ELECTROCHEM-MECHANICS CHARACTERIZATION OF SI ELECTRODE/SI BASED SOLID-STATE BATTERY

Abstract

Li-ion battery (LIB) is a popular energy storage device that predominates the market of microelectronics due to its high energy density and light weight. In the recent trend of electrification of vehicles, LIBs also showed promise in the application of electric vehicles but the energy density of current LIBs with graphite electrode doesn’t suffice the need of long driving range. Replacing graphite electrode with alloying type electrodes that have almost ten times higher energy density is thus a necessary route to improve the energy density of LIBs. However, alloying type electrodes, such as Si and Sn, typical undergo enormous volume change (up to 310%) during Li insertion and extraction, which lead to various mechanical problems such as cracking, delamination, and pulverization. These mechanical issues eventually cause catastrophic capacity fading in LIBs and thus, are central topics for the application of alloying type electrodes in next generation LIBs. This dissertation presents a three-phase experimental study of stress development in Si electrodes and Si based solid state batteries. In the first phase, ex-situ stress characterization in single-c Si electrode was performed to validate Raman spectroscopy as a promising stress characterization technique for Si electrode. In the second phase, in-situ stress characterization in patterned poly-c Si electrode with confocal micro-Raman setup was performed, to investigate the correlation between complex geometries and stress distribution in crystalline Si electrode and the critical size effect. In the last phase, a solid-state battery (SSB) platform device with lateral layout was proposed and validated for stress characterization in Si based SSBs. The platform device can also serve as a versatile testbed for electrochemistry study of bulk SSB components and interfaces. Overall, this dissertation demonstrates a methodology that combines Raman spectroscopy, novel design of electrochemical devices, and computational modeling as a powerful tool for electrochemo-mechanics study of alloying type electrodes and SSB systems.