Safe, High Specific Energy & Power Li-ion Cells

Metadata Updated: November 12, 2020

Today’s best, safe commercial Li-ion cell designs achieve ~180 Wh/kg, ~500 Wh/L, and 400 W/kg. When accounting for the lightest (1.35) parasitic mass and smallest (2.0) parasitic volume factors of proven battery construction features, this means that at the battery level we need improvements of 144% and 170%, respectively, to achieve our specific energy (>325 Wh/kg) and energy density (>540 Wh/L) performance targets. Today’s best commercial Li-ion cell designs offer the promise of a 47% and 82% improvements, respectively, over the State of the Art as shown in Fig. 1 below. Unfortunately, we can’t implement these new cell designs, which are safe enough for small consumer batteries but are unsafe for larger manned applications due to the high propensity for them to side wall rupture during thermal runaway.This proposal offers to overcome this safety issue and enable significant progress towards the Evolving Mars Campaign (EMC) target. We seek our advanced battery designs to be passively propagation resistant to a single cell thermal runaway (TR). Key to this goal is greatly reducing the risk of side wall rupture of the hot thermal runaway products ejected from the cell (a.k.a., ejecta). Side wall ruptures create a blow torch effect which, when impinging on adjacent cells, causes nearly immediate TR propagation in a closely-packed battery designs.The higher energy content (265 Wh/kg, 725 Wh/L) of the newer cell designs from LG, Panasonic, and Samsung have made them susceptible to side wall ruptures during thermal runaway, rather than venting through the intended vent path in the cell header. This is also due to higher reaction kinetics of the electrochemistry, thinner can walls, tight crimp enclosure of the cell header, and inadequate flow rate through the header vent. Tesla Motors was the first to recognize and address this issue by asking cell manufacturers to produce cell designs with bottom burst disc vents.  However, those designs exclusively for Tesla and not available to others. Thus, we must stay with lower performing cell designs or implement structural supporting features for the cells in the battery designs. Both options limit battery achievable specific energy to at best 133 Wh/kg. Being able to safely implement the newest cell designs with bottom vents will enable reaching 196 Wh/kg at the battery level. This 47% improvement would save 24 lbs per each 4 kWh MPCV battery or 96 lbs per MPCV flight or enable 1 hour flight run time for the X-57 electric plane by saving 282 lbs from their 46 kWh battery. Similar volume savings impacts are possible by retiring the side wall rupture risk, because it allows cells to be safely nested together more efficiently. These sizable mass/volume savings and safety improvements are aligned with the needs of the EMC.Safe, higher performing batteries are well aligned with EMC needs for high specific power, high specific energy batteries, long life batteries, and deep space suit specific energies  >235 Wh/kg.The required vent paths are achieved by scoring a groove pattern in bottom of the mild steel can. Although they look simple, achieving a reliably performing bottom vent is not trivial. Weaker designs are excessively susceptible to corrosion, leakage, damage, and poor performance uniformity. The important question that this research project will answer is whether our design will significantly reduce the side wall rupture risk without significant limitations, such as leakage, corrosion, and excessive performance variations.The scope of the project includes conducting TR tests on similar cells with and without the bottom vent to show the merits of the bottom vent feature. Just 3 months ago, Sony Energy became the first to make a commercially available, high performing design with a bottom vent. We have taken delivery of 400 such SONY cells last month. LG Chem, Ltd., has not publically rel

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Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020

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Harvested from NASA Data.json

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Resource Type Dataset
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Publisher Space Technology Mission Directorate
Unique Identifier Unknown
Identifier TECHPORT_91017
Data First Published 2017-09-01
Data Last Modified 2020-01-29
Public Access Level public
Bureau Code 026:00
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Program Code 026:027
Source Datajson Identifier True
Source Hash 8b63c743f7eedcc186d20b288cbf0b0c79410e1d
Source Schema Version 1.1

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