High Power Cathode Material Na4VO(PO4)2 with Open Framework for

Apr 11, 2017 - (1, 2) Li ion batteries (LIBs) have been considered the best energy storage system because of their high energy density, great cycle-li...
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High Power Cathode Material Na4VO(PO4)2 with Open Framework for Na Ion Batteries Jongsoon Kim,*,† Hyungsub Kim,‡ and Seongsu Lee‡ †

Department of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747, Republic of Korea ‡ Korea Atomic Energy Research Institute (KAERI), Daedeok-daero 989 Beon-Gil, Yuseong-gu, Daejeon 780-904, Republic of Korea S Supporting Information *

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o overcome environmental problems such as air pollution or the greenhouse effect, many researchers have

Figure 2. (a) Crystal structure of Na4VO(PO4)2 with connection between VO6 octahedra and PO4 tetrahedra, and (b) bond-valencesum energy map of Na4VO(PO4)2 in ab, ac, bc planes.

easily accessible is a critical issue currently being investigated by many researchers. Among many possible candidates, Na ion batteries (NIBs) are considered one of the best alternatives to LIBs because of the unlimited Na sources in the sea and their similar reaction mechanism.10−20 Many researchers have focused on finding outstanding and optimal electrode materials for NIBs. Similar to LIBs, layered-type cathode materials such as NaxMnO2, Na x CrO 2 , Na x VO 2 , or Na x (Fe, Mn)O 2 have received considerable attention as the best cathode materials for NIBs.16−29 However, their low redox potential (less than ∼2.7 V vs Na+/Na) and water contamination in the interlayer space of the layered structure are important issues that prevent the use of these materials as cathodes for NIBs. Layered-type cathode materials with large capacity require additional Na insertion in the structure via predischarge.22,30,31 Additionally, the extensive structural evolution during charge/discharge in layered-type cathode materials, such as the P2−O2 phase

Figure 1. (a) Refined neutron diffraction pattern of Na4VO(PO4)2 (RP, 2.76%; RI, 5.71%; RF, 4.2%; χ2, 2.87%) and (b) refined X-ray diffraction pattern of Na4VO(PO4)2 (RP, 5.94%; RI, 5.18%; RF, 5.40%; χ2, 8.45%).

attempted to find a clean and sustainable energy source and the development of new systems for efficient energy storage has received substantial attention worldwide.1,2 Li ion batteries (LIBs) have been considered the best energy storage system because of their high energy density, great cycle-life, and negligible memory effect and have been widely used for small devices such as cellular phones or laptops.3−7 However, with the explosive growth of the LIB market, the limited and localized Li sources in the world and their greatly increasing cost are major drawbacks to the use of LIBs for large-scale applications such as electric vehicles.8−10 Therefore, the development of alternatives to LIBs that are inexpensive and © 2017 American Chemical Society

Received: October 26, 2016 Revised: April 11, 2017 Published: April 11, 2017 3363

DOI: 10.1021/acs.chemmater.6b04557 Chem. Mater. 2017, 29, 3363−3366

Communication

Chemistry of Materials

Figure 3. (a) Charge/discharge curve of Na4VO(PO4)2 with its dQ/dV, (b) discharge curves of Na4VO(PO4)2 as a function of C rate (C/5, C/2, 1C, 2C, 4C, 6C, 8C, and 10C), (c) cyclability of Na4VO(PO4)2 over 200 cycles at 1C [inset: charge/discharge curves of Na4VO(PO4)2 over 200 cycles at 1C], and (d) Ragone plot of Na4VO(PO4)2, NaVOPO4, Na2(VO)P2O7, Na3V2(PO4)3, Na0.74CoO2, NaMn1/3Co1/3Ni1/3O2.

