Letter pubs.acs.org/NanoLett
MnFe2O4@C Nanofibers as High-Performance Anode for Sodium-Ion Batteries Yongchang Liu,† Ning Zhang,† Chuanming Yu,† Lifang Jiao,† and Jun Chen*,†,‡ †
Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) and State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China ‡ Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, China S Supporting Information *
ABSTRACT: MnFe2O4 nanodots (∼3.3 nm) homogeneously dispersed in porous nitrogen-doped carbon nanofibers (denoted as MFO@C) were prepared by a feasible electrospinning technique. Meanwhile, MFO@C with the character of flexible free-standing membrane was directly used as binderand current collector-free anode for sodium-ion batteries, exhibiting high electrochemical performance with high-rate capability (305 mA h g−1 at 10000 mA g−1 in comparison of 504 mA h g−1 at 100 mA g−1) and ultralong cycling life (ca. 90% capacity retention after 4200 cycles). The Na-storage mechanism was systematically studied, revealing that MnFe2O4 is converted into metallic Mn and Fe after the first discharge (MnFe2O4 + 8Na+ + 8e− → Mn + 2Fe + 4Na2O) and then to MnO and Fe2O3 during the following charge (Mn + 2Fe + 4Na2O → MnO + Fe2O3 + 8Na+ + 8e−). The subsequent cycles occur through reversible redox reactions of MnO + Fe2O3 + 8Na+ + 8e− ↔ Mn + 2Fe + 4Na2O, of which the reduction/oxidation of MnO/Mn takes place at a lower potential than that of Fe2O3/Fe. Furthermore, a soft package sodium-ion full battery with MFO@C anode and Na3V2(PO4)2F3/C cathode was assembled, delivering a stable capacity of ∼400 mA h g−1 for MFO@C (with 100 cycles at 500 mA g−1) and a promising energy density of 77.8 Wh kg−1 for the whole battery. This is owing to the distinctive structure of very-fine MnFe2O4 nanodots embedded in porous N-doped carbon nanofibers, which effectively improves the utilization rate of active materials, facilitates the transportation of electrons and Na+ ions, and prevents the particle pulverization/agglomeration upon prolonged cycling. KEYWORDS: MnFe2O4 nanodots, porous N-doped carbon nanofibers, electrospinning, free-standing anode, sodium-ion batteries
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solvothermal method.19 In comparison, electrospinning technique has been employed to prepare nanostructured electrode materials such as Sn, Sb, and MoS2 embedded in carbon nanofibers.20−23 Such tailored nanocomposites significantly improved the Na-storage performance because ultrasmall grains (especially within 10 nm) could endure the mechanical stress caused by large volume fluctuation during sodiation/ desodiation. Meanwhile, one-dimensional carbon nanofibers would effectively enhance the electronic/ionic transport. Since transition-metal oxides generally face the problems of large volume expansion and poor conductivity in SIBs,24−26 and furthermore, the synthesis of ultrasmall MnFe2O4 nanoparticles (99.6%), which is beneficial for the ultralong cycle life. The high CE and high stability over long cycling also indicate that the generated Mn and Fe intermediates are stable with the electrolyte. The exceptional high-rate capability and cycling stability of MFO@ C are summarized in Table S4 (Supporting Information), which compare favorably with those previously reported for Mn/Fe-based oxides as anodes of SIBs.8,9,24,34,39 More excitingly, this is also a very outstanding performance among all the hot-studied Na-storage anodes, including P/C,5,37 Sn/ C,21 Sb/C,22 and MoS2/C.23 The morphological and structural changes of MFO@C electrode after high-rate and long-term cycling were examined 3326
DOI: 10.1021/acs.nanolett.6b00942 Nano Lett. 2016, 16, 3321−3328
Letter
