【作者】 王俊；

【导师】 王淑兰；

【作者基本信息】 东北大学 ， 物理化学， 2015， 硕士

【摘要】 磷酸钒锂(Li3V2(P04)3)作为锂离子动力电池的首选正极材料具有价格低廉、环境友好、安全性高、循环性能突出等优点,已成为目前竞相研究的热点之一。然而Li3V2(PO4)3的电化学性能需要提高。由于Li3V2(PO4)3电子导电率和锂离子扩散速率较低,严重制约了材料在动力电池领域的应用。石墨烯作为新的碳材料能够有效的克服其缺点,掺杂少量石墨烯不仅能够提高Li3V2(PO4)3的电子电导率,同时也提高其倍率性能。采用溶胶凝胶法以氧化石墨烯(GO)为碳源合成了具有单斜结构的Li3V2(P04)3/GN复合正极材料。考察了烧结温度、烧结时间和GO的添加量对Li3V2(P04)3/GN电化学性能的影响。结果是当烧结温度在80C℃,焙烧10 h合成的Li3V2(PO4)3/GN具有较高电化学性能。采用循环伏安法和交流阻抗技术研究了 Li3V2(P04)3/GN的电极过程动力学过程。电化学性能测试结果表明,当GO和Li3V2(PO4)3质量比为0.02:1时Li3V2(PO4)3/GN在0.1 C、0.5 C、1C和2 C倍率下具有良好的放电比容量,分别为128.3、124.6、122.1和117.6 mAh/g。在该实验条件下,氧化石墨烯被还原为石墨烯(GN),以GN为碳材料制备Li3V2(P04)3/GN复合物。XRD和SEM结果表明,少量的石墨烯没有改变磷酸钒锂的晶体结构。电化学测试结果表明,Li3V2(P04)3/GN复合材料在0.1 C和10 C倍率下放电比容量分别达到140.6和111 mAh/g。在60次充放电循环后放电比容量保持在108 mAh/g。抗坏血酸(VC)改性氧化石墨烯(mGO)为碳材料制备的Li3V2(PO4)3/GN复合材料在0.1 C和10C下放电比容量分别为134.9mAh/g和91.4mAh/g。更多还原

【Abstract】 As a promising cathode material for lithium ion battery,Li3V2(PO4)3 has recently attracted wide attention in the research field and scientific community because of its relatively low cost,environment-friendly,high safety and good cycle ability,etc.However,the electrochemical performance of Li3V2(PO4)3 is needed to improve due to its low intrinsic electronic conductivity and the poor lithium ion diffusivity,which brings big obstacle to the application in high-rate battery.Graphene(GN)as new carbon material can be an effect way to overcome this obstacle restriction and has been investigated in this work.Little amount of graphene coating can not only improve the conductivity of Li3V2(PO4)3 but also increase the rate capability of Li3V2(PO4)3.Monoclinic Li3V2(POa)3/GN composite was successfully synthesized by the sol-gel method using graphene oxide(GO)as the carbon material.The effects of sintering temperature、sintering time and the amount of GO added on the electrochemical properties of Li3V2(PO4)3/GN composite were investigated.It was observed that the Li3V2(PO4)3/GN prepared at 800 ℃ and 10 h displayed the best electrochemical performance.The electrode process kinetics of the Li3V2(PO4)3/GN composite was studied by cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The electrochemical measurement showed that the mass ratio of GO and Li3V2(PO4)3 was 0.02:1 and the Li3V2(PO4)3/GN had special discharge capacity of 128.3、124.6、122.1 and 117.6 mAh/g at 0.1 C、0.5 C、1 C and 2 C.In this process,the graphene oxide was reduced to graphene(GN)as carbon material,Li3V2(PO4)3/GN composite synthesized with GN.The results of SEM and XRD showed little GN did not destroy the structure of Li3V2(PO4)3,The electrochemical measurement showed the special discharge capacity of Li3V2(PO4)3/GN composite was 140.6 and 111 mAh/g at 0.1 C and 10 C.After 60 charge and discharge cycles,discharge capacity of Li3V2(PO4)3/GN remained 110.8 mAh/g.Graphene oxide modified by VC(mGO)as carbon material,Li3V2(PO4)3/GN composite synthesized with mGO had discharge capacity of 134.9 and 91.4 mAh/g at 0.1 C and 10 C.更多还原