paths, which would enable easy Na diffusion into the structure. In addition, the redox potential of Na4VO(PO4)2 is higher than that of other layered oxide cathode materials for NIBs because of the combination of the V4+/V5+ redox reaction, which is known to have a high redox potential for LIBs and NIBs, and the inductive effect of P ions. Na4VO(PO4)2 was successfully prepared through a conventional solid state synthesis method at 700 °C. The detailed synthesis process is described in the Supporting Information. The particle size of pristine Na4VO(PO4)2 measured using scanning electron microscopy (SEM) was larger than ∼2 μm (Figure S1) and its Brunauer−Emmett−Teller (BET) surface area was 0.8605 ± 0.0037 m2 g−1 (Figure S2). Based on neutron diffraction (ND) and X-ray diffraction (XRD), it was notified that the space group of Na4VO(PO4)2 is orthorhombic Pbca and no contamination or second phases were detected in this material, as observed in Figure 1. The detailed structural information on Na4VO(PO4)2 was successfully obtained through Rietveld refinement of its neutron diffraction pattern (Table T1) and matches well with previous reports.35 The lattice parameters of Na4VO(PO4)2 were a = 15.9491(6) Å, b = 14.4620(12) Å, and c = 6.9989(3) Å. The low R-factor confirms the accuracy of this Rietveld refinement (RP, 2.76%; RI, 5.71%; RF, 4.2%; χ2, 2.087%). A schematic of the Na4VO(PO4)2 structure based on the obtained structural information is presented in Figure 2a. There are infinite chains of VO6 octahedra with point-sharing between each VO6 in the Na4VO(PO4)2 structure and isolated infinite chains of neighboring VO6 octahedra linked additionally by tetrahedral PO4 groups. Through this structural relationship

Figure 4. XRD patterns of Na4VO(PO4)2, Na3.5VO(PO4)2, and Na3VO(PO4)2 (*: Al peak).

transition, is accompanied by a large lattice/volume change, resulting in poor electrochemical properties.32 Therefore, the development of new cathode materials with high operation voltages as well as fast Na diffusion paths like layered-type cathode materials is needed. In this study, we explored a new NIB cathode material with a high redox potential and open framework for fast Na diffusion. Recent works have demonstrated that NIB cathode materials with the redox couple of V ions and the inductive effect of P ions, such as Na3V2(PO4)3 or Na3V2(PO4)2F, exhibit relatively high operation voltages.9,11,33,34 Our target material as the new cathode material for NIBs is Na4VO(PO4)2. It was assumed that large amounts of Na in Na4VO(PO4)2 with open framework could provide numerous possible Na diffusion 3364

DOI: 10.1021/acs.chemmater.6b04557 Chem. Mater. 2017, 29, 3363−3366

Communication

Chemistry of Materials

In summary, we explored the use of Na4VO(PO4)2 as a new cathode material for NIBs through several experiments. Outstanding power capability might arise from numerous possible Na diffusion paths in the Na4VO(PO4)2, suggested by high Na contents and open framework and identified through Rietveld refinement and neutron/X-ray diffraction. Electrochemical analyses revealed that Na4VO(PO4)2 has great power capability and reasonable cyclability with an average voltage of ∼3.5 V (vs Na+/Na) based on the one-phase reaction mechanism. We postulate that this work provides a method for developing new electrode materials for NIBs.

