Crystallite Size Control of Prussian White Analogues for Nonaqueous

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Crystallite Size Control of Prussian White Analogues for Non-Aqueous Potassium-Ion Batteries Guang He, and Linda F. Nazar ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.7b00179 • Publication Date (Web): 04 Apr 2017 Downloaded from http://pubs.acs.org on April 7, 2017

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ACS Energy Letters

Crystallite Size Control of Prussian White Analogues for Non-Aqueous Potassium-Ion Batteries Guang He† and Linda F. Nazar* Department of Chemistry and the Waterloo Institute of Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada †

Currently at: Institute for New Energy Materials & Low-Carbon Technologies, Tianjin University of Technology,

China

Abstract Non-aqueous potassium-ion batteries have emerged as possible low cost alternatives to Liion batteries for large-scale energy storage, owing to their ability to use graphitic carbon as the negative electrode. Positive electrode materials remain a challenge. Here, we report control of the crystal dimensions of the Prussian white hexacyanoferrate (HCF), K1.7Fe[Fe(CN)6]0.9, using solution chemistry to obtain either nano, sub-micron or micron crystallites. We observe a very strong effect of crystallite size on electrochemical behavior. The optimal cathode material comprised of 20 nm crystallites delivers a close-to-theoretical reversible capacity of 140 mAh g-1 with two well-defined plateaus at 4.0 and 3.2 V vs. K/K+ on discharge. Slightly inferior electrochemical behavior is observed for crystallites up to ~ 160 - 200 nm in diameter, but unlike

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the analogous Na HCFs, micron-sized crystals show very limited capacity. For the nano-sized crystallites, however, the energy density of ~ 500 Wh/kg is comparable to the best Na HCF cathode materials. At a relatively high current density of 100 mA g-1, half-cells cycled with EC/DEC and 5% FEC demonstrate an initial discharge capacity of 120 mAh g-1 with a capacity retention of 85% after 100 cycles, and 65% after 300 cycles.

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Much interest in alternatives to lithium-ion batteries has emerged recently, focused on potentially lower cost systems based on alkali and alkaline earth-ion batteries based on Na+, K+, Mg2+ and Zn2+. Much of the work has concerned sodium-ion batteries (NIBs) which exhibit advantages such as the low-cost of sodium-based electrodes and electrolyte salts, and good mobility of Na+ in solid state lattices. 1 - 7 While potassium-ion batteries (KIBs) have been actively investigated with aqueous electrolytes, however,8,9,10 reports of potassium intercalation batteries utilizing organic electrolytes are still rare. This is due to the low capacities and poor K+ion mobility of many candidate positive electrodes. New motivation for studying such materials arises from recent exciting advances at the negative electrode. In the last two years, highly reversible potassium (de)intercalation in graphite electrodes was achieved in non-aqueous electrochemical cells.11,12,13 This is in sharp contrast to sodium ions, which do not intercalate into graphitic carbon. Discharge results in the product KC8, corresponding to a capacity on the order of 300 mAh g-1 below 0.25 V vs. K/K+, showing that the practical aspects of LIBs could potentially be extended to KIBs. Hard carbons are also suitable candidates for low-potential K insertion. 14 KIBs have a further advantage because the K/K+ couple has a lower standard potential compared to Na/Na+ (SHE -2.94 V vs. -2.71 V), which can significantly offset the lower gravimetric capacity of the heavier alkali ion. Inspired by the above, a few studies on cathodes for non-aqueous KIBs have rapidly emerged. Ji et al. reported reversible capacities of 130-200 mAh g-1 with both 3,4,9,10-perylenetetracarboxylicacid–dianhydride (PTCDA) and poly(anthraquinonyl sulfide) (PAQS) between 3.5 and 1.5 V vs. K/K+.15,16 The overall energy density is < 250 Wh kg-1 for either cathode material. Passerini et al. studied the layered oxide cathode K0.3MnO2, which exhibited a discharge capacity of < 70 mAh g-1 in a similar window of 1.5-3.5 V vs. K/K+, and complex

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multiple discharge steps. 17

