Lithium Cell Packaging Material Anti-Corrosion Adhesion
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Solution Overview
Problem
The existing packaging materials for lithium cells face challenges in developing high lamination strength within a short aging time, maintaining resistance to electrolytic solutions, and ensuring insulating properties during cold forming, primarily due to slow reaction rates and corrosion issues caused by hydrofluoric acid infiltration.
Innovation Solution
A laminate structure comprising a substrate layer, a first adhesive layer, a metal foil layer, a multilayered anti-corrosion treatment layer, a second adhesive layer, and a sealant layer, where the anti-corrosion treatment layer contains a rare earth element oxide and phosphoric acid or phosphate salts, and the second adhesive layer includes reactive compounds such as glycidyl compounds and carbodiimides, forming covalent bonds to enhance adhesion and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a carboxy group-containing polyolefin resin and a polyfunctional isocyanate compound are used as the adhesive layer, then the lamination strength between the sealant layer and the metal foil layer is improved, but the reaction rate is slow requiring prolonged aging time
Solution Approach 1:
The patent changes the chemical parameters of the adhesive layer by using acid-modified polyolefin resin with specific acid modification levels (0.1-10 mmol/g) and controlling the molecular weight and structure. This parameter optimization enables faster reaction kinetics while maintaining high lamination strength, reducing the required aging time from prolonged periods to more practical timeframes.
Solution Approach 2:
The patent creates a composite adhesive system combining acid-modified polyolefin resin with specific additives and modifiers. This composite material approach allows the adhesive to achieve both rapid bonding and high strength simultaneously, resolving the contradiction between fast reaction and strong adhesion.
2Ease of operation
If the sealant layer is made highly permeable to electrolytic solution, then the electrolytic solution can infiltrate effectively, but the lamination strength between the metal foil layer and the sealant layer is lowered due to corrosion
Solution Approach 1:
The patent introduces an anti-corrosion treatment layer as an intermediary between the metal foil layer and the sealant layer. This intermediate layer allows electrolytic solution permeation for effective infiltration while simultaneously protecting the metal foil from corrosion by hydrofluoric acid, thereby maintaining lamination strength despite high solution permeability.
Solution Approach 2:
The patent converts the harmful effect of electrolytic solution infiltration (which causes corrosion) into a beneficial outcome by applying anti-corrosion treatment. The treatment transforms the corrosive environment into a controlled condition where infiltration occurs without damage, effectively turning the harm of solution penetration into a benefit of maintained structural integrity.
3Ease of operation
If hydrofluoric acid is generated by hydrolytic reaction of lithium salt, then the electrolytic solution functions properly, but the metal surface is corroded and lamination strength is lowered
Solution Approach 1:
The patent applies anti-corrosion treatment to convert the harmful effect of hydrofluoric acid corrosion into a beneficial situation. The treatment allows the acid to be generated for electrolytic solution functionality while preventing it from attacking the metal surface, effectively neutralizing the harm while preserving the beneficial chemical reactions.
Solution Approach 2:
The patent applies anti-corrosion treatment in advance before the corrosion problem occurs. This preliminary protective action prevents the harmful effects of hydrofluoric acid on the metal surface while allowing the electrolytic solution to function normally, addressing the corrosion issue before it can damage the structure.
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 proposed packaging material achieves high lamination strength, excellent electrolytic solution resistance, and maintains insulating properties by forming covalently bonded interfaces, preventing corrosion and infiltration, and ensuring robust adhesion even under stress during cold forming.
Implementation Method 1
the anti-corrosion treatment layer...contains a rare earth element oxide, and 1 to 100 parts by mass of phosphoric acid or a phosphate salt per 100 parts by mass of the rare earth element oxide
Implementation Method 2
the second adhesive layer includes reactive compounds such as glycidyl compounds and carbodiimides, forming covalent bonds to enhance adhesion and resistance
Implementation Method 3
The electrolytic solution has high permeability in the sealant layer. Accordingly, it has been experienced that an electrolytic solution infiltrated in the sealant layer of lithium ion cells causes the lamination strength between the metal foil layer and the sealant layer to be lowered
Implementation Method 4
ensuring insulating properties by forming covalently bonded interfaces, preventing corrosion and infiltration, and ensuring robust adhesion even under stress during cold forming
Data Source
Figure 1
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Figure 4
AI summary
A packaging material for lithium cell of the present invention includes a laminate of a substrate layer, a first adhesive layer, a metal foil layer, an anti-corrosion treatment layer of a single-layer or plural-layer structure, a second adhesive layer and a sealant layer stacked in this order. The anti-corrosion treatment layer is provided on the side of the second adhesive layer and contains a rare earth element oxide, 1 to 100 parts by mass of phosphoric acid or a phosphate salt per 100 parts by mass of the rare earth element oxide, and at least one polymer selected from the group of a cationic polymer and an anionic polymer wherein the at least one polymer is contained at least in the layer contacting with the second adhesive layer and the second adhesive layer contains a compound reactive with the at least one polymer contained in the layer contacting with the second adhesive layer.