UC San Diego

All-solid-state batteries (ASSBs) have gained lots of attention by both science and industry field. There are numerous benefits of adopting ASSB. First, because of inorganic solid-state electrolytes (SSEs), ASSBs have less safety concerns compared to the conventional liquid lithium-ion batteries (LIBs). Another reason is that, the energy density of ASSBs could exceeds that of LIBs with the premise of utilizing alloy-type or Li metal anode. Despite the extensive studies for decades, the alloy-type, especially Si anode, and Li metal failed to achieve reasonable cyclability up to the practical level. However, the recent studies shed light on excellent compatibility of argyrodite solid electrolyte, Li6PS5Cl, and anode-free (Li metal) anode and pure Si anode. First half of this dissertation is on the study of critical current density (CCD) of Li metal-ASSBs. The low CCD of Li metal-ASSBs hindered the practical operation of the cell, whereas inconsistent CCDs reported in academia. The variation of CCDs could be attributed to the various factors, such as temperature, solid electrolyte chemistry or pressure. The relationship between the fabrication pressure contact hold time of Li metal vs CCD is reported, elucidating the effect of controlled Li deformation on CCD. Further, the volumetric expansion of full cell configuration of Li metal-ASSB was mitigated to achieve higher CCDs at room temperature. Alloy-type Si anode was investigated in this thesis as well. Si-ASSBs have shown promising performance without continual solid-electrolyte interface (SEI) growth. However, the first cycle irreversible capacity loss yields low initial Coulombic efficiency (ICE) of Si, limiting the energy density. To address this, we adopt a prelithiaiton strategy to increase ICE and conductivity of Si-ASSBs. A significant ICE was observed for Li1Si anode paired with lithium cobalt oxide (LCO) cathode. A high areal capacity of up to 10 mAh cm-2 was attained using this Li1Si anode, suggesting that the prelithiation method may be suitable for high-loading next-generation all-solid-state batteries. The N/P ratio of Si in ASSBs showed peculiar behavior compared to liquid LIBs, which further broaden a usage of Si not only as anode but potentially as part of current collector. Overall, this dissertation offers an understanding of high-capacity anode for ASSBs which could lead to safe and high energy density cells, one step closer to commercialization.