Towards High‐Voltage Aqueous Metal‐Ion Batteries Beyond 1.5 V: The Zinc/Zinc Hexacyanoferrate System
Towards High‐Voltage Aqueous Metal‐Ion Batteries Beyond 1.5 V: The Zinc/Zinc Hexacyanoferrate System
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DOI：
10.1002/aenm.201400930
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发表时间：
2015
影响因子：
27.8
通讯作者：
Leyuan Zhang;Liang Chen;Xufeng Zhou;Zhaoping Liu
中科院分区：
文献类型：
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作者：
Leyuan Zhang;Liang Chen;Xufeng Zhou;Zhaoping Liu
许多研究集中在立方mehcf作为Li +， Na +和K +等碱性阳离子的宿主。最近，崔的研究小组发现六氰高铁酸镍也可以作为二价碱土阳离子的宿主：mg2 +， ca2 +， sr2 +和ba2 +。六氰高铁酸锌（ZnHCFs）具有不同于立方甲基高铁酸锌的开放框架结构。对于如图a所示的菱面体ZnHCFs， fec6八面体通过CN配体与zn4四面体连接，形成具有大开放位点的多孔三维框架，其中碱性阳离子a （a = Na +， K +和Cs +）和水分子位于其中。这样的框架使znhcf具有作为各种用途的插入主机的可能性。ZnHCFs作为Na +插层化合物的可行性已经被Chio和同事证实。[27]然而，据我们所知，没有报道试图利用ZnHCFs作为二价阳离子（如zn2 +）的插层宿主。在这里，我们展示了ZnHCFs作为水性锌电池正极材料的首次使用。当与锌阳极结合时，六氰高铁酸锌产生约1.7 V的平均工作电压，这是水溶液锌离子电池的最高记录，并且基于活性电极材料的总质量，它还提供了100 Wh Kg−1的比能量密度。采用本课组开发的高温共沉淀法合成了两种具有菱形结构的六氰高铁酸锌(k2zn3 [Fe(CN) 6] 2， KZnHCF和zn3 [Fe(CN) 6] 2, ZnHCF)（见实验部分）。为了确认它们的晶体结构，进行了x射线衍射（XRD）分析（图1b）。KZnHCF和ZnHCF的XRD峰分别与k2 zn2 [Fe(CN) 6] 2 (h2o) 9 （JCPDS # 33-1061）和z3 [Fe(CN) 6] 2 （JCPDS # 38-0688）有良好的关联，表明两种化合物在同一组R3 C中结晶，没有任何杂质。从扫描电镜（SEM）图像可以看出，KZnHCF颗粒的粒径分布较窄，平均粒径为200 nm，而ZnHCF颗粒的粒径分布较宽，从200 nm到几μm不等。电感耦合等离子体发射光谱（ICP-OES）测定了两种样品的摩尔K:Zn:Fe比值，KZnHCF为0.94:1.44:1，ZnHCF为0.08:1.44:1。这些比率也非常接近名义比率（1:1.5:1和0:1.5:1），并且与文献中的数据非常吻合。b[28]
Many studies focus on cubic MeHCFs as hosts for alkaline cations such as Li + , Na + and K + . Recently, Cui's group found that nickel hexacyanoferrates can also act as hosts for divalent alkaline earth cations: Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ . [ 26 ] Zinc hexacyanoferrates (ZnHCFs) exhibit different open-framework structure as compared to cubic MeHCFs. For rhombohedral ZnHCFs as shown in Figure 1 a, the FeC 6 octahedra are linked to ZnN 4 tetrahedra via CN ligands to form a porous 3D framework with large open sites in which alkaline cations A (A = Na + , K + and Cs + ) and water molecules are located. Such a framework endows ZnHCFs with the possibility of behaving as intercalation hosts for various cations. The feasibility of ZnHCFs as Na + -intercalation compounds has been demonstrated by Chio and co-workers. [ 27 ] However to the best of our knowledge, no attempts to utilize ZnHCFs as intercalation hosts for divalent cations such as Zn 2+ have been reported. Here we demonstrate the fi rst use of ZnHCFs as cathode materials for aqueous zincion batteries. When combined with a zinc anode, zinc hexacyanoferrate yields an average operation voltage of ca. 1.7 V, which is the highest recorded for aqueous zinc-ion batteries and it also delivers a specifi c energy density of 100 Wh Kg −1 based on the total mass of the active electrode materials. Two zinc hexacyanoferrates (K 2 Zn 3 [Fe(CN) 6 ] 2 , KZnHCF and Zn 3 [Fe(CN) 6 ] 2 , ZnHCF) with the rhombohedral structure were synthesized using high temperature co-precipitation method developed in our group (see Experimental Section). To confi rm their crystal structures, X-ray diffraction (XRD) analyses are conducted (Figure 1 b). The XRD peaks of KZnHCF and ZnHCF are well-indexed to K 2 Zn 3 [Fe(CN) 6 ] 2 (H 2 O) 9 (JCPDS # 33–1061) and Zn 3 [Fe(CN) 6 ] 2 (JCPDS # 38–0688), respectively, which indicates that two compounds crystalize in the same group of R3 C without any impurities. From their scanning electron microscopy (SEM) images, it can be seen that KZnHCF particles have a narrow size distribution with an average size of 200 nm, while ZnHCF particles exhibit a wider size distribution ranging from 200 nm to several μm. The molar K:Zn:Fe ratios of two samples determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) are found to be 0.94:1.44:1 for KZnHCF and 0.08:1.44:1 for ZnHCF, respectively. These ratios are also very close to the nominal ones (1:1.5:1 and 0:1.5:1), and agree well with the data in the literature. [ 28 ]