Inset is the galvanostatic charge/discharge cycling behavior of the crumpled Zn air cells at a current density of 0.5 mA cm–2. a) Schematic of the manufacturing procedure for the MH paper air cathode, along with its photograph. Photographs showing dispersion stability of the cathode suspension: (b) without and (c) with a dispersant (SDS/urea = 5/5 (w/w)). Electrochemical analysis of the ILG-Zn electrodes as a function of IL gel thickness. b), (c) Galvanostatic Zn plating/stripping profiles of the AE-containing Zn/Zn symmetric cells at a current density of 0.5 mA cm−2. Angry.
Galvanostatic Zn plating/stripping cyclability of the (ILG-Zn/ILG-Zn) symmetric cell, (ILG-Zn/bare Zn) asymmetric cell and (bare Zn/bare Zn) symmetric cell at a current density of 0.1 mA cm− 2. Galvanostatic Zn plating/stripping cyclability of the AE-containing Zn/Zn symmetric cells (ILG-Zn vs. bare Zn) at a higher areal capacity of 1.8 mAh cm−2 (equivalent to 90% DODZn) and current density of 0 .5 mA cm −2 . -Zn) after being precycled at a current density of 0.1 C; (a) Bare Zn and (b) ILG-Zn. c) GITT profiles of Zn/MnO2-full cells (bare Zn vs. ILG.
Introduction
Introduction of Aqueous Zinc-based Rechargeable Battery Systems
Zn in aqueous metal–air battery has received much more attention due to its higher energy density (1218 W h kg−1 and 6136 W h L−1 ) and cell voltage, which is particularly desirable for mobile and portable devices (e.g. EV and personal electronics).11 A Zn-air battery is usually composed of four main components shown in Figure 2a: an air cathode, a Zn anode, an alkaline electrolyte, and a separator. During discharge, the Zn-air battery acts as an energy generator through the electrochemical coupling of Zn metal with an air electrode in the presence of an alkaline electrolyte with an inexhaustible cathode reactant (oxygen) from the atmosphere. The electrons released at Zn travel through the external load to the air electrode, while.
During charging, the Zn air battery is able to store electrical energy through the oxygen evolution reaction (OER) (Reverse reaction (1)), which occurs at the electrode-electrolyte interface, while Zn is deposited on the anode surface (Reaction of backward (2)).
Issues of Rechargeability of Aqueous Zinc-based Battery Systems
As a consequence, these parasitic interfacial reactions between Zn anodes and aqueous electrolytes result in poor reversibility of Zn coating/stripping along with the consumption of Zn and electrolyte. stability, but this leads to suboptimal utilization of its theoretical capacity. In this thesis, focusing on aqueous Zn-based rechargeable battery systems, a monolithic electrode architecture, including active materials/current collector, and a novel protective layer are proposed to extend Zn anode cycle life far beyond those achievable with conventional battery . technologies. Furthermore, PTFE nanoparticles are adopted as a hydrophobic binder to prevent electrolyte flooding and provide airways in the MH paper air cathode.
Meanwhile, the highly entangled network structure (based on a fibrous mixture of NBSCF, N-CNTs, and CNFs) of the MH paper-air cathode exhibits significantly improved electrochemical rechargeability and mechanical flexibility under various deformation conditions. Despite such solutions at the electrode structure level, aqueous Zn-based rechargeable batteries still have an inherent obstacle of the chemical/electrochemical instability of Zn anodes with aqueous electrolytes, which are the major challenges faced by RZABs. As a proof of concept, the hydrophobic ionic liquid (IL) skinny gels are proposed as a new class of water-repellent ion-conducting protective layers tailored for Zn anodes.
The weak IL gel consists of IL hydrophobic solvent (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI)), Zn salt (Zn(TFSI)2) and thiolene polymer-compatible backbone (ultraviolet (UV)- cured tris(3-mercaptopropionate) trimethylolpropane (TMPMP, “thiol”) and trimethylolpropane triacrylate (TMPTA, “ene”)). BMPTFSI, used as a hydrophobic solvent for electrolytes,50 is expected to prevent access of aqueous electrolytes to Zn anodes. Furthermore, the BMP+ cations of BMPTFSI, due to their electroprotective effect,51 can contribute to the uniform and stable coating of Zn on Zn anodes.
The thiolene polymers, which are known to exhibit mechanical compliance,52 enable the IL skinny gel to conformally deposit on the Zn surface and to maintain its structural integrity during plating/stripping cycling. Driven by the rationally designed material chemistry and structural engineering, the IL skinny gel deposited on Zn anodes can effectively suppress water-activated interfacial parasitic reactions, such as electrolyte consumption and Zn corrosion, thus providing reliable Zn plating/stripping- cyclability below 90% depth of discharge (DODZn), which is difficult to obtain with previously reported protective layers.
One-Dimensional Nanofiber-Based Electrode Architecture for Rechargeable Zinc-air Batteries
Rechargeable and Flexible Zinc-Air Batteries Based on Multifunctional Heteronanomat Architecture
- Introduction
- Experimental
- Results and Discussion
- Conclusions
The morphologies of the HM electrodes were characterized by field emission scanning electron microscopy (FE-SEM) (S-4800, HITACHI) and X-ray spectroscopy (EDS) (JSM 6400, JEOL). The composition ratio of the HM electrodes was determined from TGA (SDT Q600, TA Instruments) under an air atmosphere (heating rate = 5 °C min−1). The skin resistances of the HM electrodes were measured using a four-point probe technique (CMT-SR1000N, Advanced Instrument Technology).
