Aqueous Multivalent Charge Storage Mechanism in Aromatic Diamine-Based Organic Electrodes

Abstract

Rechargeable batteries employing aqueous electrolytes are more reliable and cost-effective as well as possess high ionic conductivity compared to the flammable organic electrolyte solutions. Among these types of batteries, aqueous batteries with multivalent ions attract more attention in terms of providing high energy density. Herein, electrochemical behavior of an organic electrode based on a highly aromatic polymer containing 2,3-diaminophenazine repeating unit, namely poly­(ortho-phenylenediamine) (PoPD), is tested in two different multivalent ions (Zn2+ and Al3+) containing aqueous electrolytes, that is, in zinc sulfate and aluminum chloride solutions. PoPD is synthesized via electropolymerization, and its ion transport and storage mechanism are comprehensively investigated by structural and electrochemical analyses. The electrochemical quartz crystal microbalance, time-dependent Fourier transform infrared, and electrochemical impedance spectroscopy analyses as well as ex situ X-ray diffraction observations established that along with the Zn2+ or Al3+ ions, reversible proton insertion/extraction also takes place. Contrary to the most of the organic electrodes that requires the use of conductive carbon additives, the electrodeposited PoPD electrode is intrinsically electrically conductive enough, resulting in a binder and additive free electrode assembly. In addition, its discharge products do not dissolve in aqueous medium. As a whole, the resulting PoPD electrode delivers excellent rate performances with prolonged cycle life in which discharge capacities of ∼110 mAh g–1 in 0.25 M AlCl3 and ∼93 mAh g–1 in 1 M ZnSO4 aqueous electrolyte after 1000 cycles at a current density of 5C have been achieved.

Polyphosphazene Based Inorganic‐Organic Hybrid Cathode Containing Pyrene Tetraone Sides for Aqueous Zinc‐Ion Batteries

“…Figure S9 shows a reversible frequency decrease/increase which is accompanied by a non‐negligable increase/decrease of the R m values, indicating a deviation from the linear relationship between the Δ f and Δ m . This can be attributed to at least two factors: (i) viscoelastic changes of the PPAPT film due to Zn 2+ (de‐)coordination during an anodic/cathodic scan of the potential and (ii) a concomitant H + (de‐)coordination along with Zn 2+ which results in local pH changes and thus, ZHS formation [12,67,68] . Since, the Δ f and Δ R m do not show a significant irreversibility (Figures 5b, d and S9), we can consider that the initial state of the electrode is restored within one electrochemical cycle.…”

“…This can be attributed to at least two factors: (i) viscoelastic changes of the PPAPT film due to Zn 2 + (de-)coordination during an anodic/cathodic scan of the potential and (ii) a concomitant H + (de-)coordination along with Zn 2 + which results in local pH changes and thus, ZHS formation. [12,67,68] Since, the Δf and ΔR m do not show a significant irreversibility (Figures 5b, d and S9), we can consider that the initial state of the electrode is restored within one electrochemical cycle. This observation is in perfect agreement with the FT-IR and XPS analyses above demonstrating that Zn 2 + or H + cations can reversibly (de-)coordination the PPAPT/KB electrodes during the discharge-charge process.…”

“…The energy storage mechanism of numerous organic electrode materials in aqueous electrolyte zinc ion batteries is generally based on the following redox reactions: i) insertion of zinc ions with water molecules, [48] ii) reversible co-insertion [12,22] of H + and Zn 2 + , iii) bare H + or H 3 O + hydronium (in)coordination. [28,49] Moreover, the proposed reactions of redox active organic electrodes have been demonstrated by various characterization techniques such as in-situ EQCM, [12,50] Raman [22] and ex-situ SEM-EDS, [51] FTIR, [51] NMR, [49,52] XRD, [22] XPS [52] and DFT (density functional theory) computational methods. [18] To study the charge storage mechanism, first of all, we employed ex-situ XRD to observe the change in the pristine PPAPT/KB electrode and after the first discharge process in 2 M ZnSO 4 electrolyte.…”

“…[5,6] Hence, the merits of zinc anode make aqueous rechargeable zinc-ion batteries (ARZBs) an up-and-coming system for grid-scale storage. [7,8] Regarding the development of cathode materials, various transition metal oxide-based (vanadium oxide, [9] manganese dioxide [10] ) or organic electrode (quinone-based, [11] conductive polymer [12] ) materials are proposed that play a significant role for providing improved electrochemical properties and cycling performance. [13] Considering the environmental problems and the depletion of natural resources, it is highly desirable to explore renewable electrode materials for ARZBs, consisting of abundant C, H, O, N and S elements on Earth, which can be obtained artificially or directly from biomass sources.…”

Universality of Benzoquinone-based Anodes toward Various Metal Cations in Aqueous Rechargeable Batteries

“…Quinone − and polyimide (PI) ,− anode materials, which store charge via an ion coordination mechanism between the cation and carbonyl group, ,− can deliver the ultra-long cycle life and high specific capacity benefiting from their intrinsic structural flexibility and abundant active sites to store charges . Additionally, quinone-based anode materials can reversible store not only small univalent cations (Li + , Na + , and K + ) but also large multivalent cations (Zn 2+ , Mg 2+ , Ca 2+ , and Al 3+ ) with weak molecular structural vibrations owing to their conjugated and open structure, implying their universality to various cations. ,− A 1,4,5,8-naphthalenetetracarboxylic dianhydride-derived PI anode reported by Qin et al delivered a high specific capacity (∼160 mA h g –1 ) and long cycle life in both 5 M LiNO 3 and 5 M NaNO 3 solutions, indicating the universality of the PI anode to Li + and Na + .…”