Other electrode materials include KTi2(PO4)3 that exhibits a

reversible capacity of 80 mAh g-1 with a low potential of ~1.7 V vs. K/K+.18 The above work proves reversible insertion/extraction of K-ions is possible in different frameworks. Prussian blue analogues (also called hexacyanoferrates or HCFs) have attracted tremendous interest as hosts for large alkali ions such as Na+ and K+. Hexacyanoferrate cathodes such as NaxMFe(CN)6⋅yH2O (M=Fe, Mn, Co and Ni) cathodes have been reported for non-aqueous NIBs, 19-27 and an interesting dual ion configuration achieved with a K-Na liquid alloy anode showed promising results.28 Potassium HCF analogues, however, have been mostly utilized for aqueous batteries.18,29,30,31 The first work on a non-aqueous potassium-based HCF cathode was published in 2004 by Eftekhari et al., 32 who studied potassium intercalation in a KFeFe(CN)6 thin film-electrode. Surprisingly, this work was not followed up upon until extremely recently. During the course of finishing this manuscript, preliminary work has just appeared on K-batteries based on HCF materials. Zhang et al. reported on a vacancy-ridden, hydrated HCF cathode with a very low potassium content ( K0.22Fe[Fe(CN)6]0.805□0.195•4H2O) that requires pre-potassiation;33 the full cell exhibited a capacity of 70 mAhg-1 with very low initial coulombic efficiency that increased to 90% over cycling. Even more recently, it was communicated that two manganese HCFs – K1.9Mn[Fe(CN)6]0.92•0.75H2O and K1.7Mn[Fe(CN)6]0.9•1.1 H2O – exhibited excellent reversible capacities, after initial activation cycling of about 100 mAh g-1 vs a Na-K alloy in KClO4/PC electrolyte at a 1C rate with an average potential of 3.6V. 34 In a full cell (vs a graphitic anode) K1.75Mn[Fe(CN)6]0.93•0.16H2O has been reported to deliver a discharge capacity of 60 mAh g-1 over 60 cycles.35 A communication that surveys the electrochemical behavior of fully hydrated HCF materials with approximate compositions K1.5M[Fe(CN)6]0.92•nH2O (M = Mn, Fe, Ni, Cu; n ≈ 2 - 3) shows that these Prussian white HCFs exhibit very different cycling

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performance as a function of M.36 The difference was tentatively attributed to many factors such as water content, crystal defects and crystal integrity. The above materials were obtained by simple precipitation of particles, either from aqueous chlorides; from KCl solutions; or by a Na+-ion assisted method. Herein, we report for the first time the crystallization of K1.69Fe[Fe(CN)6]0.90•0.4 H2O by a novel citrate chelation route which provides excellent control of crystallize size and morphology. The factors that dictate good cell performance in non-aqueous KIBs were evaluated to gain insight on the correlation between particle size and electrochemical behavior. We find that KHCFs exhibit inferior electrochemical performance to their sodium NaHCFs with a similar crystallite size; nonetheless, a high energy density of 500 Wh kg-1 was obtained with an electrode comprised of HCF nanocrystallites. Long-term cycling was realized with a capacity retention of 65% over 300 cycles, with 98% coulombic efficiency. This performance is equal to the best cathodes for both KIBs and NIBs. Our preliminary results on HCF cathodes also show that the reactivity of potassium metal with alkylcarbonates such as PC is an obstacle to the studies of K half-cells (even in the presence of FEC as an electrolyte additive). Prussian white samples with either an ultra-small (~ 20 nm) or intermediate (~ 170 -200 nm) crystallite size (denoted as KFeHCF-S, and KFeHCF-M respectively) were synthesized by a modified citrate-assisted co-precipitation method. 37 , 38 , 39 The crystallite size was tuned by varying the amount of citrate; whereas micron-sized crystals (KFeHCF-L) were synthesized using K4Fe(CN)4 as both Fe and K source (see Supporting Information for details). Based on inductively coupled plasma (ICP) analysis coupled with thermogravimetric analysis (TGA) below 180°C to determine water content (Figure S1, Table S1), the composition of the three materials are defined as K1.69Fe[Fe(CN)6]0.90•0.4H2O (KFeHCF-S); K1.78Fe[Fe(CN)6]0.92•0.4H2O