The air permeability, i.e. the time required for air passage of the GDL in the HM air cathode was estimated by a Gurley densometer (4110N, Gurley). TGA profiles of the (a) HM Zn anode and (b) PEI/SWCNT mixture mat. c) Calculation used to estimate the Zn content in the HM Zn anode. The aforementioned electrospray/electrospinning process allowed for seamless union of the catalyst layer with the GDL in the HM air cathode (Figure 9c).
This hydrophobic nature of the HM air cathode is expected to mitigate flooding concerns. Insets are photographs of the HM electrodes (after 1000 bending and twisting cycles, respectively) and the mechanically ruptured control electrodes (Zn foil anodes and MEET air cathodes). To verify this beneficial effect, galvanostatic charge/discharge profiles of the Zn air cells (Zn foil anodes/MEET air cathodes) containing PVA/PAA GPE were investigated as a function of cycle number (Figure 12c).
The HM frameworks of the electrodes played a key role in the structural stability of the resulting Zn air cells. Inset is the galvanostatic charge/discharge cycling behavior of the crimped Zn air cells at a current density of 0.5 mA cm-2.
Monolithic Heteronanomat Paper Air Cathodes Toward Rechargeable and Origami-Foldable Zinc-Air Batteries
- Introduction
- Experimental
- Results and Discussion
- Conclusions
Meanwhile, the highly entangled network structure (based on a fibrous mixture of NBSCF, N-CNTs, and CNFs) of the MH paper air cathode exhibits significantly improved mechanical flexibility under various deformation conditions. For coin-type Zn-air batteries, the basic electrochemical performances of the MH paper-air cathode were characterized using a coin-type (CR2032) Zn-air battery (assembled with a Zn foil (Alfa Aesar) anode, an alkaline electrolyte (6 M KOH and 0.2 M Zn(OAc)2), and a glass fiber separator membrane (EL-CELL, ECC1-01-0012)). The mechanical stability of the MH paper air cathodes was quantitatively investigated using a universal tensile tester (Petrol LAB, DA-01) under the bending conditions.
This all-fibrous structure of MH paper air cathode is favorable to produce a highly porous structure. The dispersion uniformity of the air cathode made of MH paper was investigated by analyzing the cross-sectional EDS image (Figure 15). The inset shows a low-magnification image. e) Photograph of MH paper air cathode without CNF.
Cross-sectional EDS images (Nd, Ba, Sr, Co, Fe, N, C, O, and F elements are shown by the colored dots) of the MH paper air cathode. The effect of CNFs on the formation of the electrolyte channel in the MH paper air cathode was investigated. A narrow discharge-charge voltage gap (0.7 V) was observed at a current density of 1 mA cm−2, demonstrating the efficient bifunctional electrocatalytic reaction of the MH paper-air cathode.
This cycling retention is a good demonstration of the structural/electrochemical advantages of the MH paper air cathode. The highly complex network structure (based on a fibrous mixture of NBSCF, N-CNT, and CNF) of the MH paper air cathode played an important role in increasing the mechanical flexibility under different deformation modes.
Water-Repellent Ionic Liquid Skinny Gels Customized for Aqueous Zinc-Ion Battery Anodes
- Introduction
- Experimental
- Results and Discussion
- Conclusion
The role of skinny IL gel as a water-resistant non-conductive protective layer is conceptually illustrated in Scheme 1. Electrochemical characteristics of IE (0.3 m Zn(TFSI)2 in BMPTFSI). a) Galvanostatic stacking/stripping cycling of the symmetric Zn/Zn cell with a current density of 0.1 mA cm−2. The optimal IL weak gel thickness was determined considering a trade-off between cell overpotential and cycling stability of Zn/Zn symmetric cells.
Electrochemical analysis of the ILG-Zn electrodes as a function of IL gel thickness. b), (c) Galvanostatic Zn plating/stripping profiles of the AE-containing Zn/Zn symmetric cells at a current density of 0.5 mA cm−2. To further elucidate this beneficial effect of the IL skinny gel, in situ DEMS of Zn/Zn symmetric cells was performed. The reversible Zn plating/stripping behavior of the ILG-Zn electrode was investigated using Zn/Zn symmetric cells.
This electrochemical reliability of the ILG-Zn electrode was also observed at faster current densities of 1.0 and 2.0 mA cm−2 (Figure 34b), indicating the facile transport of Zn2+ ions through the weak IL gel. The favorable effect of the ILG-Zn electrode on cycling retention was observed at a higher surface capacity of 1.8 mAh cm−2 (corresponding to 90% of DODZn) and a current density of 0.5 mA cm− 2 (Figure 35). Such structural stabilization of the ILG-Zn electrode was verified by performing XPS analysis (Figure 36b).
The bare Zn electrode showed a weaker intensity of the Zn 2p3/2 peak than the ILG-Zn electrode. -Zn) after being previously reused at a current density of 0.1 C; (a) Bare Zn and (b) ILG-Zn. c) GITT profiles of the Zn/MnO2 full cells (bare Zn vs. The cycle performance of the Zn/MnO2 full cells was investigated at a faster current density of 2 C (Figure 40a).
These full cell results emphasize the viable role of IL skinny gel acting as a water-repellent ion-conducting protective layer.
