Composite-Coated Battery Separator for End Shrinkage Control
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Solution Overview
Problem
Conventional cylindrical lithium secondary batteries face issues with high resistance, heat generation, and internal shorts due to thermal shrinkage of the separator, particularly in large-scale applications, leading to potential fires and non-uniform electrolyte wetting.
Innovation Solution
A separator with a porous coating layer having distinct regions: a first region with a higher content of inorganic particles at the ends and a second region with a lower content, enhancing heat resistance and electrolyte wetting by optimizing the distribution of inorganic particles and binder material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the separator structure is modified to improve heat resistance, then thermal stability is enhanced, but electrolyte wetting uniformity deteriorates
Solution Approach 1:
The separator structure modifies different regions with different properties: the first region at the ends has high inorganic particle content for thermal stability, while the second region in the middle has lower inorganic particle content and higher porosity to ensure uniform electrolyte wetting. This local differentiation allows the separator to achieve both thermal stability and electrolyte wetting uniformity simultaneously.
Solution Approach 2:
The separator changes the parameter of inorganic particle content ratio spatially, with the first region having 70-95 wt% inorganic particles and the second region having 30-70 wt% inorganic particles. This parameter variation allows optimization of thermal stability in the first region while maintaining electrolyte wetting uniformity in the second region, resolving the contradiction between these two requirements.
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 separator design reduces internal resistance and prevents circuit shorts, improving the safety and performance of large-scale cylindrical batteries by maintaining uniform electrolyte distribution and heat resistance.
Implementation Method 1
it is known that the type of unit cell of secondary batteries includes cylindrical, prismatic and pouch-type. In the case of cylindrical secondary battery cells, a battery is manufactured by winding a positive electrode and a negative electrode with a separator or an insulator interposed between them to form a jellyroll-type electrode assembly
Implementation Method 2
when an electrolyte solution is injected, it results in non-uniform electrolyte wetting paths and low uniformity in electrolyte wetting
Data Source
AI summary
A separator according to the present disclosure has an organic/inorganic composite porous coating layer on a surface of a polymer substrate, wherein the organic/inorganic composite porous coating layer includes a first region including a larger amount of inorganic particles and a second region including a smaller amount of inorganic particles so that heat resistance at the side of the battery is improved by the first region, thereby solving a short circuit problem caused by shrinkage at two ends of the separator.