Graphical Abstract

Nanomaterials with electrochemical activity are always suffering from aggregations, particularly during the high-temperature synthesis processes, which will lead to decreased energy-storage performance. Here, hierarchically structured lithium titanate/nitrogen-doped porous graphene fiber nanocomposites were synthesized by using confined growth of Li4Ti5O12 (LTO) nanoparticles in nitrogen-doped mesoporous graphene fibers (NPGF). NPGFs with uniform pore structure are used as templates for hosting LTO precursors, followed by high-temperature treatment at 800 ℃ under argon (Ar). LTO nanoparticles with size of several nanometers are successfully synthesized in the mesopores of NPGFs, forming nanostructured LTO/NPGF composite fibers. As an anode material for lithium-ion batteries, such nanocomposite architecture offers effective electron and ion transport, and robust structure. Such nanocomposites in the electrodes delivered a high reversible capacity (164 mAh·g–1 at 0.3 C), excellent rate capability (102 mAh·g–1 at 10 C), and long cycling stability.
Etacheri, V.; Marom, R.; Elazari, R.; Salitra, G.; Aurbach, D. Challenges in the development of advanced Li-ion batteries: A review. Energy Environ. Sci. 2011, 4, 3243–3262.
Scrosati, B.; Garche, J. Lithium batteries: Status, prospects and future. J. Power Sources 2010, 195, 2419–2430.
Yi, T. -F.; Yang, S. -Y.; Xie, Y. Recent advances of Li4Ti5O12 as a promising next generation anode material for high power lithium-ion batteries. J. Mater. Chem. A 2015, 3, 5750–5777.
Naoi, K.; Naoi, W.; Aoyagi, S.; Miyamoto, J. -I.; Kamino, T. New generation "nanohybrid supercapacitor". Acc. Chem. Res. 2013, 46, 1075–1083.
Wang, Y. -Q.; Gu, L.; Guo, Y. -G.; Li, H.; He, X. -Q.; Tsukimoto, S.; Ikuhara, Y.; Wan, L. -J. Rutile-TiO2 nanocoating for a high-rate Li4Ti5O12 anode of a lithium-ion battery. J. Am. Chem. Soc. 2012, 134, 7874–7879.
Lim, J.; Choi, E.; Mathew, V.; Kim, D.; Ahn, D.; Gim, J.; Kang, S. -H.; Kim, J. Enhanced high-rate performance of Li4Ti5O12 nanoparticles for rechargeable Li-ion batteries. J. Electrochem. Soc. 2011, 158, A275–A280.
Jiang, C. H.; Ichihara, M.; Honma, I.; Zhou, H. S. Effect of particle dispersion on high rate performance of nano-sized Li4Ti5O12 anode. Electrochim. Acta 2007, 52, 6470–6475.
Haridas, A. K.; Sharma, C. S.; Rao, T. N. Donut-shaped Li4Ti5O12 structures as a high performance anode material for lithium ion batteries. Small 2015, 11, 290–294.
Zhang, Y. L.; Hu, X. B.; Xu, Y. L.; Ding, M. L. Recent progress of Li4Ti5O12 with different morphologies as anode material. Acta Chim. Sin. 2013, 71, 1341–1353.
Jung, H. -G.; Myung, S. -T.; Yoon, C. S.; Son, S. -B.; Oh, K. H.; Amine, K.; Scrosati, B.; Sun, Y. -K. Microscale spherical carbon-coated Li4Ti5O12 as ultra high power anode material for lithium batteries. Energy Environ. Sci. 2011, 4, 1345–1351.
Ganapathy, S.; Wagemaker, M. Nanosize storage properties in spinel Li4Ti5O12 explained by anisotropic surface lithium insertion. ACS Nano 2012, 6, 8702–8712.
Bruce, P. G.; Scrosati, B.; Tarascon, J. M. Nanomaterials for rechargeable lithium batteries. Angew. Chem., Int. Ed. 2008, 47, 2930–2946.
Cheng, J.; Che, R. C.; Liang, C. Y.; Liu, J. W.; Wang, M.; Xu, J. J. Hierarchical hollow Li4Ti5O12 urchin-like microspheres with ultra-high specific surface area for high rate lithium ion batteries. Nano Res. 2014, 7, 1043–1053.
