Lithium Battery Electrode Edge Coating for Insulation and Adhesion
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with weak interfacial adhesive force between the separator and counter electrodes, leading to peeling and increased risk of short circuits due to electrode expansion and contraction, and inadequate insulation at the electrode edges, which can cause defects during cell assembly.
Innovation Solution
An electrode design featuring a current collector, electrode layer, insulating layer, and a coating member with specific first and second coating regions that contact the electrode surface and insulating layer, respectively, to enhance adhesive force and prevent short circuits by maintaining insulation even at high temperatures and during assembly distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous separator with a porous coating layer is used to prevent short circuits, then insulation properties are improved, but interfacial adhesive force with the counter electrode becomes weak
Solution Approach 1:
The separator is divided into multiple functional layers: a porous substrate layer and a porous coating layer with inorganic particles. This segmentation allows each layer to perform its specific function - the substrate provides structural support while the coating layer provides insulation, resolving the contradiction between insulation and adhesion.
Solution Approach 2:
The separator uses a composite structure combining organic porous substrate material with inorganic filler particles (such as alumina, silica, or titania) in the coating layer. This composite material approach enables simultaneous achievement of high insulation properties from the inorganic particles and adequate adhesion through the binder polymer matrix.
2Reliability
If a porous coating layer with inorganic particles is formed on a porous substrate, then insulation properties are improved, but processability during battery assembly deteriorates
Solution Approach 1:
The porosity of the coating layer is controlled within a specific range (30-70%) to balance insulation properties and processability. The inorganic filler content is also optimized (1-50 parts by weight per 100 parts binder) to achieve adequate insulation without excessive rigidity that would hinder assembly operations.
Solution Approach 2:
The separator exhibits different properties in different regions: the porous substrate provides flexibility and conformability for easy assembly, while the porous coating layer with inorganic particles provides localized insulation at critical interfaces with the electrode, resolving the contradiction between overall processability and localized insulation requirements.
3Reliability
If the separator lacks sufficient adhesive force, then insulation properties are maintained, but interfacial peeling occurs due to electrode expansion and contraction
Solution Approach 1:
The porous substrate is designed as a flexible thin film structure that can accommodate electrode expansion and contraction during charge-discharge cycles. This flexibility maintains intimate contact between the separator and electrode surfaces, preventing interfacial peeling while preserving insulation properties.
Solution Approach 2:
The binder polymer in the porous coating layer provides continuous adhesive bonding between the separator and the electrode surface. This continuous adhesion force counteracts the periodic expansion and contraction stresses, maintaining stable interfacial contact throughout battery operation while preserving the insulation function.
Data Source
AI summary
The present invention relates to an electrode for a lithium secondary battery comprising: an electrode portion that includes a current collector, an electrode layer formed on the current collector, and an insulating layer formed on the electrode layer, and further comprising: a coating member that includes a first coating region in contact with a side surface of the electrode portion and a second coating region that continues to the first coating region and makes contact with a portion of the insulating layer, and a lithium secondary battery including the same.