The dendritic issue in aqueous zinc‐ion batteries (ZBs) using neutral/mild electrolytes has remained an intensive controversy for a long time: some researchers assert that dendrites severely exist while others claim great cycling stability without any protection. This issue is clarified by investigating charge/discharge‐condition‐dependent formation of Zn dendrites. Lifespan degradation (120 to 1.2 h) and voltage hysteresis deterioration (134 to 380 mV) are observed with increased current densities due to the formation of Zn dendrites (edge size: 0.69–4.37 µm). In addition, the capacity is also found to remarkably affect the appearance of the dendrites as well. Therefore, at small current densities or loading mass, Zn dendrites might not be an issue, while the large conditions may rapidly ruin batteries. Based on this discovery, a first‐in‐class electrohealing methodology is developed to eliminate already‐formed dendrites, generating extremely prolonged lifespans by 410% at 7.5 mA cm–2 and 516% at 10 mA cm–2. Morphological analysis reveals that vertically aligned Zn dendrites with sharp tips gradually become passivated and finally generate a smooth surface. This developed electrohealing strategy may promote research on metal dendrites in various batteries evolving from passive prevention to active elimination, rescuing in‐service batteries in situ to achieve elongated lifetime.

While α-MnO2 has been intensively studied for zinc batteries, δ-MnO2 is usually believed to be more suitable for ion storage with its layered structure. Unfortunately, the extraordinary Zn ion storage performance that δ-MnO2 should exhibit has not yet been achieved due to the frustrating structural degradation during charge–discharge cycles. Here, we found the Na ion and water molecules pre-intercalation can effectively activate stable Zn ion storage of δ-MnO2. Our results reveal that the resulted Zn//pre-intercalated δ-MnO2 battery delivers an extraordinarily high-rate performance, with a high capacity of 278 mAh g–1 at 1 C and up to 20 C, and a high capacity of 106 mAh g–1 can still be measured. The capacity retention is as high as 98% after charged–discharged up to 10,000 cycles benefiting from smooth Zn ion diffusion in the pre-intercalated structure. Further in situ /ex situ characterization confirms the superfast Zn ion diffusion in the pre-intercalated structure at room temperature. In addition, utilizing the well-chosen electrode material and modified polyurethane shell, we fabricated a quasi-solid-state healable Zn-δ-MnO2, which can be self-healed after multiple catastrophic damages, emphasizing the advanced features of aqueous Zn ion battery for wearable applications.

In this paper, we propose the design of a family of hydrogel electrolytes that featuring freezing resistance, flexibility, safety, superior ionic conductivity and long-term stability to realize anti-freezing flexible aqueous batteries.

Emerging research toward next-generation flexible and wearable electronics has stimulated the efforts to build highly wearable, durable, and deformable energy devices with excellent electrochemical performances. Here, we develop a high-performance, waterproof, tailorable, and stretchable yarn zinc ion battery (ZIB) using double-helix yarn electrodes and a cross-linked polyacrylamide (PAM) electrolyte. Due to the high ionic conductivity of the PAM electrolyte and helix structured electrodes, the yarn ZIB delivers a high specific capacity and volumetric energy density (302.1 mAh g and 53.8 mWh cm, respectively) as well as excellent cycling stability (98.5% capacity retention after 500 cycles). More importantly, the quasi-solid-state yarn ZIB also demonstrates superior knittability, good stretchability (up to 300% strain), and superior waterproof capability (high capacity retention of 96.5% after 12 h underwater operation). In addition, the long yarn ZIB can be tailored into short ones, and each part still functions well. Owing to its weavable and tailorable nature, a 1.1 m long yarn ZIB was cut into eight parts and woven into a textile that was used to power a long flexible belt embedded with 100 LEDs and a 100 cm flexible electroluminescent panel.

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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...

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2 is maintained during the charging-discharging for up to 10 000 cycles. For wearable applications, the flexible solid-state batteries can be used as reliable and portable sources to power different wearable electronics such as a commercial smart watch, electroluminescent panel, and color electroluminescence line, which shows their large potentials for use in next-generation flexible and wearable battery technologies.