Xihui Nan,Chaofeng Liu,Changkun Zhang,Wenda Ma,Kan Wang,Zhuoyu Li,Guozhong Cao
V2(PO4)O/C is a promising new anode material for lithium ion batteries with excellent electrochemical properties, synthesized by a facile one pot hydrothermal method, followed by a two-step calcination process. The composite can deliver a reversible capacity of 445 mA h g−1, 409 mA h g−1 and 382 mA h g−1 at 1.0, 1.5 and 2.0 A g−1. The capacity retentions of V2(PO4)O/C cycled at 1 and 5 A g−1 for 200 cycles are 90% and 80%, respectively. The excellent electrochemical properties are mainly attributed to the following three factors: (1) face-sharing [VO6] octahedral arrays endow the crystal with a high intrinsic electronic conductivity; (2) the good lithium ion diffusion coefficient of the material contributes for reducing electrochemical and concentration polarization in the charge–discharge process; and (3) porous microstructure and nanoscale particles not only permit effective contact between the electrolyte and active material, but also provide more space to accommodate volume change during the discharge/charge processes. The results in this study provide convincing evidence that V2(PO4)O/C has significant research value for future practical applications.
Bin Xiao,Wen-hai Zhang,Hai-feng Xia,Zhi-teng Wang,Lin-bo Tang,Chang-sheng An,Zhen-jiang He,Hui Tong,Jun-chao Zheng
V2(PO4)O is a novel promising anode material because of its stable crystal structure, low cost, and environmentally friendliness. However, its low electronic and ionic conductivity result in poor specific capacity and rate performance, hindering its industrial application. In this study, V2(PO4)O/C@CNT hollow spheres (HSs) with a core–shell structure were successfully synthesized by a simple spray drying method. Pluronic® F-127 acted as a carbon source and template, and induced the V2(PO4)O particles to form HSs. The V2(PO4)O/C@CNT HSs were composed of uniform HSs of about 0.4–0.6 μm in diameter and carbon nanotubes (CNTs). The HS structure enhances the electronic conductivity and lithium ion transport rate of V2(PO4)O/C materials and thus helps improve the electrochemical performance. CNTs not only increase the electronic conductivity and lithium ion transport rate, but also hinder the aggregation of the HSs. These activities enhance the electrochemical performance. The lithium ion storage behavior of V2(PO4)O/C@CNT HSs is systematically studied in the potential range 0.01–3.0V. The V2(PO4)O/C@CNT HS anode can achieve a high reversible capacity of 894.9 mA h g−1 at 0.1 A g−1 and can obtain a reversible capacity of 490.4 mA h g−1 at a high rate of 5 A g−1, perhaps the best electrochemical performance demonstrated so far for a V2(PO4)O anode material (specific capacity and rate performance), indicating its promise for application as an anode material in advanced lithium-ion batteries.
Bin Xiao,Wen-hai Zhang,Peng-bo Wang,Lin-bo Tang,Chang-sheng An,Zhen-jiang He,Hui Tong,Jun-chao Zheng,Bo Wang
Phosphate-based polyanion-structured materials have attracted considerable attention as anode materials in lithium-/sodium-ion batteries due to their stable crystal structure, affordability, and environmental friendliness. V 2 (PO 4 )O was encapsulated into crumpled nitrogen-doped graphene (VPO@N-G) through a facile spray-drying method in which VPO particles were completely encapsulated by N-doped graphene. For the first time, VPO@N-G was explored as an anode material for sodium-ion batteries. The Na + storage behavior of VPO@N-G was systematically investigated at the voltage range of 0.01–3.0 V (versus Na/Na + ). Results indicated that the VPO@N-G anode can deliver a highly reversible discharge capacity of 539 mAh g −1 at 0.05 A g −1 and achieve a highly reversible discharge capacity of 235.9 mAh g −1 even at a high current density of 10 A g −1 . Thus, VPO@N-G can be applied as a high-rate anode material for sodium-ion batteries.
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