Positive Current Collector Structure for Nail Penetration Safety
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Solution Overview
Problem
Lithium ion secondary batteries face safety risks due to internal short circuits caused by nail penetration, leading to excessive heat generation and potential explosions, which existing current collectors fail to adequately mitigate.
Innovation Solution
A positive current collector with a conductive layer of reduced thickness and a support layer of higher resistivity is designed, where the conductive layer has a sheet resistance growth rate of ≥50% at 3% tensile strain, reducing burrs and increasing short-circuit resistance, thereby enhancing nail penetration safety and maintaining good electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal current collector is used, then electrical conductivity is good, but burrs are easily generated during nail penetration causing internal short circuits
Solution Approach 1:
The patent uses a composite current collector consisting of a polymer support layer and a metal conductive layer. The polymer layer (PET or PI) serves as the base structure that resists burr formation during nail penetration, while the thin metal layer (300nm-2μm) provides necessary electrical conductivity. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent employs a thin film structure where the metal conductive layer is deposited as a thin coating (300nm-2μm) on the polymer support layer. This thin film approach reduces the amount of metal material that can form burrs during penetration, while still maintaining adequate electrical conductivity for current collection.
2Reliability
If the conductive layer thickness is increased, then electrical conductivity improves, but weight energy density decreases
Solution Approach 1:
The patent optimizes the thickness parameter of the metal conductive layer to a specific range (300nm-2μm), which is significantly thinner than conventional metal current collectors. This parameter change achieves the right balance between electrical conductivity and weight, improving weight energy density while maintaining sufficient conductivity through the optimized thin layer design.
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, limits damage to 'point breaks' during nail penetration, and maintains battery functionality by controlling temperature and voltage, thus improving both safety 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 T ≥ 50%
Data Source
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AI summary
A positive current collector (10), a positive electrode plate (20), a battery (5), and an apparatus, the positive current collector (10) comprising a support layer (101), provided with two opposite surfaces in a thickness direction of the support layer (101), and a conductive layer (102) arranged on at least one of the two surfaces of the support layer (101), wherein the conductive layer (102) has a thickness D1 satisfying 300 nm ≤ D1 ≤ 2µm; and when the positive current collector (10) has a the tensile strain of 3.0% or more, the conductive layer (102) has a sheet resistance growth rate of T1 ≥ 50%. The positive current collector (10) has higher safety performance and meanwhile higher electrical performance, and thus a positive electrode plate (20) and a battery (5) adopting the positive current collector (10) could have higher safety performance and meanwhile higher electro-chemical performance.