batteries (Figure 5d and Table S1), including acid electrolyte (pyrene‐4,5,9,10‐tetraone||MnO 2 on graphite felt (PTO||MnO 2 @GF) (1.3 V), [19] PTO||PbO 2 (1.27 V), [20] polypyrene‐4,5,9,10‐tetraone||Mg x CuHCF (PPTO||Mg x CuHCF) (1.12 V) [20] ), mild electrolyte (PPTO||LiMn 2 O 4 (1.13 V), [20] PPTO||Na 3 V 2 (PO 4 ) 3 (1.18 V) [20] ), and alkaline electrolyte (PPTO||LiCoO 2 (1.3 V), [20] PAQS||Ni(OH) 2 (1.45 V) [20] ). In addition, due to the high concentration of the alkaline aqueous electrolyte and high stable electrochemical kinetics of the NHCC anode materials, the NHCC‐air full battery demonstrate longer cycle life (30,000 cycles at 20 A g −1 ) and higher rate‐capacity (120 mAh g NHCC −1 at 20 A g −1 ) than the reported organic anode batteries (Figure 5e and Table S2), including poly(1, 4‐Naphthoquinone)||O 2 (PNQ||O 2 ), [21] poly(1, 4‐anthraquinone) on carbon nanotubes||O 2 (P14AQ@CNT||O 2 ), [9c] poly(vinylanthraquinone)||O 2 (PVAQ||O 2 ), [9d] poly(1,8‐dihydroxyanthraquinone)||O 2 (PDHA||O 2 ), [9f] and anthraquinone‐based conjugated microporous polymer||Ni(OH) 2 (IER‐11||Ni(OH) 2 ) [9g] . It is also worthing noting that the organic couponds are still facing challengs including low electronic conductivity, and reduced specific capacity than the metal counterpart, further efforts should be paid to these aspects to facilitate this organic compound‐Air battery configuration.…”

Redox-site accessibility of composites containing a 2D redox-active covalent organic framework: from optimization to application

“…The battery conguration was inspired by our previous studies on polymer-air batteries. [33][34][35][36] The charge/discharge prole (Fig. 7C) showed a high discharging voltage centred between 0.8-1.2 V, which corresponded to the potential window of the 0.4EDOT@TpOMe-DAQ composite electrode when cycling it in a similar acidic electrolyte (Fig.…”

Accelerating the dehydrogenation reaction of alcohols by introducing them into poly(allylamine)

“…15,[17][18][19] As molecules that can store hydrogen are densely packed in the polymer bulk, hydrogen (or proton) transfer reactions efficiently occur between these molecules. 16,[20][21][22][23][24][25][26][27][28][29] The dehydrogenation reaction of these polymer materials including a small amount of solvent, even in the solid state, proceeds with complete conversion by a metal complex catalyst. 21,[30][31][32][33][34][35] However, the aggregation of polymer chains significantly inhibits the reaction of molecules capable of storing hydrogen; hence, the reaction rate of functional molecules is lower in macromolecules than in single molecules.…”

“…1,4-Butanediol-substituted poly(allylamine) was prepared via nucleophilic substitution of poly(allylamine) with 2-bromo-1,4-butanediol in water (Scheme 1), following the procedure reported in our previous paper 28 (details are in the ESI†). The introduction degree was significantly improved by introducing bases such as K 2 CO 3 and 1,8-diazabicyclo[5.4.0]undec-7-ene ( DBU ), which act as proton scavengers during the reaction, and by using lower molecular weight poly(allylamine); this rate was adjustable between 17% and 76% (Table 2).…”