Perforated Multilayer Cell Separator for Battery Thermal Runaway
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Solution Overview
Problem
Lithium-ion batteries in electric vehicles face challenges with thermal runaway due to low thermal stability in high-energy density materials, leading to potential battery failure and safety risks from rapid temperature increases and pressure buildup.
Innovation Solution
A multilayer cell separator is introduced, comprising a metal foil sandwiched between thermal insulation sheets with through-holes, which reduces heat transfer and provides voids for expansion, thereby delaying or preventing thermal runaway and relieving pressure within the battery casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high energy density materials (nickel-rich cathode, silicone-anode) are used to increase battery energy density, then the energy density of Li-ion batteries is improved, but thermal stability deteriorates leading to thermal runaway risk
Solution Approach 1:
A multilayer cell separator is introduced as an intermediary component between adjacent battery cells. This separator comprises a metal foil layer (providing mechanical strength and thermal stability) combined with thermal insulation layers (aerogel, mica, or ceramic board) that act as heat barriers. The separator physically separates cells while thermally isolating them, preventing heat propagation during thermal runaway events.
Solution Approach 2:
The cell separator is constructed as a composite structure combining metal foil with low thermal conductivity materials (aerogel, mica, or ceramic board). This composite design leverages the high mechanical strength and thermal stability of metal foil while incorporating the excellent thermal insulation properties of the ceramic-based materials, achieving both structural integrity and thermal protection.
2Reliability
If thermal insulation sheets are made thicker to improve heat resistance, then resistance to thermal runaway is improved, but the weight of the battery pack increases
Solution Approach 1:
The thermal insulation layers utilize porous materials such as aerogel, which possess extremely low thermal conductivity despite their lightweight nature. The porous structure traps air pockets that inhibit heat transfer, providing superior thermal insulation performance without adding significant weight. This allows effective thermal protection with minimal mass penalty.
Solution Approach 2:
The multilayer separator concentrates thermal insulation functionality in specific layers rather than uniformly thickening the entire separator structure. The metal foil provides localized mechanical support while the thermal insulation layers (aerogel, mica, or ceramic board) provide localized heat barrier functionality, optimizing the weight-to-protection ratio.
3Reliability
If solid thermal insulation material is used to prevent heat transfer, then thermal insulation performance is improved, but pressure relief capability deteriorates when battery swells during thermal runaway
Solution Approach 1:
The thermal insulation sheets are selectively perforated with through-holes at specific locations rather than being completely solid. This localized perforation strategy maintains thermal insulation performance in the bulk material while creating controlled pathways for pressure relief. The holes allow gas and pressure to escape during thermal runaway without compromising the overall heat barrier function of the separator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces the weight of the battery pack while maintaining resistance to thermal runaway, allowing for safer operation by delaying heat propagation and providing space for thermal expansion, thus enhancing the safety and efficiency of electric vehicle batteries.
Implementation Method 1
the at least first and second thermal insulation sheets are made from a thermal resistance material with a heat conductivity transfer coefficient of less than 0.35 W/mK
Implementation Method 2
the metal foil has a heat reflectivity coefficient from about 0.10 to about 0.8
Implementation Method 3
voids into which a thermal runaway battery is allowed to swell and expand are provided
Data Source
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AI summary
A multilayer cell separator (100) for mitigating thermal runaway between adjacent rechargeable battery cells (220) arranged in a stacked configuration (150), said multilayer cell separator (100) comprising a metal foil (110) sandwiched between at least a first and a second thermal insulation sheet (111,112), the at least first and second thermal insulation sheets (111,112) being provided with two or more through-holes (113). A battery energy storage system (300) provided with battery modules (200) comprising said battery stacks (150) is also provided.