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Hollow–Cuboid Li3VO4/C as High-Performance Anodes for Lithium-Ion Batteries

Zhang, Changkun, Liu, Chaofeng, Nan, Xihui, Song, Huanqiao, Liu, Yaguang, Zhang, Cuiping, Cao, Guozhong
ACS applied materials 2016 v.8 no.1 pp. 680-688
Raman spectroscopy, X-ray diffraction, anodes, batteries, carbon, electrical conductivity, electrochemistry, ions, lithium, pyrolysis, reaction kinetics, surface area
Li₃VO₄ has been demonstrated to be a promising anode material for lithium-ion batteries with a low, safe voltage and large capacity. However, its poor electronic conductivity hinders its practical application particularly at a high rate. This work reports that Li₃VO₄ coated with carbon was synthesized by a one-pot, two-step method with F127 ((PEO)₁₀₀–(PPO)₆₅–(PEO)₁₀₀) as both template and carbon source, yielding a microcuboid structure. The resulting Li₃VO₄/C cuboid shows a stable capacity of 415 mAh g–¹ at 0.5 C and excellent capacity stability at high rates (e.g., 92% capacity retention after 1000 cycles at 10 C = 4 A g–¹). The lithiation/delithiation process of Li₃VO₄/C was studied by ex situ X-ray diffraction and Raman spectroscopy, which confirmed that Li₃VO₄/C underwent a reversible intercalation reaction during discharge/charge processes. The excellent electrochemical performance is attributed largely to the unique microhollow structure. The voids inside hollow structure can not only provide more space to accommodate volume change during discharge/charge processes but also allow the lithium ions insertion and extraction from both outside and inside the hollow structure with a much larger surface area or more reaction sites and shorten the lithium ions diffusion distance, which leads to smaller overpotential and faster reaction kinetics. Carbon derived from F127 through pyrolysis coats Li₃VO₄ conformably and thus offers good electrical conduction. The results in this work provide convincing evidence that the significant potential of hollow–cuboid Li₃VO₄/C for high-power batteries.