Wang, X. F.; Liu, B.; Hou, X. J.; Wang, Q. F.; Li, W. W.; Chen, D.; Shen, G. Z. Ultralong-life and high-rate web-like Li4Ti5O12 anode for high-performance flexible lithium-ion batteries. Nano Res. 2014, 7, 1073–1082.
Xu, H. H.; Hu, X. L.; Sun, Y. M.; Luo, W.; Chen, C. J.; Liu, Y.; Huang, Y. H. Highly porous Li4Ti5O12/C nanofibers for ultrafast electrochemical energy storage. Nano Energy 2014, 10, 163–171.
Feckl, J. M.; Fominykh, K.; Döblinger, M.; Fattakhova-Rohlfing, D.; Bein, T. Nanoscale porous framework of lithium titanate for ultrafast lithium insertion. Angew. Chem. , Int. Ed. 2012, 51, 7459–7463.
Shen, L. F.; Uchaker, E.; Zhang, X. G.; Cao, G. Z. Hydrogenated Li4Ti5O12 nanowire arrays for high rate lithium ion batteries. Adv. Mater. 2012, 24, 6502–6506.
Chen, S.; Xin, Y. L.; Zhou, Y. Y.; Ma, Y. R.; Zhou, H. H.; Qi, L. M. Self-supported Li4Ti5O12 nanosheet arrays for lithium ion batteries with excellent rate capability and ultralong cycle life. Energy Environ. Sci. 2014, 7, 1924–1930.
Liu, J.; Song, K. P.; van Aken, P. A.; Maier, J.; Yu, Y. Self-supported Li4Ti5O12-C nanotube arrays as high-rate and long-life anode materials for flexible Li-ion batteries. Nano Lett. 2014, 14, 2597–2603.
Kang, E.; Jung, Y. S.; Kim, G. H.; Chun, J.; Wiesner, U.; Dillon, A. C.; Kim, J. K.; Lee, J. Highly improved rate capability for a lithium-ion battery nano-Li4Ti5O12 negative electrode via carbon-coated mesoporous uniform pores with a simple self-assembly method. Adv. Funct. Mater. 2011, 21, 4349–4357.
Sorensen, E. M.; Barry, S. J.; Jung, H. -K.; Rondinelli, J. M.; Vaughey, J. T.; Poeppelmeier, K. R. Three-dimensionally ordered macroporous Li4Ti5O12: Effect of wall structure on electrochemical properties. Chem. Mater. 2006, 18, 482–489.
Kubiak, P.; Garcia, A.; Womes, M.; Aldon, L.; Olivier- Fourcade, J.; Lippens, P. -E.; Jumas, J. -C. Phase transition in the spinel Li4Ti5O12 induced by lithium insertion: Influence of the substitutions Ti/V, Ti/Mn, Ti/Fe. J. Power Sources 2003, 119–121, 626–630.
Chen, C. H.; Vaughey, J. T.; Jansen, A. N.; Dees, D. W.; Kahaian, A. J.; Goacher, T.; Thackeray, M. M. Studies of Mg-substituted Li4−xMgxTi5O12 spinel electrodes (0 ≤ x ≤ 1) for lithium batteries. J. Electrochem. Soc. 2001, 148, A102– A104.
Li, B. H.; Han, C. P.; He, Y. -B.; Yang, C.; Du, H. D.; Yang, Q. -H.; Kang, F. Y. Facile synthesis of Li4Ti5O12/C composite with super rate performance. Energy Environ. Sci. 2012, 5, 9595–9602.
Zhu, G. -N.; Wang, C. -X.; Xia, Y. -Y. A comprehensive study of effects of carbon coating on Li4Ti5O12 anode material for lithium-ion batteries. J. Electrochem. Soc. 2011, 158, A102–A109.
Zhang, Z. H.; Li, G. C.; Peng, H. R.; Chen, K. Z. Hierarchical hollow microspheres assembled from N-doped carbon coated Li4Ti5O12 nanosheets with enhanced lithium storage properties. J. Mater. Chem A 2013, 1, 15429–15434.
Pan, H. L.; Zhao, L.; Hu, Y. -S.; Li, H.; Chen, L. Q. Improved Li-storage performance of Li4Ti5O12 coated with C-N compounds derived from pyrolysis of urea through a low-temperature approach. ChemSusChem 2012, 5, 526–529.
