Solvent-Free Coating Composition for Battery Pack Thermal Runaway Protection
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Solution Overview
Problem
Existing fire-resistant and heat-resistant coating solutions for electric vehicle battery packs are either ineffective in preventing thermal runaway, corrosive, or inconvenient to apply, with solventborne systems causing substrate corrosion and waterborne systems requiring extensive drying time, while solvent-free systems require special equipment and have limited operational flexibility.
Innovation Solution
A solvent-free, one-component coating composition comprising an aromatic isocyanate-based polyurethane prepolymer, expanded graphite, ammonium polyphosphate without surface treatment, and a water scavenger, with a balanced ratio of components to provide excellent fire resistance and heat resistance without the need for solvents, ensuring the coating adheres well and dries quickly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solventborne fire retardant coating system is used, then excellent adhesion to the battery pack substrate is achieved, but serious corrosion to the plastic substrate occurs due to solvents such as esters and ketones
Solution Approach 1:
The harmful solvents (esters and ketones) are extracted and removed from the coating system entirely. The invention uses a solvent-free composition where the fire retardant coating is applied as a paste or putty that cures in place, eliminating the corrosion problem while maintaining adhesion through direct bonding to the substrate.
Solution Approach 2:
The invention changes the physical state and composition parameters of the coating system from a solvent-based liquid to a solvent-free paste or putty. This parameter change eliminates the harmful solvents while maintaining coating functionality through alternative binding mechanisms that do not rely on solvent evaporation.
2Object-affected harmful factors
If a waterborne fire retardant coating system is used, then environmental friendliness is improved, but slow volatilization of water occurs, requiring drying equipment and taking a lot of time to dry
Solution Approach 1:
Water as a solvent is extracted and removed from the coating system. The invention uses a solvent-free composition that does not rely on water or any volatile solvent for application, thereby eliminating the long drying time problem while maintaining environmental friendliness.
Solution Approach 2:
The coating is applied in a paste or putty form that is already in a semi-cured state, requiring minimal drying time. The composition is designed to cure quickly upon application without requiring extensive drying equipment or time, as the reactive components are already mixed and ready to polymerize.
3Object-affected harmful factors
If a solvent-free two-component system is used, then no substrate corrosion and no slow volatilization problems occur, but special equipment for on-site mixing is required and the coating must be used within a certain time upon mixing
Solution Approach 1:
The invention merges the previously separate two-component system into a single pre-mixed component. The fire retardant coating is provided as a ready-to-use paste or putty where all reactive components are already combined, eliminating the need for on-site mixing equipment and the associated complexity while maintaining the solvent-free advantages.
Solution Approach 2:
All mixing and preparation actions are performed in advance during manufacturing, resulting in a stable, shelf-ready single-component product. The composition is formulated to remain stable during storage and only cures after application, eliminating the need for on-site mixing and extending the usable time window.
4Reliability
If mica sheets are riveted inside the battery pack, then fire resistance and heat resistance are improved, but the relative density is relatively high, unfavorable for lightweight of the automotive body
Solution Approach 1:
The invention uses a thin film coating applied directly to the battery pack surfaces instead of thick rigid mica sheets. This coating provides fire and heat resistance while being much thinner and lighter than riveted mica sheets, thereby reducing the overall weight of the battery pack while maintaining protective functionality.
5Reliability
If a fire retardant coating is applied on the battery pack, then fire resistance and heat resistance are improved, but the coating system requires drying equipment and takes a lot of time to dry
Solution Approach 1:
The coating is formulated as a paste or putty that is pre-prepared and ready for immediate application without requiring subsequent drying equipment or extended drying time. The composition is designed to cure quickly upon application, allowing battery packs to proceed directly to assembly without waiting for drying, thereby significantly improving production efficiency.
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 coating composition effectively prevents battery pack substrates from burning through within 5 minutes of thermal runaway, providing escape time and maintaining substrate integrity, with good extrusion rate, sag resistance, and storage stability, and is easy to apply without damaging the substrate.
Implementation Method 1
expanded graphite
Implementation Method 2
ammonium polyphosphate without surface treatment
Data Source
AI summary
The present invention relates to a coating composition and use thereof, and an article comprising a coating formed from the coating composition. The coating composition comprises a polyurethane prepolymer, which comprises 60% by weight to 100% by weight of an aromatic isocyanate-based polyurethane prepolymer and 0% by weight to 40% by weight of an aliphatic and/or cycloaliphatic isocyanate-based polyurethane prepolymer, relative to the total weight of the polyurethane prepolymer; expanded graphite; ammonium polyphosphate without surface treatment; and water scavenger; wherein the isocyanate group content of the polyurethane prepolymer is of 2.5% by weight to 14% by weight, relative to the total weight of the solid constituents of the polyurethane prepolymer; the amount of the water scavenger is of 0.1% by weight to 5% by weight, relative to the total weight of the composition; the ratio of weight of the polyurethane prepolymer to weight sum of the expanded graphite and the ammonium polyphosphate without surface treatment is of 1:2-2:1; and the weight ratio of the expanded graphite to the ammonium polyphosphate without surface treatment is of 1:10-4:1.