Nano Letters using SEM and TEM. As revealed in Figure 5a,b, MFO@C after 300 cycles still retains its original appearance and structure with homogeneous distribution. The insert digital image in Figure 5a verifies that the electrode still maintains its integrity and flexibility after 300 cycles. In contrast, the large particles of H-MFO@C could not endure the deformation stress generated over repeated sodiation/desodiation,21,28 which have collapsed and aggregated to some extent after 250 cycles (Figure S14 in Supporting Information). This should account for the rapid capacity decay of H-MFO@C. The excellent performance of MFO@C/Na half cell encourages us to further evaluate its practicability in a Na-ion full cell. The MFO@C self-supported anode was paired with Na3V2(PO4)2F3/C cathode that delivers a stable capacity of ∼100 mA h g−1 in a half cell (Figure S15 in Supporting Information). An Al-plastic film soft package battery was assembled (inset of Figure 5c; for fabrication details see Experimental Section in Supporting Information). The active material weight ratio of anode to cathode was carefully balanced and set at 1:5, following the industrial standard. When tested between 1.0 and 3.5 V, the MFO@C−Na3V2(PO4)2F3/C full battery was first activated at a relatively low current density of 100 mA g−1 for 3 cycles (Figure S16 in Supporting Information). Afterward, it exhibits a discharge capacity of 406 mA h g−1 based on the mass of anodic MFO@C with an average output voltage of ∼2.3 V at 500 mA g−1 (Figure 5c). This corresponds to an energy density of 77.8 Wh kg−1 based on the total mass of the battery (6.72 g). The freedom of either binder or current collector can significantly reduce the inactive weight of battery, thus improving the energy density. After 100 cycles, the discharge capacity remains ∼392 mA h g−1, showing a high capacity retention (96.5%) with high CE of ∼99% (Figure 5d). This indicates that MFO@C nanofibers have potential for practical applications. In summary, MnFe2O4 nanodots (∼3.3 nm) were encapsulated in porous N-doped carbon nanofibers via a feasible electrospinning method. The as-prepared MFO@C nanofibers with flexible free-standing membrane were directly used as binder- and current collector-free anode for SIBs, demonstrating exceptional high-rate capability (305 mA h g−1 even at 10000 mA g−1) and ultralong cycling life (ca. 90% capacity retention over 4200 cycles). The reaction mechanism of MnFe2O4 + 8Na+ + 8e− → Mn + 2Fe + 4Na2O is taking place in the first discharge and Mn + 2Fe + 4Na2O → MnO + Fe2O3 + 8Na+ + 8e− in the first charge. While, it is MnO + Fe2O3 + 8Na+ + 8e− ↔ Mn + 2Fe + 4Na2O in the subsequent cycles. Additionally, the soft package Na-ion full battery with MFO@C anode and Na3V2(PO4)2F3/C cathode displayed a promising energy density of 77.8 Wh kg−1. As the anode of sodium-ion batteries, this tailored MFO@C nanostructure has shown prominent advantages including the uniform dispersion of ultrasmall nanoparticles in carbon matrix with high electrochemical activity, the facilitation of electrons and Na+ ions transportation in 3D conductive network interlinked by porous N-doped carbon nanofibers, and the depression of pulverization and aggregation of the active materials caused by volume change.
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Detailed experimental procedures; additional materials, electrodes, and batteries characterization (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the Programs of National NSFC (21231005 and 51231003) and MOE (113016A, B12015, and IRT13R30).
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REFERENCES
