(天津大學(xué)化工學(xué)院， 天津 300072)
摘 要: 以MgAC2為摻雜源， 采用固相反應(yīng)法在惰性氣氛下合成了摻Mg的LiFePO4正極材料， 考察了Mg2+對(duì)于目標(biāo)化合物物理及電化學(xué)性能的影響。 采用粉末X射線衍射和掃描電鏡技術(shù)對(duì)產(chǎn)物的結(jié)構(gòu)、 形貌及粒度等進(jìn)行了表征， 通過恒電流充放電和交流阻抗技術(shù)對(duì)其電化學(xué)性能進(jìn)行了研究。 結(jié)果表明： 少量的Mg2+摻雜并未影響產(chǎn)物結(jié)構(gòu)， 但卻有利于減小LiFePO4電荷轉(zhuǎn)移過程中的阻抗， 克服該過程中的動(dòng)力學(xué)限制。 在0.1C倍率下放電， 摻雜LiFePO4與未摻雜LiFePO4的初始放電容量分別為136.9和111.8 mA·h/g， 循環(huán)50次后， 容量分別為135.6和83.9 mA·h/g； 與未摻雜的LiFePO4相比， 摻鎂后的LiFePO4具有更為優(yōu)良的循環(huán)性能。
關(guān)鍵字: LiFePO4； 正極材料； Mg2+摻雜； 電化學(xué)性能
（School of Chemical Engineering and Technology, Tianjin University,
Tianjin 300072, China）
Abstract: Stoichiometric Mg-doped lithium iron phosphate (LiFePO4) cathode material was synthesized by a solid-state reaction in an inert atmosphere which used MgAC2 as dopant. The effects of Mg2+ doping on the physical and electrochemical properties of as-synthesized cathode materials were investigated. The samples were characterized by powder X-ray diffractrometry, scanning electron microscopy, and their electrochemical performance was systematically measured by impedance response and constant current charge/discharge cycling tests. The results indicate that the low concentration Mg2+ doping does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance. At 0.1C discharging rate, the reversible specific capacities of the Mg-doped lithium iron phosphates and the undoped LiFePO4 are 140 and 128 mA·h/g, respectively. After 50 cycles, the capacities are 135.6 and 83.9 mA·h/g, respectively. Comparing to the undoped LiFePO4, the Mg-doped lithium iron phosphates also displays a more stable cycle performance.
Key words: LiFePO4; cathode material; Mg2+ doping; electrochemical performance
