Thesis Advisor刘会洲
Degree Grantor中国科学院研究生院
Degree Name硕士
Degree Discipline化学工程

Na3(VO1-xPO4)2F1+2x(0≤x≤1)作为钠离子电池正极材料由于结构稳定、工作电压和理论比容高而受到科学界的广泛关注。生产电池的成本与能耗主要是由生产电池正极材料的成本与能耗决定的。当前用于合成Na3(VO1-xPO4)2F1+2x(0≤x≤1)的高温固相法和水热法普遍存在前驱体昂贵和能耗高的问题。为了进一步降低合成Na3(VO1-xPO4)2F1+2x(0≤x≤1)的成本与能耗,我们提出了分离制备一体化理念,即将钒的工业分离产物用于合成Na3(VO1-xPO4)2F1+2x(0≤x≤1)。基于分离制备一体化的理念,我们以钒的工业分离产物NaVO3为钒源,实现了一步水热制备表面包覆水热碳的Na3(VOPO4)2F,并探索了室温制备Na3(VOPO4)2F的方法。为了表征所合成的Na3(VOPO4)2F中钒的价态,我们还建立了一种利用紫外可见吸收光谱表征Na3(VO1-xPO4)2F1+2x(0≤x≤1)中钒表观价态的方法。首先,以NaVO3为钒源,葡萄糖为还原剂和碳源,我们实现了一步水热制备表面包碳的Na3(VOPO4)2F。所合成的材料是单晶,形貌特殊,粒径在6 μm左右,且具有良好的电化学性能。在2 C下的放电比容能够达到113 mAh g-1,在5 C下循环1400周后容量保持率能够达到76.7%。为进一步降低材料合成的能耗,我们以NaVO3为钒源,抗坏血酸或盐酸羟胺为还原剂,探索了Na3(VOPO4)2F的室温制备。研究了提高室温制备Na3(VOPO4)2F结晶性的方法。此外,还研究了掺杂石墨烯或包碳对Na3(VOPO4)2F倍率性能的影响。虽然所制备的Na3(VOPO4)2F的电化学性能有待进一步提高,但是我们对于提高Na3(VOPO4)2F结晶性和倍率性能的探索为今后各类聚阴离子化合物的室温制备奠定了研究基础。含有不同价态钒的Na3(VO1-xPO4)2F1+2x(0≤x≤1)具有不同的晶体结构和电化学行为,因此有必要对Na3(VO1-xPO4)2F1+2x(0≤x≤1)中钒的表观价态进行表征。由于本文中报道的两种合成Na3(VOPO4)2F的方法都需要将高价钒还原成可反应的低价钒。因此有必要对低价钒的具体价态进行表征,以确定所合成的材料中钒的表观价态。基于不同价态钒的水溶液呈现不同特征吸收峰的特点,我们提出了利用紫外可见吸收光谱定量表征Na3(VO1-xPO4)2F1+2x(0≤x≤1)中钒表观价态的办法。与之前报道的利用X射线光电子能谱、红外光谱X射线吸收近边结构谱、固体核磁共振、X射线衍射精修等表征氟磷酸钒钠中钒表观价态的方法相比,这种方法操作简单,具有广阔的应用前景。 ;Na3(VO1-xPO4)2F1+2x(0≤x≤1), cathode material of sodium-ion batteries, has attracted wide attention due to its stable chemical structure, high working voltage and discharge capacity. As it is widely known, the energy consumption and cost in producing a battery is mainly decided by the cathode producing process. However, expensive precursors and high energy consumption are still the problem in synthesis of Na3(VO1-xPO4)2F1+2x(0≤x≤1). To decrease the cost and energy consumption in producing Na3(VO1-xPO4)2F1+2x(0≤x≤1), a concept about integration of precursor separation and synthesis of material is proposed. As for the synthesis of Na3(VO1-xPO4)2F1+2x(0≤x≤1), it is integration of the extraction of vanadium and the synthesis of Na3(VO1-xPO4)2F1+2x(0≤x≤1). Based on this concept, we developed a one-pot hydrothermal method to synthesize carbon coated Na3(VOPO4)2F , and a room-temperature method to synthesize Na3(VOPO4)2F . Both of the two methods use NaVO3, industrial product isolated from vanadium slages, as vanadium sources. In order to characterize the valence of vanadium in the as-synthesized Na3(VOPO4)2F, we developed a new method based on UV-Vis absorption spectra to characterize the apparent valence of vanadium.Firstly, a one-pot hydrothermal method to synthesize carbon coated Na3(VOPO4)2F is developed, using NaVO3 as vanadium sources, glucose as carbon sources and reducing agent. The as-synthesized Na3(VOPO4)2F monocrystal has a special Rubik-like morphology with a diameter of 6 μm. The as-synthesized Na3(VOPO4)2F delivers an excellent sodium-storage property with a discharge capacity of 113 mAh g-1 at 10 C and capacity retention of 76.7% after 1400 cycles at 5 C.In order to further decrease the energy consumption in synthesis of Na3(VOPO4)2F, room-temperature synthesis of Na3(VOPO4)2F is studied. As poor crystalline limited the improvement of the Na-storage performance of the as-synthesized Na3(VOPO4)2F. Methods to improve the crystallinity of material are studied. Doping graphene and carbon coating was also studied to further improve rate performance of Na3(VOPO4)2F. Although the as-synthesized Na3(VOPO4)2F didn’t show an excellent Na-storage performance, this study established a foundation for the future research about room-termperature synthesis of polyanionic compounds.Na3(VO1-xPO4)2F1+2x(0≤x≤1) with different valence of vanadium has different crystal structure and electrochemical behavior. Hence, it is necessary to characterize the valence of vanadium in Na3(VOPO4)2F. Reducing high valence of vanadium to low valence is inevitable if NaVO3 is used as precusor. So it is necessary to characterize the specific valence of vanadium in the as-synthesized Na3(VOPO4)2F. Hence, a new method based on UV-Vis absorption spectra to characterize the apparent valence of vanadium in Na3(VOPO4)2F is developed. Compared with other methods, which use XPS, IR, XANES, solid-state NMR to characterize apparent valence of vanadium, this method is simpler and has a potential application prospects. 

Document Type学位论文
Recommended Citation
GB/T 7714
仝梓正. 基于五价钒的氟磷酸钒钠的低温制备及储钠性能研究[D]. 中国科学院研究生院,2018.
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