Super‐Stretchable Zinc–Air Batteries Based on an Alkaline‐Tolerant Dual‐Network Hydrogel Electrolyte

Abstract

remains a challenge. Meanwhile, zincair battery provides a theoretical energy density up to 1086 Wh•kg −1 , even much higher than commercial lithium-ion batteries, promising to next-generation longlasting power system. [1][2][3][4][5] In addition, the process of assembling zinc-air battery does not require water-free and/or oxygenfree environment, which is in favor of scaling up at low cost. [6][7][8][9][10] Therefore, developing stretchable zinc-air batteries with stretchability and weavability will be highly attractive as a power unit for various flexible/wearable devices.The difficulty to develop super-stretchable zinc-air battery is that it must use strong alkaline electrolyte (always 6 m KOH) to achieve decent power density considering all zinc-air batteries with neutral electrolyte possess unacceptable low power output. [11,12] On the other hand, most super-stretchable hydrogels that are considered as an essential component of a stretchable energy storage device will lose their stretchability under such strong alkaline environment. Currently, a zincair battery is typically assembled using polyvinyl alcohol (PVA)-based electrolyte. [2,[13][14][15][16][17] However, the PVA-based electrolyte possesses very poor stretchability (even worse when alkaline electrolyte infiltrated), and meanwhile it shows limited ion-transport capability, resulting in poorly electrochemical performance and mechanical flexibility. [18][19][20][21] Although other hydrogels, such as polyacrylic acid (PAA), polyacrylamide (PAM), show strong water-retention capability and high stretchability, [22,23] unfortunately, they will lose their mechanical robustness, especially the stretchability, when they are incorporated with strong alkaline electrolyte. [24][25][26] Therefore, the absence of alkaline-tolerant hydrogel electrolyte with high stretchability and excellent ion transport capability is the key challenge to fabricate super-stretchable zinc-air battery and enhance its weavability. An alternative way to fabricate stretchable zinc-air battery (very limited stretchability with a maximum strain less than 10%) has been proposed, that is to use electron/ion-inactive stretchable substrate (e.g., rubber elastomer) or strain-accommodating engineering of device structure (e.g., fiber-shaped planar structure). [27][28][29] The problem is that the stretchable components are additional, and they are not involved in any chemical reactions. In some cases, Stretchable devices need elastic hydrogel electrolyte as an essential component, while most hydrogels will lose their stretchability after being incorporated with strong alkaline solution. This is why highly stretchable zinc-air batteries have never been reported so far. Herein, super-stretchable, flat-(800% stretchable) and fiber-shaped (500% stretchable) zinc-air batteries are first developed by designing an alkaline-tolerant dual-network hydrogel electrolyte. In the dualnetwork hydrogel electrolyte, sodium polyacrylate (PANa) chains contribute to the formation of soft domains and the carboxyl gr...

Hydrogen‐Free and Dendrite‐Free All‐Solid‐State Zn‐Ion Batteries

“…Metallic Zn is regarded as a promising anode material for energy storage system, due to its high theoretical capacity (820 mAh g −1 ), intrinsically safe nature and competitive cost. [ 1–7 ] Unfortunately, a deep‐seated issue in aqueous electrolyte Zn based batteries is that, due to more negative reduction potential of Zn than hydrogen (−0.762 V vs standard hydrogen electrode (SHE)), the Zn is thermodynamically unstable in aqueous system and the parasitic hydrogen evolution reaction (HER) is inevitable (although it can be very slow) in the widely used alkaline or mild‐acid aqueous electrolytes [ 8,9 ] (Figure S1, Supporting Information). While being very slow, during long‐term operation, it will eventually lead to the consumption of Zn and electrolyte, as well as battery swell with the generated hydrogen.…”

Achieving High‐Voltage and High‐Capacity Aqueous Rechargeable Zinc Ion Battery by Incorporating Two‐Species Redox Reaction

“…[52] So, a solid-state cable-type battery is constructed and its configuration is schematically illustrated in Figure 6a, including a spiral Zn anode, freestanding PAM with F77 skin electrolyte, and the CoFe(CN) 6 painted carbon nanotube (CNT) paper. [52] So, a solid-state cable-type battery is constructed and its configuration is schematically illustrated in Figure 6a, including a spiral Zn anode, freestanding PAM with F77 skin electrolyte, and the CoFe(CN) 6 painted carbon nanotube (CNT) paper.…”

Uniform Virus‐Like Co–N–Cs Electrocatalyst Derived from Prussian Blue Analog for Stretchable Fiber‐Shaped Zn–Air Batteries

“…Even though significant research has been carried out on flexible ZABs, their large‐scale commercialization is yet to be realized, especially for their stretchable and wearable versions. In this regard, there are two primary obstacles to be overcome, which are: 1) the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) involved in the air cathode during the discharging and charging processes, and 2) the stretchability of ZAB components, especially the solid‐state electrolyte, which suffers from an instability in strong alkaline solutions . Therefore, adequately addressing these two obstacles is of utmost importance for the realization of large‐scale commercialization of stretchable and wearable ZABs.…”

“…For the electrolyte, we synthesized a super‐stretchable dual‐network hydrogel PANa‐cellulose electrolyte with good alkaline‐tolerance. The cellulose and the MBAA‐assisted toughening, the hydrogen bond cross‐linking, and the carboxyl groups neutralized by hydroxyl, as well as the cellulose, which act as an alkaline stabilizer, contribute to good alkaline tolerance . By using the hydrogel electrolyte and integrating the virus‐like Co–N–Cs air cathode and a zinc spring anode, fiber‐shaped ZABs can be fabricated.…”