title: Co-intercalation of Mg(2+) and Na(+) in Na(0.69)Fe2(CN)6 as a High-Voltage Cathode for Magnesium Batteries.
abstract: Thanks to the advantages of low cost and good safety, magnesium metal batteries get the limelight as substituent for lithium ion batteries. However, the energy density of state-of-the-art magnesium batteries is not high enough because of their low operating potential; thus, it is necessary to improve the energy density by developing new high-voltage cathode materials. In this study, nanosized Berlin green Fe2(CN)6 and Prussian blue Na(0.69)Fe2(CN)6 are compared as high-voltage cathode materials for magnesium batteries. Interestingly, while Mg(2+) ions cannot be intercalated in Fe2(CN)6, Na(0.69)Fe2(CN)6 shows reversible intercalation and deintercalation of Mg(2+) ions, although they have the same crystal structure except for the presence of Na(+) ions. This phenomenon is attributed to the fact that Mg(2+) ions are more stable in Na(+)-containing Na(0.69)Fe2(CN)6 than in Na(+)-free Fe2(CN)6, indicating Na(+) ions in Na(0.69)Fe2(CN)6 plays a crucial role in stabilizing Mg(2+) ions. Na(0.69)Fe2(CN)6 delivers reversible capacity of approximately 70 mA h g(-1) at 3.0 V vs Mg/Mg(2+) and shows stable cycle performance over 35 cycles. Therefore, Prussian blue analogues are promising structures for high-voltage cathode materials in Mg batteries. Furthermore, this co-intercalation effect suggests new avenues for the development of cathode materials in hybrid magnesium batteries that use both Mg(2+) and Na(+) ions as charge carriers.
authors.affiliation: School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University , 1, Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea.
authors.forename: Dong-Min
authors.initials: DM
authors.lastname: Kim
authors.affiliation: School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University , 1, Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea.
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Kim
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50, UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, South Korea.
authors.forename: Durairaj
authors.initials: D
authors.lastname: Arumugam
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50, UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, South Korea.
authors.forename: Sang Won
authors.initials: SW
authors.lastname: Woo
authors.affiliation: Advanced Batteries Research Center, Korea Electronics Technology Institute (KETI) , 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, South Korea.
authors.forename: Yong Nam
authors.initials: YN
authors.lastname: Jo
authors.affiliation: Advanced Batteries Research Center, Korea Electronics Technology Institute (KETI) , 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, South Korea.
authors.forename: Min-Sik
authors.initials: MS
authors.lastname: Park
authors.affiliation: Advanced Batteries Research Center, Korea Electronics Technology Institute (KETI) , 25, Saenari-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13509, South Korea.
authors.forename: Young-Jun
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50, UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, South Korea.
authors.forename: Nam-Soon
authors.initials: NS
authors.lastname: Choi
authors.affiliation: School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University , 1, Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea.
authors.forename: Kyu Tae
authors.initials: KT
authors.lastname: Lee
keywords: Prussian blue analogue; cathode; electrochemical performance; electrochemistry; magnesium battery