高容量富锂锰基正极材料的制备与改性研究

发布时间：2018-06-01 15:49

本文选题：富锂锰基材料 + 离子取代　；参考：《上海应用技术大学》2017年硕士论文

【摘要】：为改善富锂锰基材料充放电过程中首周不可逆容量高、循环稳定性和倍率性能较差等缺陷,本文依次引入Al3+和Rb+少量替代过渡金属层离子和锂层离子,并结合其形貌、结构及电化学性能具体分析了材料的最佳配比。采用喷雾干燥辅助固相合成技术制得材料Li1.2Mn0.54-xAlxNi0.13Co0.13O2(LMO-Alx,x=0、0.03、0.05、0.10、0.15)。研究发现,LMO-Alo.05材料的电化学性能最佳,0.2C充放电过程中材料的放电比容量最高可达249.9 mAh g-1,50圈循环后保持率为99.2%。这首先归因于LMO-Al0.05材料电导率的提高(3.87×10-8Scm-1),相较于LMO材料的电导率仅2.52×10-8Scm-1。此外,A13+的引入增大了材料晶胞体积,使得锂离子扩散系数从4.18×10-13cm2 s-1 (LMO)提高至 1.22×10-12cm2s-1 (LMO-Al005)。通过碳酸盐共沉淀法合成了材料Li1.2-xRbxMn0.54Ni0.13Co0.13O2 (Rbx-LMO,x=0、0.01、0.03、0.05)。结果表明,x=0.03时,Rb0.03-LMO材料经0.2C充放电100圈后容量由239 mAh g-1衰减至221.9 mAh g-1,保持率为92.8%,相比于LMO材料容量保持率仅82.9%。此外,倍率性能方面,Rb0.03-LMO材料也显示出较为优异的快速充放电能力,0.05C～5C各倍率放电容量均比LMO材料高出20～30%。这是因为,引入半径较大的Rb+拓宽了晶胞的锂层层间距,锂离子扩散系数由8.95×10-16cm2s-1(LMO)增至1.63×10-15cm2 s-1(Rb0.03-LMO);其次,键能更强的Rb-O键可抑制高压过程氧的释放,为脱锂态的富锂锰基材料提供结构支撑,缓解充放电过程中材料结构的转变,改善材料的结构稳定性,进而提高其电化学性能。
[Abstract]:In order to improve the defects such as high first cycle irreversible capacity, poor cyclic stability and poor rate performance during charge and discharge of Li-rich manganese based materials, a small amount of Al3 and RB were introduced to replace transition metal layer ions and lithium layer ions, and their morphology was combined. The structure and electrochemical properties of the materials were analyzed in detail. The material Li1.2Mn0.54-xAlxNi0.13Co0.13O2 LMO-AlxUXO2LMO-AlxCXO0O0. 03N0. 03N0. 05A0. 10N0. 15m was prepared by spray drying assisted solid state synthesis technique. It is found that the electrochemical performance of LMO-Alo.05 is the best. The discharge specific capacity of LMO-Alo.05 can reach 249.9 mAh g ~ (-1) ~ (50) cycle and the retention rate is 99.2 during the charge-discharge process. This is attributed to the increase of electrical conductivity of LMO-Al0.05 material (3.87 脳 10-8 Scm-1), which is only 2.52 脳 10-8 Scm-1 compared with that of LMO material. In addition, the introduction of A13 increases the unit cell volume and increases the diffusion coefficient of lithium ion from 4.18 脳 10-13cm2 s-1 to 1.22 脳 10-12cm2s-1 / LMO-Al005. The material Li1.2-xRbxMn0.54Ni0.13Co0.13O2 Rbx-LMOX (0. 01%) was synthesized by carbonate coprecipitation method. The results show that the capacity of Rb0.03-LMO material decreases from 239 mAh g ~ (-1) to 221.9 mAh g ~ (-1) from 221.9 mAh g ~ (-1) to 221.9 mAh g ~ (-1) after 0.2C charge-discharge at 0.03, and the retention rate is 92.8%, compared with that of LMO material, the capacity retention rate is only 82.9%. In addition, the Rb0.03-LMO material also shows excellent rapid charge and discharge capacity of 0.05Cn5C, and the discharge capacity of Rb0.03-LMO material is 20% higher than that of LMO material. This is because the introduction of RB with a larger radius widens the interlayer spacing of lithium, and the diffusion coefficient of lithium ion increases from 8.95 脳 10 ~ (-16) cm ~ (-2) to 1.63 脳 10-15cm2 ~ (-1) Rb 0.03-LMOO _ 3. Secondly, the release of oxygen during high pressure can be inhibited by Rb-O bond with stronger bond energy. It provides structural support for lithium-rich manganese based materials in delithium-state, alleviates the structural transformation of materials during charge and discharge, improves the structural stability of materials, and then improves their electrochemical properties.
【学位授予单位】：上海应用技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB34

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