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.

No 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...

Prussian blue analogue (PBA)-type metal hexacyanoferrates are considered as significant cathodes for zinc batteries (ZBs). However, these PBA-type cathodes, such as cyanogroup iron hexacyanoferrate (FeHCF), suffer from ephemeral lifespan (≤1000 cycles), and inferior rate capability (1 A g −1 ). This is because the redox active sites of multivalent iron (Fe(III/II)) can only be very limited activated and thus utilized. This is attributed to the spatial resistance caused by the compact cooperation interaction between Fe and the surrounded cyanogroup, and the inferior conductivity. Here, it is found that high-voltage scanning can effectively activate the C-coordinated Fe in FeHCF cathode in ZBs. Thanks to this activation, the Zn-FeHCF hybrid-ion battery achieves a record-breaking cycling performance of 5000 (82% capacity retention) and 10 000 cycles (73% capacity retention), respectively, together with a superior rate capability of maintaining 53.2% capacity at superhigh current density of 8 A g −1 (≈97 C). The reversible distortion and recovery of the crystalline structure caused by the (de)insertion of zinc and lithium ions is revealed. It is believed that this work represents a substantial advance on PBA electrode materials and may essentially promote application of PBA materials. Zinc BatteriesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.Zinc batteries (ZBs) established on the storage of divalent zinc ion in cathodic hosts are being intensively studied because of the high energy density of metallic zinc anode and the intrinsic safety performance. [1][2][3][4] The appropriate plating/stripping voltage (≈-0.76 V vs SHE) of zinc makes it electrochemically stable in water, which enables ZBs to avoid the employment of toxic organic electrolytes and complex assembly processes in glovebox compared with the lithium and sodium counterparts. [5][6][7] This advantage of zinc anode enables researchers to pay more attention to develop cathodic host materials. [8][9][10][11][12] Among these materials, MnO 2based cathodes possess high specific capacity based on the single electron transfer reaction of Mn(IV)/Mn(III), while the

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.