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(KFeHCF-M); and K0.68Fe[Fe(CN)6]0.89•0.7H2O (KFeHCF-L). All samples showed a small weight loss of 2-3 wt% between 150 °C and 300 °C, indicating low levels of interstitial water in the lattice after drying under vacuum. K2FeFe(CN)6 is isostructural to monoclinic K2MnMn(CN)6.40 Figure 1a illustrates that the iron is either bound to six carbon atoms of the C≡N ligands to form FeC6 octahedra, or bound to

b S.G.: P21/n a=10.1245, b=7.3051, c=7.0594 Å β=90.46° ! 2 = 6.9, wRp = 5.3

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Figure 1. Physical (a-c) and electrochemical (d-f) characterization of KFeHCF-S: (a) Local environments of monoclinic K2FeFe(CN)6 show the connectivity of FeCN6 (brown) and FeNC6 (grey) octahedra. The silver, brown and purple balls represent nitrogen, carbon and potassium, respectively. (b) powder XRD diffraction pattern and Rietveld refinement show a pure phase of KFeHCF-S; (c) HR-TEM images of KFeHCF-S, average particle size is ~20 nm. (d) cyclic voltammogram (at 0.05 mV s-1); (e) Initial discharge/charge profile; inset shows the dQ/dV plot derived from the profile.

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six nitrogen atoms of the C≡N ligands to form FeN6 octahedra, and potassium is located in the void space between the octahedra.41,42 The X-ray diffraction (XRD) pattern of the KFeHCF-S shows a pure phase (Figure 1b), indexed in the space group P21/n. The crystallite size is ̴ 25 nm as calculated from the Scherrer equation, consistent with the estimation of 20 nm (Figure 1c) from high-resolution transmission electron microscopy (HR-TEM) where the well defined lattice fringes confirm the nanoparticles are highly crystalline. The fundamentals of potassium insertion/extraction in KFeHCF-S were evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge protocols. The CV curves demonstrate two pairs of peaks at 3.6/3.1 V and 4.1/3.7 V vs. K/K+, which correlate with the redox reactions of Fe2+/Fe3+ couples in different coordination environments (Figure 1d).36 The low-potential peaks are derived from redox on the Fe site with a high-spin configuration that is coordinated to nitrogen, while the high-potential peaks are from the Fe site with a low-spin configuration that coordinates to carbon. 27,43 The initial charge and discharge capacities are 132 mAh g-1 and 140 mAh g-1 at 10 mA g-1, corresponding to 1.7 and 1.8 potassium ions per formula, respectively (i.e, theoretical values). The voltage-capacity profile demonstrates two distinct plateaus; the precise potentials obtained from the dQ/dV curve (Figure 1e inset) are 3.28 V and 3.93 V vs. K/K+ on discharge. By comparison, an optimal Na2FeFe(CN)6 cathode shows a high capacity in a Na-ion cell of 160 mAh g-1 and similar two-step potential profiles at 3.00 and 3.30 V.36 While the sodium electrode has a higher capacity, the potassium electrode is superior in potential. As a result, the two electrodes actually offer a similar energy density of 500 Wh kg-1. Long-term cycling performance is discussed below. Ex-situ XRD patterns of KFeHCF-S after charge (Figure 2a) and subsequent discharge (Figure 2b) show the expected structural transformation on cycling based on the Na

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Figure 2. (a) XRD patterns and full profile refinement of the KFeHCF-S electrodes; (b) Schematic illustration demonstrates the reversible structural transition from monoclinic K2FeFe(CN)6 to cubic FeFe(CN)6 upon potassium extraction/insertion. The purple, yellow, green, silver and brown colors represent potassium, Fe (low-spin), Fe (high-spin), carbon and nitrogen, respectively.

analogue.27,38.

