Composite Separator Coating to Limit Wrinkling and Air Permeability
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Solution Overview
Problem
The dry processing method for battery separators results in wrinkled surfaces due to uniaxial stretching, leading to solid precipitation and affecting battery performance and safety, and existing coated separators increase air permeability, compromising electrical performance.
Innovation Solution
A composite separator with an adhesive coating comprising polyethylene wax particles and inorganic particles, applied via dry processing, which balances adhesion force and reduces air permeability increases before and after hot pressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a surface coating treatment is applied to the separator obtained after stretching in the dry processing, then the problem of the wrinkled surface of the separator can be solved, but the air permeability increment before and after applying the adhesive coating and before and after hot pressing increases notably, which seriously affects the electrical performance of downstream batteries
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (D90 ratio between 0.3-0.85:1) and weight ratio (5-75% inorganic particles) of the coating materials, as well as the weight of polyethylene wax particles per unit area (0.2-4 g/m2). These parameter optimizations enable the adhesive coating to smooth the separator surface while minimizing air permeability increase, thus resolving the contradiction between surface smoothness and air permeability.
Solution Approach 2:
The patent uses composite materials by combining polyethylene wax particles with inorganic particles (such as alumina, silica, or boehmite) in specific ratios. This composite coating structure leverages the adhesive properties of polyethylene wax and the structural support of inorganic particles to achieve both surface smoothing and controlled porosity, effectively balancing surface quality and air permeability.
2Strength
If the adhesive coating includes only polyethylene wax particles, then the adhesion force is good, but the air permeability increase before and after hot pressing is notably higher, affecting electrical performance
Solution Approach 1:
The patent resolves this contradiction by creating a composite coating system that combines polyethylene wax particles (providing adhesion) with inorganic particles (providing structural integrity and porosity control). The specific weight ratio (5-75% inorganic particles) and particle size ratio (D90 ratio of 0.3-0.85:1) ensure that the coating maintains good adhesion while limiting air permeability increase during hot pressing.
Solution Approach 2:
The patent applies local quality by creating a coating with heterogeneous composition where polyethylene wax particles are distributed among inorganic particles. This local distribution allows different regions of the coating to perform different functions: polyethylene wax provides adhesion at the interface, while inorganic particles maintain pore structure and limit air permeability increase in the bulk coating.
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 composite separator effectively prevents wrinkling and pore blockage, maintaining electrical performance by adjusting the weight and size ratios of polyethylene wax and inorganic particles, ensuring adhesion and reducing air permeability.
Implementation Method 1
the adhesive coating includes polyethylene wax particles and inorganic particles... capable of being bonded to a positive electrode sheet and/or a negative electrode sheet
Implementation Method 2
the polyethylene wax particles... can play a good adhesive role, prevent dimensional changes caused by the release of the internal stress, and improve a problem of wrinkling of the separator upon electrolyte injection
Implementation Method 3
By adjusting the weight ratio and the size ratio of the polyethylene wax particles and the inorganic particles and the weight of the polyethylene wax particles per unit area, the air permeability increase before and after providing the adhesive coating and before and after hot pressing of the composite separator can be reduced
Data Source
Figure 1~2
AI summary
This application provides a composite separator and a battery. In a first aspect, this application provides a composite separator, which includes a base film and an adhesive coating. The adhesive coating includes polyethylene wax particles and inorganic particles. The polyethylene wax particles can play a good adhesive role, prevent dimensional changes caused by release of internal stress, and improve the problem of wrinkling of the separator upon electrolyte injection. The inorganic particles play a supporting role. By adjusting the weight ratio and the size ratio of the polyethylene wax particles and the inorganic particles, and the weight of the polyethylene wax particles per unit area, the air permeability increase before and after providing the adhesive coating and the air permeability increase of the composite separator before and after hot pressing can be reduced on the basis of ensuring the adhesion force of the composite separator, and the electrical performance of the battery can be improved.