Shen, L. F.; Zhang, X. G.; Uchaker, E.; Yuan, C. Z.; Cao, G. Z. Li4Ti5O12 nanoparticles embedded in a mesoporous carbon matrix as a superior anode material for high rate lithium ion batteries. Adv. Energy Mater. 2012, 2, 691–698.
Shen, L. F.; Li, H. S.; Uchaker, E.; Zhang, X. G.; Cao, G. Z. General strategy for designing core–shell nanostructured materials for high-power lithium ion batteries. Nano Lett. 2012, 12, 5673–5678.
Kim, K. -T.; Yu, C. -Y.; Yoon, C. S.; Kim, S. -J.; Sun, Y. -K.; Myung, S. -T. Carbon-coated Li4Ti5O12 nanowires showing high rate capability as an anode material for rechargeable sodium batteries. Nano Energy 2015, 12, 725–734.
Li, H. Q.; Zhou, H. S. Enhancing the performances of Li- ion batteries by carbon-coating: Present and future. Chem. Commun. 2012, 48, 1201–1217.
Yuan, T.; Cai, R.; Shao, Z. P. Different effect of the atmospheres on the phase formation and performance of Li4Ti5O12 prepared from ball-milling-assisted solid-phase reaction with pristine and carbon-precoated TiO2 as starting materials. J. Phys. Chem. C 2011, 115, 4943–4952.
Jia, X. L.; Kan, Y. F.; Zhu, X.; Ning, G. Q.; Lu, Y. F.; Wei, F. Building flexible Li4Ti5O12/CNT lithium-ion battery anodes with superior rate performance and ultralong cycling stability. Nano Energy 2014, 10, 344–352.
Yuan, T.; Li, W. -T.; Zhang, W. M.; He, Y. -S.; Zhang, C. M.; Liao, X. -Z.; Ma, Z. -F. One-pot spray-dried graphene sheets- encapsulated nano-Li4Ti5O12 microspheres for a hybrid BatCap system. Ind. Eng. Chem. Res. 2014, 53, 10849–10857.
Zhu, G. -N.; Liu, H. -J.; Zhuang, J. -H.; Wang, C. -X.; Wang, Y. -G.; Xia, Y. -Y. Carbon-coated nano-sized Li4Ti5O12 nanoporous micro-sphere as anode material for high-rate lithium-ion batteries. Energy Environ. Sci. 2011, 4, 4016–4022.
Vujković, M.; Stojković, I.; Mitrić, M.; Mentus, S.; Cvjetićanin, N. Hydrothermal synthesis of Li4Ti5O12/C nanostructured composites: Morphology and electrochemical performance. Mater. Res. Bull. 2013, 48, 218–223.
Liu, T. T.; Ni, H. F.; Song, W. -L.; Fan, L. -Z. Enhanced electrochemical performance of Li4Ti5O12 as anode material for lithium-ion batteries with different carbons as support. J. Alloys Compd. 2015, 646, 189–194.
Shi, Y.; Wen, L.; Li, F.; Cheng, H. -M. Nanosized Li4Ti5O12/ graphene hybrid materials with low polarization for high rate lithium ion batteries. J. Power Sources 2011, 196, 8610– 8617.
Li, N.; Chen, Z. P.; Ren, W. C.; Li, F.; Cheng, H. -M. Flexible graphene-based lithium ion batteries with ultrafast charge and discharge rates. Proc. Natl. Acad. Sci. USA 2012, 109, 17360–17365.
Bonaccorso, F.; Colombo, L.; Yu, G.; Stoller, M.; Tozzini, V.; Ferrari, A. C.; Ruoff, R. S.; Pellegrini, V. Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage. Science 2015, 347, 1246501.
Zhao, B. T.; Ran, R.; Liu, M. L.; Shao, Z. P. A comprehensive review of Li4Ti5O12-based electrodes for lithium-ion batteries: The latest advancements and future perspectives. Mater. Sci. Eng. : R 2015, 98, 1–71.
Naoi, K.; Ishimoto, S.; Isobe, Y.; Aoyagi, S. High-rate nano-crystalline Li4Ti5O12 attached on carbon nano-fibers for hybrid supercapacitors. J. Power Sources 2010, 195, 6250–6254.
