Separator Heat-Resistant Insulating Layer Thermal Shrinkage
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Solution Overview
Problem
Conventional separators for lithium-ion secondary batteries used in electric vehicles face challenges with thermal shrinkage, leading to potential internal short circuits due to mechanical weakness and increased stress under high temperatures, which is not adequately addressed by existing solutions.
Innovation Solution
A separator with a heat-resistant insulating layer composed of a porous resin base layer and a ceramic layer containing inorganic particles and a binder, which reduces thermal shrinkage and enhances mechanical strength, ensuring the shutdown function while maintaining ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermoplastic resin separator is used to achieve shutdown function, then the shutdown function is improved, but mechanical strength deteriorates under high temperature
Solution Approach 1:
The patent applies composite materials by combining thermoplastic resin (providing shutdown function) with heat-resistant inorganic particles such as alumina, silica, or zirconia (providing mechanical strength and thermal stability). This composite structure allows the separator to maintain both the shutdown function through the thermoplastic resin and mechanical strength through the heat-resistant inorganic particles, even at high temperatures up to 200°C.
2Power
If separator size is increased to achieve high power and capacity, then battery performance is improved, but thermal shrinkage increases
Solution Approach 1:
The patent changes the thermal parameters of the separator by incorporating heat-resistant inorganic particles that raise the thermal stability threshold. The inorganic particles maintain structural integrity at temperatures up to 200°C, preventing the thermal shrinkage that would normally occur in thermoplastic resin separators when battery size and power are increased, thereby maintaining separator stability in large-format batteries.
3Stability of the object's composition
If heat treatment is applied to reduce thermal shrinkage, then thermal stability is improved, but internal stress increases
Solution Approach 1:
The composite structure of thermoplastic resin combined with heat-resistant inorganic particles provides inherent thermal stability without requiring aggressive heat treatment. The inorganic particles act as a thermal scaffold that maintains separator dimensions at high temperatures, reducing the need for post-manufacturing heat treatment and thereby minimizing internal stress accumulation.
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 proposed separator exhibits excellent thermal shrinkage resistance and mechanical strength, preventing internal short circuits and ensuring safe operation of lithium-ion secondary batteries, even under increased temperatures, thus enhancing the reliability and safety of electric vehicles.
Implementation Method 1
a heat-resistant insulating layer which is provided on at least one side of the porous resin base layer and contains inorganic particles and a binder
Implementation Method 2
exhibits excellent thermal shrinkage resistance
Implementation Method 3
when the battery reaches a high temperature, the resin constituting the separator melts and clogs up the pores to shut down the movement of lithium ions
Data Source
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AI summary
A separator having a heat-resistant insulating layer of the present invention includes a porous resin base layer and a heat-resistant insulating layer which is formed on one or both sides of the porous resin base layer and contains inorganic particles and a binder. The porous resin base layer contains a resin having a melting temperature of 120°C to 200°C. The separator is configured so that the ratio of the basis weight of the heat-resistant insulating layer to the basis weight of the porous resin base layer is not less than 0.5. Accordingly, the separator having a heat-resistant insulating layer of the present invention exhibits excellent thermal shrinkage resistance while ensuring a shutdown function.