Abstract
Nano-sized LiFePO4·Li3V2(PO4)3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine LiFePO4 and monoclinic Li3V2(PO4)3 phases with small amounts of V-doped LiFePO4 and Fe-doped Li3V2(PO4)3. The magnetic properties of LiFePO4·Li3V2(PO4)3/C are significantly different from LiFePO4/C. Trace quantities of ferromagnetic impurities and Fe2P are verified in LiFePO4/C and LiFePO4·Li3V2(PO4)3/C by magnetic tests, respectively. LiFe-PO4·Li3V2(PO4)3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates. The initial discharge capacities are 136.4 and 130.0 mA h g−1, and the capacity retentions are more than 98% after 100 cycles at 2 C and 5 C, respectively, remarkably better than those of LiFePO4/C. The excellent electrochemical performances are ascribed to the mutual doping of V3+ and Fe2+, complementary advantages of LiFePO4 and Li3V2(PO4)3 phases, the residual high-ordered carbon and Fe2P with outstanding electric conductivity in the nanocomposite.
摘要
本文采用冷冻干燥与溶胶-凝胶相结合的方法制备了纳米复合材料LiFePO4·Li3V2(PO4)3/C. XRD结果表明该复合材料主要由橄榄石型LiFePO4和单斜晶系Li3V2(PO4)3相组成, 同时包含少量的V掺杂LiFePO4和Fe掺杂Li3V2(PO4)3. 磁学测试结果表明, LiFePO4·Li3V2(PO4)3/C的磁学特性显著区别于LiFePO4/C, 并且痕量的铁磁性杂质和Fe2P杂质分别存在于LiFePO4/C和LiFePO4·Li3V2(PO4)3/C中. LiFePO4·Li3V2-(PO4)3/C具有相对优良的循环稳定性, 尤其是在大倍率条件下. 在2 C和5 C时, 首次放电容量分别为136.4和130.0 mA h g-1, 100周循环后保持率在98%以上, 优于LiFePO4/C的电化学性能. LiFePO4·Li3V2(PO4)3/C电化学性能的改善归因于V3+和Fe2+的相互掺杂, LiFePO4和Li3V2-(PO4)3相的优势互补, 残留的高有序碳以及导电性优异的Fe2P.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (21673051), Guangdong Province Science & Technology Bureau (2014A010106029, 2014B010106005 and 2016A010104015), Guangzhou Science & Innovative Committee (201604030037), the Youth Foundation of Guangdong University of Technology (252151038), the link project of the National Natural Science Foundation of China and Guangdong Province (U1401246), and the Science and Technology Program of Guangzhou City of China (201508030018).
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Author contributions Liu L designed the experiments and wrote the initial manuscript; Xiao W and Guo J performed the experiments with support from Liu L, Cui Y and Chen Y; Shi Z and Chou S guided the work. All authors contribute to analysis of the data and advice for the paper writing.
Conflict of interest The authors declare that they have no conflict of interest.
Liying Liu received her PhD degree in 2006 from Northeastern University. Then she joined Guangdong University of Technology as a lecturer until now. Meanwhile, she worked as a post-doctoral fellow in Mcnair Technology Co., Ltd. from 2008 to 2010, as a visiting fellow at University of Wollongong in Australia from 2016 to 2017. Her research focuses on energy storage materials for batteries.
Zhicong Shi is a professor at Guangdong University of Technology, where he presently serves as the Head of Department of New Energy Materials and Devices and the Director of Guangdong Engineering Centre for New Energy Materials and Devices. He received his PhD in physical chemistry from Xiamen University in 2005. His current research interests include novel materials for batteries, supercapacitors and fuel cells.
ShuLei Chou is a senior research fellow in ISEM at University of Wollongong (UOW). He obtained his Bachelor (1999) and Master degree (2004) in Nankai University, China. His PhD degree was received from UOW with the best thesis award in 2010. His research has been focused on energy storage materials for battery applications, especially on novel composite materials, new binders and new electrolytes for Li/Na batteries.
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Liu, L., Xiao, W., Guo, J. et al. Nanocomposite LiFePO4·Li3V2(PO4)3/C synthesized by freeze-drying assisted sol-gel method and its magnetic and electrochemical properties. Sci. China Mater. 61, 39–47 (2018). https://doi.org/10.1007/s40843-017-9114-0
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DOI: https://doi.org/10.1007/s40843-017-9114-0