Microstructural and Interface Engineering of Garnet-Type Fast Ion-Conductor for Use in Solid-State Batteries

Solid-state electrolyte;Solid-state battery;Interfacial impedance;Charge transfer;critical current density;Li-ion conductivity;Metallic Li anode;Mechanical Engineering;Engineering;Mechanical Engineering

Sharafi, AsmaSiegel, Donald Jason ;

University of Michigan

关键词: Solid-state electrolyte;    Solid-state battery;    Interfacial impedance;    Charge transfer;    critical current density;    Li-ion conductivity;    Metallic Li anode;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/140865/sharafi_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Large-scale adoption of electric vehicles requires batteries with higher energy density, lower cost, and improved safety compared to state-of-the-art (SOA) Li-ion batteries. This dissertation addresses the great-unmet need to develop beyond Li-ion batteries to facilitate the transition to electric power trains. The successful integration of metallic Li anodes into rechargeable batteries will enable a step increase in energy density compared to SOA Li-ion technology. However, the unstable nature of the electrode-electrolyte interface has limited the use of metallic Li anodes when paired with conventional organic solvent-based electrolytes. One approach to stabilize the metallic Li anode interface involves the integration of a solid-state electrolyte (SSE). Theoretical predictions suggest that Li dendrites will not form if a SSE exhibits a shear modulus that is approximately twice the shear modulus of metallic Li (GLi= 4.2 GPa) or higher. This criterion indicates that ceramic Li-ion conducting solid-state electrolytes (SSE) can prevent dendrites. Thus, the development of solid-state batteries using SSE has been overlooked as a potential means to stabilize the metallic Li anode during cycling.The garnet-type Li-ion conductor, Li7La3Zr2O12 (LLZO), is an example of a SSE that exhibits the unique combination of high Li-ion conductivity (1 mS.cm-1 at 298 K) and stability against metallic Li. Additionally, LLZO has a shear modulus 14 times higher than metallic Li, thus should act as a physical barrier to prevent Li dendrite formation according to computational analysis.However, despite satisfying the shear modulus criterion, Li metal propagation has been observed in polycrystalline LLZO. This dissertation hypothesizes that atomistic and microstructural defects such as porosity, grain boundaries, interfaces, and surface impurities govern the stability of the Li-LLZO interface.The effect of each defect was isolated through ceramic processing and analyzed using a suite of characterization tools such as X-ray diffraction, electron backscatter, scanning and transmission electron microscopy, electron energy loss, acoustic, and Raman spectroscopy, direct current cycling and complex impedance, Vickers indentation, and fracture toughness measurements. The overarching goal of this dissertation was to better understand the phenomena that control the stability of the Li-LLZO interface, quantify the contributions of each defect, and develop engineering approaches to tailor the LLZO microstructure and interface for maximum resistance to Li metal propagation during cycling. The implications of this dissertation could accelerate the development of high energy density solid-state batteries.