Application of Fluid Immersion for Increased Safety and Efficiency of Lithium-Ion Battery and Electronic Devices
Publication Date: 2014-Apr-30
The IP.com Prior Art Database
Lithium-ion batteries are in widespread use worldwide in a vast array of electronic and electric devices ranging from hybrid and electric vehicles to power tools, portable computers and mobile devices. While generally safe and reliable energy storage devices, lithium-ion batteries are subject to a catastrophic failure mode known as thermal runaway1 under certain conditions. The focus of the work described herein is on mitigating the danger caused by thermal runaway resulting from mechanical damage and external heat. Lithium-ion batteries present a significant fire hazard. The wide-spread adoption and use of lithium-ion batteries, coupled with the potentially catastrophic failure mode of thermal runaway, has created a fire safety issue that requires a solution. Mechanical damage and internal shorts cannot always be avoided and the resulting energy release must be contained or lessened. Testing was performed on 6-cell lithium-ion battery packs assembled with fully charged 18650 type cells. A nail puncture was used to create an internal short in a single lithium-ion cell in a battery pack. A baseline, unprotected test was performed in a standard air atmosphere. The internal short caused nearly instant thermal runaway within the cell and a subsequent explosion that vented high temperature materials. The high energy release triggered by the puncture dramatically increased the temperature of the pierced cell. This high temperature heat source along with the freely burning electrolyte solution caused a cell-to-cell cascading thermal runaway event that was significantly more energetic than the initial event. This work reports on a new approach to mitigate this risk. Experiments showed that immersion of the battery packs in a dielectric fluid greatly reduced the maximum surface temperature of the initial cell with the internal short, no external combustion was observed, and the cell-to-cell cascading thermal runaway event was completely eliminated. This paper will further describe the experimental approach, results, and implications of this work.