Organizational Unit:
School of Materials Science and Engineering

Permanent Link
https://hdl.handle.net/1853/70762
Research Organization Registry ID
Description
Previous Names
Parent Organization
Parent Organization
Organizational Unit
Includes Organization(s)
ArchiveSpace Name Record
https://finding-aids.library.gatech.edu/agents/corporate_entities/1126

Filters

1 1
2022 2
2
1 1
2
2
Reset filters

Settings
search.filters.applied.f.advisor: McDowell, Matthew ×

Publication Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Probing Interfacial Dynamics in Solid-State Lithium Metal Batteries
    (Georgia Institute of Technology, 2022-05-03) Lewis, John A.
    Solid-state batteries (SSBs) are a promising technology to surpass the energy density and safety of conventional lithium-ion batteries. These devices replace the flammable liquid electrolyte with a more stable solid-state electrolyte (SSE) that can conduct lithium ions. The rigid mechanical properties of SSEs are also promising for enabling the energy dense lithium metal anode, which is plagued by dendrite formation and dead lithium in liquid electrolytes. Despite advances towards SSEs with high ionic conductivity, the understanding and control over solid electrode/SSE interfaces have emerged as major challenges in the development of SSBs. Chemo-mechanical degradation is expected to be more severe in SSBs compared to conventional liquid-electrolyte-batteries because the SSE cannot reconfigure like liquids. Understanding chemical transformations at interfaces, mechanical damage, and lithium filament growth is therefore critical for engineering SSBs. This dissertation investigated the underlying mechanisms of these interfacial phenomenon to better inform the design of SSBs. First, severe SSE decomposition caused by electrochemical side reactions with lithium metal was found when the reacted species exhibited mixed ionic-electronic conduction. Continuous decomposition ultimately resulted in fracture due to the build-up of internal stress, and this process was accelerated when operating at higher rates. Second, the dynamic evolution of Li/SSE interfaces was probed using operando X-ray tomography. 3D images of SSBs were obtained during operation, which were then processed using segmentation to quantify how phases change and link their behavior directly to the measured electrochemistry. Analysis revealed that the significant loss of interfacial contact was responsible for cell failure. Third, the relationships between unstable Li metal deposition and electrochemical parameters, such as current density and areal capacity, were investigated. A new metric called the threshold capacity was introduced and used to evaluate lithium deposition behavior in SSBs. Cycling of cells with areal capacity controlled to be well below the threshold capacity greatly improved cell lifetime, while approaching the threshold capacity resulted in rapid short circuiting. Fourth, the mechanisms of anode-free SSBs were investigated, in which lithium metal was deposited onto a bare copper current collector during the first charge. Stripping lithium from the copper current collector was found to cause significant degradation that severely limited cycling lifetime. Lastly, the energy densities of various battery chemistries were calculated at the cell-level. Alloy anodes in SSBs were shown to have competitive energy densities, and their mechanistic advantages over alloy anodes with liquid electrolytes and lithium metal SSBs are discussed.
  • Thumbnail Image
    Item
    Characterizing Solid State Battery Degradation Using Optical Microscopy and Operando X-Ray Tomography
    (Georgia Institute of Technology, 2022-05) Prakash, Dhruv
    The implementation of solid-state electrolytes (SSEs) into lithium-ion batteries shows much promise in enabling the use of higher energy density anodes, such as pure lithium metal. However, the implementation of SSEs and lithium metal anodes in lithium-ion batteries is currently not possible due to degradation mechanisms that lead to premature failure of the battery. These mechanisms, such as the formation of a new phase known as the interphase and the growth of lithium metal dendrites, are initiated at the interface between the anode and electrolyte and are linked to the current density at which the battery is cycled. Reported are two methods of characterizing the interfacial degradation phenomena that occur between lithium metal anodes and the SSE Li10SnP2S12 (LSPS). A novel symmetric battery setup was developed to allow an operando optical microscopy study of the lithium metal and SSE interface as charge was passed through the battery. Though this characterization method presented challenges, interphase formation and dendrite growth were both observed. Further, operando x-ray computed tomography of a novel cell geometry provided detailed three dimensional scans that also showed evidence of interphase growth and dendrite formation. Additionally, interfacial void formation was identified, indicating a loss of contact that increases current density. These results provide insight into the failure of solid-state batteries and show how operando optical microscopy and x-ray tomography can be used to gain a more complete understanding of the degradation of higher energy density lithium-ion batteries.