TCNQ Confined in Porous Organic Structure as Cathode for Aqueous Zinc Battery

Abstract

The rechargeable Zn 2+ ion batteries are promising for the sustainable energy storage device applications. Recently they have been extensively evaluated for finding new cathode material and prevention of dendrite growth at Zn plate anode. Herein we have evaluated redox active organic molecule 7,7,8,8Tetracyanoquino dimethane (TCNQ) as a cathode material for aqueous zinc battery with zinc plates as anode in 1 M ZnSO 4 . The charging/discharging of the battery was associated with formation and deformation of Zn-TCNQ complex, which was confirmed by XRD and FTIR. The specific capacity of cathode was found to be 123.2 mAh g −1 at 100 mA current density with 96% coulombic efficiency. Whereas specific capacity at 1 A current density was found to be 60 mAh g −1 with 94% coulombic efficiency. In a cycling experiments we observed the fading of capacity with time by partial dissolution of Zn-TCNQ complex. The fading of capacity was prevented by confining TCNQ molecules inside the nano structures of newly prepared covalent organic polymers. The confinement remarkably increased the capacitance to 171 mAh g −1 at 1 A current density. As the material is readily available and the absence of toxic inflammable volatile organic electrolytes in our battery this material offers a very good choice as cathode material for zinc battery.

Constructing Advanced Aqueous Zinc‐Ion Batteries with 2D Carbon‐Rich Materials

“…The introduction of multifunctional CCP additive effectively improved the electrochemical performance, leading to a boosted capacity of up to 171 mAh g −1 with longer cycling stability versus pure TCNQ cathode. [ 97 ] Grzybowski et al reported a systematic work of 2D COF‐protected zinc anodes using a series of 1,3,5‐triphloroglucinol (TFP)‐based COFs (labeled as a DIP series). The authors designed a dip‐coating method to fabricate large self‐assembling COF films (30 × 12 cm 2 ) on zinc and other substrates (Figure 9c) with a controllable thickness varying from 5 to over 100 nm.…”

Significantly raising tetracyanoquinodimethane electrode performance in zinc‐ion battery at low temperatures by eliminating impurities

“…Figure S9 shows that at pristine state (Supporting Information: Figure S9a,d), XPS peak for -C≡N is the main functional group, while at 0.5 V (Supporting Information: Figure S9b two new diffraction peaks are generated near 2θ = 9.2°and 21.8°and the peak intensity continuously enhances along discharging, indicating that a new substance is formed, which is preliminarily determined to be Zn-TCNQ. 20 When charging is completed, the diffraction peaks are recovered to that of the initial state, indicating a highly reversible process of p-TCNQ during charging/discharging.…”

“…When discharged to 0.77 V, rod morphology is observed on the surface of the electrode; when fully discharged to 0.5 V, more rods appeared, exhibiting the formation of Zn-TCNQ, since it was reported to be onedimensional rods. 20 When charged to 1.16 V, the TCNQ particles gradually recover. At a fully charged state (1.35 V vs. Zn 2+ /Zn), the TCNQ electrode returns to its original morphology, which also illustrates the reversibility of TCNQ along charging and discharging.…”

“…[15][16][17][18][19] Recently, TCNQ was employed as a cathode for AZIBs at room temperature. 20 Unfortunately, it only delivered half of its theoretic capacity at a current density of 100 mA g −1 in 1 M ZnSO 4 electrolyte and the capacity dropped fast with cycles (only 50% capacity retention after 30 cycles) due to the partial dissolution of Zn-TCNQ. Later, Shen et al 21 improved the capacity and cyclability of Zn//TCNQ battery by using 2 M Na 2 SO 4 , 1 M ZnSO 4 , and 1 M Al 2 (SO 4 ) 3 as electrolytes.…”

Charge-Transfer Complex-Based Artificial Layers for Stable and Efficient Zn Metal Anodes

“…The high carrier mobility in Zn(TCNQ) 2 could induce low interfacial impedance and high current-carrying capacity, resulting in uniform surface current distributions of Zn anode. 30 Furthermore, the oxidation potential of Zn(TCNQ) 2 can be confirmed to be 1.125 V (vs Zn/Zn 2+ ), 23 suggesting that Zn(TCNQ) 2 will not undergo redox reactions during the Zn plating/stripping process. Importantly, the cyano groups (−CN) in Zn(TCNQ) 2 can capture and immobilize the highly active H 2 O molecules from [Zn(H 2 O) 6 ] 2+ via hydrogen bonding, which could accelerate the desolvation process of Zn 2+ .…”