Dong, K.; Markötter, H.; Sun, F.; Hilger, A.; Kardjilov, N.; Banhart, J.; Manke, I.: In situ and Operando Tracking of Microstructure and Volume Evolution of Silicon Electrodes by using Synchrotron X-ray Imaging. ChemSusChem 12 (2019), p. 261-269
Advanced lithium-ion batteries with high capacity density, high rate capability, and excellent long life are crucial for next-generation energy storage systems, such as portable electronics, electric vehicles, and hybrid electric vehicles. Owing to a relatively low specific capacity (372 mAhg1), traditional graphitebased anode materials can hardly meet the future high capacity demand. Given the outstanding theoretical capacity of silicon (4200 mAhg1, approximately 10 times that of the conventional graphite anode) the specific energy of silicon-based batteries could be significantly increased, leading to improved portability and an extended service time after full charging. The abundance of silicon in nature and relatively low working potential provide a wide application prospect at an affordable price. The alloying reaction between Si and Li+ enables a much higher specific capacity but is also accompanied by a large volume change. Assuming a silicon eletrode with the maximum possible alloying formula of Li4.4Si, the corresponding maximum volume expansion is around 400 %, as calculated from the volume change of the crystal structure. Volume expansion and shrinkage during lithium insertion and extraction lead to repetitive strain and structural change, which finally result in mechanical deformation and irreversible capacity fading of the whole electrode.[2b] Therefore, large volume change is widely regarded as the primary explanation for a short lifetime.