【作者】 徐燕；

【导师】 王欣；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2011， 硕士

【摘要】 本文首先研究了锂铁磷酸盐LiFePO₄的制备情况,通过在氮气保护气氛下,以Li₂CO₃、NH4H2PO₄、Fe₂O₃和葡萄糖为原料,利用碳热还原法合成了碳包覆的LiFePO₄材料。对LiFePO₄常压下的结构进行了研究,并给出了LiFePO₄常压下的拉曼活性振动模式。随后利用拉曼光谱和同步辐射X射线衍射技术对LiFePO₄进行了高压原位研究,给出了LiFePO₄随压力变化的拉曼光谱和晶格常数。本文还在LiFePO₄碳包覆的基础上进行了金属离子掺杂研究,本文分别掺杂了Zn²⁺、Cu²⁺、Ni²⁺、Co²⁺、Co³⁺、Mn⁴⁺金属离子,并对掺杂样品进行了表征,且讨论了掺杂结果。更多还原

【Abstract】 As a new replaceable energy material, lithium ion batteries have attracted a lot of research interests. Lithium ion battery has high capacity, and is environmentally recycled. Now, the studies of lithium ion batteries are mainly concentrated in battery capacity and enhanced electrochemical performance. By improving the anode materials of lithium ion batteries to higher battery capacity, it has become the current research direction. Among these anode materials, lithium iron phosphate LiFePO₄ has been investigated quite thoroughly. LiFePO₄ has low toxicity and good reversibility, and the big anions in crystal structure can stable the whole structure. By carbon-encapsulating or metal ions doping, it can improve the capacity of LiFePO₄.In this thesis, at the protective atmosphere with nitrogen,Li₂CO₃, Fe₂O₃ and glucose NH4H2PO₄ used as raw materials, carbon-encapsulated LiFePO₄ materials have been synthesized by carbonthermal reduction method. The XRD analysis shows the agreements with the standard PDF card. Meanwhile, the crystal structure of LiFePO₄ was studied, and besides its Raman active vibration modes at ambient pressure.Raman spectroscopy and synchrotron radiation X-ray diffraction technique are used for in-situ studies of LiFePO₄ under high pressure. The Raman spectra and the changes of lattice constants at high pressure have been presented. High-pressure Raman spectra show that all Raman modes are shifted to higher wave numbers with the increase of the pressure. Some Raman modes related with the vibrations of PO₄ cluster are obviously enhanced at high pressure. While releasing the pressures, no internal stress is found. The lattice constants and the unit cell volume become smaller continuously with the pressure increasing pressure.The doping effects of different kinds of metal ions have been studied on the base of carbon-encapsulated LiFePO₄. In this thesis, doping of Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Co³⁺, and Mn⁴⁺ metal ions have been investigated, and the samples are characterized by XRD and Raman spectroscopy. The results show that the metal ions can be easily doped into LiFePO₄, without any new structure change. Namely, they can from solid solution with LiFePO₄ as LiFe_1-xM_xPO₄ (M = Zn²⁺ Cu²⁺, Ni²⁺, Co²⁺, Co³⁺, Mn⁴⁺).更多还原