Activating C‐Coordinated Iron of Iron Hexacyanoferrate for Zn Hybrid‐Ion Batteries with 10 000‐Cycle Lifespan and Superior Rate Capability

Abstract

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

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.…”

Initiating Hexagonal MoO3 for Superb‐Stable and Fast NH4+ Storage Based on Hydrogen Bond Chemistry

“…After investigation of the electrochemical behavior and mechanism of NH 4 + storage in h‐MoO 3 , we further evaluated its performance in a full battery configuration by pairing with CuFe PBA cathode due to the stable performance of PBA. [ 1,31,32 ] All the detailed characterizations upon cathode material, including XRD, SEM, and TEM results, were demonstrated in Figure S10 in the Supporting Information. The CV analysis of the CuFe PBA cathode exhibited the reaction potential in Figure a, while the curves maintained its shape even at scan rate of 50 mV s −1 with outstanding stability for fast NH 4 + storage.…”

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

“…Various cathode materials have been developed to navigate these challenges. [17] Recently, hexacyanometallates with a typical formula of A x M′[M″(CN) 6 ] y ⋅nH 2 O (simply denoted as M′/M″ PBA) are investigated as cathode active materials for aqueous batteries including Li-, Na-, Mg-, Ca-, and Zn-ion batteries, where the A …”