Lithium Battery Separator Coating for Low Resistance and Heat Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high energy density, high capacity, and stability due to issues with membrane resistance and thermal shrinkage, which affect their performance and lifetime.
Innovation Solution
A separator for rechargeable lithium batteries is developed with a porous substrate coated with a (meth)acryl-based binder and a combination of organic and inorganic fillers, including cubic and amorphous inorganic fillers, to reduce membrane resistance and thermal shrinkage, enhancing the battery's capacity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional separator is used, then the battery can operate, but the membrane resistance is high which limits capacity
Solution Approach 1:
The separator employs a porous substrate structure that allows efficient lithium ion transport while maintaining mechanical integrity. The porous configuration reduces membrane resistance by providing multiple pathways for ion conduction, directly addressing the contradiction between capacity and resistance.
Solution Approach 2:
The separator utilizes a composite coating layer combining (meth)acryl-based binder with both organic and inorganic fillers. This composite material structure optimizes both electrical properties (reducing membrane resistance) and thermal properties (controlling shrinkage), resolving the contradiction between capacity and reliability.
2Reliability
If the separator lacks thermal stability, then manufacturing is easier, but thermal shrinkage is high which reduces stability and lifetime
Solution Approach 1:
The separator achieves low thermal shrinkage rate (≤5% at 100°C for 1 hour) by carefully controlling the composition ratios of binder to filler (1:9 to 4:6 by weight) and the particle size distribution of fillers (0.1-10 μm). These parameter optimizations maintain structural stability while ensuring battery reliability.
Solution Approach 2:
The composite coating layer with specific binder-filler composition provides thermal stability while maintaining flexibility. The combination of organic binder and inorganic/organic fillers creates a thermally stable network that resists shrinkage, directly improving battery stability and lifetime.
3Quantity of substance
If the separator coating is too thick, then thermal resistance improves, but membrane resistance increases reducing capacity
Solution Approach 1:
The porous coating layer structure provides thermal insulation while maintaining high ion conductivity. The interconnected pore network allows lithium ions to pass through efficiently (low membrane resistance) while the porous matrix provides thermal barrier properties, resolving the contradiction between capacity and heat resistance.
Solution Approach 2:
The separator achieves different local properties within the coating layer: the binder provides adhesive and flexible matrix properties, while the distributed filler particles provide thermal stability and structural reinforcement. This local quality differentiation allows simultaneous optimization of capacity and heat 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 separator achieves low membrane resistance and thermal shrinkage, thereby increasing the battery's capacity, stability, and lifetime by improving heat resistance and air permeability.
Implementation Method 1
a separator for a rechargeable lithium battery with an increased capacity of a rechargeable lithium battery having a low membrane resistance
Implementation Method 2
a separator for rechargeable lithium battery that has a low thermal shrinkage rate, thereby increasing the stability and lifetime of the rechargeable lithium battery
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present disclosure relates to a separator for a rechargeable lithium battery, and a rechargeable lithium battery, and the separator that includes a porous substrate, and a coating layer on at least one surface of the porous substrate and including a binder and a filler. The binder includes a (meth)acryl-based binder including a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from hydroxyalkyl (meth)acrylate, and a third structural unit derived from (meth)acrylamido sulfonic acid or a salt thereof. The filler includes an organic filler and an inorganic filler. The organic filler includes a cross-linked polymer filler. The inorganic filler includes one or more of a first inorganic filler, which has an average particle size of 50 to 250 nm and is cubic, and a second inorganic filler, which has an average particle size of 100 to 350 nm and is amorphous.