Tang, Y. F.; Huang, F. Q.; Zhao, W.; Liu, Z. Q.; Wan, D. Y. Synthesis of graphene-supported Li4Ti5O12 nanosheets for high rate battery application. J. Mater. Chem. 2012, 22, 11257–11260.
Ni, H. F.; Fan, L. -Z. Nano-Li4Ti5O12 anchored on carbon nanotubes by liquid phase deposition as anode material for high rate lithium-ion batteries. J. Power Sources 2012, 214, 195–199.
Shi, Y.; Gao, J.; Abruña, H. D.; Liu, H. K.; Li, H. J.; Wang, J. Z.; Wu, Y. P. Rapid synthesis of Li4Ti5O12/graphene composite with superior rate capability by a microwave- assisted hydrothermal method. Nano Energy 2014, 8, 297–304.
Shen, L. F.; Yuan, C. Z.; Luo, H. J.; Zhang, X. G.; Yang, S. D.; Lu, X. J. In situ synthesis of high-loading Li4Ti5O12- graphene hybrid nanostructures for high rate lithium ion batteries. Nanoscale 2011, 3, 572–574.
Jia, X. L.; Zhang, G. L.; Wang, T. H.; Zhu, X.; Yang, F.; Li, Y. F.; Lu, Y. F.; Wei, F. Monolithic nitrogen-doped graphene frameworks as ultrahigh-rate anodes for lithium ion batteries. J. Mater. Chem. A 2015, 3, 15738–15744.
Zhao, L.; Hu, Y. -S.; Li, H.; Wang, Z. X.; Chen, L. Q. Porous Li4Ti5O12 coated with N-doped carbon from ionic liquids for Li-ion batteries. Adv. Mater. 2011, 23, 1385–1388.
Jia, X. L.; Cheng, Y. H.; Lu, Y. F.; Wei, F. Building robust carbon nanotube-interweaved-nanocrystal architecture for high-performance anode materials. ACS Nano 2014, 8, 9265–9273.
Augustyn, V.; Come, J.; Lowe, M. A.; Kim, J. W.; Taberna, P. -L.; Tolbert, S. H.; Abruña, H. D.; Simon, P.; Dunn, B. High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance. Nat. Mater. 2013, 12, 518–522.
Xu, G. B.; Li, W.; Yang, L. W.; Wei, X. L.; Ding, J. W.; Zhong, J. X.; Chu, P. K. Highly-crystalline ultrathin Li4Ti5O12 nanosheets decorated with silver nanocrystals as a high- performance anode material for lithium ion batteries. J. Power Sources 2015, 276, 247–254.
Yang, Y. C.; Qiao, B. H.; Yang, X. M.; Fang, L. B.; Pan, C. C.; Song, W. X.; Hou, H. S.; Ji, X. B. Lithium titanate tailored by cathodically induced graphene for an ultrafast lithium ion battery. Adv. Funct. Mater. 2014, 24, 4349–4356.
Rakhi, R. B.; Chen, W.; Cha, D.; Alshareef, H. N. Nanostructured ternary electrodes for energy-storage applications. Adv. Energy Mater. 2012, 2, 381–389.
Jia, X. L.; Chen, Z.; Suwarnasarn, A.; Rice, L.; Wang, X. L.; Sohn, H. S.; Zhang, Q.; Wu, B. M.; Wei, F.; Lu, Y. F. High- performance flexible lithium-ion electrodes based on robust network architecture. Energy Environ. Sci. 2012, 5, 6845– 6849.
Song, M. -S.; Benayad, A.; Choi, Y. -M.; Park, K. -S. Does Li4Ti5O12 need carbon in lithium ion batteries? Carbon-free electrode with exceptionally high electrode capacity. Chem. Commun. 2012, 48, 516–518.
Young, D.; Ransil, A.; Amin, R.; Li, Z.; Chiang, Y. -M. Electronic conductivity in the Li4/3Ti5/3O4–Li7/3Ti5/3O4 system and variation with state-of-charge as a Li battery anode. Adv. Energy Mater. 2013, 3, 1125–1129.
Zhang, Z. H.; Li, G. C.; Peng, H. R.; Chen, K. Z. Hierarchical hollow microspheres assembled from N-doped carbon coated Li4Ti5O12 nanosheets with enhanced lithium storage properties. J. Mater. Chem. A 2013, 1, 15429–15434.