After full extraction of K from KFeHCF-S; (“K2Fe2+[Fe2+(CN)6]”) to form

Fe3+[Fe3+(CN)6], the lattice transforms to cubic. Upon re-insertion of K-ions, the cubic symmetry is reduced to monoclinic and this process is highly reversible. The bulky K+ ion has long been a concern for the development of KIBs. Its radius of 1.40 Å is 84% and 40% larger than for Li+ (0.76 Å) and Na+ (1.00 Å), respectively.26 This does not only impact the volumetric energy of KIBs, but also hinders the kinetics. To illustrate the latter point, two materials, KFeHCF-M and KFeHCF-L, with larger crystallite sizes were fabricated for comparison with the KFeHCF-S electrodes. KFeHCF-M was synthesized with the same co-

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Figure 3. Correlation between particle size and electrochemical performance at a current density of 20 mA g-1: (a,b,c) TEM images and (d,e,f) galvanostatic discharge/charge with KFeHCF-S, KFeHCF-M and KFeHCF-L, respectively; note difference in y-axis scale. HR-TEM confirm the average KFeHCF-S and KFeHCF-M cubes are ~ 20 nm and < 200 nm, respectively, while the KFeHCF-L cubes are > 1.5 µm. The specific capacity was calculated using the actual composition of each sample.

precipitation strategy as KFeHCF-S, but using five fold more potassium citrate. Citrate is well known to chelate to transition metal ions such as iron, and thus slows the crystallization of K2FeFe(CN)6. The KFeHCF-M material exhibits a similar XRD pattern as KFeHCF-S (Figure S2), but the crystallites exhibit a more pronounced cubic morphology, and a much larger size of

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~170 - 200 nm (Figure 3a,b). The reaction to produce the KFeHCF-L was fairly slow even at 60 °C, which allowed the cubes to grow to micron dimensions (Figure 3c). The KFeHCF-M electrode demonstrates a similar two-step voltage profile to KFeHCF-S on discharge, but the capacity is slightly reduced to 125 mAh/g (Figure 3e), only 8% lower than for the KFeHCF-S electrode (Figure 3d) at the same current density. Further increasing the particle size to the submicron scale, however, results in a drastically decreased capacity of 10 mAh g-1. The lower K-ion content of the KFeHCF-L sample may affect the performance of the electrode, at least on the first cycle. Nonetheless, typical sodium HCFs cathodes with micron-scale particle size and similar Na-ion content to our material offer much higher capacities of >120 mAh g-1.43 The difference in performance shows that HCF cathodes suffer from more severe kinetic barriers in KIBs. Nonetheless, the high energy density obtained with the KFeHCF-S cathode is comparable with the best electrodes in NIBs, and it is higher than other metal ion batteries. The high reactivity between potassium metal and some alkyl carbonate electrolytes is another challenge in KIBs in half-cell configurations. Simple experiments showed that contact of potassium metal with EC/DEC showed no change overnight (although a film appeared after several days); but electrolytes such as PC, or EC/DMC reacted rapidly over several hours to produce a distinct opaque film on the surface of the potassium. Figure 4a shows the voltage profiles of a KFeHCF-S half-cell run in EC/DEC with 0.5M KPF6 on the 1st, 10th, 50th and 80th cycles at 100 mA g-1. Even with this “best” carbonate solvent, the cell exhibits regular chargedischarge behavior during the first cycles, but the charge process becomes unstable over cycling and the cell exhibits a low average coulombic efficiency of < 90%. The orange/yellow color of the glassfiber separator shows evidence of electrolyte reactivity (Figure S3). The addition of 2% or 5% FEC fluoroethylene carbonate (FEC) (as commonly used for sodium metal anode cells) 44

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Figure 4. Cycling performance of KFeHCF-S cathodes with and without FEC in the electrolytes: (a) capacity-voltage profiles (1st: black curves, 10th: red curves, 50th: blue curves and 80th: pink curves) and cycling stability. The charge process becomes unstable after 20 cycles, and the cells is eventually dead after about 80 cycles as the charge could not be completed (Inset in a). (b) Cells with 2% (blue) and 5% (purple) FEC show much improved Coulombic efficiency compared to the cell with no FEC (black), but unstable charge still occurs after 170 cycles for the cell with 2% FEC. (c) Both cells with 2% (blue) and 5% (purple) FEC demonstrate similar capacity retention of 60% after 300 cycles. All galvanostatic studies were conducted at 100 mA g-1.

