Enabling the study of stress states using in situ μSXRD in the silicon nanowire anode during electrochemical lithiation in a specially designed Li-ion battery test cell

摘要

Synchrotron X-ray microdiffraction has proven to be effective in revealing insights of mechanical stress and other mechanics considerations in small scale crystalline structures in many important technological applications, such as microelectronics, nanotechnology and energy systems. In the present study, a special Li-ion battery test cell was designed to enable an in situ synchrotron X-ray microdiffraction experiment to elucidate the mechanical stress states during the first electrochemical cycle of lithiation in single-crystalline silicon nanowires (SiNWs). Silicon is considered as a promising anode material for the next generation lithium-ion battery due to its high capacity at nanoscale. However, silicon expands up to 300% during lithiation, which induces high stresses and leads to fractures. To design silicon nanostructures that could minimize fracture, it is important to understand and characterize stress states in the silicon nanostructures during lithiation. The stress of the crystalline core of the SiNWs during electrochemical lithiation was determined (at different levels of the electrochemical lithiation) using the in situ synchrotron X-ray microdiffraction technique. We found that the crystalline core of the SiNWs became highly compressive (up to -?325.5 MPa) once lithiation started. This finding helps unravel insights about mechanical stress states in the SiNWs during the electrochemical lithiation, which could potentially pave the path to fracture-free design of silicon nanostructure anode materials in the next generation lithium-ion battery.