Separator Heat-Absorbing Layer for Thermal Management
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Solution Overview
Problem
Lithium ion secondary batteries face challenges with heat management during high current discharge, as the heat generated can cause thermal decomposition of the separator, leading to short circuits and increased risk of thermal reactions, especially when using metal-based negative electrode active materials.
Innovation Solution
A separator with a heat-absorbing layer containing specific particles and a resin material, such as boehmite, yttrium oxide, or carbon nanotubes, is introduced between the electrodes to absorb heat without transferring it, enhancing thermal insulation and preventing thermal decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a metallic material (silicon, tin, or compound) is used as negative electrode active material to increase capacity, then the theoretical capacity is improved (about 994 mAh/g for tin vs. about 372 mAh/g for graphite), but the heat generation during discharge increases and current density per unit area increases
Solution Approach 1:
A heat-absorbing layer is introduced as an intermediary substance between the negative electrode and the separator. This layer acts as a thermal buffer that absorbs excess heat generated by the metallic negative electrode material, preventing direct heat transfer to the separator and positive electrode, thereby resolving the contradiction between high capacity and heat generation
Solution Approach 2:
The heat-absorbing layer is constructed as a composite material containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a resin matrix. This composite structure combines the high heat capacity and thermal stability of inorganic particles with the binding and structural properties of the resin, enabling effective heat absorption while maintaining mechanical integrity
2Reliability
If inorganic particles of alumina are applied on the surface of the separator to maintain insulation during abnormal heat generation, then reliability is improved, but the heat generated in the negative electrode is transferred to the positive electrode side due to high thermal conductivity of alumina
Solution Approach 1:
The heat-absorbing layer serves as a thermal intermediary positioned between the negative electrode and the separator. It absorbs heat locally at the negative electrode interface through its high heat capacity, preventing heat conduction to the separator and positive electrode, thus resolving the contradiction between maintaining insulation and preventing heat transfer
Solution Approach 2:
The heat-absorbing layer is specifically positioned on the negative electrode side of the separator, creating a localized heat management zone. This local application ensures that heat absorption occurs precisely where it is generated, without affecting the overall thermal properties of the separator or causing heat transfer to the positive electrode
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 suppresses the transfer of heat from the negative electrode to the positive electrode, reducing the risk of thermal decomposition and enhancing the reliability of lithium ion secondary batteries during high energy discharge scenarios.
Implementation Method 1
a layer which absorbs heat generated in a negative electrode and does not transfer the heat to the positive electrode
Implementation Method 2
maintain insulation between the positive electrode and the negative electrode and thereby preventing the extension of a short circuit, even in the case of abnormal heat generation
Data Source
Figure 1~2
Figure 3A~3D
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AI summary
The present invention relates to a layer disposed between a positive electrode and a negative electrode, which is a layer containing particles and a resin material, and having a porous structure with a heat capacity per unit area of 0.0001 J/Kcm2 or more and a heat capacity per unit volume of 3.0 J/Kcm3 or less.