remarkably improved the coulombic efficiencies of the cells to 98% (Figure 4b). The cell with 2% FEC still suffered from sudden capacity fluctuation after 170 cycles, while the cell with 5% FEC cycled up to 300 cycles (Figure 4c). Nevertheless, the latter shows a capacity drop at about the 30th cycle and 210th cycle, and electrolyte decomposition was suggested by the orange color of the separator after cycling. Thus FEC enhances the coulombic efficiency and long term cycling

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but it cannot completely prevent electrolyte side reactions as it is successively consumed on cycling. Full cells – or different electrolytes - are necessary to explore long term cycling to screen new potassium cathodes. A comparison between the KFeHCF-S electrode and three “optimal” sodium HCF cathodes is presented in Table 1. Among the four materials, the potassium cathode has a lower capacity, but the energy density is offset by the higher cell voltage. As a result, the cells are comparable each other in terms of energy density. The sodium HCF cathodes still exhibit superiority in rate

Table 1: Electrochemical performance of KFeHCF-S compared to typical sodium HCF cathodes

capacity (mAh g-1)

working potential (V)

rate performance (mAh g-1)

170 3.0 at 25 mA g-1 155 3.3/3.0 Na1.92FeFe(CN)627 at 10 mA g-1 150 3.5 Na1.89MnFe(CN)626 at 15 mA g-1 140 K1.69FeFe(CN)6 3.3/3.9 at 10 mA g-1 (this work) and cycling performance (Figure S4 and Figure 4c), Na0.61FeFe(CN)621

120 at ~ 0.53 C (100 mA g-1) 155 at 1C 145 at 1C

cycling 100% after 160th 72% after 1000th 75% after 500th

120 at ~ 0.62 C 60% after 300th (100 mA g-1) which highlights the importance of

structural optimization for potassium cathode materials.

In summary, three KFeHCF materials with different crystallite sizes were synthesized by controlled chemistry routes and examined in potassium cells. While electrochemical performance is much more sensitive to crystallite size than for their sodium HCF counterparts we estimate an upper limit for optimal performance on the order of 200 -300 nm - a high energy density of 500 Wh kg-1 was realized with the electrode composed of nanocrystallites. In half-cell configurations, propylene carbonate (PC) is reactive with potassium, but even with the less reactive EC/DEC electrolyte, the addition of FEC was crucial to enhance the coulombic 12


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efficiency and long-term cycling capability. Our findings reveal that nanocrystallite particle dimensions for active potassium cathode materials are of utmost importance, even for relatively flexible solids such as the hexacyanoferrate. Thus, searches for future novel cathode materials such as rigid oxides - are unlikely to be fruitful unless crystallites are controlled to small dimensions.

ASSOCIATED CONTENT Supporting Information Experimental methods, thermogravimetric analysis of the electrode active materials, XRD patterns of KFeHCF-M and KFeHCF-L materials, electrochemical cycling in the absence of FEC, and rate performance data are provided in the SI. AUTHOR INFORMATION Corresponding Authors E-mail: [email protected] (L.F.N.) Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was supported by funding from NSERC Canada through the Discovery Grant and Canada Research Chair programs. REFERENCES

