| 1. |
- Brant, William, et al.
(författare)
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Selective Control of Composition in Prussian White for Enhanced Material Properties
- 2019
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 31:18, s. 7203-7211
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Tidskriftsartikel (refereegranskat)abstract
- Sodium-ion batteries based on Prussian blue analogues (PBAs) are ideal for large-scale energy storage applications due to the ability to meet the huge volumes and low costs required. For Na2-xFe[Fe(CN)(6)](1-y)center dot zH(2)O, realizing its commercial potential means fine control of the concentration of sodium, Fe(CN)(6) vacancies, and water content. To date, there is a huge variation in the literature of composition leading to variable electrochemical performance. In this work, we break down the synthesis of PBAs into three steps for controlling the sodium, vacancy, and water content via an inexpensive, scalable synthesis method. We produce rhombohedral Prussian white Na1.88(5)Fe[Fe-(CN)(6)]center dot 0.18(9)H2O with an initial capacity of 158 mAh/g retaining 90% capacity after 50 cycles. Subsequent characterization revealed that the increased polarization on the 3 V plateau is coincident with a phase transition and reduced utilization of the high-spin Fe(III)/Fe(II) redox couple. This reveals a clear target for subsequent improvements of the material to boost long-term cycling stability. These results will be of great interest for the myriad of applications of PBAs, such as catalysis, magnetism, electrochromics, and gas sorption.
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| 2. |
- Mink, Janos, et al.
(författare)
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Vibrational properties and bonding analysis of copper hexacyanoferrate complexes in solid state
- 2019
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Ingår i: Applied spectroscopy reviews (Softcover ed.). - : Informa UK Limited. - 0570-4928 .- 1520-569X. ; 54:5, s. 369-424
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Forskningsöversikt (refereegranskat)abstract
- Vibrational spectroscopic study of crystalline copper hexacyanoferrate complexes of composition K4Cu6II [Fe-II(CN)(6)](4)nH(2)O (1) and Cu-6(II)[Fe-III(CN)(6)](4)nH(2)O (2) with -Cu-N equivalent to C-Fe- bridging structures have been performed. The cubic Fmm (O-h(5)) unit-cells contain ideally 4 Fe and 4 Cu ions which were calculated by periodic density functional theory (DFT) (using the Gaussian09 C.01 software package) for ideal lattice compositions of K8Cu4II[Fe-II(CN)(6)](4) (1a), K4Cu4II[Fe-III(CN)(6)](4) (2a) and with lattice water molecules KCu4II[Fe-III(CN)(6)](3)6H(2)O (3a). Systematically, non-linear Cu-N equivalent to C structure was fitted with Cu-N equivalent to C bond angles about 155 degrees for complexes 1a, 2a, and 3a. Practically, all optically active internal modes of Fe(CN6)(n-) moieties resulted from factor group analysis as 4A(1g) + 6E(g) + 4F(1g) + 10F(1u) were experimentally observed and assigned. Some low-frequency translatory and librational modes were also interpreted. Vibrational bands were assigned to cis- and trans-Cu(NC)(4)(OH2) complexes which are formed in the lattice holes of both complexes. Vibrational spectra and force constants of a great number of transition metal hexacyano complexes of compositions K-4[M-II(CN)(6)], K-3[M-III(CN)(6)], CsLi2[M-III(CN)(6)] and Prussian blue analogues have been reexamined and recalculated. Internal and external modes of 6 different lattice water species (coordinated, hydrogen bonded, or zeolitic type) have been interpreted for complex 2 using results of periodic DFT calculation of model complex 3a.
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| 3. |
- Renman, Viktor, et al.
(författare)
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Manganese Hexacyanomanganate as a Positive Electrode for Nonaqueous Li-, Na-, and K-Ion Batteries
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 123:36, s. 22040-22049
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Tidskriftsartikel (refereegranskat)abstract
- K2Mn[Mn(CN)(6)] is synthesized, characterized, and evaluated as possible positive electrode material in nonaqueous Li-, Na-, and K-ion batteries. This compound belongs to the rich and versatile family of hexacyanometallates displaying distinctive structural properties, which makes it interesting for ion insertion purposes. It can be viewed as a perovskite-like compound in which CN-bridged Mn(CN)(6) octahedra form an open framework structure with sufficiently large diffusion channels able to accommodate a variety of insertion cations. By means of galvanostatic cycling and cyclic voltammetry tests in nonaqueous alkali metal half-cells, it is demonstrated that this material is able to reversibly host Li+, Na+, and K+ ions via electrochemical insertion/deinsertion within a wide voltage range. The general electrochemical features are similar for all of these three ion insertion chemistries. An in operando X-ray diffraction investigation indicates that the original monoclinic structure is transformed into a cubic one during charging (i.e., removal of cations from the host framework) and that such a process is reversible upon subsequent cell discharge and cation reuptake.
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