Polyolefin Separator White Index and Carbonate Reduction Control
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Solution Overview
Problem
Existing separators for nonaqueous electrolyte secondary batteries, such as lithium-ion batteries, face challenges in maintaining battery performance and safety due to issues like heat generation and short-circuits between electrodes, which can lead to reduced energy density and stability.
Innovation Solution
A separator with a first layer made of porous polyolefin, having a white index between 85 and 98, and a reduction rate of diethyl carbonate between 0.048 mg/s and 0.067 mg/s, which inhibits physical contact between electrodes and allows controlled ion permeability, thereby preventing heat-induced short-circuits and maintaining battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous polyolefin separator is used to prevent physical contact between electrodes, then safety is improved, but ion transport efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the white index of the porous polyolefin separator within a specific range (85-98) and adjusting the reduction rate of diethyl carbonate (0.048-0.067 mg/s). These parameter optimizations modify the separator's properties to achieve both high safety through effective electrode separation and maintained ion transport efficiency, resolving the contradiction between reliability and productivity.
2Reliability
If the separator structure is optimized to control ion permeability, then battery performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses parameter changes by defining specific ranges for the white index (85-98) and diethyl carbonate reduction rate (0.048-0.067 mg/s) to optimize separator performance. This approach achieves improved battery performance through controlled ion permeability while avoiding excessive manufacturing complexity by focusing on key measurable parameters rather than overly complex structural designs.
3Reliability
If the separator prevents heat-induced short-circuits, then safety is improved, but energy density deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the white index and diethyl carbonate reduction rate of the separator to achieve the thinnest effective separator structure. This allows the separator to prevent heat-induced short-circuits and maintain safety while minimizing the space occupied by the separator, thereby preserving maximum energy density in the battery.
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 effectively prevents performance degradation and ensures high safety by controlling ion transport and electrolyte retention, maintaining battery performance and energy density over multiple charge-discharge cycles.
Implementation Method 1
a first layer which consists of a porous polyolefin
Implementation Method 2
functions as a film transmitting the electrolyte solution and carrier ions
Data Source
AI summary
Provided are a separator capable of being used for a secondary battery such as a nonaqueous electrolyte-solution secondary battery and a secondary battery including the separator. A separator having a first layer including a porous polyethylene and an organic additive is provided. A white index of the first layer is equal to or more than 85 and equal to or less than 98, and a reduction rate of diethyl carbonate dropped on the first layer is equal to or higher than 0.048 mg/s and equal to or lower than 0.067 mg/s. The separator may further include a porous layer over the first layer.