锂离子电池硅负极活性材料的改性研究
发布时间：2018-09-06 17:24
【摘要】：在对高比容量能源需求强烈的当下,硅基材料成为了锂离子电池负极材料的研究宠儿。针对硅负极材料导电性差,体积效应大,SEI膜不稳定等问题,本文结合微量掺杂、纳米化、硅碳复合化等改性方法,成功制备了多种比容量高、循环性能好、首次库伦效率高的硅/碳复合锂电负极材料。一方面,将应用于太阳能电池的磷掺杂n型硅作为负极材料,然后进行碳包覆,制备了n-Si/C复合材料,并对其制备工艺进行了优化,电化学性能作了分析;另一方面,采用不同的硅源,利用石墨烯进行复合,制备了三种硅/石墨烯复合材料,并通过电化学工作站、充放电测试等作了分析表征。此外,对亚微米硅/GNS的内在反应动力学还作了初步探讨。1、减小颗粒尺寸能够提高硅的循环稳定性,但改善程度有限;微量P(或B)掺杂不影响硅的结构,却能显著改善硅的导电性以及循环性能;n型硅以及亚微米硅是更为理想的硅电极材料。2、采用高温固相法制备了性能优异的n-Si/C复合材料,其30次后的放电容量为1101.4mAhg-1,首次库伦效率高达85.6%。对该材料制备工艺及电极制作条件进行了研究,结果发现:最佳烧结工艺为600℃/1h,最佳碳源为葡萄糖,最佳n型硅、碳比为1:1;添加石墨后,复合材料放电比容量增加,循环稳定性大大提高,首次库伦效率提高至81.1%;二次包覆后,复合材料循环可逆性与首次库伦效率都得到提升,其30次后放电容量为1054.3mAhg-1;在电极片制作中,集流体选用铜箔效果更好,极片干燥温度使用80℃最佳,极片热处理也有利于电极性能提升。3、通过原位复合及直接机械混合的方式制备了循环性能好、比容量高、导电性好的硅/石墨烯(MS@Si/GNS,nano@Si/GNS,p-Si/GNS)复合负极材料。重点对MS@Si/GNS进行了工艺参数的研究,经各种测试手段发现:原位复合制得SG1具有更高的首次容量,库伦效率以及导电性;随石墨烯含量的增加,MS@Si/GNS首次放电容量逐渐降低,循环性能依次提高,阻抗值逐渐减小;CNT的加入以及极片热处理都有助于MS@Si/GNS循环性能的改善和导电性的提高。4、通过SSCV研究,EIS分析及锂离子扩散系数计算发现,MS@Si/GNS表现出了优异的循环可逆性及高的锂离子迁移率,DLi可达2.9×10-12 cm2s-1,比纯亚微米硅高出一个数量级,不同次数的各R值变化较小,电极结构稳定性良好。
[Abstract]:At present, silicon-based materials have become the favorite of lithium ion battery anode materials in high specific capacity energy demand. Aiming at the problems of poor electrical conductivity and large volume effect of silicon negative electrode materials and the instability of SEI film, this paper has successfully prepared various kinds of high specific capacity and good cycling performance by combining the modification methods of micro-doping, nanocrystalline and silicon-carbon composite. The first high Coulomb efficiency silicon / carbon composite lithium anode material. On the one hand, phosphorus-doped n-type silicon, which is used in solar cells, is used as negative electrode material, then carbon coating is carried out to prepare n-Si/C composite, and its preparation process is optimized and electrochemical performance is analyzed. Three kinds of silicon / graphene composites were prepared by using different silicon sources and graphene, and were characterized by electrochemical workstation and charge-discharge test. In addition, the intrinsic reaction kinetics of sub-micron silicon / GNS is also discussed. The decrease of particle size can improve the cycling stability of silicon, but the improvement is limited, and the microamount of P (or B) doping does not affect the structure of silicon. However, the electrical conductivity and cycling properties of silicon can be significantly improved. The n-type silicon and sub-micron silicon are more ideal silicon electrode materials. The n-Si/C composites with excellent properties have been prepared by high temperature solid state method. The discharge capacity is 1101.4 mAhg-1 after 30 times, and the first Coulomb efficiency is 85.6%. The results show that the optimum sintering process is 600 鈩，
本文编号：2227035
[Abstract]:At present, silicon-based materials have become the favorite of lithium ion battery anode materials in high specific capacity energy demand. Aiming at the problems of poor electrical conductivity and large volume effect of silicon negative electrode materials and the instability of SEI film, this paper has successfully prepared various kinds of high specific capacity and good cycling performance by combining the modification methods of micro-doping, nanocrystalline and silicon-carbon composite. The first high Coulomb efficiency silicon / carbon composite lithium anode material. On the one hand, phosphorus-doped n-type silicon, which is used in solar cells, is used as negative electrode material, then carbon coating is carried out to prepare n-Si/C composite, and its preparation process is optimized and electrochemical performance is analyzed. Three kinds of silicon / graphene composites were prepared by using different silicon sources and graphene, and were characterized by electrochemical workstation and charge-discharge test. In addition, the intrinsic reaction kinetics of sub-micron silicon / GNS is also discussed. The decrease of particle size can improve the cycling stability of silicon, but the improvement is limited, and the microamount of P (or B) doping does not affect the structure of silicon. However, the electrical conductivity and cycling properties of silicon can be significantly improved. The n-type silicon and sub-micron silicon are more ideal silicon electrode materials. The n-Si/C composites with excellent properties have been prepared by high temperature solid state method. The discharge capacity is 1101.4 mAhg-1 after 30 times, and the first Coulomb efficiency is 85.6%. The results show that the optimum sintering process is 600 鈩，
本文编号：2227035
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