Internal Short Circuit Device for Improved Lithium-Ion Battery Design
Energy storage cells (also referred to herein as "cells" or "batteries") sold for consumer use in portable electronic devices and other applications have occasional failure in the field. These cells have typically passed a wide variety of safety tests, such as those required by governmental shipping regulations and by other certification organizations, but fail after the cells have been in use over time (e.g., several months), even though there have been no other reported problems with the cells that fail. Regardless, these failures can result in the cells overheating, and in some cases, going into thermal runaway wherein the cell can ignite and burn. For example, these incidents have been reported in the media as "the burning laptop" and have resulted in the recall of millions of batteries. At least some of these failures have been attributed to a latent defect introduced during the cell manufacturing process that escapes detection during initial acceptance testing and results in an internal short circuit between the positive and negative components of a cell (electrodes or current collectors) after having been in use for some time.
Due to the dormant nature of this flaw, battery manufacturers have found it difficult to precisely identify and study. NREL’s device introduces a latent flaw into a battery that may be activated to produce an ISC. NREL uses the ISC device to better understand the failure modes of Li-ion cells and to validate NREL’s abuse models.
The device can be placed anywhere within the cell and can be used with both spirally wound and flat-plate cells containing any of the common Li-ion electrochemical systems. Producing a true internal short, the device is small compared to other shorting tools being developed by industry and does not rely on mechanically deforming the battery to activate the short, as do most of the other test methodologies. With the internal short in place, the battery can be used and cycled within normal operating conditions without activating the internal short device. This allows the battery to be aged prior to activation.
The internal short produced by NREL’s device is consistent and is being developed as an analysis tool for battery manufacturers and other national laboratories as well as original equipment manufacturers (OEMs). This has broad-reaching applications as automakers bring electrified vehicles to market in larger numbers.Description
NREL scientists have produced a method for placing a thermal switch into the battery that can be activated by temperature. Exemplary embodiments may be utilized with spirally-wound and stacked flat-plate cells containing any of the common lithium-ion, lithium sulfur, or lithium air electrochemical components. The thermal switch placed in the battery would only activate once a predetermined temperature is achieved. Therefore, the battery can be used and cycled as long as the thermal switch temperature does not exceed the switch's activation temperature. Once the thermal switch is activated, the cathode and anode of the battery would be electrically connected and an internal short would result.
The switch consists of a piece of non-conductive material, typically a piece of separator material already used within the battery, whose length and width can be as small as 0.010" or as long as several inches. An electrically conductive material is placed on the piece of separator material. A partial list of how an electrically conductive material can deposited are through chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, thermal evaporator, electron beam evaporator, sputtering, and plating. A sheet of electrically conductive material can also be cut to the desired shape and placed, melted, or glued onto the non-conductive material. The electrically conductive material would have a melting point between 10°C and 150°C and have a thickness of less than 500 microns. The thermal switch would consist of two pieces of electrically conductive material that are separated by a small gap - between 0.0005" and 0.25".
Exemplary positioning of the switch includes but is not limited to: 1) between the cathode and anode, 2) between the cathode and the negative electrode, 3) between the anode and the positive electrode, and 4) between the positive and negative electrodes.Benefits
- Enhanced energy storage safety
- Easily integrated into existing batteries
- Multiple methods for creating internal short
- Energy Storage
- Battery Safety
- Electric Vehicles
For further information, please read NREL's news item on this FLC award-winning technology.Patents and Patent Applications
|Title and Abstract||
Passive safety device and internal short tested method for energy storage cells and systems
A passive safety device for an energy storage cell for positioning between two electrically conductive layers of the energy storage cell. The safety device also comprising a separator and a non-conductive layer. A first electrically conductive material is provided on the non-conductive layer. A first opening is formed through the separator between the first electrically conductive material and one of the electrically conductive layers of the energy storage device. A second electrically conductive material is provided adjacent the first electrically conductive material on the non-conductive layer, wherein a space is formed on the non-conductive layer between the first and second electrically conductive materials. A second opening is formed through the non-conductive layer between the second electrically conductive material and another of the electrically conductive layers of the energy storage device. The first and second electrically conductive materials combine and exit at least partially through the first and second openings to connect the two electrically conductive layers of the energy storage device at a predetermined temperature.
|National Renewable Energy Laboratory||09/22/2015
|Technology ID||Development Stage||Availability||Published||Last Updated|
|NREL ROI 10-46||Development||Available||01/08/2013||11/23/2015|