Dual-Binder Separator Coating for Adhesion and Ion Permeability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing separators for electrochemical devices face issues with adhesion to electrodes and porous substrates, leading to poor resistance and air permeability, particularly in stacked lithium secondary batteries.
Innovation Solution
A separator design utilizing two types of binder polymers with different electrolyte uptake ranges is applied, enhancing adhesion and maintaining low resistance and high air permeability by forming a synergistic porous coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder is coated on the surface of a porous polymer substrate to bind with an electrode, then adhesion to the electrode is improved, but the function of the separator as an ion channel is degraded
Solution Approach 1:
The coating layer is designed with a porous structure having controlled pore size and distribution, allowing ion transport through the coating layer while maintaining adhesion to the electrode. The porous structure prevents the coating from blocking ion channels, thus resolving the contradiction between adhesion improvement and ion channel function preservation.
Solution Approach 2:
The coating layer exhibits different properties at different locations: the outer surface provides strong adhesion to the electrode, while the inner regions maintain porosity for ion transport. This spatial variation in properties allows simultaneous achievement of adhesion and ion conductivity.
2Productivity
If phase separation kinetics are excessively high during binder coating, then coating formation is accelerated, but most binder forms large pores resulting in low adhesion between substrate and coating layer
Solution Approach 1:
The phase separation kinetics are controlled by adjusting parameters such as solvent composition, coating thickness, and drying conditions. By optimizing these parameters, the phase separation rate is moderated to form a coating layer with appropriate pore size distribution that ensures both formation efficiency and strong adhesion.
3Strength
If phase separation kinetics are excessively low during binder coating, then adhesion between substrate and coating layer is improved, but most binder forms small pores or no porous structure resulting in high resistance
Solution Approach 1:
The phase separation kinetics are precisely controlled by adjusting coating parameters and environmental conditions to achieve an optimal intermediate rate. This controlled kinetics produces a coating layer with balanced adhesion properties and appropriate porosity, preventing both excessive pore formation and insufficient pore structure.
4Ease of manufacture
If a single type of binder polymer is used in the porous coating layer, then manufacturing is simplified, but both adhesion to electrode and adhesion to substrate cannot be simultaneously optimized
Solution Approach 1:
The coating layer uses a composite binder system comprising multiple polymer types with complementary properties. This composite approach enables simultaneous optimization of adhesion to both the substrate and electrode, as well as control over pore structure and ion conductivity, which would be difficult to achieve with a single polymer.
Solution Approach 2:
Different binder polymers are strategically selected to provide different functions within the same coating layer: one polymer primarily provides substrate adhesion while another provides electrode adhesion and ion conductivity. This functional differentiation within the coating layer achieves dual adhesion optimization.
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 improved adhesion to electrodes and substrates, ensuring low resistance and high air permeability, thereby optimizing battery performance.
Implementation Method 1
the binder polymer comprises a first binder polymer and a second binder polymer, the first binder polymer has an electrolyte uptake of 80-165%, and the second binder polymer has an electrolyte uptake of 20-40%
Implementation Method 2
a process for forming pores in the coated binder through phase separation is used
Data Source
Figure 1~2
AI summary
Disclosed is a separator for an electrochemical device which comprises: a porous substrate having a plurality of pores; and a porous coating layer positioned on at least one surface of the porous substrate, and including a plurality of inorganic particles and a binder polymer positioned on the whole or a part of the surface of the inorganic particles to connect the inorganic particles with one another and fix them, wherein the binder polymer comprises a first binder polymer and a second binder polymer, the first binder polymer has an electrolyte uptake of 80-165%, and the second binder polymer has an electrolyte uptake of 20-40%. An electrochemical device including the separator is also disclosed.