(1) Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Chem. Rev. 2014, 114, 11636−11682. (2) Sun, J.; Lee, H. W.; Pasta, M.; Yuan, H.; Zheng, G.; Sun, Y.; Li, Y.; Cui, Y. Nat. Nanotechnol. 2015, 10, 980−985. (3) Kundu, D.; Talie, E.; Duffort, V.; Nazar, L. F. Angew. Chem., Int. Ed. 2015, 54, 3431−3448. (4) Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S. Adv. Funct. Mater. 2013, 23, 947−958. (5) Song, J.; Yu, Z.; Gordin, M. L.; Hu, S.; Yi, R.; Tang, D.; Walter, T.; Regula, M.; Choi, D.; Li, X.; Manivannan, A.; Wang, D. H. Nano Lett. 2014, 14, 6329−6335. (6) Park, Y. U.; Seo, D. H.; Kwon, H. S.; Kim, B.; Kim, J.; Kim, H.; Kim, I.; Yoo, H. L.; Kang, K. J. Am. Chem. Soc. 2013, 135, 13870− 13878. (7) Chevrier, V. L.; Ceder, G. J. Electrochem. Soc. 2011, 158, A1011− A1014. (8) Oh, S. M.; Myung, S. T.; Yoon, C. S.; Lu, J.; Hassoun, J.; Scrosati, B.; Amine, K.; Sun, Y. K. Nano Lett. 2014, 14, 1620−1626. (9) Zhang, N.; Han, X.; Liu, Y.; Hu, X.; Zhao, Q.; Chen, J. Adv. Energy Mater. 2015, 5, 1401123. (10) Rahman, M. M.; Glushenkov, A. M.; Ramireddy, T.; Chen, Y. Chem. Commun. 2014, 50, 5057−5060. (11) Alcantara, R.; Jaraba, M.; Lavela, P.; Tirado, J. L. Chem. Mater. 2002, 4, 2847−2848. (12) Yuan, C.; Yu, H. B.; Xie, Y.; Lou, X. W. Angew. Chem., Int. Ed. 2014, 53, 1488−1504. (13) Wang, N.; Ma, X.; Wang, Y.; Yang, J.; Qian, Y. T. J. Mater. Chem. A 2015, 3, 9550−9555. (14) Xiao, Y.; Zai, J.; Tao, L.; Li, B.; Han, Q.; Yu, C.; Qian, X. Phys. Chem. Chem. Phys. 2013, 15, 3939−3945. (15) Sankar, K. V.; Selvan, R. K. J. Power Sources 2015, 275, 399−407. (16) Zhu, H.; Zhang, S.; Huang, Y. X.; Wu, L.; Sun, S. H. Nano Lett. 2013, 13, 2947−2951. (17) Zhang, Z. J.; Wang, Z. L.; Chakoumakos, B. C.; Yin, J. S. J. Am. Chem. Soc. 1998, 120, 1800−1804. (18) Zeng, H.; Rice, P. M.; Wang, S. X.; Sun, S. H. J. Am. Chem. Soc. 2004, 126, 11458−11459. (19) Liu, S.; Xie, J.; Sun, Q.; Du, G.; Zhang, S.; Cao, G.; Zhu, T.; Zhao, X. Nano Energy 2014, 8, 84−94. (20) Peng, S.; Li, L.; Hu, Y.; Srinivasan, M.; Cheng, F.; Chen, J.; Ramakrishna, S. ACS Nano 2015, 9, 1945−1954. (21) Liu, Y. C.; Zhang, N.; Jiao, L. F.; Chen, J. Adv. Mater. 2015, 27, 6702−6707. (22) Zhu, Y.; Han, X.; Xu, Y.; Liu, Y.; Zheng, S.; Xu, K.; Hu, L.; Wang, C. S. ACS Nano 2013, 7, 6378−6386. (23) Zhu, C.; Mu, X.; van Aken, P. A.; Yu, Y.; Maier, J. Angew. Chem., Int. Ed. 2014, 53, 2152−2156. (24) Jian, Z.; Zhao, B.; Liu, P.; Li, F.; Zheng, M.; Chen, M.; Shi, Y.; Zhou, H. S. Chem. Commun. 2014, 50, 1215−1217. (25) Klavetter, K. C.; Garcia, S.; Dahal, N.; Snider, J. L.; Souza, J. P.; Cell, T. H.; Cassara, M. A.; Heller, A.; Humphrey, S. M.; Mullins, C. B. J. Mater. Chem. A 2014, 2, 14209−14221.
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.nanolett.6b00942. 3327
DOI: 10.1021/acs.nanolett.6b00942 Nano Lett. 2016, 16, 3321−3328
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Nano Letters (26) Lu, Y.; Zhang, N.; Zhao, Q.; Liang, J.; Chen, J. Nanoscale 2015, 7, 2770−2776. (27) Kang, E.; Park, J.; Hwang, Y.; Kang, M.; Park, J. G.; Hyeon, T. J. Phys. Chem. B 2004, 108, 13932−13935. (28) Zhu, Z.; Wang, S.; Du, J.; Jin, Q.; Zhang, T.; Cheng, F. Y.; Chen, J. Nano Lett. 2014, 14, 153−157. (29) Ding, J.; Wang, H.; Li, Z.; Kohandehghan, A.; Cui, K.; Xu, Z.; Zahiri, B.; Tan, X.; Lotfabad, E. M.; Olsen, B. C.; Mitlin, D. ACS Nano 2013, 7, 11004−11015. (30) Jeon, K. J.; Moon, H. R.; Ruminski, A. M.; Jiang, B.; Kisielowski, C.; Bardhan, R.; Urban, J. J. Nat. Mater. 2011, 10, 286−290. (31) Liu, B.; Hu, X.; Xu, H.; Luo, W.; Sun, Y.; Huang, Y. H. Sci. Rep. 2014, 4, 4229. (32) Zhu, X.; Zhu, Y.; Murali, S.; Stoller, M. D.; Ruoff, R. S. ACS Nano 2011, 5, 3333−3338. (33) Sheng, Z. H.; Shao, L.; Chen, J. J.; Bao, W. J.; Wang, F. B.; Xia, X. H. ACS Nano 2011, 5, 4350−4358. (34) Zhao, Y.; Feng, Z.; Xu, Z. J. Nanoscale 2015, 7, 9520−9525. (35) Cao, Y.; Xiao, L.; Sushko, M. L.; Wang, W.; Schwenzer, B.; Xiao, J.; Nie, Z.; Saraf, L. V.; Yang, Z.; Liu, J. Nano Lett. 2012, 12, 3783− 3787. (36) Chen, J.; Xu, L.; Li, W.; Gou, X. Adv. Mater. 2005, 17, 582−586. (37) Qian, J.; Wu, X.; Cao, Y.; Ai, X.; Yang, H. Angew. Chem. 2013, 125, 4731−4734. (38) Ji, L.; Gu, M.; Shao, Y.; Li, X.; Engelhard, M. H.; Arey, B. W.; Wang, W.; Nie, Z.; Xiao, J.; Wang, C.; Zhang, J. G.; Liu, J. Adv. Mater. 2014, 26, 2901−2908. (39) Jiang, Y.; Hu, M.; Zhang, D.; Yuan, T.; Sun, W.; Xu, B.; Yan, M. Nano Energy 2014, 5, 60−66.
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DOI: 10.1021/acs.nanolett.6b00942 Nano Lett. 2016, 16, 3321−3328
