Battery Pouch Inner Coating for Friction Damage Prevention
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to pouch damage from external friction, leading to electrolyte leakage and potential explosion, with existing solutions being cumbersome and inadequate in ensuring structural safety.
Innovation Solution
A lithium secondary battery design featuring a pouch with a coating portion along its inner lateral surface, providing enhanced protection against damage and improving structural safety without requiring new equipment or modifying existing manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pouch is used to house the electrode assembly, then the battery structure is simple and manufacturing is easy, but the pouch is prone to damage from external friction and edge contact, leading to electrolyte leakage and safety issues
Solution Approach 1:
The pouch is constructed as a composite structure comprising an inner pouch and an outer pouch. The inner pouch is made of a first material (e.g., aluminum foil or metalized film) providing barrier and structural properties, while the outer pouch is made of a second material (e.g., plastic film) providing flexibility and protection. This composite material approach enhances the overall durability and safety of the pouch while maintaining manufacturing simplicity.
Solution Approach 2:
The patent introduces a cushioning layer or protective structure between the electrode assembly edges and the pouch wall. This cushioning element absorbs mechanical stress and prevents direct contact between sharp electrode edges and the pouch, thereby preventing punctures and leaks before they can occur during battery assembly or operation.
2Reliability
If the pouch edges are reinforced to prevent damage, then structural safety improves, but the manufacturing process becomes cumbersome and complex
Solution Approach 1:
The reinforcement structure is integrated with the pouch sealing process itself. The outer pouch extends beyond the inner pouch at the edges, and the sealing is performed by heat or ultrasonic welding that simultaneously seals both layers together. This merging of reinforcement and sealing functions into a single manufacturing step avoids adding separate reinforcement steps while maintaining edge durability.
Solution Approach 2:
The patent uses flexible thin film materials for the pouch construction, particularly the outer pouch made of plastic film. These flexible films can be easily formed and sealed using conventional pouch sealing equipment, providing edge reinforcement without requiring rigid structural elements or complex assembly steps. The flexibility allows the pouch to absorb mechanical stress while maintaining structural integrity.
3Strength
If the pouch is made thicker to prevent damage, then durability improves, but the battery volume increases and energy density decreases
Solution Approach 1:
Instead of increasing the thickness of a single pouch layer, the patent uses a composite structure with multiple thinner layers. The inner pouch (first material) and outer pouch (second material) each have optimized thin thicknesses, but their combination provides superior strength and durability. This approach maintains low overall pouch thickness while achieving high durability, thereby preserving battery volume and energy density.
Data Source
AI summary
A lithium secondary battery according to exemplary embodiments includes an electrode assembly and a pouch in which the electrode assembly is housed. The pouch includes a housing portion configured to house the electrode assembly; a peripheral portion around the housing portion; and a coating portion formed along an inner lateral surface of the housing portion and spaced apart from a side portion of the electrode assembly.