Intumescent Coating for Battery Pack Thermal Runaway

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Solution Overview

Problem

Thermal runaway in secondary batteries, such as lithium-ion cells, poses a significant risk of property damage and safety hazards due to uncontrolled heat generation and potential cascading reactions within battery packs, especially in large applications like electric vehicles, where conventional methods to enhance failure resistance through increased casing thickness are impractical due to weight constraints.

Innovation Solution

Application of a layer of intumescent material on the housing and interconnects within the battery pack, which absorbs thermal energy, expands to create a thermal barrier, and hardens to contain heat and gas, thereby inhibiting the propagation of thermal runaway events among adjacent cells.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the battery pack uses secondary batteries (lithium-ion cells) to achieve high energy density and rechargeability, then the energy efficiency and environmental benefits are improved, but the thermal stability deteriorates and the risk of thermal runaway increases

Engineering Contradiction:

Improveenergy efficiencyVSAvoidthermal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A thermal barrier material is introduced as an intermediary substance between adjacent battery cells. This material has low thermal conductivity and acts as a mediator to block heat transfer pathways, preventing thermal runaway propagation while allowing the high-energy-density lithium-ion cells to maintain their energy efficiency advantages

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention utilizes the intumescent properties of certain materials that expand when exposed to heat, converting the harmful thermal energy into a beneficial protective barrier. The material swells to form a carbonaceous char layer that insulates adjacent cells, transforming the thermal runaway heat into a protective mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If the casing thickness is increased to enhance failure resistance and contain thermal runaway, then the safety is improved, but the weight increases which is impractical for large applications like electric vehicles

Engineering Contradiction:

Improvefailure resistanceVSAvoidbattery pack weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

Instead of uniformly increasing the entire battery pack casing thickness, the invention applies thermal barrier materials locally at critical interfaces between adjacent cells. This localized approach provides targeted protection against thermal runaway propagation while minimizing the overall weight increase of the battery pack

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention employs composite material structures combining the original battery casing with additional thermal barrier layers. These composite structures provide enhanced thermal containment and failure resistance through the synergistic combination of structural integrity from the original casing and thermal insulation from the barrier materials

Inventive Principle:

Principle #40Composite materials

3Reliability

If a layer of intumescent material is applied to the housing and interconnects to create a thermal barrier, then the thermal runaway propagation resistance is improved, but the device complexity increases

Engineering Contradiction:

Improvethermal runaway propagation resistanceVSAvoidbattery pack structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thermal barrier material serves multiple functions simultaneously: it acts as a thermal insulator to block heat transfer, provides structural support to maintain cell spacing, and offers chemical stability to resist degradation from thermal runaway byproducts. This multi-functionality reduces the need for separate components and simplifies the overall battery pack structure

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 intumescent coating delays the onset of thermal runaway, reduces collateral damage, and prevents adjacent cells from entering thermal runaway, effectively minimizing the risk of cascading failures by providing a thermal barrier and directing excess heat towards cooling conduits.

Implementation Method 1

a layer of intumescent material on the housing and interconnects within the battery pack, which absorbs thermal energy

Methodology Applied

Scientific EffectThermal energy absorption: Absorption (EM radiation)

Implementation Method 2

expands to create a thermal barrier

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

layer of intumescent material coating the first housing member inner surface, the second housing member inner surface

Methodology Applied

Scientific EffectIntumescent material expansion: Intumescent Materials

Implementation Method 4

directing excess heat towards cooling conduits

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Data Source

PatentUS7820319B2Cell thermal runaway propagation resistant battery pack

Publication Date: 2010.10.26 TESLA INC

AI summary

A means for inhibiting the propagation of thermal runaway within a plurality of batteries is provided, wherein the means is comprised of a layer of intumescent material covering the interior surfaces of the battery pack.