Coated Battery Separator for Low Resistance and Thermal Stability
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, capacity, stability, and reliability due to high membrane resistance and thermal shrinkage, which affect their performance and lifetime.
Innovation Solution
A separator for rechargeable lithium batteries is developed, comprising a porous substrate with a coating layer containing a (meth)acryl-based binder and cubic fillers of specific particle diameters, which reduces membrane resistance and thermal shrinkage, enhancing bonding strength and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional separator is used, then the battery structure is simple, but the membrane resistance is high which reduces battery capacity
Solution Approach 1:
The separator comprises a porous substrate and a coating layer formed on the substrate, where the coating layer contains binder and cubic filler. This composite structure combines the porous substrate providing basic separation function with the coating layer containing conductive fillers to reduce membrane resistance, achieving both low resistance and effective separation.
Solution Approach 2:
The separator uses a porous substrate as the base structure, which provides ion transport pathways while maintaining separation between electrodes. The porous structure allows efficient lithium ion conduction, contributing to low membrane resistance and high battery capacity.
2Duration of action of stationary object
If a conventional separator is used, then the manufacturing process is simple, but the thermal shrinkage rate is high which reduces battery stability and lifetime
Solution Approach 1:
The coating layer is formed by combining binder and cubic filler materials, creating a composite structure that provides thermal stability. The cubic filler particles act as spacers maintaining structural integrity at elevated temperatures, preventing excessive thermal shrinkage and improving battery lifetime.
Solution Approach 2:
The separator achieves low thermal shrinkage rate (5% or less at 150°C for 30 minutes) through the specific composition and structure of the coating layer, where the binder and cubic filler work together to maintain dimensional stability under thermal stress, thereby extending battery operational life.
3Reliability
If a conventional separator is used, then the structure is simple, but the bonding strength to electrode is insufficient which reduces reliability
Solution Approach 1:
The coating layer functions as an adhesive interface between the porous substrate and the electrode, containing binder material that provides strong bonding. This composite coating structure simultaneously achieves strong electrode adhesion and low membrane resistance through the inclusion of conductive cubic fillers.
Solution Approach 2:
The coating layer is applied specifically on the surface of the porous substrate that contacts the electrode, providing localized adhesive properties where needed. This targeted approach enhances bonding strength at the critical interface without requiring complex modifications throughout the entire separator structure.
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 improves the capacity, stability, and lifetime of lithium batteries by providing low electrical resistance, high heat resistance, and strong bonding to electrodes, thereby increasing the battery's overall performance.
Implementation Method 1
a coating layer located on at least one surface of the porous substrate. The coating layer includes a heat-resistant layer including a binder
Implementation Method 2
the adhesive binder includes a cross-linked (meth)acryl-based adhesive binder
Implementation Method 3
which has low membrane resistance, thereby increasing the capacity of a rechargeable lithium battery
Implementation Method 4
The filler includes a cubic filler having a particle diameter D50 ranging from about 50 nm to about 250 nm, thereby increasing the stability and lifetime
Data Source
AI summary
Examples of the present disclosure relate to a separator for a rechargeable lithium battery, and a rechargeable lithium battery including the separator. The separator for a rechargeable lithium battery includes a porous substrate and a coating layer located on at least one surface of the porous substrate. The coating layer includes a heat-resistant layer including a binder and a filler, and an adhesive layer including an adhesive binder located on the heat-resistant layer, the binder includes a (meth)acryl-based binder including a first structural unit derived from (meth)acrylic acid or a derivative of (meth)acrylic acid, a second structural unit derived from hydroxyalkyl (meth)acrylate, and a sulfonate group-containing third structural unit. The filler includes a cubic filler having a particle diameter D50 ranging from about 50 nm to about 250 nm, and the adhesive binder includes a cross-linked (meth)acryl-based adhesive binder.