LCP Battery Pack Covers for Moisture Barrier Reliability
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Solution Overview
Problem
Pouch type lithium ion battery packs face issues with moisture penetration due to hydrolysis of the adhesive layer between the Nylon and Aluminum layers, leading to corrosion, electrolyte contamination, and reduced cycle life and reliability.
Innovation Solution
Replacing the Aluminum laminate film with liquid crystal polymer (LCP) covers in the battery pack to reduce moisture permeability and eliminate the need for an insulation layer, while incorporating sensor devices for condition detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum laminate film is used for battery packaging, then moisture barrier property is improved, but adhesive layer deteriorates due to hydrolysis causing Nylon layer to peel off and Al layer to be exposed
Solution Approach 1:
The patent removes the problematic adhesive layer between the Nylon and Aluminum layers by directly bonding the Aluminum layer to the PET layer. This extraction eliminates the hydrolysis vulnerability while maintaining the moisture barrier function of the Aluminum layer.
Solution Approach 2:
The patent creates a new composite structure with PET, Aluminum, and CPP layers bonded directly without an adhesive layer. This composite material approach eliminates the weak link (adhesive layer) while preserving the functional benefits of each layer.
2Strength
If adhesive layer is used to bond Nylon and Aluminum layers, then lamination is achieved, but moisture penetration increases due to adhesive layer hydrolysis
Solution Approach 1:
The adhesive layer is completely removed from the structure. Instead of using an adhesive layer that is vulnerable to hydrolysis, the patent relies on direct bonding between layers, eliminating the source of moisture penetration through adhesive degradation.
3Strength
If Al layer is exposed to atmosphere, then adhesion is improved, but pitting corrosion occurs on thin aluminum film
Solution Approach 1:
The Aluminum layer is directly bonded to the PET layer during the lamination process, creating a stable bond before any exposure to atmosphere or moisture can occur. This preliminary bonding action prevents the need for subsequent exposure that would lead to corrosion.
4Reliability
If moisture penetrates inside battery, then sealing is achieved, but electrolyte contamination and degradation occur
Solution Approach 1:
The vulnerable adhesive layer is removed, eliminating the primary pathway for moisture penetration. This extraction prevents moisture from reaching the electrolyte and causing contamination, while the direct-laminated structure maintains effective sealing.
5Measurement precision
If sensor devices are incorporated in LCP cover, then condition detection is enabled, but production complexity increases
Solution Approach 1:
The LCP cover serves multiple functions: it provides the moisture barrier, acts as the structural housing, and incorporates sensor devices for condition monitoring. This multi-functionality reduces the need for separate components and simplifies the overall production process.
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
Enhances the moisture barrier properties, improves cycle life and reliability, simplifies production, and reduces the risk of corrosion and electrolyte contamination, while allowing for more efficient application design.
Implementation Method 1
the LCP has lower moisture permeability compare to the CPP (necessary layer of the Al laminate film), and, therefore, it is possible to improve for preventing the moisture penetration by replacing the Al laminate film to the LCP
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
This disclosure concerns a battery pack 2 comprising: a first cover 4 and a second cover 6, and an energy storage element 8 being contained in a sealed state between the first and the second covers, and wherein at least one of the first cover 4 and the second cover 6 comprises or is formed of a liquid crystal polymer, LCP.