Polymer Binder Softening for Battery Separator Thermal Shutdown
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Solution Overview
Problem
Lithium-ion batteries face challenges with thermal runaway due to high-adhesion separators that hinder heat dissipation, leading to potential fires and explosions when short circuits occur.
Innovation Solution
A polymer binder with a softening point of 60° C. to 100° C. is developed, which softens and melts at high temperatures, causing adhesion failure in the porous coating of a laminated porous film, thereby preventing thermal runaway by separating the electrode plates and blocking current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-adhesion separator is used to tightly bond electrode plates and separator, then bonding forces are improved and battery hardness is increased, but heat dissipation is hindered leading to thermal runaway risk
Solution Approach 1:
The patent changes the bonding mechanism from permanent strong bonding to temperature-dependent bonding. The polymer binder is designed with a specific glass transition temperature range (50-150°C) so that it provides strong bonding at normal operating temperatures but loses adhesion at elevated temperatures, enabling automatic separation for safety
Solution Approach 2:
The bonding characteristics of the separator are made dynamic rather than static. The adhesion strength of the polymer binder changes dynamically with temperature, providing high bonding force during normal operation and automatically reducing to zero when thermal runaway occurs, allowing the separator to adapt to different operational states
2Object-affected harmful factors
If a polymer binder with low softening point is used to enable heat dissipation, then thermal runaway prevention is improved, but bonding forces at high temperature are reduced
Solution Approach 1:
The patent utilizes the phase transition (glass transition) of the polymer binder as the core mechanism. The binder transitions from a glassy state with strong bonding capability at room temperature to a rubbery or molten state with lost adhesion at elevated temperatures, automatically achieving separator function without requiring additional release mechanisms
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 polymer binder effectively prevents thermal runaway by ensuring interface separation between the porous coating and electrode plates, thereby preventing heat buildup and potential fires, while maintaining sufficient bonding forces at room temperature to resist mechanical impacts.
Implementation Method 1
A polymer binder with a softening point of 60°C to 100°C is developed, which softens and melts at high temperatures
Implementation Method 2
the polymer binder softens and melts at high temperature, causing adhesion failure in the porous coating
Implementation Method 3
maintaining sufficient bonding forces at room temperature to resist mechanical impacts
Data Source
AI summary
A polymer binder having softening point of 60° C. to 100° C. including a copolymer formed by polymerizing a first monomer, a second monomer, and a third monomer. The first monomer includes at least one of compounds shown in formula (I) or formula (II). The second monomer includes at least one of compounds shown in formula (III) or formula (IV). The third monomer includes at least one of compounds shown in formula (V):R11 is selected from an alkyl group having 0 to 3 carbon atoms; n1 is an integer between 2 and 5; R21 is selected from hydrogen or an alkyl group having 1 to 5 carbon atoms, and M is hydrogen or an alkali metal cation; R22 is selected from hydrogen or an alkyl group having 1 to 5 carbon atoms; and R31 is selected from an alkyl group having 1 to 5 carbon atoms.