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Kim, G. H.

Publications and source records attributed to Kim, G. H..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Effects of repetitive bending on the magnetoresistance of a flexible spin-valve

A positive magnetostrictive single layer (CoFe) and top-pinned spin-valve structure with positive magnetostrictive free (NiFe) and pinned (CoFe) layers were deposited on flexible polyethylene terephthalate film to investigate the changes in the magnetic properties in flexible environments, especially with a repetitive bending process. It was found that the stress, applied by repetitive bending, changes significantly the magnetic anisotropy of both layers in a single and spin-valve structure depending on the direction of applied stress. The changes in magnetic anisotropy were understood in terms of the inverse magnetostriction effect (the Villari effect) and the elastic recovery force from the flexibility of the polymer substrate. Repetitive bending with tensile stress transverse (or parallel) to the magnetic easy axis was found to enhance (or reduce) the magnetic anisotropy and, consequently, the magnetoresistance ratio of a spin-valve. The observed effects of bending stress in this study should be considered for the practical applications of electro-magnetic devices, especially magneto-striction sensor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

NREL Energy Storage Projects: FY2013 Annual Report

In FY13, DOE funded NREL to make technical contributions to various R&D activities. This report summarizes NREL's R&D projects in FY13 in support of the USABC; Battery Testing, Analysis, and Design; ABR; and BATT program elements. The FY13 projects under NREL's Energy Storage R&D program are discussed in depth in this report.

25 ENERGY STORAGE↗
DOE OSTI2014

Coupling of Mechanical Behavior of Cell Components to Electrochemical-Thermal Models for Computer-Aided Engineering of Batteries under Abuse (Presentation)

The EV Everywhere Grand Challenge aims to produce plug-in electric vehicles as affordable and convenient for the American family as gasoline-powered vehicles by 2022. Among the requirements set by the challenge, electric vehicles must be as safe as conventional vehicles, and EV batteries must not lead to unsafe situations under abuse conditions. NREL's project started in October 2013, based on a proposal in response to the January 2013 DOE VTO FOA, with the goal of developing computer aided engineering tools to accelerate the development of safer lithium ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2014

Models for Battery Reliability and Lifetime

Models describing battery degradation physics are needed to more accurately understand how battery usage and next-generation battery designs can be optimized for performance and lifetime. Such lifetime models may also reduce the cost of battery aging experiments and shorten the time required to validate battery lifetime. Models for chemical degradation and mechanical stress are reviewed. Experimental analysis of aging data from a commercial iron-phosphate lithium-ion (Li-ion) cell elucidates the relative importance of several mechanical stress-induced degradation mechanisms.

25 ENERGY STORAGE↗
DOE OSTI2013

Progress of the Computer-Aided Engineering of Electric Drive Vehicle Batteries (CAEBAT) (Presentation)

This presentation, Progress of Computer-Aided Engineering of Electric Drive Vehicle Batteries (CAEBAT) is about simulation and computer-aided engineering (CAE) tools that are widely used to speed up the research and development cycle and reduce the number of build-and-break steps, particularly in the automotive industry. Realizing this, DOE?s Vehicle Technologies Program initiated the CAEBAT project in April 2010 to develop a suite of software tools for designing batteries.

25 ENERGY STORAGE↗
DOE OSTI2013

Tools for Designing Thermal Management of Batteries in Electric Drive Vehicles (Presentation)

Temperature has a significant impact on life, performance, and safety of lithium-ion battery technology, which is expected to be the energy storage of choice for electric drive vehicles (xEVs). High temperatures degrade Li-ion cells faster while low temperatures reduce power and energy capabilities that could have cost, reliability, range, or drivability implications. Thermal management of battery packs in xEVs is essential to keep the cells in the desired temperature range and also reduce cell-to-cell temperature variations, both of which impact life and performance. The value that the battery thermal management system provides in reducing battery life and improving performance outweighs its additional cost and complexity. Tools that are essential for thermal management of batteries are infrared thermal imaging, isothermal calorimetry, thermal conductivity meter and computer-aided thermal analysis design software. This presentation provides details of these tools that NREL has used and we believe are needed to design right-sized battery thermal management systems.

25 ENERGY STORAGE↗