Zn²⁺ Induced Phase Transformation of K₂MnFe(CN)₆ Boosts Highly Stable Zinc‐Ion Storage

Abstract

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...

Multi‐Component Crosslinked Hydrogel Electrolyte toward Dendrite‐Free Aqueous Zn Ion Batteries with High Temperature Adaptability

“…h) Ragone plots of Zn 3 V 2 O 8 //Zn/PDZ-H full cell compared with previously reported Zn ion cell. [29,30,32,33,35,38,39,[41][42][43] www.afm-journal.de www.advancedsciencenews.com…”

“…[31] Ragone plot in Figure 4h exhibits that the Zn 3 V 2 O 8 //Zn/PDZ-H full cell delivers a high energy density of 412.3 Wh Kg −1 at a power density of 206.1 W kg −1 , which has significantly exceeded the previously reported aqueous ZIBs (Table S1, Supporting Information). [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]…”

Synthesis of Nitrogen‐Doped KMn8O16 with Oxygen Vacancy for Stable Zinc‐Ion Batteries

“…A significant challenge remains to construct highly reversible cathode materials with good electrochemical properties. [9][10][11][12] The current cathode materials for AZIBs mainly include manganese-based materials, [13][14][15][16] vanadium-based materials, [17][18][19][20][21] Prussian blue and its analogs, [22][23] and organic compounds. [24][25][26] Among them, MnO 2 characterized by high theoretical capacity (308 mAh g −1 , contributed capacity of single electron transfer), cost-effectiveness, high natural abundance, and environmental friendliness has attracted extensive scientific attention.…”

ZnV2O4‐Textured Carbon Composite Contacting a ZIF‐8 MOF Layer for a High Performance Non‐Aqueous Zinc‐Ion Battery

“…[1][2][3] The cathode in a ZIB is required to have an open structure enabling easy intercalation and deintercalation of Zn(II) ions, during discharging and charging processes, to maximize energy storage via diffusion and Faradaic mechanisms. A variety of crystalline transition metal oxides [6][7][8][9][10] and Prussian blue analogues [11][12][13][14] endowed with channel dimensions in excess of 1.5 Å [which is approximately twice the ionic radius of Zn(II) ion] have been deployed as cathodes in ZIBs.…”