Dual-Coated Battery Separator for Silicon Anode Lamination
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Solution Overview
Problem
The use of silicon-based negative electrode materials in lithium secondary batteries leads to increased deformation of the separator pores during the lamination process due to high pressure and heat, resulting in reduced dielectric breakdown voltage and battery performance.
Innovation Solution
A separator for electrochemical devices is designed with a porous polymer substrate coated with a first polymer resin having higher solubility in the electrolyte and a second polymer resin with lower solubility, along with inorganic particles, to maintain pore integrity and enhance compression and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high pressure and heat are applied during the lamination process to increase binding force between electrode and separator, then binding force increases, but pore deformation occurs leading to reduced dielectric breakdown voltage
Solution Approach 1:
The coating layer is divided into multiple layers with different polymer resins having different solubility parameters. The first coating layer uses a polymer with solubility parameter 17-27 MPa^1/2 that dissolves in electrolyte to maintain pore integrity, while the second coating layer uses a polymer with solubility parameter <17 or >27 MPa^1/2 that provides mechanical strength and compression resistance. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
The separator combines multiple materials with different properties: the porous polymer substrate provides the base structure, the first polymer resin (soluble in electrolyte) protects pores from deformation, and the second polymer resin (insoluble or less soluble) provides compression and heat resistance. This composite structure resolves the contradiction by integrating materials that individually address different aspects of the problem.
2Strength
If high pressure is applied during lamination to improve electrode-separator binding, then binding force increases, but pore structure deforms reducing ion transport efficiency
Solution Approach 1:
The coating layer is segmented into functional layers: the first coating layer with soluble polymer protects the pore structure to maintain ion transport pathways, while the second coating layer with insoluble polymer provides the mechanical binding strength. This segmentation allows the pore structure to remain intact for ion transport while achieving strong binding force.
Solution Approach 2:
The solubility parameter of the polymer resins is carefully selected and controlled. The first polymer resin has a solubility parameter of 17-27 MPa^1/2 allowing it to dissolve in the electrolyte and coat the pores without causing deformation, while the second polymer resin has solubility parameter <17 or >27 MPa^1/2 to remain insoluble and provide structural support. This parameter control ensures both pore integrity and binding strength.
3Strength
If heat is applied during lamination to enhance binding force, then binding force increases, but heat resistance of separator decreases
Solution Approach 1:
The separator uses a composite structure where the second coating layer contains polymer resin with solubility parameter <17 or >27 MPa^1/2 that is insoluble in electrolyte and provides high heat resistance. This layer is applied over the first coating layer, creating a composite structure where the outer layer protects against heat while the inner layer maintains pore structure, achieving both binding force 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 solution prevents pore deformation, improves compression resistance and heat resistance, and maintains battery performance by preventing electrical shorts and ensuring effective ion transport.
Implementation Method 1
The solubility of the first polymer resin in the electrolyte is higher than the solubility of the second polymer resin in the electrolyte
Implementation Method 2
when the temperature inside the battery rises above a predetermined level, the separator also serves to prevent an internal electric shortage by shutting down the pores located in the surfaces of the separator
Data Source
AI summary
A separator for an electrochemical device includes a porous polymer substrate; a first coating layer provided on at least one surface of the porous polymer substrate and containing a first polymer resin of a first solubility in an electrolyte; and a second coating layer provided on the first coating layer and including a second polymer resin of a second solubility in the electrolyte, and inorganic particles, wherein the first solubility is higher than the second solubility in the electrolyte, and the separator is provided on a negative electrode containing a silicon (Si).