DEVELOPMENT OF LI+ AND NA+ CONDUCTING CERAMICS AND CERAMIC STRUCTURES FOR USE IN SOLID STATE BATTERIES

A solid state lithium metal battery based on a lithium garnet material was developed, constructed and tested. Specifically, a porous-dense-porous trilayer structure was fabricated by tape casting, a roll-to-roll technique conducive to high volume manufacturing. The high density and thin center layer (< 20 μm) effectively blocks dendrites even over hundreds of cycles. The microstructured porous layers, serving as electrode supports, are demonstrated to increase the interfacial surface area available to the electrodes and increase cathode loading. Reproducibility of flat, well sintered ceramics was achieved with consistent powderbed lattice parameter and ball milling of powderbed. Together, the resistance of the LLCZN trilayer was measured at an average of 7.6 ohm-cm2 in a symmetric lithium cell, significantly lower than any other reported literature results. Building on these results, a full cell with a lithium metal anode, LLCZN trilayer electrolyte, and LiCoO2 cathode was cycled 100 cycles without decay and an average ASR of 117 ohm-cm2. After cycling, the cell was held at open circuit for 24 hours without any voltage fade, demonstrating the absence of a dendrite or short-circuit of any type. Cost calculations guided the optimization of a trilayer structure predicted that resulting cells will be highly competitive in the marketplace as intrinsically safe lithium batteries with energy densities greater than 300 Wh/kg and 1000 Wh/L for under $100/kWh. Also in the pursuit of solid state batteries, an improved Na+ superionic conductor (NASICON) composition, Na3Zr2Si2PO12, was developed with a conductivity of 1.9x10-3 S/cm. New super-lithiated lithium garnet compositions, Li7.06La3Zr1.94Y0.06O12 and Li7.16La3Zr1.84Y0.16O12, were developed and studied revealing insights about the mechanisms of conductivity in lithium garnets.

Phase II Archaeological Excavations at 99 Main Street, 18AP21 (Sign of the Whale), Annapolis, Maryland

Historical Annapolis Foundation (HAF) conducted terrestrial archaeological investigations at site 18AP21 in the city of Annapolis, Maryland. Excavations were carried out at this National Register site ostensibly as a Phase II project to evaluate the site and assess the need for further work. The site is at 99 Main Street in the center of downtown Annapolis, near the Annapolis waterfront. The project was carried out as part of the advanced work for the Annapolis History Center project, to be built in the adjoining buildings of 99 Main and 196 Green Streets. The buildings are the property of the Historic Annapolis Foundation and located in Maryland Research Unit 7. The excavations were undertaken by HAF, and funded by HAFF. The work was conducted for HAF and MHT, who holds an archaeological easement on the property. This preliminary phase of work included stratigraphic excavation of two testpit units. These two units revealed that the site of the existing 99 Main Street building was the location of three previous constructions. The current building at 99 Main Street, built in 1791, was preceded by an earlier brick dwelling, evidenced by a stout pier of bricks, which was attached to a wooden-sided structure that stood on a foundation of brick and stone. Ceramics indicate that these buildings date to the early-middle of the 18th century. A third structure of post-in-ground construction, evidenced by recovery of burned posts and wood fragments, likely existed prior to these, but evidence was scant. These excavations reveal that the site of 18AP21 holds potential for understanding Annapolis's early cultural developments, especially in the area of initial settlement and the origins of waterfront commerce. The assemblage of artifacts recovered includes a broad sample of common 18th century pottery such as creamware and Chinese export porcelain, and also includes some early colonial types such as tin-glazed earthenware and various red-bodied slipwares. The excavations do not provide conclusive evidence of the construction sequence. Consultation with MHT representatives indicates that further work at the site will likely be needed before modifications to the floor of the building can progress.