Highly Crystallized Na2CoFe(CN)6 with Suppressed Lattice Defects ...

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Highly Crystallized Na2CoFe(CN)6 with Suppressed Lattice Defects as Superior Cathode Material for Sodium-ion Batteries Xianyong Wu†, Chenghao Wu†, Congxiao Wei†, Ling Hu†, Jiangfeng Qian,* † Yuliang Cao†, Xinping Ai†, Jiulin Wang ‡, Hanxi Yang*†

† ‡

College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072, China.

School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China. * Address correspondence to [email protected]; [email protected] ;

S-1

1. Chemical compositions of these two Na2CoFe(CN)6 samples Table S1. Elemental contents of these Na2CoFe(CN)6 materials Na

Co

Fe

C

N

H

As-prepared Na2CoFe(CN)6

11.9%

16.5%

15.6%

20.0%

23.4%

1.3%

Control Na2CoFe(CN)6

9.0%

17.5%

14.6%

18.8%

22.0%

2.0%

In general, Prussian blue compounds have a theoretical chemical formula of Na2MII[FeII(CN)6] with a stoichiometric Na/M/Fe ratio = 2:1:1. However, conventional synthesis of Prussian blue is based on a rapid precipitation reaction of M2+ cations and [Fe(CN)6]4- anions in aqueous solution, leading to the formation of Fe(CN)6 vacancies coordinated with water molecules in the lattice. Moreover, the Na content would be simultaneously decreased due to charge balance. Hence, the actual chemical composition of Prussian blue can be expressed as Na2-xM[Fe(CN)6]1-y·□y·zH2O (□ stands for the Fe(CN)6 vacancies; 0<x