摘要
通过高温固相法合成了掺杂Zr4+的正极材料Li1-xZrxFePO4(x=0、0.005、0.01、0.02、0.03、0.04)。采用X射线衍射(XRD)、扫描电镜(SEM)、恒流充放电、交流阻抗(ACI)和正电子湮没寿命谱(PALS)等分析测试技术对掺杂材料的晶体结构、形貌、电化学性能和微观缺陷进行研究。结果表明,在整个掺杂范围内,所有样品都具有单一的橄榄石结构,且样品表面形貌和颗粒尺寸的变化较小;掺杂系列样品中,Li0.99Zr0.01FePO4具有最好的电化学性能,在0.1C充放电倍率下,首次放电比容量达到141.6mAh/g,高于未掺杂的LiFePO4的容量107.4mAh/g,经30次循环后Li0.99Zr0.01FePO4的容量保持率为75.8%。交流阻抗谱研究表明,掺杂Zr4+使锂离子脱嵌过程中电荷转移反应的阻抗明显减小;正电子湮没寿命谱研究表明掺杂Zr4+可以在样品晶格内部产生空位缺陷,使正电子湮没寿命增加,从而提高材料电导率。
Zr^4＋-doped cathode materials Li1-xZrxFePO4（x=0,0.005,0.01,0.02,0.03,0.04） were prepared by high temperature solid phase method.The structure,morphology,electrochemical performance and micro-defects of the materials were investigated by using the technique of X-ray diffraction（XRD）,scanning electron microscope（SEM）,constant current charge-discharge,AC impedance （ACI） and positron annihilation lifetime spectrum（PALS）.The results showed that all samples had the same solely olivine structure,and the morphology and particle size had little changes;additionally,Li0.99Zr0.01FePO4 exhibited the best electrochemical performances at 0.1C discharge rate among all the samples,its first specific capacity of discharge was up to 141.6mAh/g,which was much higher than that of pure LiFePO4 （107.4mAh/g）;and after 30 charge/discharge cycles,the capacity retention rates of Li0.99Zr0.01FePO4 was measured as 75.8%.Finaly,the research of AC impedance spectroscopy showed that the impedance of charge transfer reaction had been de decreased greatly due to doped Zr^4＋ while lithium ion embedded into the cathode material;and positron annihilation lifetime spectrum showed that the internal crystal lattice could cause vacant defect because of doping Zr^4＋,so that the positron annihilation lifetime would be increased,and the electrical conductivity of materials would be improved.
出处
《功能材料》
EI
CAS
CSCD
北大核心
2010年第4期726-729,共4页
Journal of Functional Materials
基金
国家自然科学基金资助项目(50874074
50474092)
广东省自然科学基金资助项目(8151806001000028)
深圳市科技计划资助项目(ZYC200903250150A
200505)
关键词
磷酸铁锂
正极材料
离子掺杂
lithium iron phosphate
cathode material
ion doped
