Microstructural Aspects of Electrode Material Degradation Mechanisms in Li-ion Batteries

锂离子电池是最先进的能量存储系统，被广泛用于可充电便携式电子设备，也被考虑用于大规模生产的混合动力和电动汽车。了解锂离子电池充电和放电过程中电极降解机制的微观结构方面对于设计具有低阻抗增长和高容量的节能电池至关重要。拟议的研究计划旨在开发先进的表征方法，用于识别通常由石墨或硅制成的负极电池电极的表面和亚表面损伤的微观机制。 在电化学测试期间使用数字光学显微镜和拉曼光谱仪实施原位观察系统将确定由于电极表面上的颗粒的剥落和破碎而引起的表面降解损伤的严重性。在电解质分解和固体电解质界面的形成过程中发生的组成变化将被同时确定。FIB和TEM显微镜从模型电极材料，如HOPG与石墨烯层平行和正常的界面，和已知的晶体取向的Si样品切除的样品的应用，将阐明在这些电极中操作的裂纹萌生和传播过程的细节。注意将给予的局部应力和应力强度的确定在裂纹尖端，预计合理的插层产品在控制裂纹扩展速率的作用。 结果将以图表或电极损坏图的形式进行总结，显示损坏特征与循环时间和温度、电压扫描速率和电解质成分的关系。通过将微观信息与电化学性能相关联，将出现改进电极微观结构的新设计方法。至少有六名HQP将接受培训，以使加拿大经济的新兴能源材料部门受益。

Li-ion batteries are state-of-the-art energy storage systems that are being employed in a wide range of rechargeable portable electronic devices and also considered for mass-produced hybrid and electric vehicles. Understanding microstructural aspects of the electrode degradation mechanism during charging and discharging of Li-ion batteries is of key importance in order to design energy efficient batteries with low impedance growth and high capacity. The proposed research program aims at developing advanced characterization methods for identifying the micromechanisms of surface and subsurface damage in negative battery electrodes produced typically from graphite or silicon. The implementation of an in-situ observation system during electrochemical tests using a digital optical microscope and a Raman spectrometer will determine severity of surface degradation damage due to exfoliation and fragmentation of particles on electrode surfaces. The compositional changes that occur during the electrolyte decomposition and formation of solid electrolyte interface will be simultaneously identified. Application of FIB and TEM microscopy to samples excised from model electrode materials, such as HOPG with graphene layers parallel and normal to the interface, and Si samples with known crystallographic orientations, will elucidate details of crack initiation and propagation processes that operate in these electrodes. Attention will be given to the determination of local stresses and stress intensities at crack tips that are expected to rationalize the role of the intercalation products in controlling the crack growth rates. The results will be summarized in the form of diagrams or Electrode Damage Maps that will show the damage features as a function of cycling time and temperature, voltage scan rate and the electrolyte composition. By correlating the microscopic information to electrochemical performance, new design methods for improved electrode microstructures will arise. At least six HQP will be trained to the benefit of emerging energy materials sectors of the Canadian economy.