among V, O, and P, a high redox potential is expected to be achieved for Na4VO(PO4)2 because of the inductive effect, similar to other phosphate electrode materials. One of the noticeable characteristic of the Na4VO(PO4)2 structure is the possible existence of various Na diffusion paths in the structure. There are four symmetrically distinguishable Na sites in the structure, and these Na ions surround the VO6 infinite chains with PO4 like a net. To more clearly identify possible Na diffusion paths in the crystal structure, a bond-valence-sum (BVS) energy map was prepared using the Bond_Str program implemented in the FullProf package.36,37 The BVS method is based on the assumption that ion diffusion in the cell occurs along paths where the difference between the bond-valence and nominal valence (ΔV) remains as small as possible. The obtained isosurface for the ΔV threshold of 0.001 is presented in Figure 2b and predicts a possible Na diffusion pathway in Na4VO(PO4)2. Through this analysis, it is supposed that all Na ions of Na4VO(PO4)2 are closely connected to each other in structure. Therefore, we could expect Na4VO(PO4)2 to exhibit great power capability. To evaluate the possibility of Na4VO(PO4)2 as a cathode material for NIBs, several electrochemical properties were measured. A 2032-type Na cell was fabricated with Na4VO(PO4)2 as the working electrode, Na metal as the counter and reference electrode, and 1 M NaPF6 electrolyte in a 1:1 mixture of propylene carbonate and ethylene carbonate as the electrolyte. Figure 3a presents the charge/discharge profile of Na4VO(PO4)2 and the corresponding dQ/dV curve. It was clearly revealed that one Na ion in Na4VO(PO4)2 can be reversibly (de)intercalated from the structure by the V4+/V5+ redox reaction with an average voltage of ∼3.5 V (vs Na+/Na), which means that the theoretical capacity of Na4VO(PO4)2 is 78 mAh g−1. To verify the power capability of Na4VO(PO4)2, we measured its discharge capacities as a function of the current rate (C/5, C/2, 1C, 2C, 4C, 6C, 8C, 10C). As observed in Figure 3b, Na 4VO(PO4 )2 exhibited outstanding power capability. Even At 10C, the capacity was ∼53% of the theoretical capacity, despite the micron particle size. This finding agrees well with the expected data based on the BVS analysis. Furthermore, the Ragone plot in Figure 3d demonstrates that Na4VO(PO4)2 has outstanding power capability as a potential cathode material for NIBs compared with other cathode materials.9,38−41 Figure 3c shows the cyclability of Na4VO(PO4)2. At a charge/discharge rate of 1C, a discharge capacity of ∼65 mAh g−1 (∼85% of the theoretical capacity) was achieved in the first cycle, with discharge capacities of up to ∼77% of the initial capacity attained over more than 200 cycles. To verify the phase reaction of Na4VO(PO4)2 during charge/ discharge, we performed ex situ XRD analyses for various Na content in the Na4−x(PO4)2 (0 ≤ x ≤ 1) structure. As observed in Figure 4, the (002), (020), and (021) peaks were remarkably sensitive to the changes in Na occupancy. During Na deintercalation from the structure, the (002) peak shifted toward high 2θ angle, which indicates shrinkage of the c lattice, and the intensity of the (020) peak decreased whereas that of the (021) peak increased. The lattice parameters of Na4VO(PO4)2 changed as a function of the Na content in the structure, as shown in Table T2. On the basis of these structural changes, we concluded that the reaction mechanism of Na4VO(PO4)2 is the one-phase reaction during the (de)sodiation process.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.6b04557. Experimental details, structural information on Na4VO(PO4)2, SEM image, BET analysis (PDF)

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AUTHOR INFORMATION

Corresponding Author

*J. Kim. E-mail: [email protected]. ORCID

Jongsoon Kim: 0000-0002-4122-4874 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the faculty research fund of Sejong University in 2017 and the National Research Foundation of Korea (NRF) under contract NRF-2012M2A2A6002461.