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(1) Masquelier, C.; Croguennec, L. Polyanionic (Phosphates, Silicates, Sulfates) Frameworks as Electrode Materials for Rechargeable Li (or Na) Batteries. Chem. Rev. 2013, 113, 6552– 6591. (2) Kundu, D.; Talaie, E.; Duffort, V.; Nazar, L. F. The Emerging Chemistry of Sodium Ion Batteries for Electrochemical Energy Storage. Angew. Chem. Int. Ed. 2015, 45, 3431–3448. (3) Han, M. H.; Gonzalo, E.; Singh, G.; Rojo, T. A Comprehensive Review of Sodium Layered Oxides: Powerful Cathodes for Na-Ion Batteries. Energy Environ. Sci. 2014, 8, 81–102. (4) Talaie, E.; Duffort, V.; Smith, H. L.; Fultz, B.; Nazar, L. F. Structure of the High Voltage Phase of Layered P2-Na2/3-Z[Mn1/2Fe1/2]O2 and the Positive Effect of Ni Substitution on its Stability. Energy Environ. Sci. 2015, 8, 2512–2523. (5) Barpanda, P.; Oyama, G.; Nishimura, S.-I.; Chung, S.-C.; Yamada, A. A 3.8-V EarthAbundant Sodium Battery Electrode. Nat. Commun. 2014, 5, 4358. (6) Qie, L.; Chen, W.; Xiong, X.; Hu, C.; Zou, F.; Hu, P.; Huang, Y. Sulfur-Doped Carbon with Enlarged Interlayer Distance as a High-Performance Anode Material for Sodium-Ion Batteries. Adv. Sci. 2015, 2, 1500195. (7) Wang, Y.; Xiao, R.; Hu, Y.-S.; Avdeev, M.; Chen L. P2-Na0.6[Cr0.6Ti0.4]O2 CationDisordered Electrode for High-rate Symmetric Rechargeable Sodium-ion Batteries. Nat. Commun. 2015, 6, 6954. (8) Itaya, K.; Ataka, T.; Toshima, S. Spectroelectrochemistry and Electrochemical Preparation Method of Prussian Blue Modified Electrodes. J. Am. Chem. Soc. 1982, 104, 4767–4772. (9) Kim, H.; Hong, J.; Park, K.-Y.; Kim, H.; Kim, S.-W.; Kang, K. Aqueous Rechargeable Li and Na-Ion Batteries. Chem. Rev. 2014, 114, 11788–11827..

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(10) Wessells, C. D.; Huggins, R. A.; Cui, Y. Copper Hexacyanoferrate Battery Electrodes with Long Cycle Life and High Power. Nat. Commun. 2011, 2, 550. (11) Jian, Z.; Luo, W.; Ji, X. Carbon Electrodes for K-Ion Batteries. J. Am. Chem. Soc. 2015, 137, 11566–11569. (12) Komaba, S.; Hasegawa, T.; Dahbi, M.; Kubota, K. Potassium Intercalation into Graphite to Realize High-Voltage/High-Power Potassium Ion Batteries and Potassium Ion Capacitors. Electrochem. Commun. 2015, 60, 172–175. (13) Luo, W.; Wan, J.; Ozdemir, B.; Bao, W.; Chen, Y.; Dai, J.; Lin, H.; Xu, Y.; Gu, F.; Barone, V.; et al. Potassium Ion Batteries with Graphitic Materials. Nano Lett. 2015, 15, 7671–7677. (14) Jian, Z.; Xing, Z.; Bommier, C.; Li, Z.; Ji, X. Hard Carbon Microspheres: Potassium-Ion Anode Versus Sodium-Ion Anode. Adv. Energy Mater. 2015, 6, 1501874. (15) Chen, Y.; Luo, W.; Carter, M.; Zhou, L.; Dai, J.; Fu, K.; Lacey, S.; Li, T.; Wan, L.; Han, X. Organic Electrode for Non-Aqueous Potassium-Ion Batteries. Nano Energy 2015, 18, 205211. (16) Jian, Z.; Liang, Y.; Pérez, I. A. R.; Yao, Y.; Ji, X. Poly(Anthraquinonyl Sulfide) Cathode for Potassium-Ion Batteries. Electrochem. Commun. 2016, 71, 5–8. (17) Vaalma, C.; Giffin, G. A.; Buchholz, D.; Passerini, S. Non-Aqueous K-Ion Battery Based on Layered K0.3MnO2 and Hard Carbon/Carbon Black. J. Electrochem. Soc. 2016, 163, A1295–A1299. (18) Han, J.; Niu, Y.; Bao, S.-J.; Yu, Y.-N.; Lu, S.-Y.; Xu, M. Nanocubic KTi2(PO4)3 Electrodes for Potassium-Ion Batteries. Chem. Commun. 2016, 52, 11661–11664. (19) Lu, Y.; Wang, L.; Cheng, J.; Goodenough, J. B. Prussian Blue: A New Framework of Electrode Materials for Sodium Batteries. Chem. Commun. 2012, 48, 6544–6546.

