Heat-Diffusible Separator Film for Lithium-Ion Battery Thermal Stability
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Solution Overview
Problem
Secondary battery separators exhibit severe heat contraction above 100°C, leading to potential short circuits and instability due to their material properties and manufacturing processes, particularly in lithium ion batteries, where heat stability is a significant concern.
Innovation Solution
A heat-diffusible separator is developed with a porous heat transfer film having higher surface-direction heat conductivity than thickness-direction conductivity, integrated with a porous polymer substrate and a porous coating layer containing inorganic particles, to rapidly diffuse heat generated locally within the battery cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous heat transfer film is added to enhance heat diffusion, then heat stability is improved, but separator thickness increases
Solution Approach 1:
The patent employs a porous heat transfer film with high thermal conductivity to diffuse heat locally generated in the battery cell. The porous structure allows efficient heat transfer while maintaining a thin profile, preventing short circuits caused by heat-induced separator contraction without significantly increasing overall separator thickness.
Solution Approach 2:
The separator is constructed as a composite structure combining a base separator layer with an additional porous heat transfer film layer. This composite approach integrates the heat diffusion function into the separator structure, improving thermal stability while controlling overall thickness through optimized layer composition and design.
2Reliability
If separator thickness is increased to improve heat stability, then heat resistance is improved, but energy density deteriorates
Solution Approach 1:
The porous heat transfer film provides high thermal conductivity and heat diffusion capability in a thin configuration. This allows the separator to achieve improved heat resistance without the substantial thickness increase that would otherwise be required, thereby preserving battery cell space and maintaining energy density.
Solution Approach 2:
The patent changes the thermal conductivity parameter of the separator by incorporating the porous heat transfer film with high thermal conductivity. This parameter modification enables the separator to achieve better heat resistance at a thinner thickness, avoiding the energy density loss that would result from simply increasing the thickness of a conventional separator.
3Temperature
If local heat generation occurs in the battery cell, then temperature rises causing separator melt, but heat diffusion capability is insufficient
Solution Approach 1:
The porous heat transfer film serves as a thermal management layer that rapidly diffuses locally generated heat throughout the separator structure. This heat diffusion capability prevents localized temperature hotspots from causing separator melt and maintains separator stability even when local heating occurs during battery operation.
Solution Approach 2:
The porous heat transfer film acts as an intermediary thermal management layer between the electrodes and the separator base layer. It mediates the heat transfer process by absorbing and diffusing local heat generation before it can cause the separator to melt, thereby protecting the separator structure and maintaining battery safety.
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 effectively enhances heat diffusion, preventing short circuits and improving battery stability and lifetime by optimizing heat-diffusion effects through the use of a porous heat transfer film with a 20-fold greater surface heat conductivity.
Implementation Method 1
a porous heat transfer film formed on at least one surface of the separator... rapidly diffuse heats generated locally on a separator
Implementation Method 2
The porous heat transfer film may have an open cell type structure in which internal pores are present in a connected form with each other
Data Source
AI summary
The present disclosure provides a heat-diffusible separator including a separator, and a porous heat transfer film formed on at least one surface of the separator.