锂离子电池锡负极材料在不同嵌锂状态下的力学性能研究

发布时间：2018-10-08 11:25

【摘要】：随着人类社会的进步和科技的不断发展,不可再生资源逐渐枯竭,具有能量密度高、循环寿命长、价格低廉、安全、无污染等优点的新型锂离子电池成为人们眼中的新宠。目前,锂离子电池负极材料以石墨化碳材料为主,它具有良好的层状结构,有利于锂离子的嵌入和脱出。但石墨化碳负极材料最大的不足是理论容量不高(372 mAh·g-1),目前实际应用的已经接近于理论极限,但是仍不能满足人们对锂离子电池比能量的高需求。锡负极材料具有较高的理论比容量(994mAh·g-1),是石墨化碳负极材料的2.5倍多,且金属锡价格便宜,资源丰富。但是作为负极材料在使用过程中,由于锂离子的嵌入和脱出会产生非常大的体积变形(~300%),这直接造成了锂离子电池电化学性能的衰退,严重制约了锡负极材料在锂离子电池应用。为了更有效地利用锡负极材料,需要对其破坏机理进行研究。本论文主要开展了金属锡负极材料的电沉积法制备、电化学性能以及力学性能表征。本实验中用到X射线衍射仪、原子力显微镜、扫描电子显微镜、电化学工作站、纳米压痕仪等设备,对制备材料的化学成分、表面形貌、电化学性能以及力学性能等进行测试和分析。本论文的主要研究内容如下:(1)通过Π定理进行纳米压痕问题中的量纲分析,获得金属材料基本力学性能与压痕测试中的相关参量间的无量纲函数关系,为利用数值方法建立两者之间的具体无量纲函数关系式提供理论指导。(2)以0.4 mm铜带为基底,运用电沉积法制备锂离子电池金属锡薄膜负极材料。装配测试电池,分析金属锡负极材料的电化学性能。金属锡负极材料首次放电比容量和充电比容量分别高达755 mAh·g-1和697 mAh·g-1,且具有非常好的充放电电压平台。但是锂离子电池恒流充放电过程中,实际比容量衰减非常快,在第10个循环的时候,放电比容量已经接近于零,具有非常差的循环性能。为了研究金属锡负极材料的破坏机理,实验中定量的获得了不同锂化状态下的金属锡负极材料。(3)通过纳米压痕仪对不同锂化状态下的金属锡薄膜负极材料进行压痕测试。运用Matlab软件计算出材料的弹性模量、屈服强度、应变硬化指数,绘制应力应变关系。得到首次嵌锂状态下材料的的弹性模量为60.3 GPa、屈服强度为32.6 MPa、应变硬化指数为0.3,同时绘制这些参数和SOC的关系曲线。通过数据分析,定量的解释了锂离子电池锡负极材料循环性能差的原因,为金属锡在锂离子电池上的设计和运用提供理论基础。
[Abstract]:With the progress of human society and the continuous development of science and technology, non-renewable resources gradually exhausted, with the advantages of high energy density, long cycle life, low price, safety, no pollution and so on, the new lithium ion battery has become a new pet in people's eyes. At present, the cathode material of lithium ion battery is mainly graphitic carbon material, which has a good layered structure, which is beneficial to the intercalation and removal of lithium ion. However, the biggest deficiency of graphitized carbon anode materials is that the theoretical capacity is not high (372 mAh g ~ (-1), and the practical application is close to the theoretical limit, but it still can not meet the high demand for the specific energy of lithium ion batteries. Tin anode material has high theoretical specific capacity (994mAh g-1), which is more than 2.5 times of graphitized carbon anode material, and tin is cheap and rich in resources. However, as anode materials, the intercalation and removal of lithium ions will result in very large volume deformation (300%), which directly results in the degradation of electrochemical performance of lithium ion batteries, which seriously restricts the application of tin anode materials in lithium ion batteries. In order to make more effective use of tin anode materials, it is necessary to study its failure mechanism. In this paper, the electrodeposition, electrochemical and mechanical properties of tin anode materials were studied. In this experiment, X-ray diffractometer, atomic force microscope, scanning electron microscope, electrochemical workstation, nano-indentation instrument were used to analyze the chemical composition and surface morphology of the prepared materials. Electrochemical and mechanical properties were tested and analyzed. The main contents of this thesis are as follows: (1) the dimensionless function relationship between the basic mechanical properties of metal materials and the related parameters in indentation testing is obtained by dimensionless analysis of nano-indentation problem based on 蟺 theorem. In order to establish the dimensionless functional relationship between the two by numerical method, theoretical guidance is provided. (2) on the basis of 0.4 mm copper strip, the metal tin thin film anode material of lithium ion battery is prepared by electrodeposition method. Assemble and test the battery and analyze the electrochemical performance of the metal tin anode material. The initial discharge capacity and charge specific capacity of the metal tin anode material are as high as 755 mAh g -1 and 697 mAh g -1, respectively, and have a very good charge-discharge voltage platform. However, during the constant current charging and discharging of Li-ion batteries, the actual specific capacity decay is very fast. At the 10th cycle, the discharge specific capacity is close to zero, and has a very poor cycle performance. In order to study the failure mechanism of metal tin anode materials, the metal tin anode materials in different lithium state were quantitatively obtained in the experiment. (3) the indentation of metal tin film negative electrode materials in different lithium state was tested by nano-indentation instrument. The elastic modulus, yield strength, strain hardening index and stress-strain relationship of the material were calculated by Matlab software. The elastic modulus of the first lithium intercalated material is 60.3 GPa, the yield strength is 32.6 MPa, strain hardening exponent, and the relationship curve between these parameters and SOC is drawn. Through the data analysis, the reason for the poor cycling performance of lithium ion battery tin anode material is quantitatively explained, which provides a theoretical basis for the design and application of metal tin in lithium ion battery.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM912

【相似文献】