性能的影響
(華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640)
摘 要: 以有機(jī)(檸檬酸鐵)和無機(jī)(Fe2O3或Fe3O4)三價(jià)鐵混合物為鐵源，以有機(jī)鐵源中的有機(jī)酸根為碳源和還原劑，通過固相−碳熱還原法制備LiFePO4/C正極材料，考察無機(jī)三價(jià)鐵源對(duì)正極材料結(jié)構(gòu)和性能的影響。采用XRD、SEM和恒流充放電測試等方法對(duì)正極材料的結(jié)構(gòu)、表觀形貌及電化學(xué)性能進(jìn)行研究。結(jié)果表明：以Fe2O3為無機(jī)三價(jià)鐵源合成的LiFePO4/C材料的晶相單一、晶粒尺寸較小、電化學(xué)性能較好，以0.1C放電時(shí)，其第三次放電比容量達(dá)136 mA∙h/g，循環(huán)20周后基本無衰減；而由Fe3O4為鐵源制得的材料中含有其它雜質(zhì)相，晶粒尺寸較大，電化學(xué)性能較差，以0.1C放電倍率放電時(shí)，其第三次放電比容量僅為118 mA∙h/g，循環(huán)20周后衰減近17%。
關(guān)鍵字: LiFePO4；鋰離子電池；正極材料；碳熱還原法；三價(jià)鐵源
LiFePO4/C prepared by carbothermal reduction method
（College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:LiFePO4/C cathale material were synthesized by solid state-carbothermal reduction method using organic (citrate ferric) and inorganic (Fe2O3 or Fe3O4) trivalent iron compounds as iron precursors and using the organic acid radical in organic iron precursor as both reducing agent and carbon source. The influences of inorganic Fe3+ sources on the structures and performances of the material were investigated. The structure, morphology and electrochemical properties of LiFePO4/C were analyzed by XRD, SEM and galvanostatic charge-discharge method, respectively. The results indicate that the sample synthesized by Fe2O3 has fine particle size, single crystal structure and excellent electrochemical performances, the third discharge capacity remains 136 mA/h∙g at 0.1C with almost no capacity fading after 20 cycles. While the third discharge capacity of sample obtained from Fe3O4 with large particle size and some impurities is only 118 mA∙h/g at 0.1C, with about 17% capacity fading after 20 cycles.
Key words: LiFePO4; lithium ion battery; cathode material; carbothermal reduction method; trivalent iron source