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(20) Wang, L.; Lu, Y.; Liu, J.; Xu, M.; Cheng, J.; Zhang, D.; Goodenough, J. B. A Superior Low-Cost Cathode for a Na-Ion Battery. Angew. Chem. Int. Ed. 2013, 52, 1964–1967. (21) You, Y.; Wu, X.-L.; Yin, Y.-X.; Guo, Y.-G. High-Quality Prussian Blue Crystals as Superior Cathode Materials for Room-Temperature Sodium-Ion Batteries. Energy Environ. Sci. 2014, 7, 1643–1645. (22) Lee, H.-W.; Wang, R. Y.; Pasta, M.; Lee, S. W.; Liu, N.; Cui, Y. Manganese Hexacyanomanganate Open Framework as a High-Capacity Positive Electrode Material for Sodium-Ion Batteries. Nat. Commun. 2014, 5, 5280. (23) Liu, Y.; Qiao, Y.; Zhang, W.; Li, Z.; Ji, X.; Miao, L.; Yuan, L.; Hu, X.; Huang, Y. Sodium Storage in Na-Rich NaxFeFe(CN)6 Nanocubes. Nano Energy 2015, 12, 386–393. (24) Yue, Y.; Binder, A. J.; Guo, B.; Zhang, Z.; Qiao, Z.-A.; Tian, C.; Dai, S. Mesoporous Prussian Blue Analogues: Template-Free Synthesis and Sodium-Ion Battery Applications. Angew. Chem. Int. Ed. 2014, 53, 3134–3137. (25) Wu, X.; Deng, W.; Qian, J.; Cao, Y.; Ai, X.; Yang, H. Single-Crystal FeFe(CN)6 Nanoparticles: a High Capacity and High Rate Cathode for Na-Ion Batteries. J. Mater. Chem. A 2013, 1, 10130–10135. (26) Song, J.; Wang, L.; Lu, Y.; Liu, J.; Guo, B.; Xiao, P.; Lee, J.-J.; Yang, X.-Q.; Henkelman, G.; Goodenough, J. B. Removal of Interstitial H2O in Hexacyanometallates for a Superior Cathode of a Sodium-Ion Battery. J. Am. Chem. Soc. 2015, 137, 2658–2664. (27) Wang, L.; Song, J.; Qiao, R.; Wray, L. A.; Hossain, M. A.; Chuang, Y.-D.; Yang, W.; Lu, Y.; Evans, D.; Lee, J.-J.; et al. Rhombohedral Prussian White as Cathode for Rechargeable Sodium-Ion Batteries. J. Am. Chem. Soc. 2015, 137, 2548–2554.

