采用两步固相法配合表面活性剂制备LiMn0.7Fe0.3PO4/C正极材料的研究
收稿日期: 2024-04-26
网络出版日期: 2024-05-22
基金资助
国家地区科学基金项目(52364045)
Study on preparation of LiMn0.7Fe0.3PO4/C cathode materials by two-step solid-phase method with surfactant
Received date: 2024-04-26
Online published: 2024-05-22
磷酸锰铁锂复合材料能够兼具磷酸铁锂和磷酸锰锂优点，得到较高的能量密度，但锰铁比过高反而会降低材料的离子电导率和电子电导率。为了提高电导率并降低材料阻抗，采用表面活性剂油酸辅助的两步固相方法，制备了粒径较小、孔隙分布均匀且碳包覆薄厚均匀适中的LiMn0.7Fe0.3PO4/C正极材料（LFMP/C-3）。循环充放电测试表明，该材料在1C下放电比容量为119.6 mA·h/g，循环100次后为102.8 mA·h/g，循环效率为88.87%。经倍率测试得出，在0.1C、0.5C、1C、2C、5C和10C倍率下的平均放电比容量分别为141.08、132.70、128.44、105.86、89.10、83.40 mA·h/g，在之后的0.1C倍率下仍能恢复到开始5次的平均水平。循环伏安（CV）和交流阻抗（EIS）测试表明，LFMP/C-3样品具备较小的极化程度、最低的电荷转移阻抗（139.75 Ω/s1/2）和较高的锂离子扩散系数（1.46×10-14 cm2/s）。结果表明，油酸的加入可获得良好的形貌特征，从而促进锂离子的脱嵌，提高材料的离子电导率和电子电导率，提高磷酸锰铁锂正极材料的电化学性能。
关键词： LiMn0.7Fe0.3PO4/C; 碳包覆; 固相法; 电化学; 正极材料
马镰仁 , 谢红艳 . 采用两步固相法配合表面活性剂制备LiMn0.7Fe0.3PO4/C正极材料的研究[J]. 无机盐工业, 2024 , 56(11) : 39 -44 . DOI: 10.19964/j.issn.1006-4990.2024-0235
The olivine structure of lithium manganese iron phosphate lithium composite materials can combine the advantages of lithium iron phosphate and lithium manganese phosphate，achieving higher energy density.However，an excessively high manganese iron ratio can reduce the materials's ionic and electronic conductivity.To improve conductivity and reduce material impedance，a two-step solid-phase method with the surfactant oleic acid was used to obtain LiMn0.7Fe0.3PO4/C cathode material（LFMP/C-3） with smaller morphology，uniform pore distribution，and moderately even carbon coating thickness.Cycling charge and discharge test results showed that cycling discharge capacity at 1C was 119.6 mA·h/g，which decreased to 102.8 mA·h/g after 100 cycles with a cycling efficiency of 88.87%.Rate capability testing revealed average discharge capacities at 0.1C，0.5C，1C，2C，5C，and 10C rates were 141.08，132.70，128.44，105.86，89.10 and 83.40 mA·h/g respectively，and it could recover to the initial 5-cycle average at 0.1C rate.Cyclic voltammetry and electrochemical impedance spectroscopy showed that the LFMP/C-3 sample exhibited the lower polarization degree，the lowest charge transfer impedance（139.75 Ω/s1/2），and a higher lithium ion diffusion coefficient（1.46×10-14 cm2/s）.The results indicated that the addition of oleic acid could improve the morphology characteristics，facilitate lithium ion intercalation，enhance material ionic and electronic conductivity，and improve the electrochemical performance of lithium manganese iron phosphate cathode materials.
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