Aqueous zinc-ion batteries (ZIBs) have emerged as the most promising alternative energy storage system, but the development of a suitable cathode and the issues of Zn anodes have remained challenging. Herein, an effective strategy of high-capacity layered Mg0.1V2O5·H2O (MgVO) nanobelts together with a concentrated 3 M Zn­(CF3SO3)2 polyacrylamide gel electrolyte was proposed to achieve a durable and practical ZIB system. By adopting the designed concentrated gel electrolyte which not only inherits the high-voltage window and wide operating temperature of the concentrated electrolyte but also addresses the Zn dendrite formation problem, the prepared cathode exhibits an ultrahigh capacity of 470 mAh g–1 and a high rate capability of 345 mAh g–1 at 5.0 A g–1, and the assembled quasi-solid-state ZIBs achieve 95% capacity retention over 3000 cycles as well as a wide operating temperature from −30 to 80 °C, demonstrating a promising prospect for large-scale energy storage. In situ X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) investigations also demonstrate a complex reaction mechanism for this cathode involving the (de)­insertion of Zn2+, H+, and water molecules during cycling. The water molecules will reinsert into the interlayer and act as “pillars” to stabilize the host structure when Zn2+ is fully extracted.

and cycle life. However, LIBs suffer from issues including flammability, toxicity, cost, and scarcity of Li metal. [4,5] Rechargeable batteries based on an aqueous electrolyte and earth-abundant elements are regarded as a more sustainable alternative to the current LIBs. Aqueous metal-ion batteries are inherently safe, eco-friendly, cheap, and capable of operating at large currents. [6][7][8] Aqueous zinc-ion battery (ZIB) is one of the types and offers a high theoretical capacity (820 mAh g −1 ) and a low electrochemical potential of metallic Zinc (−0.76 V vs standard hydrogen electrode), [9][10][11][12][13] but the development of highly stable cathode for ZIBs is still challenging.Prussian blue analogues (PBAs) with a formula of A x M[Fe(CN) 6 ] y •nH 2 O (0 < x < 2, 0 < y ≤ 1, A = alkaline metal, M = transition metal) have been considered as promising cathode materials for aqueous alkali metalion batteries. The capacity of PBAs can reach more than 120 mAh g −1 [14][15][16][17] and the stability is excellent, due to the presence of two redox couples and robust 3D open-framework structures allowing the insertion of a variety of alkaline ions without distortion. [18][19][20] However, PBAs only provide a relatively low specific capacity for Zn 2+ cations (typically less than 80 mAh g −1 ), and intercalation of Zn 2+ can lead to uncontrolled phase transition and consequent performance degrading. [9,21,22] Liu et al. first proposed a ZIB using a rhombohedral Zn 3 [Fe(CN) 6 ] 2 (ZnHCF) cathode, which exhibited a low capacity of 65.4 mAh g −1 with 76% capacity retention after 100 cycles. [23] A cubic structure PBA (CuHCF) was synthesized for Zn 2+ storage, and this cathode completed 100 cycles with a capacity of 56 mAh g −1 . [24] Mantia et al. suggested that the capacity decay in CuHCF can be attributed to a phase transition to a second phase which is electrochemically less active. [25,26] To reduce the influence of phase transition resulted from Zn 2+ insertion, researchers employed electrolytes with a low or even zero Zn 2+ concentration to make NiHCF//Zn, [27] CuHCF//Zn, [28] and NaFe-PB//Zn [29] hybrid-ion batteries. Nonetheless, the storage capacities of Zn 2+ in these cathodes were still low despite that the cycle life was improved by increasing the scanning voltage. [30] In this work, we introduce a high voltage aqueous PBA-Zn hybrid-ion battery with KMnHCF (K 1.6 Mn[Fe(CN) 6 ] 0.94 •0.63H 2 O) cathode, zinc foil anode, and 30 m KFSI + 1 m Zn(CF 3 SO 3 ) 2 Prussian blue analogues (PBAs), featuring an open framework for accommodating large ions and tunable valence states, have garnered wide interest in the context of aqueous zinc-ion batteries (ZIBs). However, PBAs in ZIBs currently still suffer from low capacity and poor cycling stability due to structural instability. Here a K 2 MnFe(CN) 6 cathode achieving a very stable capacity of 100 mAh g −1 is reported in a ZIB charged/discharged to 400 cycles. Interestingly, such a stable capacity is attributed to the fact that the K 2 MnFe(CN) 6 cathode is gradually t...

Aqueous zinc hybrid capacitors are receiving intensive scientific interest for their merits of both capacitors and batteries in achieving safety, high power and energy density as well as long cycle...

To meet the urgent demand for energy storage systems, K-ion batteries (KIBs), with low cost and comparable electrochemical performance, have become one of the most promising alternatives to Li-ion batteries.

Aqueous zinc‐ion batteries (ZIBs) have been extensively studied due to their inherent safety and high energy density for large‐scale energy storage. However, the practical application is significantly limited by the growing Zn dendrites on metallic Zn anode during cycling. Herein, an environmental biomolecular electrolyte additive, fibroin (FI), is proposed to guide the homogeneous Zn deposition and stabilize Zn anode. This work demonstrates that the FI molecules with abundant electron‐rich groups (NH, OH, and CO) can anchor on Zn anode surface to provide more nucleation sites and suppress the side reactions, and the strong interaction with water molecules can simultaneously regulate the Zn2+ coordination environment facilitating the uniform deposition of Zn. As a consequence, only 0.5 wt% FI additive enables a highly reversible Zn plating/stripping over 4000 h at 1 mA cm−2, indicating a sufficient advance in performance over state‐of‐the‐art Zn anodes. Furthermore, when applied to a full battery (NaVO/Zn), the cell exhibits excellent capacity retention of 98.4% after 1000 cycles as well as high Coulombic efficiency of 99%, whereas the cell only operates for 68 cycles without FI additive. This work offers a non‐toxic, low‐cost, effective additive strategy to solve dendrites problems and achieve long‐life and high‐performance rechargeable aqueous ZIBs.