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(28) Xue, L.; Gao, H.; Zhou, W.; Xin, S.; Park, K.; Li, Y.; Goodenough, J. B. Liquid K-Na Alloy Anode Enables Dendrite-Free Potassium Batteries. Adv. Mater. 2016, 28, 9608–9612. (29) Wessells, C. D.; Peddada, S. V.; Huggins, R. A.; Cui, Y. Nickel Hexacyanoferrate Nanoparticle Electrodes for Aqueous Sodium and Potassium Ion Batteries. Nano Lett. 2011, 11, 5421–5425. (30) Wessells, C. D.; Peddada, S. V.; McDowell, M. T.; Huggins, R. A.; Cui, Y. The Effect of Insertion Species on Nanostructured Open Framework Hexacyanoferrate Battery Electrodes. J. Electrochem. Soc. 2012, 159, A98–A103. (31) Padigi, P.; Thiebes, J.; Swan, M.; Goncher, G.; Evans, D.; Solanki, R. Prussian Green: A High Rate Capacity Cathode for Potassium Ion Batteries. Electrochimica Acta 2015, 166, 32–39. (32) Eftekhari, A. Potassium Secondary Cell Based on Prussian Blue Cathode. J. Power Sources 2004, 126, 221–228. (33) Zhang, C.; Xu, Y.; Zhou, M.; Liang, L.; Dong, H.; Wu, M.; Yang, Y.; Lei, Y. Potassium Prussian Blue Nanoparticles: A Low-Cost Cathode Material for Potassium-Ion Batteries. Adv. Funct. Mater. 2017, 27, 1604307. (34) Xue, L.; Li, Y.; Gao, H.; Zhou, W.; Kaveevivitchai, W.; Manthiram, A.; Goodenough, J. B. Low-Cost High-Energy Potassium Cathode. J. Am. Chem. Soc. 2017, 139, 2164–2167. (35) Bie, X.; Hubota, K.; Kosaka, T.; Chihara, K.; Komaba, S. A Novel K-ion Battery: Hexacyanoferrate(II)/Graphite Cell. J. Mater. Chem. A 2017, 5, 4325–4330. (36) Wu, X.; Jian, Z.; Li, Z.; Ji, X. Prussian White Analogues as Promising Cathode for NonAqueous Potassium-Ion Batteries. Electrochem. Commun. 2017, 77, 54–57.

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(37) Ji, Z.; Han, B.; Liang, H.; Zhou, C.; Gao, Q.; Xia, K.; Wu, J. On the Mechanism of the Improved Operation Voltage of Rhombohedral Nickel Hexacyanoferrate as Cathodes for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 33619–33625. (38) Tang, Y.; Zhang, W.; Xue, L.; Ding, X.; Wang, T.; Liu, X.; Liu, J.; Li, X.; Huang, Y. Polypyrrole-Promoted Superior Cyclability and Rate Capability of NaxFe[Fe(CN)6] Cathodes for Sodium-Ion Batteries. J. Mater. Chem. A 2016, 4, 6036–6041. (39) Wu, X.; Wu, C.; Wei, C.; Hu, L.; Qian, J.; Cao, Y.; Ai, X.; Wang, J.; Yang, H. Highly Crystallized Na2CoFe(CN)6 with Suppressed Lattice Defects as Superior Cathode Material for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 5393–5399. (40) Her, J.-H.; Stephens, P. W.; Kareis, C. M.; Moore, J. G.; Min, K. S.; Park, J.-W.; Bali, G.; Kennon, B. S.; Miller, J. S. Anomalous Non-Prussian Blue Structures and Magnetic Ordering of K2MnII[MnII(CN)6] and Rb2MnII[MnII(CN)6]. Inorg. Chem. 2010, 49, 1524– 1534. (41) Kareis, C. M.; Lapidus, S. H.; Her, J.-H.; Stephens, P. W.; Miller, J. S. Non-Prussian Blue Structures and Magnetic Ordering of Na2MnII[MnII(CN)6] and Na2MnII[MnII(CN)6]·2H2O. J. Am. Chem. Soc. 2012, 134, 2246–2254. (42) Xiao, P.; Song, J.; Wang, L.; Goodenough, J. B.; Henkelman, G. Theoretical Study of the Structural Evolution of a Na2FeMn(CN)6 Cathode Upon Na Intercalation. Chem. Mater. 2015, 27, 3763–3768. (43) You, Y.; Yu, X.; Y. Yin, Nam, K.-W; Guo, Y.-G. Sodium Iron Hexacyanoferrate with High Na Content as a Na-Rich Cathode Material for Na-Ion Batteries. Nano Res. 2014, 8, 117– 128.

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(44) Komaba, S.; Ishikawa, T.; Yabuuchi, N.; Murata, W.; Ito, A.; Ohsawa, Y. Fluorinated Ethylene Carbonate as Electrolyte Additive for Rechargeable Na Batteries. ACS Appl. Mater. Interfaces 2011, 3, 4165–4168.

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Crystallite Size Control of Prussian White Analogues for Nonaqueous

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