摘要
以Li_2CO_3、FeC_2O_4·2H_2O、MgO、NH_4H_2PO_4为原料,无水葡萄糖为碳源,采用高温固相合成法制备获得4%Mg^(2+)掺杂的LiFe_(0.96)Mg_(0.04)PO_4/C,并通过分别减少2%Mg^(2+)和2%Fe^(2+)合成了非化学计量比的LiFe_(0.96)Mg_(0.02)PO_4/C和LiFe_(0.94)Mg_(0.04)PO_4/C材料。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、红外光谱分析(FTIR)、扫描电镜(SEM)、透射电镜(TEM)表征了Fe^(2+)和Mg^(2+)含量的变化对材料的物质构成、形貌及结构的影响。通过交流阻抗(EIS)及恒流充放电循环测试对材料的电化学性能进行表征。研究结果表明Mg^(2+)均匀地掺入LiFePO_4的晶格中,非化学计量比的LiFe_(0.96)Mg_(0.02)PO_4/C和LiFe_(0.94)Mg_(0.04)PO_4/C材料的晶胞体积减小,导电性杂质Fe_2P的含量升高,Li-Fe错位现象减少;其中,LiFe_(0.94)Mg_(0.04)PO_4/C表现出最优的充放电容量、倍率性能以及循环性能,0.1C、20C倍率下的放电比容量分别为161.2mAh/g、74.7mAh/g,500次循环后20C的容量保持率达到97.3%。
LiFe0.94Mg0.04PO4/C,LiFe0.96Mg0.02PO4/C and LiFe0.96Mg0.04PO4/C have been synthesized by a solid-state reaction using Li2CO3,FeC2O4·2H2O,MgO,and NH4H2PO4as starting materials and C6H6O6as carbon source.X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and Fourier transform infrared spectroscopy(FTIR)were used to investigate the effect of Fe2+or Mg2+on the morphology and structure of the prepared materials.The electrochemical performances of different samples were characterized by galvanostatic charge/discharge test and electrochemical impedance spectroscopy(EIS).The results indicated that the crystal lattice parameters and the Li-Fe anti-site defects were reduced,whereas the content of conductive Fe2P in non-stoichiometric lithium iron phosphate increased when Mg was doped,and LiFe0.94Mg0.04PO4/C exhibited the highest discharge performance,rate capability and excellent cycle performance,whose initial capacities were161.2mAh/g at0.1C,and74.7mAh/g at20C and the retention rate was97.3%at20C after500cycles.
作者
冯颖
刘凯
霍涛涛
张敏卿
Abdul Waqas ANJUM
FENG Ying;LIU Kai;HUO Taotao;ZHANG Minqing(School of Chemical Engineering and Technology,Tianjin University,Tianjin 300350,China)
出处
《化工进展》
EI
CAS
CSCD
北大核心
2017年第8期3006-3012,共7页
Chemical Industry and Engineering Progress
基金
国家自然科学基金项目(21476158
21621004)
关键词
磷酸铁锂
非化学计量比
电化学
纳米材料
合成
优化
lithium iron phosphate
non-stoichiometric
electrochemistry
nanomaterials
synthesis
optimization
