Li-Ion Battery Pack Shielding System

The Thermal Ejecta Shielding System comprises strategically layered materials that fasten to the top of a Li-ion cylindrical battery pack casing. It can protect individual battery cells in a battery pack by shielding them from a neighboring cell’s hot thermal ejecta during a TR event while providing primary functions of connecting, insulating, grounding, and distributing power. In laboratory testing, this technology improved the resistance to TR collateral damage of a PPR battery pack by overcoming two primary drawbacks of its design. Modern Li-ion cylindrical battery cell packs comprise a nickel bus plate that aligns with and connects the positive buttons along the battery tops to distribute power. Insulating G10 composite layers sandwich the bus plate atop the cells, however, these are rendered vulnerable to burn-through during a TR event due to their thinness, and they can allow escaping thermal ejecta to penetrate the button cavities of neighboring battery cells within the battery pack. Additionally, the nickel and composite bussing layering is prone to separation, or "tenting", when subjected to extreme heat, as it relies solely on an adhesive bond to prevent delamination. The hot ejecta spray stemming from a battery cell undergoing a TR event can weaken this adhesive bond. These issues can lead to adjacent battery cell damage resulting in their reduced performance, zero-voltage, or susceptibility to a larger TR event. The Li-Ion Battery Pack Shielding System was developed from a multi-pronged strategy to improve upon the drawbacks by introducing these novel components and accompanying features: • Capture Plate Cell “Chimney” - Redirects ablative ejecta away from adjacent cells and creates a volume for liquid “sealer” protection; • Adhesively Backed Mica Cell Donut - Provides an insulative layer to protect the positive bus plate from creating a short circuit to the negative cell can during TR; • Adhesive Transfer Tape - Provides an adhesive layer for a more uniform/reproducible bond between the nickel bussing, mica, the G10/FR4 insulating layer, and the aluminum layers; • Continuous Mica Cell Cover Sheet - Replaces individually installed mica covers (upper layer of G10/FR4) with a single sheet of perforated mica; • Rupture Sheet Cover Plate - Introduces a thin aluminum fastener plate above the Continuous Mica Cell Cover Sheet to prevent delamination of bussing sandwich layers; • Narrowed Bus Plate Tab - Introduces a narrowed tab to allow for unrestricted header expansion and severing/separation during TR; • Steel Ring - Protects cell from spin groove ruptures and redirects ablative ejecta away from adjacent cells; and • Liquid Cell Covers - Introduces a high temperature liquid “sealer” to fill the void between cell button and mica cover to prevent ejecta burn-through from compromising the seal. Innovators at NASA Johnson Space Center have designed a thermal runaway (TR) shielding system for Li-ion cylindrical battery packs to inhibit collateral damage to adjacent battery cells during a TR event. This shielding system technology introduces eight novel improvements (detailed below) to a state-of-the-art “Passively Propagation Resistant” (PPR) battery pack that may be applied to other Li-ion battery packs for safety and performance improvements. TR is caused by a battery cell short-circuiting combined with the cell’s inability to contain the resulting increase in pressure and temperature. For example, this inability could lead to a rupture from either end of a cylindrical cell, where ensuing hot ejecta spray could damage neighboring cells in a battery pack – or could trigger the neighboring cells into TR, which in turn could escalate into a catastrophic fire. Numerous industries such as automotive, aviation, aerospace, and consumer electronics utilize Li-ion battery cells that are assembled into modules or battery-packs to provide energy storage. This Li-Ion Battery Pack Shielding System technology has a technology readiness level (TRL) of 6 (System/sub-system model or prototype demonstration in an operational environment), and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.