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REFERENCES

(1) Tarascon, J. M.; Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature 2001, 414 (6861), 359−367. (2) Armand, M.; Tarascon, J. M. Building better batteries. Nature 2008, 451 (7179), 652−657. (3) Du, X. Y.; He, W.; Zhang, X. D.; Yue, Y. Z.; Liu, H.; Zhang, X. G.; Min, D. D.; Ge, X. X.; Du, Y. Enhancing the electrochemical performance of lithium ion batteries using mesoporous Li3V2(PO4)3/ C microspheres. J. Mater. Chem. 2012, 22 (13), 5960−5969. (4) Kim, J.; Yoo, J.-K.; Jung, Y. S.; Kang, K. Li3V2(PO4)3/Conducting Polymer as a High Power 4 V-Class Lithium Battery Electrode. Adv. Energy Mater. 2013, 3 (8), 1004−1007. (5) Peng, G.; Yao, X.; Wan, H.; Huang, B.; Yin, J.; Ding, F.; Xu, X. Insights on the fundamental lithium storage behavior of all-solid-state lithium batteries containing the LiNi0.8Co0.15Al0.05O2 cathode and sulfide electrolyte. J. Power Sources 2016, 307, 724−730. (6) Eames, C.; Armstrong, A. R.; Bruce, P. G.; Islam, M. S. Insights into Changes in Voltage and Structure of Li2FeSiO4 Polymorphs for Lithium-Ion Batteries. Chem. Mater. 2012, 24 (11), 2155−2161. (7) Ma, D. L.; Cao, Z. Y.; Wang, H. G.; Huang, X. L.; Wang, L. M.; Zhang, X. B. Three-dimensionally ordered macroporous FeF3 and its in situ homogenous polymerization coating for high energy and power density lithium ion batteries. Energy Environ. Sci. 2012, 5 (9), 8538− 8542. (8) Kim, S. W.; Seo, D. H.; Ma, X. H.; Ceder, G.; Kang, K. Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2 (7), 710−721. (9) Lim, S. Y.; Kim, H.; Shakoor, R. A.; Jung, Y.; Choi, J. W. Electrochemical and Thermal Properties of NASICON Structured Na3V2(PO4)3 as a Sodium Rechargeable Battery Cathode: A 3365

