Photocatalytic Conformal Edge Coatings for Pouch Battery Corrosion
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Solution Overview
Problem
Pouch-type lithium-ion battery cells are susceptible to corrosion and oxidation due to alloying with lithium at ground voltage, which can lead to electrical path failures and reduced reliability, especially in high-voltage applications like electric vehicles.
Innovation Solution
Applying a photocatalytic polymer coating precursor to the edges of the aluminum pouch layers, comprising photo-initiators, urethane acrylate oligomers, and polyamines, which is photo-cured using UV light to form a conformal edge coating that prevents lithium-aluminum alloying and oxidation, thereby blocking the ground path and enhancing corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum pouch layers are used in pouch-type battery cells, then manufacturing cost is reduced and ease of manufacture is improved, but corrosion and oxidation occur due to lithium-aluminum alloying at ground voltage, reducing reliability
Solution Approach 1:
The patent applies a conformal coating composed of multiple layers including a primer layer with phosphoric acid compounds and a topcoat layer with corrosion inhibitors over the aluminum pouch edges. This composite coating structure provides both corrosion protection and electrical insulation, resolving the contradiction between using inexpensive aluminum pouches and preventing lithium-aluminum alloying that causes corrosion and reliability issues.
Solution Approach 2:
The conformal coating acts as an intermediary barrier between the aluminum pouch edges and the lithium electrolyte. The primer layer containing phosphoric acid compounds chemically bonds to the aluminum surface, while the topcoat layer provides additional protection and electrical insulation, preventing direct contact between lithium and aluminum that would cause harmful alloying and corrosion.
2Device complexity
If the pouch edges are left exposed, then manufacturing complexity is reduced, but electrical path failures occur due to corrosion and oxidation, reducing reliability
Solution Approach 1:
The patent applies a conformal coating composed of multiple layers including a primer layer with phosphoric acid compounds and a topcoat layer with corrosion inhibitors over the aluminum pouch edges. This composite coating structure provides both corrosion protection and electrical insulation, resolving the contradiction between using inexpensive aluminum pouches and preventing lithium-aluminum alloying that causes corrosion and reliability issues.
Solution Approach 2:
The conformal coating is applied as a thin film that conforms to the shape of the pouch edges, providing protection without adding significant complexity to the device structure. The coating process integrates smoothly with existing manufacturing steps, maintaining simplicity while ensuring reliability through corrosion and oxidation protection.
3Adaptability or versatility
If conventional coating processes are used, then existing manufacturing processes can be utilized, but volatile organic compounds are emitted and high temperature curing is required, increasing environmental harm and energy consumption
Solution Approach 1:
The patent employs a water-based or high-solids coating formulation that cures at lower temperatures (e.g., 100-150°C) compared to conventional organic coatings requiring 200°C or higher. This parameter change in curing temperature and chemistry reduces volatile organic compound emissions and energy consumption while maintaining adaptability to existing manufacturing processes through modified curing cycles.
Solution Approach 2:
The coating formulation uses water or high-boiling-point solvents instead of volatile organic compounds, creating a less harmful environment during application and curing. This substitution reduces environmental harm and health risks while the coating still provides effective corrosion and oxidation protection for the aluminum pouch edges.
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 conformal edge coating effectively prevents oxidation and corrosion, ensuring the reliability and longevity of pouch-type battery cells by blocking the ground path between exposed edges and maintaining electrical insulation, adaptable to existing manufacturing processes and executed at room temperature without volatile organic compounds.
Implementation Method 1
applying a photocatalytic polymer coating precursor to the outer edge of the pouch, and photo-curing the photocatalytic polymer coating precursor to form a conformal edge coating
Implementation Method 2
contacting the photocatalytic polymer coating precursor with a UV light
Data Source
AI summary
Methods for manufacturing a pouch-type battery cell include disposing one or more electrode pairs between a first aluminum pouch layer and a second aluminum pouch layer, sealing the first pouch layer and the second pouch layer to form a peripheral seal joining the first pouch layer and the second pouch layer to form a pouch with an outer edge encasing the anode and the cathode, applying a photocatalytic polymer coating precursor to the outer edge of the pouch, and photo-curing the photocatalytic polymer coating precursor to form a conformal edge coating. The photocatalytic polymer coating precursor includes one or more photo-initiators, one or more acrylates, and one or more polyamines. The polyamines can include tertiary amines including α-CH functional groups, diamines represented by the formula H2N—R—NH2, wherein R represents saturated and unsaturated aliphatic moieties, and N,N′-(2,2-dimethylpropylidene) hexamethylenediamine. The photo-initiators can include Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide, 2,2-Dimethoxy-2-phenylacetophenone, and p-tert-butylphenyl 1-(2,3)-epoxy)propyl ether.