Sodium Borate Foam Sheet for Battery Thermal Runaway Delay
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Solution Overview
Problem
Existing thermal management solutions for batteries, such as lithium-ion batteries, face challenges in preventing thermal runaway propagation, especially in large format applications, where thin sheets with effective thermal management properties are difficult to achieve without compromising energy density or introducing flame retardants that impact electrochemical performance.
Innovation Solution
A thermal management sheet comprising cured polyurethane foam with sodium borate, which is formed by combining a polyol and polyisocyanate components, providing a flexible and porous layer with specific weight percentages of sodium borate, surfactant, and catalyst, offering effective thermal insulation, puncture resistance, and improved flame resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If increased insulation is incorporated between cells to reduce thermal heat transfer, then thermal runaway prevention is improved, but energy density is reduced
Solution Approach 1:
The patent changes the thermal and physical parameters of the insulation material by incorporating sodium borate into polyurethane foam, achieving superior thermal runaway prevention at lower thicknesses. This allows reduced insulation thickness while maintaining or improving thermal safety, thereby preserving energy density.
Solution Approach 2:
The patent uses composite materials combining polyurethane foam with sodium borate to create an insulation layer that provides both thermal insulation and active thermal runaway mitigation. This composite approach achieves better thermal safety performance per unit thickness compared to conventional insulation materials, allowing reduced overall thickness and improved energy density.
2Reliability
If flame retardant additives are added to electrolyte to prevent thermal runaway, then thermal runaway prevention is improved, but electrochemical performance is reduced
Solution Approach 1:
The patent extracts the flame retardant function from the electrolyte and relocates it to a separate insulation layer between cells. This separation allows the electrolyte to maintain its electrochemical performance while the insulation layer provides thermal runaway prevention through its sodium borate-containing polyurethane foam composition.
Solution Approach 2:
The patent introduces an intermediary insulation layer with sodium borate polyurethane foam between cells, which acts as a mediator to prevent thermal runaway propagation without interfering with the electrolyte's electrochemical function. This intermediary layer provides thermal safety while allowing the electrolyte to operate optimally.
3Quantity of substance
If thin thermal management sheets are used to maintain energy density, then energy density is improved, but thermal management effectiveness is reduced
Solution Approach 1:
The patent changes the compositional parameters of the thermal management sheet by incorporating sodium borate into the polyurethane foam, which fundamentally alters the material's thermal response characteristics. This enables thin sheets to achieve superior thermal runaway prevention performance that would normally require much thicker conventional insulation layers.
Solution Approach 2:
The patent utilizes the porous structure of polyurethane foam to provide effective thermal management in thin configurations. The cellular structure provides thermal insulation while the sodium borate content provides active thermal runaway mitigation, allowing thin sheet designs that maintain both energy density and thermal safety effectiveness.
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 thermal management sheet effectively delays or prevents thermal runaway by absorbing heat, maintaining thermal insulation across multiple cycles, and providing pressure management, while maintaining energy density and electrochemical performance.
Implementation Method 1
the cured polyurethane foam has a density of 12 to 35 pounds per cubic foot (pcf) (192 to 561 kilograms per cubic meter (kg/m3))... providing effective thermal insulation
Implementation Method 2
The thermal management sheet effectively delays or prevents thermal runaway by absorbing heat
Data Source
AI summary
A method of forming a thermal management sheet for a battery including cured polyurethane foam, the method including combining an active hydrogen-containing component including a polyol and an isocyanate component including a polyisocyanate to form an uncured polyurethane foam; and curing the uncured polyurethane foam to form the cured polyurethane foam, wherein the uncured polyurethane foam includes, based on a total weight of the uncured polyurethane foam, 3 to 68 weight percent of sodium borate, 0.1 to 7 weight percent of surfactant, and 0.001 to 9 weight percent of catalyst, wherein the cured polyurethane foam has a density of 12 to 35 pounds per cubic foot, and wherein the cured polyurethane foam has a thickness of 1 to 30 millimeters.