Composite Separator Coating Gradient for Battery Adhesion
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Solution Overview
Problem
The existing electrode-separator assembly techniques in secondary batteries face issues such as lifting phenomena, distortion, and reduced capacity due to inadequate adhesive properties, which hinder the development of high-capacity batteries and prevent battery enlargement.
Innovation Solution
A composite separator with a coating layer containing inorganic particles and a core-shell organic particle binder, where the core-shell organic particle binder is more concentrated on the surface than on the substrate contact side, enhancing adhesion and preventing lifting, while maintaining permeability and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a coating layer with inorganic particles and organic particle binder is applied to improve adhesion between electrode and separator, then adhesive property is improved, but permeability of separator is lowered
Solution Approach 1:
The coating layer is designed with non-uniform distribution of core-shell organic particles, where the particle concentration is higher near the electrode contact surface and lower near the separator substrate. This gradient structure provides stronger adhesion at the electrode interface while maintaining higher permeability near the separator, thus resolving the contradiction between adhesive property and permeability.
Solution Approach 2:
The coating layer uses a composite structure combining inorganic particles (for thermal stability and structural support) with core-shell organic particles (for adhesion and flexibility). The core-shell structure specifically provides enhanced bonding at the electrode interface while the inorganic framework maintains porosity, achieving both improved adhesion and preserved permeability.
2Strength
If heat and pressure are applied during integration to improve fusing force, then adhesion between electrode and separator is improved, but lifting phenomenon and distortion occur
Solution Approach 1:
The core-shell organic particles undergo phase transition or softening at specific temperature ranges during the heating process. The shell material softens first to provide flexibility and conform to the electrode surface, preventing distortion, while the core material maintains structural integrity. This controlled parameter change enables strong bonding without causing lifting or permanent deformation.
Solution Approach 2:
The coating layer acts as a cushioning layer between the electrode and separator, absorbing and distributing the stress and pressure applied during integration. This prevents direct transmission of excessive force that would cause distortion or lifting, while still enabling sufficient fusing force for strong adhesion.
3Strength
If coating layer is made more adhesive to prevent lifting, then adhesion is improved, but slipperiness with electrode is reduced causing wrinkles and poor assemblability
Solution Approach 1:
The coating layer exhibits spatially varying properties: the region near the electrode surface has higher organic particle concentration providing slipperiness for easy assembly, while the region near the separator has higher inorganic particle content providing strong adhesion and lifting prevention. This local differentiation resolves the contradiction between slipperiness and adhesion.
Solution Approach 2:
The core-shell organic particles provide dynamic behavior where the shell phase becomes more compliant under pressure or during assembly operations, enabling slipperiness and easy positioning. Once assembled, the particles maintain their adhesive properties to prevent lifting during battery operation, thus providing both slipperiness and adhesion at different operational stages.
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 effectively prevents lifting and distortion, improves cycle characteristics, and achieves high capacity without significantly lowering separator permeability, ensuring excellent adhesion and reduced shrinkage.
Implementation Method 1
a coating layer for improving an adhesive property between an electrode and a separator
Implementation Method 2
when heat and pressure are applied during the integration process of an electrode and a separator
Implementation Method 3
when heat and pressure are applied during the integration process of an electrode and a separator
Data Source
Figure 1
AI summary
Provided are a composite separator and an electrochemical device using the same. More specifically, provided is a composite separator including a coating layer for improving an adhesive property between an electrode and a separator.