Metallised Polymeric Current Collectors With Delamination Resistance
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Solution Overview
Problem
Existing metal foil current collectors in lithium-ion batteries face issues such as excessive current flow leading to short-circuiting and overheating, high mass and size contributing to battery weight, and poor adhesion between the polymeric substrate and metal layers due to exposure to elevated temperatures during manufacturing and use.
Innovation Solution
A biaxially oriented polymeric substrate layer with a thickness of no more than 12 μm and metal layers up to 1000 nm, exhibiting positive thermal expansion and improved adhesion, formed through specific manufacturing processes to maintain energy density and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metal foil current collectors are used, then electrical conductivity is improved, but the risk of short-circuiting and thermal runaway increases
Solution Approach 1:
The patent uses a composite structure consisting of a polymeric substrate layer combined with metal layers. The polymeric substrate provides electrical insulation to prevent short-circuiting and thermal runaway, while the metal layers provide the necessary electrical conductivity for current collection. This composite approach resolves the contradiction by integrating both insulating and conductive properties in a single current collector structure.
2Use of energy by moving object
If metal foil current collectors are used, then electrical conductivity is improved, but the mass and size of the battery increase
Solution Approach 1:
The patent employs thin polymeric film substrates with thicknesses ranging from 1 μm to 12 μm, which are significantly thinner than conventional metal foil current collectors (typically 12 μm to 20 μm). These thin films maintain sufficient mechanical strength while reducing the overall mass of the current collector. The metal layers are also kept thin (100 nm to 1000 nm) while providing adequate conductivity, further reducing weight.
Solution Approach 2:
The composite structure allows the use of thinner metal layers (100 nm to 1000 nm) compared to conventional metal foils, as the polymeric substrate provides structural support. This reduces the total metal content and mass while maintaining electrical conductivity through the optimized metal layer design.
3Ease of manufacture
If the polymeric substrate layer is exposed to elevated temperatures during manufacturing, then metal deposition is achieved, but adhesion between the metal layer and polymeric substrate deteriorates
Solution Approach 1:
The patent selects polymeric substrates with specific glass transition temperatures (Tg) ranging from 80°C to 150°C, and melting temperatures (Tm) from 200°C to 280°C. By carefully controlling the deposition temperature to be below the Tg and well below the Tm, the patent maintains adhesion strength while enabling metal deposition. The thermal expansion coefficient of the polymeric substrate is also optimized to match the metal layer, reducing thermal stress and preventing delamination during temperature cycling.
4Quantity of substance
If the polymeric substrate layer thickness is reduced, then energy density is improved, but mechanical strength deteriorates
Solution Approach 1:
The composite structure combines a thin polymeric substrate (1 μm to 12 μm) with metal layers (100 nm to 1000 nm). The metal layers serve as reinforcement, providing mechanical strength to the thin polymeric substrate. This allows the substrate to be made thinner for improved energy density while the metal layers prevent mechanical failure.
Solution Approach 2:
The patent applies metal layers selectively on the surface of the polymeric substrate, concentrating the reinforcement where it is most needed for mechanical strength and electrical conductivity. The bulk of the substrate can remain thin to minimize mass, while the localized metal layers provide the necessary structural support.
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 solution provides current collectors with enhanced adhesion and delamination resistance, maintaining energy density while preventing excessive current flow and thermal runaway, thus ensuring safer and more efficient battery operation.
Implementation Method 1
the polymeric substrate layer exhibits positive thermal expansion in air at 200° C. (and preferably no more than 3.0%) in each of the transverse direction (TD) and the machine direction (MD)
Data Source
AI summary
A current collector comprising a biaxially oriented polymeric substrate layer and a first metal layer on a side of the polymeric substrate layer, wherein the polymeric substrate layer exhibits positive thermal expansion in air at 200° C. in each of the transverse direction (TD) and machine direction (MD). The polymeric substrate layer has a thickness of no more than 12 pm and the first metal layer has a thickness of no more than 1000 nm.