固相法合成具有纳米尺寸的Li2CrxMn1-xSiO4/C正极材料及其电化学性能的表征

摘要本文采用高温固相法合成Li2MnSiO4正极材料，并研究了不同合成温度、碳包覆、不同Cr含量取代、Li含量对Li2MnSiO4晶体结构、粒度分布、充放电性能及其循环性能的影响。通过XRD物相分析发现，合成温度为700℃时，Li2MnSiO4为正交晶系Pmn21，当温度继续升高，Li2MnSiO4转变为单斜晶系P21/n。通过比较充放电性能可知正交晶系Pmn21的Li2MnSiO4（O-Li2MnSiO4）放电比容量（31mAhg-1）及循环稳定性（10圈放电比容量保持率为40%）较好。对O-Li2MnSiO4进行碳包覆（O-Li2MnSiO4/C）研究发现，首次放电比容量升至43mAhg-1。通过对O-Li2MnSiO4/C 中的Mn进行部分Cr取代发现，当Cr取代量为0.05时，样品Li2Cr0.05Mn0.95SiO4/C的放电比容量最高（90.1 mAhg-1）。通过研究Li含量对Li2Cr0.05Mn0.95SiO4/C的性能影响可知，Li过量有助于提高样品的放电比容量。当Li过量10%时，Li2Cr0.05Mn0.95SiO4/C的首次放电比容量为138.9 mAhg-1。29309
毕业论文关键词：硅酸锰锂；充放电性能；XRD；铬
Abstract Li2MnSiO4 anode materials were synthesized by high-temperature solid-phase method. The influence of different synthetic temperatures, carbon-coating, different contents of Cr doping and Li on the size distribution, charge-discharge capacity and cyclic performance of Li2MnSiO4 were investigated. Through the phase analysis of Li2MnSiO4 samples by XRD, orthorhombic Li2MnSiO4 (O-Li2MnSiO4)sample was obtained at 700℃, which transfers to monoclinic Li2MnSiO4 (M-Li2MnSiO4) when the synthetic temperature increases to 750℃. The initial specific discharge capacity (31 mAhg-1) and the capacity retention of the O-Li2MnSiO4 sample is better than that of the M-Li2MnSiO4. Coating O-Li2MnSiO4 with carbon (O-Li2MnSiO4/C) drives the initial discharge specific capacity increasing to 43mAhg-1. When the O-Li2MnSiO4/C was doped with varied Cr content from 0 to 0.1, the Li2Cr0.05Mn0.95SiO4/C has the highest initial discharge capacity (90.1 mAhg-1). A 10% Li excess Li2Cr0.05Mn0.95SiO4/C sample has an improved initial discharge specific capacity (138.9 mAhg-1) than that of both the 5% Li excess Li2Cr0.05Mn0.95SiO4/C and no Li excess Li2Cr0.05Mn0.95SiO4/C samples.
Keywords: Manganese lithium silicate；Charge and discharge property；XRD；Chromium
目录
1 绪论    1
1.1 锂离子电池的简介    1
1.1.1 锂离子电池的发展现状    1
1.1.2 锂离子电池的工作原理    2
1.1.3 Li2MSiO4的结构特点    3
1.1.4 Li2MSiO4的制备方法    5
1.1.5 Li2MnSiO4存在的问题及改进方法    7
1.2 课题内容    8
1.2.1 课题研究的目的和意义    8
1.2.2 课题研究内容    8
1.2.3 研究方案    8
2 实验内容    10
2.1 实验原料    10
2.2 实验仪器和设备    10
2.3 Li2CrxMn1-xSiO4/C正极材料的制备    11
2.3.1 原料的预处理    11
2.3.2样品的制备    11
2.3.3 电极片的制作    12
2.3.4 扣式电池的组装    12
2.4 实验研究的方法    12
2.4.1 X射线衍射法物相分析    12
2.4.2充放电性能测试法    12
3 实验结果和分析    13
3.1 物理性能表征    13
3.1.1 不同温度对Li2MnSiO4的影响    13
3.1.2 碳包覆对O-Li2MnSiO4的影响    16
3.1.3 不同Cr含量取代对O-Li2MnSiO4/C的影响    17
3.1.4 Li过量对Li2Cr0.05Mn0.95SiO4/C的影响    25
4.实验结论    29
致谢    30
参考文献    31 固相法合成具有纳米尺寸的Li2CrxMn1-xSiO4/C正极材料及其电化学性能的表征:http://www.751com.cn/cailiao/lunwen_24496.html