Composite Negative Current Collector for Lightweight Battery Electrodes
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Solution Overview
Problem
Conventional metal current collectors in secondary batteries are thick and dense, which compromises the energy density of batteries despite meeting conductivity requirements, leading to reduced performance in weight energy density and overall electrochemical performance.
Innovation Solution
A negative current collector with a support layer of lower density and a conductive layer of reduced thickness, where the conductive layer's sheet resistance growth rate is controlled to prevent significant resistance increase during tensile deformation, ensuring good conductivity and current collection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal current collectors with large thickness are used, then conductivity and current collection performance are satisfied, but weight energy density is reduced
Solution Approach 1:
The patent employs a composite current collector structure consisting of a polymer support layer (PET, PI, or PBT) combined with a thin metal conductive layer (Cu, Al, or alloy). This composite structure leverages the low density and mechanical strength of polymers while utilizing the high conductivity of thin metal layers, achieving both lightweight design and satisfactory electrical performance.
Solution Approach 2:
The patent replaces traditional thick metal foils with thin-film composite structures where the conductive layer thickness is reduced to 1-10 μm. The polymer support layer provides mechanical flexibility and strength, enabling the use of ultra-thin conductive layers that would otherwise be too fragile, thus significantly reducing weight while maintaining functionality.
2Weight of moving object
If conductive layer thickness is reduced, then weight is decreased, but sheet resistance increases significantly during tensile deformation
Solution Approach 1:
The patent optimizes the thickness parameter of the conductive layer to a specific range (1-10 μm) and controls the sheet resistance growth rate during tensile deformation to ≤5%. This parameter optimization ensures that the thin conductive layer maintains stable electrical properties under mechanical stress while achieving significant weight reduction.
Solution Approach 2:
The polymer support layer acts as an intermediary that provides mechanical support and stress distribution to the thin conductive layer. During tensile deformation, the polymer layer absorbs and distributes mechanical stresses, preventing excessive stress concentration in the thin conductive layer and thereby minimizing sheet resistance increases.
3Weight of moving object
If polymer support layer is used instead of metal, then density is reduced, but mechanical strength may be insufficient
Solution Approach 1:
The patent creates a composite structure where the polymer support layer (providing low density and mechanical strength) is combined with a thin metal conductive layer (providing high conductivity). The polymer layer uses materials like PET, PI, or PBT which offer excellent mechanical properties and chemical stability, while the thin metal layer provides the necessary electrical conductivity.
Solution Approach 2:
The current collector is segmented into two functional layers: the polymer support layer that provides mechanical strength and structural integrity, and the thin metal conductive layer that provides electrical conductivity. This segmentation allows each layer to be optimized for its specific function, with the polymer layer bearing mechanical loads and the metal layer conducting electricity efficiently.
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 results in an electrochemical device with higher weight energy density and improved comprehensive electrochemical performance, including rate, cycle, and dynamic performance, while maintaining mechanical stability and reducing resistance and negative polarization.
Implementation Method 1
the conductive layer is made of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloys, etc., formed by vapor deposition
Data Source
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AI summary
The present disclosure provides a negative current collector (10), a negative electrode plate (20), an electrochemical device, and an apparatus. The negative current collector (10) includes a support layer, and a conductive layer (102) disposed on at least one of two opposite surfaces of the support layer (101) in a thickness direction of the support layer; wherein the support layer (101) has a smaller density than the conductive layer (102); the conductive layer (102) has a thickness D1 satisfying 300nm≤D1≤2µm, preferably 500nm≤D1≤1.5µm; and when the negative current collector (10) has a tensile strain of 1.5%, the conductive layer (102) has a sheet resistance growth rate T satisfying T≤5%.