基于海藻酸钠粘结剂的锂离子电池硅基负极材料的性能研究

发布时间：2018-06-01 14:13

本文选题：锂离子电池 + 硅基负极材料　；参考：《陕西科技大学》2017年硕士论文

【摘要】：硅的理论比容量高达4200 mAh/g,有望成为新一代的高容量负极材料之一。但锂离子在嵌锂和脱锂过程中,引起硅颗粒体积膨胀和电极结构崩破,导致硅与集流体的导电性变弱,影响电池的电化学性能。为了改善这一个问题,本文通过研究海藻酸钠在不同硅基复合负极材料(硅负极材料、硅/石墨烯负极材料、硅/铁负极材料)中的电化学性能,并分析负极材料与海藻酸钠复合浆料的流变特性。试图改善电极结构,探索出比容量高、电极循环稳定好的锂离子电池。本论文主要工作及结果如下:(1)制备了3种不同海藻酸钠粘结剂含量的锂离子电池硅负极浆料,并对其浆料进行流变性和触变性测试与比较,筛选出海藻酸钠粘结剂合适含量为20%,该含量下负极浆料颗粒可形成均匀,稳定的分散结构。测试了该体系电化学性能,结果表明,当负极材料(纳米硅)、导电剂、粘结剂质量比是6:2:2时,首次放电比容量为2200 mAh/g,库伦效率达到87%。但循环50圈后,放电比容量低于800 mAh/g。锂离子电池在嵌锂和脱锂过程中,硅会发生体积膨胀,导致硅材料粉化、剥落、失去电接触,因此容量衰减很快,循环稳定性较差。(2)为了改善硅负极锂离子电池的循环稳定性,可通过改善硅颗粒与集流体之间的电接触来实现。本文在硅负极中引入导电性能优异的石墨烯材料,制得硅/石墨烯负极材料。测试了3种不同海藻酸钠粘结剂含量的硅/石墨烯负极浆料的流变性和触变性,选择出最佳海藻酸钠粘结剂含量仍为20%。在负极材料、导电剂、粘结剂质量比是6:2:2的基础上,测试了含量分别为10%、20%、30%的3种硅/石墨烯锂离子电池的电化学性能。实验结果显示,石墨烯含量减小,比容量增大,内阻降低。10%含量的硅/石墨烯锂离子电池在循环50圈后,放电比容量大于1800 mAh/g;循环100圈后,放电比容量在1650 mAh/g左右,因此适量的石墨烯有利于提高锂离子的循环性。(3)为了提高硅基锂离子电池的循环稳定性,可通过制备多孔硅/金属复合材料为硅体积的膨胀预留空间。本文通过酸化处理硅铁合金制备了多微孔硅/铁合金负极材料。测试了基于海藻酸钠粘结剂的多微孔硅/铁负极浆料的流变性和触变性,确定了海藻酸钠粘结剂合适含量为20%。当负极材料(多微孔硅/铁)、导电剂、粘结剂质量比分别为6:2:2时,首次放电比容量高达2600 mAh/g,循环50圈后,充放电比容量大约为1250 mAh/g。比容量有所下降,但多孔的结构有效的增强了循环性能的稳定性。
[Abstract]:The theoretical specific capacity of silicon is as high as 4200 mAh/ g, which is expected to be one of the new generation of high capacity anode materials. However, during the process of lithium intercalation and delithium removal, the volume expansion of silicon particles and the breakdown of electrode structure lead to the weakening of the conductivity of silicon and collector, which affects the electrochemical performance of the battery. In order to improve this problem, the electrochemical properties of sodium alginate in different silicon based composite anode materials (silicon anode material, silicon / graphene negative electrode material, silicon / iron negative electrode material) were studied. The rheological properties of negative electrode material and sodium alginate composite slurry were analyzed. This paper attempts to improve the electrode structure and explore the lithium ion battery with high specific capacity and stable electrode cycle. The main work and results of this paper are as follows: (1) three kinds of sodium alginate binders were prepared, and the rheological properties and thixotropy of the slurry were measured and compared. The suitable content of sodium alginate binder is 20%, under which the particles of negative electrode slurry can form uniform and stable dispersion structure. The electrochemical properties of the system have been tested. The results show that when the mass ratio of nanocrystalline silicon, conductive agent and binder is 6:2:2, the first discharge specific capacity is 2200 mg / g, and the Coulomb efficiency is 87%. But after 50 cycles, the specific discharge capacity is less than 800 mg / g. In the process of lithium intercalation and delithium removal, the volume expansion of silicon will occur, which will cause the silicon material to be powdered, peeled off, and lose electrical contact. Therefore, the capacity of lithium ion battery decreases rapidly and the cycle stability is poor.) in order to improve the cycle stability of silicon anode lithium ion battery, This can be achieved by improving the electrical contact between silicon particles and collecting fluids. In this paper, silicon / graphene anode materials are prepared by introducing graphene materials with excellent conductivity into silicon anode. The rheology and thixotropy of three kinds of silicon / graphene negative paste with different content of sodium alginate binder were tested, and the optimum content of sodium alginate binder was still 20. On the basis of 6:2:2 mass ratio of negative electrode material, conductive agent and binder, the electrochemical properties of three kinds of silicon / graphene lithium-ion batteries with the content of 10% and 20% were tested. The experimental results show that the specific discharge capacity of silicon / graphene lithium-ion battery with the content of graphene decreases and the specific capacity increases, and the specific discharge capacity of the silicon / graphene lithium ion battery containing 10% lower internal resistance is greater than 1800 mg / g after 50 cycles, and the discharge specific capacity is about 1650 mAh/g after 100 cycles. In order to improve the cycle stability of silicon-based lithium-ion batteries, porous silicon / metal composites can be prepared to reserve space for silicon volume expansion. In this paper, multiporous silicon / ferroalloy anode materials were prepared by acidification treatment of ferrosilicon alloys. The rheological properties and thixotropy of multipore silicon / iron negative paste based on sodium alginate binder were tested. The suitable content of sodium alginate binder was determined to be 20%. When the mass ratio of multipore silicon / iron, conductive agent and binder is 6:2:2, the initial discharge specific capacity is up to 2600 mAh-g, and after 50 cycles, the charge / discharge capacity is about 1250 mAh/ g. The specific capacity decreased, but the porous structure effectively enhanced the stability of the cycle performance.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332;TM912

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