Cellulose-Based Multilayer Separator for Secondary Batteries
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Solution Overview
Problem
Conventional cellulose-based separators for secondary batteries offer high physical strength but fail to effectively shut down current in abnormal operating environments, lacking the necessary blocking function.
Innovation Solution
A separator comprising a cellulose-based nanofiber substrate with polyethylene nano particles and a polyolefin resin layer, which provides improved shut-down characteristics and physical strength, achieved through a lamination method with specific thickness and composition controls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator is used, then high porosity and ion conductivity are achieved, but extreme thermal shrinkage at high temperatures occurs
Solution Approach 1:
The patent uses a composite structure combining polyolefin resin (providing porosity and ion conductivity) with cellulose nanofibers (providing thermal stability and physical strength). This composite approach allows the separator to maintain high ion conductivity while resisting thermal shrinkage at elevated temperatures, as the cellulose component provides dimensional stability.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the separator by controlling the pore size (30-80 nm), porosity (30-80%), and thickness (5-20 μm) of the polyolefin layer, as well as the concentration and treatment of cellulose nanofibers. These parameter adjustments optimize both ion conductivity and thermal resistance properties.
2Reliability
If a polyolefin-based separator is used, then excellent chemical resistance and mechanical property are achieved, but physical vulnerability occurs
Solution Approach 1:
The patent creates a composite separator where cellulose nanofibers are embedded within or layered with polyolefin resin. The cellulose component provides enhanced physical strength and mechanical integrity, while the polyolefin matrix maintains chemical resistance. This synergistic combination resolves the contradiction between chemical resistance and physical strength.
Solution Approach 2:
The patent applies different materials to different regions or layers of the separator structure. The polyolefin provides chemical resistance in the matrix, while cellulose nanofibers provide physical strength reinforcement. This local differentiation of material properties allows each component to excel at its specific function.
3Strength
If cellulose is used to prepare a separator, then high physical strength is achieved, but the shut-down function is lost
Solution Approach 1:
The patent combines cellulose nanofibers (providing physical strength) with polyolefin resin (providing shut-down function). The polyolefin component melts at specific temperatures to close pores and stop ion transport, while the cellulose framework maintains structural integrity. This composite structure simultaneously achieves both high physical strength and effective shut-down functionality.
Solution Approach 2:
The patent adjusts the melting point parameters of the polyolefin component (selecting resins with melting points of 100-140°C) and controls the physical parameters of cellulose (nanofiber diameter 10-500 nm, length 1-10 μm) to optimize both the shut-down temperature response and physical strength characteristics of the separator.
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 enhances the safety and stability of secondary batteries by ensuring effective shut-down functionality and maintaining high physical strength, thereby improving overall battery performance and safety.
Implementation Method 1
The polyethylene nano particle may have a melting point of 80 to 100℃
Implementation Method 2
the polyolefin resin may have a melting point of 100 to 140℃
Data Source
AI summary
The present invention relates to a separator for a secondary battery which is capable of improving a shut-down function of a cellulose-based multilayer separator physically having high strength. The separator for a secondary battery comprises a substrate formed of cellulose-based nanofibers and polyethylene nanoparticles; and a resin layer stacked on one surface or both surfaces of the substrate, the resin being formed from a polyolefin.