Cylindrical Battery Covering Interface for Moisture and Tracking Resistance
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Solution Overview
Problem
Conventional cylindrical secondary batteries face issues with insufficient adhesion between the exterior portion and the covering portion, leading to moisture ingress and potential short circuits due to tracking phenomena.
Innovation Solution
The cylindrical secondary battery design includes a cylindrical exterior portion with a calculated average roughness (Ra) of 0.7 to 1.5 μm and a maximum height roughness (Rz) of the covering portion's inner surface in the radial direction of 2.5 μm or less, enhancing adhesion and preventing moisture infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional cylindrical secondary battery uses a smooth exterior portion and covering portion interface, then the manufacturing process is simple, but the adhesion between the exterior portion and covering portion is insufficient leading to moisture ingress and tracking phenomena
Solution Approach 1:
The patent applies local quality by creating a specific roughness profile at the bottom inner surface of the exterior portion where it contacts the covering portion. The Ra value is controlled to 0.7-1.5 μm in this specific local area, while other areas may have different surface characteristics. This localized surface treatment improves adhesion precisely where needed without complicating the entire manufacturing process.
Solution Approach 2:
The patent utilizes parameter changes by controlling the surface roughness parameters (Ra and Rz) of the exterior portion's bottom inner surface. By adjusting the Ra to 0.7-1.5 μm and Rz to 2.5 μm or less, the patent optimizes the adhesion properties between the exterior portion and covering portion, preventing moisture ingress and tracking phenomena while maintaining manufacturing feasibility.
2Reliability
If the exterior portion has higher surface roughness to improve adhesion, then the adhesion between exterior portion and covering portion improves, but the manufacturing precision required to control the roughness parameters increases
Solution Approach 1:
The patent defines specific parameter ranges (Ra: 0.7-1.5 μm, Rz: 2.5 μm or less) that balance adhesion improvement with manufacturing feasibility. These parameter specifications provide clear manufacturing targets while ensuring reliable prevention of moisture ingress and tracking phenomena between the exterior portion and covering portion.
Solution Approach 2:
The surface roughness control is applied specifically to the bottom inner surface of the exterior portion where contact with the covering portion occurs. This localized approach focuses manufacturing precision only where it is most needed for adhesion, rather than requiring high precision across the entire exterior portion surface.
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
This design effectively suppresses moisture ingress and tracking phenomena, reducing the risk of short circuits and improving the overall adhesion between the exterior and covering portions.
Implementation Method 1
improve the adhesion between the exterior portion and the covering portion
Data Source
AI summary
A cylindrical secondary battery is provided and includes a cylindrical exterior portion including a battery element therein and including opposite end portions and an outer peripheral surface disposed therebetween; and a covering portion covering at least a part of both the end portions of the exterior portion and an entire outer peripheral surface, wherein the exterior portion includes a cylindrical main body having an opening on one end side and a bottom on another end side opposite to the one end side, and a lid closing the opening, a calculated average roughness (Ra) of the cylindrical main body is 0.7 to 1.5 μm, and a maximum height roughness (Rz) of an inner surface of the covering portion in a radial direction of the bottom of the main body is 2.5 μm or less.