Positive Current Collector Coating for Nail Penetration Resistance
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Solution Overview
Problem
Secondary batteries, such as lithium ion batteries, are prone to safety risks due to nail penetration, which can cause short circuits, large currents, and heat generation, leading to smoking, igniting, or explosion.
Innovation Solution
A positive current collector with a conductive layer having a thickness of 300 nm to 2 μm and a tensile strain of 3% or more, featuring a sheet resistance growth rate of 50% or higher, is used to reduce burr formation and increase short-circuit resistance, thereby enhancing nail penetration safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal current collector is used, then good electrical conductivity is achieved, but burr formation increases during nail penetration causing short circuits
Solution Approach 1:
The patent uses a composite current collector structure consisting of a metal foil substrate coated with a polymer layer. This composite structure combines the electrical conductivity of metal with the burr-reducing properties of polymer materials, thereby reducing burr formation during nail penetration while maintaining good electrical conductivity.
Solution Approach 2:
The patent changes the physical and chemical parameters of the current collector surface by applying a polymer coating with specific thickness (1-10 μm) and compositional characteristics. This parameter modification reduces the tendency to form burrs during mechanical penetration while preserving the underlying metal's electrical conductivity.
2Weight of moving object
If the conductive layer thickness is reduced to increase weight energy density, then weight energy density improves, but electrical conductivity may deteriorate
Solution Approach 1:
The patent employs a composite structure where a thin polymer coating (1-10 μm) is applied on a metal foil substrate. This allows the use of thinner conductive layers to reduce weight while the metal substrate maintains electrical conductivity, achieving both weight reduction and conductivity preservation.
Solution Approach 2:
The patent applies different material properties to different layers: the polymer coating provides mechanical protection and burr reduction, while the thin metal substrate provides electrical conductivity. This local differentiation of material functions allows thickness optimization for weight reduction without compromising conductivity.
3Reliability
If a thicker conductive layer is used to maintain conductivity, then electrical conductivity is preserved, but weight energy density decreases
Solution Approach 1:
The composite structure of polymer coating on metal foil allows the metal layer to be made thinner than traditional solid metal collectors, reducing weight while the polymer layer compensates for mechanical strength requirements, thereby maintaining conductivity with reduced weight.
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 significantly reduces the risk of internal short circuits and heat generation during nail penetration, limiting damage to the battery to the penetration site while maintaining good electrical conductivity and electrochemical performance.
Implementation Method 1
when the positive current collector has a tensile strain of 3% or more, the conductive layer has a sheet resistance growth rate of T1≥50%
Data Source
AI summary
A positive current collector, a positive electrode plate, a battery, and an apparatus, the positive current collector comprising a support layer, provided with two opposite surfaces in a thickness direction of the support layer, and a conductive layer arranged on at least one of the two surfaces of the support layer, wherein the conductive layer has a thickness D1 satisfying 300 nm≤D1≤2 μm; and when the positive current collector has a the tensile strain of 3.0% or more, the conductive layer has a sheet resistance growth rate of T1≥50%. The positive current collector has higher safety performance and meanwhile higher electrical performance, and thus a positive electrode plate and a battery adopting the positive current collector could have higher safety performance and meanwhile higher electro-chemical performance.