Sandia National Labs FY20 LDRD Annual Report

FY20 ANNUAL REPORT

An interfacial synaptic transistor for fast neuromorphic computing. A novel electronic memory device called an electrochemical random-access memory (ECRAM), which is ideally suited for energy- efficient brain-inspired computing, was the outcome of this innovative LDRD project. The ECRAM device is based on fast, low-voltage manipulation of oxygen vacancies in a nanoscale, transition metal oxide channel. By tuning the bulk vacancy concentration within the 3D bulk of the channel, the team solved the challenge of stochastic switching that has plagued filament-based memristors.

This provides a compelling artificial synapse for energy-efficient training of deep neural networks, which are then used to process information such as rapid and accurate recognition of images and sounds. The work resulted in a filed patent application and a paper published in the Advanced Materials ). (PIs: Yiyang Li, Alec Talin)

Filamentary-Resistive Random Access Memory (RRAM) compared to Bulk-RRAM.

The relationship between electrochemistry and mechanics in batteries. Lithium metal is the “holy grail” anode material to enable the next-generation of high-energy-density batteries. Because lithium metal anodes undergo large volume and morphology changes during cycling, this project focused on studying the effects of applied interfacial stress on lithium metal anode cycling. The team found that interfacial stress can significantly affect performance and volumetric energy density, which led to a patent application and two papers in preparation. Sandia successfully partnered

with ThermoFisher to develop a new technique for imaging entire coin cell batteries without disassembly using ThermoFisher’s new Tribeam scanning electron microscope. Ultimately, the project demonstrated that bulk electrodeposited lithium can bear residual stress and showed for the first time that the residual stress can be characterized by X-ray diffraction, resulting in a journal article published in Powder Diffraction . (PI: Katie Harrison) Scanning electron micrographs of intact angled-sections of high- rate cycled Li-metal coin cell batteries. (a) uncycled cell, including: stainless-steel cap, Cu current collector (salmon), stack of two Celgard 2325 separators (blue), Li metal (pink), bottom Cu current collector (salmon), and lower stainless-steel disc, (b) 1st Li cycle plating, (c) 1st Li cycle stripping, (d) 11th cycle plating, (e) 51st cycle plating, and (f) 101st cycle plating step. The battery cycling process causes destruction of the separators.

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LABORATORY DIRECTED RESEARCH & DEVELOPMENT