DOI: 10.1021/acs.chemmater.6b04557 Chem. Mater. 2017, 29, 3363−3366

Communication

Chemistry of Materials Combined Experimental and Theoretical Study. J. Electrochem. Soc. 2012, 159 (9), A1393−A1397. (10) Kim, J.; Park, I.; Kim, H.; Park, K. Y.; Park, Y. U.; Kang, K. Tailoring a New 4V-Class Cathode Material for Na-Ion Batteries. Adv. Energy Mater. 2016, 6 (6), 1502147. (11) Shakoor, R. A.; Seo, D. H.; Kim, H.; Park, Y. U.; Kim, J.; Kim, S. W.; Gwon, H.; Lee, S.; Kang, K. A combined first principles and experimental study on Na3V2(PO4)2F3 for rechargeable Na batteries. J. Mater. Chem. 2012, 22 (38), 20535−20541. (12) Kim, H.; Shakoor, R. A.; Park, C.; Lim, S. Y.; Kim, J. S.; Jo, Y. N.; Cho, W.; Miyasaka, K.; Kahraman, R.; Jung, Y.; Choi, J. W. Na2FeP2O7 as a Promising Iron-Based Pyrophosphate Cathode for Sodium Rechargeable Batteries: A Combined Experimental and Theoretical Study. Adv. Funct. Mater. 2013, 23 (9), 1147−1155. (13) Hwang, J. Y.; Myung, S. T.; Aurbach, D.; Sun, Y. K. Effect of nickel and iron on structural and electrochemical properties of O3 type layer cathode materials for sodium-ion batteries. J. Power Sources 2016, 324, 106−112. (14) Wu, X. H.; Xu, G. L.; Zhong, G. M.; Gong, Z. L.; McDonald, M. J.; Zheng, S. Y.; Fu, R. Q.; Chen, Z. H.; Amine, K.; Yang, Y. Insights into the Effects of Zinc Doping on Structural Phase Transition of P2Type Sodium Nickel Manganese Oxide Cathodes for High-Energy Sodium Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8 (34), 22227−22237. (15) Mei, Y. N.; Huang, Y. H.; Hu, X. L. Nanostructured Ti-based anode materials for Na-ion batteries. J. Mater. Chem. A 2016, 4 (31), 12001−12013. (16) Shen, Y. B.; Birgisson, S.; Iversen, B. B. A P2-NaxCo0.7Mn0.3O2 (x approximate to 1.0) cathode material for Na-ion batteries with superior rate and cycle capability. J. Mater. Chem. A 2016, 4 (31), 12281−12288. (17) Zhang, X. H.; Pang, W. L.; Wan, F.; Guo, J. Z.; Lu, H. Y.; Li, J. Y.; Xing, Y. M.; Zhang, J. P.; Wu, X. L. P2-Na2/3Ni1/3Mn5/9Al1/9O2 Microparticles as Superior Cathode Material for Sodium-Ion Batteries: Enhanced Properties and Mechanisam via Graphene Connection. ACS Appl. Mater. Interfaces 2016, 8 (32), 20650−20659. (18) Yu, C.-Y.; Park, J.-S.; Jung, H.-G.; Chung, K.-Y.; Aurbach, D.; Sun, Y.-K.; Myung, S.-T. NaCrO2 cathode for high-rate sodium-ion batteries. Energy Environ. Sci. 2015, 8 (7), 2019−2026. (19) Singh, G.; Miguel Lopez del Amo, J.; Galceran, M.; Perez-Villar, S.; Rojo, T. Structural evolution during sodium deintercalation/ intercalation in Na2/3Fe1/2Mn1/2O2. J. Mater. Chem. A 2015, 3 (13), 6954−6961. (20) Yabuuchi, N.; Hara, R.; Kubota, K.; Paulsen, J.; Kumakura, S.; Komaba, S. A new electrode material for rechargeable sodium batteries: P2-type Na2/3Mg0.28Mn0.72O2 with anomalously high reversible capacity. J. Mater. Chem. A 2014, 2 (40), 16851−16855. (21) Liang, C.; Kong, F.; Longo, R. C.; Kc, S.; Kim, J.-S.; Jeon, S.; Choi, S.; Cho, K. Unraveling the Origin of Instability in Ni-Rich LiNi1−2xCoxMnxO2 (NCM) Cathode Materials. J. Phys. Chem. C 2016, 120 (12), 6383−6393. (22) Huon Han, M.; Gonzalo, E.; Sharma, N.; Miguel Lopez del Amo, J.; Armand, M.; Avdeev, M.; Saiz Garitaonandia, J. J.; Rojo, T. High-Performance P2-Phase Na2/3Mn0.8Fe0.1Ti0.1O2 Cathode Material for Ambient-Temperature Sodium-Ion Batteries. Chem. Mater. 2016, 28 (1), 106−116. (23) Fu, B.; Zhou, X.; Wang, Y. High-rate performance electrospun Na0.44MnO2 nanofibers as cathode material for sodium-ion batteries. J. Power Sources 2016, 310, 102−108. (24) Yuan, D. D.; Wang, Y. X.; Cao, Y. L.; Ai, X. P.; Yang, H. X. Improved Electrochemical Performance of Fe-Substituted NaNi0.5Mn0.5O2 Cathode Materials for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7 (16), 8585−8591. (25) Wang, Y.; Liu, J.; Lee, B.; Qiao, R.; Yang, Z.; Xu, S.; Yu, X.; Gu, L.; Hu, Y.-S.; Yang, W.; Kang, K.; Li, H.; Yang, X.-Q.; Chen, L.; Huang, X. Ti-substituted tunnel-type Na0.44MnO2 oxide as a negative electrode for aqueous sodium-ion batteries. Nat. Commun. 2015, 6, 6401.

