Very Low Impedance Battery Architecture for Electrified Vehicles

Thomas D. Kaun, Joel Sandahl
2012 unpublished
Rolled-Ribbon is design and manufacturing method for battery cells that incorporates features of very short path length to bring current flow as well as heat from the cell and battery. Disc-shaped cells can be stacked to form a dense and efficient battery architecture for electrified vehicles. Relative to competing architectures, Rolled-Ribbon combines the low-cost winding and dimensional stability of the cylindrical format with fullytabbed, very short electrodes of a prismatic (that is
more » ... ic (that is replicated by winding). The very short electrode of the cells and the quasi-bipolar arrangement approximately lower cell structural impedance (ACIR) by 50% and DCpulse impedance by 25% for Li-ion battery. As such, Rolled-Ribbon overcomes the power/energy tradeoffs faced by competing architectures. Specific energy is increased with larger cells and high power is maintained. Rolled-Ribbon TM Battery Technology Broad adoption of EV (electric vehicles) is being held back by excessive cost of Li-ion batteries and excessive volume and weight to limit vehicle size and range. Adoption of Rolled-Ribbon battery architecture poses a cost-effective alternative to the cylindrical cell and "pouch/prismatic" battery with competitive advantages for safety, durability and sustainability. InvenTek's proprietary (1) Rolled-Ribbon battery architecture promotes the volume efficiency and thermal management efficiency to operate safely at significantly (almost double) higher energy densities than state-of-art battery systems. Rolled-Ribbon (R-R) is particularly beneficial for the production of large-format cells (6-30 Ah capacity) for high power density. R-R battery packs with larger 30 Ah capacity cells display high energy density about double that of pouch/prismatic for EV. The R-R cell technology (2) uses long, narrow electrodes with interwoven separator to fabricate large, disk-shaped cells. A typical cell might be 13mm in height by 125mm in diameter. The wound configuration is housed within a sealed, disc-shaped enclosure, where the entire faces of the housing, top and bottom cell terminals, make distributed pressure contact with the narrow electrode ribbons. The Rolled-Ribbon architecture eliminates the welded current collectors present in cylindrical and prismatic type cells, which increase cell resistance, robbing power from the cell and generating damaging heat. It enables efficient high power delivery. Further, the narrow electrodes are efficient in thermally conducting heat to the large diameter top and bottom housing covers, Figure 2 . This results in uniform internal temperature distribution that can enable longer cell life in power applications, typical of hybrid and electric vehicles. An independent modeling of cell thermal properties at NREL (3) confirms that a disc-shaped, pancake cell affords the best heat dissipation to eliminate hotspots. The Rolled-Ribbon design is favored in a modeling trade-off study on electrical and thermal performance of various cylindrical cell designs. From FY 2008 DOE Progress Report Energy Storage Research and Development David Howell, January 2009, opposing terminal designs is favored over same-side terminal designs by promoting more uniform active material usage. The R-R
doi:10.1149/1.3702862 fatcat:th4czjmwzjdehjec4fc7nj7mw4