Intercalation of Mg2+ into electrodeposited Prussian Blue Analogue thin films from aqueous electrolytes

The Misconception of Mg2+ Insertion into Prussian Blue Analogue Structures from Aqueous Solution

“…Cycling in 1 M MgCl 2 was found to be sufficiently stable only for the K‐NiHCF, NiHCF and CuHCF materials, while for the K‐FeHCF and FeHCF structures a very fast capacity decay is observed during the first five cycles (Figure 2b). For the K‐NiHCF, NiHCF and CuHCF materials, the redox activity in Mg 2+ ‐containing solution is frequently ascribed to the (de)insertion of a doubly charged cation [13–15,18,19,24] . However, further study indicated that such an assignment is erroneous.…”

“…Aqueous Mg‐ion batteries [13–17] eliminate the problems of Mg anode passivation, instability, flammability and toxicity of an organic electrolyte, yet leave the question of the suitable cathodes and anodes demonstrating facile Mg 2+ diffusion open. Here, PBA‐based materials represent quite a natural choice of a cathode material for aqueous Mg‐ion batteries, as numerous reports have emphasized the high diffusion rates of divalent cations in PBA structures, as well as the excellent cycle life and energy efficiency of PBA cathodes in aqueous electrolytes [13–16,18–23] . The highly reversible cycling of PBA electrodes in divalent ion solutions was ascribed to the insertion of divalent cations such as magnesium, [13–15,18,19,24] calcium, [15] barium, [15] strontium [15] and zinc [20–22,25,26] into nickel, [13–15,19] copper, [20–22,24,25] zinc, [26] cobalt, [19] indium, [19] vanadium [19] and iron hexacyanoferrates [18] .…”

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

“…[ 37 ] first reported the Mg 2+ ion insertion in K 0.1 Cu [Fe(CN) 6 ] 0.7 ·3.6H 2 O, the research on PBAs as hosts for Mg 2+ ion was widely conducted. Especially, in recent years, PBA materials including K 0.86 Ni[Fe(CN) 6 ] 0.954 , [ 87 ] Na 1.4 Ni 1.3 Fe(CN) 6 , [ 133 ] Na 2 Co[Fe(CN) 6 ], [ 134 ] etc., have been investigated as cathodes in aqueous/non aqueous Mg‐ion batteries. For instance, Marzak et al.…”

“…For instance, Marzak et al. [ 134 ] systematically investigated the intercalation of Mg 2+ ion into the electrodeposited Na 2 Ni[Fe(CN) 6 ], Na 2 Co[Fe(CN) 6 ], Na 2 VO x [Fe(CN) 6 ], and NaIn[Fe(CN) 6 ] cathodes, and found that the NaIn[Fe(CN) 6 ] showed better stability upon repeated Mg 2+ storage comparing with the other three systems. The authors also revealed that not only the solvation energy of the carrier ions, but also the electronic structure of the electrode materials depending on the nature of the transition metals determined the Mg‐ion insertion electrochemistry in the PBA cathodes.…”

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

“…We then envisage the potential of cooperative strategy in practical application, by assembling the full cells with Prussian blue analogs (PBAs), also called as HCFs, as cathode materials. Although PBAs have been well known for the capability of magnesium storage, the prototype cells with PBAs cathode and Mg metal anode have never been reported elsewhere, possibly due to the limitation in the voltage window of the state-of-the-art electrolytes [44][45][46]. The morphologies and phase characterizations of NiHCF and MnHCF are displayed in Fig.…”