(26) Qiao, R.; Dai, K.; Mao, J.; Weng, T.-C.; Sokaras, D.; Nordlund, D.; Song, X.; Battaglia, V. S.; Hussain, Z.; Liu, G.; Yang, W. Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries. Nano Energy 2015, 16, 186−195. (27) Mu, L.; Xu, S.; Li, Y.; Hu, Y.-S.; Li, H.; Chen, L.; Huang, X. Prototype Sodium-Ion Batteries Using an Air-Stable and Co/Ni-Free O3-Layered Metal Oxide Cathode. Adv. Mater. 2015, 27 (43), 6928− 6933. (28) Moretti, A.; Secchiaroli, M.; Buchholz, D.; Giuli, G.; Marassi, R.; Passerini, S. Exploring the Low Voltage Behavior of V2O5 Aerogel as Intercalation Host for Sodium Ion Battery. J. Electrochem. Soc. 2015, 162 (14), A2723−A2728. (29) Zhao, J.; Xu, J.; Lee, D. H.; Dimov, N.; Meng, Y. S.; Okada, S. Electrochemical and thermal properties of P2-type Na2/3Fe1/3Mn2/3O2 for Na-ion batteries. J. Power Sources 2014, 264, 235−239. (30) Caballero, A.; Hernan, L.; Morales, J.; Sanchez, L.; Pena, J. S.; Aranda, M. A. G. Synthesis and characterization of high-temperature hexagonal P2-Na0.6MnO2 and its electrochemical behaviour as cathode in sodium cells. J. Mater. Chem. 2002, 12 (4), 1142−1147. (31) Lu, Z. H.; Dahn, J. R. Intercalation of water in P2, T2 and O2 structure AzCoxNi1/3‑xMn2/3O2. Chem. Mater. 2001, 13 (4), 1252− 1257. (32) Kim, H.; Kim, H.; Ding, Z.; Lee, M. H.; Lim, K.; Yoon, G.; Kang, K. Recent Progress in Electrode Materials for Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6 (19), 1600943. (33) Jian, Z. L.; Han, W. Z.; Lu, X.; Yang, H. X.; Hu, Y. S.; Zhou, J.; Zhou, Z. B.; Li, J. Q.; Chen, W.; Chen, D. F.; Chen, L. Q. Superior Electrochemical Performance and Storage Mechanism of Na3V2(PO4)3 Cathode for Room-Temperature Sodium-Ion Batteries. Adv. Energy Mater. 2013, 3 (2), 156−160. (34) Wang, H.; Jiang, D.; Zhang, Y.; Li, G.; Lan, X.; Zhong, H.; Zhang, Z.; Jiang, Y. Self-combustion synthesis of Na3V2(PO4)3 nanoparticles coated with carbon shell as cathode materials for sodium-ion batteries. Electrochim. Acta 2015, 155, 23−28. (35) Panin, R. V.; Shpanchenko, R. V.; Mironov, A. V.; Velikodny, Y. A.; Antipov, E. V.; Hadermann, J.; Tarnopolsky, V. A.; Yaroslavtsev, A. B.; Kaul, E. E.; Geibel, C. Crystal structure, polymorphism, and properties of the new vanadyl phosphate Na4VO(PO4)2. Chem. Mater. 2004, 16 (6), 1048−1055. (36) Rodrıguez-Carvajal, J. Commission on powder diffraction (IUCr). Newsletter 2001, 26, 12−19. (37) Adams, S. Relationship between bond valence and bond softness of alkali halides and chalcogenides. Acta Crystallogr., Sect. B: Struct. Sci. 2001, 57, 278−287. (38) Chen, C. Y.; Matsumoto, K.; Nohira, T.; Hagiwara, R. Improved Electrochemical Performance of NaVOPO4 Positive Electrodes at Elevated Temperature in an Ionic Liquid Electrolyte. J. Electrochem. Soc. 2015, 162 (10), A2093−A2098. (39) Barpanda, P.; Liu, G. D.; Avdeev, M.; Yamada, A. tNa2(VO)P2O7: A 3.8 V Pyrophosphate Insertion Material for Sodium-Ion Batteries. ChemElectroChem 2014, 1 (9), 1488−1491. (40) Ding, J. J.; Zhou, Y. N.; Sun, Q.; Yu, X. Q.; Yang, X. Q.; Fu, Z. W. Electrochemical properties of P2-phase Na0.74CoO2 compounds as cathode material for rechargeable sodium-ion batteries. Electrochim. Acta 2013, 87, 388−393. (41) Sathiya, M.; Hemalatha, K.; Ramesha, K.; Tarascon, J. M.; Prakash, A. S. Synthesis, Structure, and Electrochemical Properties of the Layered Sodium Insertion Cathode Material: NaNi1/3Mn1/3Co1/3O2. Chem. Mater. 2012, 24 (10), 1846−1853.

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DOI: 10.1021/acs.chemmater.6b04557 Chem. Mater. 2017, 29, 3363−3366