Porous Insulator with Composite Matrix for Battery Thermal Stability
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Solution Overview
Problem
Conventional lithium ion secondary battery separators made from polyolefin microporous films are prone to thermal shrinkage, leading to short circuits between the cathode and anode, which can cause thermal runaway due to their low heat resistance and strain-induced pore shrinkage.
Innovation Solution
A porous insulator comprising a polymer compound with communicating pores and a solid having a lower melting point or glass transition temperature than the polymer compound, which maintains the shape of the porous structure upon heating, preventing short circuits by blocking ion flow and adhering to the active material to suppress temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin microporous film is used as a separator, then the shutdown function is provided, but thermal shrinkage occurs causing short circuits between cathode and anode
Solution Approach 1:
The patent uses a composite structure consisting of a heat-resistant polymer matrix (polyimide, polyamide, or aramid) combined with inorganic filler particles (oxide, nitride, or carbide). This composite material provides both the shutdown function through the polymer's melting at around 150°C and shape stability through the heat-resistant matrix that maintains structural integrity at elevated temperatures, preventing thermal shrinkage that would cause short circuits.
Solution Approach 2:
The patent changes the thermal parameters of the separator material by selecting polymers with specific melting points (around 150°C for shutdown function) and combining them with inorganic fillers having high thermal stability. This parameter optimization allows the separator to maintain its pore structure and dimensions at operating temperatures while still providing thermal shutdown protection.
2Reliability
If the separator provides shutdown function through thermal deformation, then safety is improved, but heat resistance is insufficient leading to short circuits
Solution Approach 1:
The separator combines a heat-resistant polymer matrix (polyimide, polyamide, or aramid) with inorganic filler particles to create a composite material that maintains structural stability at high temperatures. The matrix provides heat resistance while the filler enhances dimensional stability, allowing the separator to resist thermal shrinkage and prevent short circuits even when exposed to elevated temperatures during battery operation.
3Quantity of substance
If pores are formed in the separator, then ion permeability is improved, but strain-induced pore shrinkage occurs reducing effectiveness
Solution Approach 1:
The patent incorporates inorganic filler particles (oxide, nitride, or carbide) into the polymer matrix to create a composite separator structure. These rigid filler particles act as spacers that maintain pore openings and prevent pore collapse or shrinkage under thermal and mechanical strain, thereby preserving both ion permeability and structural stability during battery operation.
Solution Approach 2:
The patent employs a porous structure formed within the heat-resistant polymer matrix containing inorganic fillers. This porous design allows efficient ion transport while the heat-resistant matrix and filler particles work together to maintain pore geometry and prevent shrinkage, ensuring sustained ion permeability even under thermal stress.
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 enhances the safety and durability of nonaqueous power storage elements by preventing short circuits and abnormal heat generation, while maintaining high ion permeability and porosity, thus improving the overall performance and safety of lithium ion secondary batteries.
Implementation Method 1
a solid having a melting point or glass transition temperature lower than that of the polymer compound
Implementation Method 2
a solid having a melting point or glass transition temperature lower than that of the polymer compound
Data Source
AI summary
A porous insulator is provided. The porous insulator comprises a porous structure comprising a polymer compound having communicating pores, and a solid having a melting point or glass transition temperature lower than that of the polymer compound.