Battery Separator Coating for Heat Resistance Without Airflow Loss
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Solution Overview
Problem
Conventional separators for lithium secondary batteries lack sufficient heat resistance, adherence, and uniform application, leading to potential mechanical shrinkage and electrode contact during high temperature exposure, which can cause battery explosions.
Innovation Solution
A separator for lithium secondary batteries featuring a porous substrate coated with a (meth)acrylic copolymer containing specific structural units and inorganic particles, enhancing heat resistance, adherence, and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separator is coated with a mixture of inorganic particles and organic binder to increase heat resistance, then heat resistance is improved, but air permeability deteriorates
Solution Approach 1:
The patent employs a porous inorganic particle structure in the coating layer, where particles are arranged with interstitial spaces that allow ion and fluid permeability. The porous substrate itself provides a controlled pore structure that maintains air permeability while the coating layer adds heat resistance through the porous inorganic particle network.
Solution Approach 2:
The patent creates a composite coating layer combining organic binder polymer and inorganic particles (such as alumina, silica, or boehmite) in specific weight ratios. This composite structure allows the organic component to provide adherence and flexibility while the inorganic porous particles provide heat resistance and maintain permeability pathways.
2Temperature
If a separator is coated with inorganic particles and organic binder to increase heat resistance, then heat resistance is improved, but adherence deteriorates
Solution Approach 1:
The organic binder polymer acts as an intermediary substance between the porous substrate and the inorganic particles. It chemically or physically bonds to both surfaces, creating a cohesive interface that transfers stress effectively. The binder fills gaps and creates anchoring points, ensuring strong adherence despite the presence of inorganic particles.
Solution Approach 2:
The composite coating layer combines the adhesive properties of organic binder polymers with the thermal stability of inorganic particles. The organic component provides flexibility and bonding capability, while the inorganic particles provide structural integrity and heat resistance, creating a synergistic effect that improves both adherence and thermal performance.
3Quantity of substance
If the separator structure is simplified to maintain air permeability, then air permeability is maintained, but heat resistance deteriorates
Solution Approach 1:
The patent utilizes porous inorganic particles with controlled pore sizes and distributions that allow air and ion permeability while providing thermal stability. The porous structure creates pathways for fluid flow that are not blocked by the coating layer, maintaining air permeability comparable to the uncoated substrate.
Solution Approach 2:
The composite coating layer is designed with specific inorganic particle compositions (such as alumina, silica, boehmite) that inherently provide high heat resistance. These inorganic particles form a thermally stable network that maintains structural integrity at elevated temperatures while their porous arrangement preserves permeability characteristics.
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 exhibits improved heat resistance, adherence, and air permeability, reducing shrinkage and maintaining stability under high temperatures, thereby preventing electrode contact and potential explosions.
Implementation Method 1
a separator for a lithium secondary battery including a porous substrate; and a coating layer on at least one surface of the porous substrate
Implementation Method 2
maintains ion conductivity continuously to enable charge and discharge of a battery
Data Source
Figure 1
AI summary
The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery including same, the separator including: a porous substrate; and a coating layer on at least one surface of the porous substrate. The coating layer includes a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide, a second structural unit derived from (meth)acrylonitrile, and a third structural unit derived from (meth)acrylamido sulfonic acid, (meth)acrylamido sulfonic acid salt, or a combination thereof. The first structural unit is included in an amount of 55 mol% to 90 mol% based on 100 mol% of the (meth)acrylic copolymer and the second structural unit and third structural unit are each independently included in 5 mol% to 40 mol% based on 100 mol% of the (meth)acrylic copolymer. The (meth)acrylic copolymer has a weight average molecular weight of 200,000 to 700,000.