Intrinsic Properties of Individual Constituents of Silicon-Electrolyte Interphase

The stabilization of a solid electrolyte interphase (SEI) is one of the great challenges to utilize superior theoretical capacity (about 3,600 mAh g-1, almost 10 times higher than that of graphite) of a silicon (Si) as an anode in a next-generation advanced lithium-ion battery (LIB). A SEI remains a poorly understood and hardly studied topic relative to the research devoted to battery components due to its intrinsic properties of complexity, reactivity and continuous evolution. However, the SEI plays a key role in prevention of further electrolyte reduction and desolvation of Li+ ions, which is directly related to electrochemical performance, lifetime and safety of batteries. For example, the unstable SEI on a Si anode leads to initial irreversible capacity losses, poor cycling stability and a limited cycle life. 2-4 In this study each 'individual' component of SEI on a Si anode was prepared as a thin film, and the physical, electrochemical, mechanical and structural properties of prepared films were characterized using a variety of analytical equipment including electrochemical impedance spectroscopy, operando X-ray photoelectron spectroscopy, atomic force microscope, Fourier-transform infrared spectroscopy, scanning spreading resistance microscopy and time-of-flight secondary ion mass spectrometry. This study can provide a strong guidance to aid in the development of new electrolytes, additives and binders to stabilize SEI layer on a silicon anode by identifying beneficial components and providing mechanical explanation of a variety of reactions and phenomena in a SEI.