Battery Separator Substrate Roughness for Adhesion and Wear Resistance
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Solution Overview
Problem
Existing separators in lithium secondary batteries face issues with adhesion strength and wear resistance, leading to internal short circuits and voltage drops due to the scratching of porous coating layers, which are exacerbated by volume expansion of the negative electrode during charging and discharging.
Innovation Solution
A separator substrate with surface roughness of 80-160 nm is manufactured by controlling the temperature atmosphere between extrusion and cooling steps, enhancing adhesion strength and wear resistance through improved surface characteristics, and a porous coating layer with inorganic particles and a binder polymer is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a porous coating layer is applied to improve heat resistance, then thermal stability is improved, but adhesion strength deteriorates due to scratching during electrode assembly manufacturing
Solution Approach 1:
The patent changes the surface roughness parameter of the porous substrate to a specific range (Sa 80-160 nm) to optimize both adhesion strength and coating layer stability. This parameter optimization prevents excessive scratching while maintaining heat resistance properties of the porous coating layer.
Solution Approach 2:
The patent applies different surface roughness characteristics to different parts of the porous substrate to achieve optimal performance. The controlled surface roughness in the specific range provides sufficient adhesion for the coating layer while maintaining the necessary thermal stability properties.
2Reliability
If the porous coating layer is made more durable against friction, then wear resistance is improved, but manufacturing complexity increases due to precise surface roughness control
Solution Approach 1:
The patent optimizes the surface roughness parameter to a specific range (Sa 80-160 nm) that naturally provides wear resistance without requiring additional complex manufacturing steps. This parameter control achieves durability while maintaining manufacturing feasibility.
3Strength
If the surface roughness is increased to improve adhesion, then adhesion strength is improved, but wear resistance deteriorates due to excessive surface irregularities
Solution Approach 1:
The patent identifies and implements an optimal surface roughness range (Sa 80-160 nm) that balances adhesion strength and wear resistance. This specific parameter range provides sufficient surface area for coating adhesion while avoiding excessive irregularities that would compromise wear resistance.
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 improved separator substrate and coating layer enhance adhesion strength, wear resistance, and mechanical properties, preventing separator breakage and reducing voltage drops, thereby improving the safety and performance of electrochemical devices.
Implementation Method 1
improve adhesion strength between the separator substrate and the porous coating layer
Implementation Method 2
when exposed to high temperature, the SRS or CCS may suppress the shrinkage of the porous substrate
Data Source
AI summary
A separator substrate, a separator including the separator substrate, an electrode assembly including the separator, and an electrochemical device including the electrode assembly. The separator substrate has a surface roughness value (Sa) of from 80 nm to 160 nm on at least one surface. Accordingly, a separator using the separator substrate maintains high adhesive strength, and has improved wear resistance.