Lightweight Negative Current Collector With Stable Sheet Resistance
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Solution Overview
Problem
Conventional metal current collectors in secondary batteries have a high thickness and density, leading to low energy density and inability to meet increasing market demands for higher energy density while maintaining conductivity and current collection performance.
Innovation Solution
A negative current collector with a support layer and a metal conductive layer of reduced thickness (300 nm to 2 μm) and density (8.0 g/cm3 to 8.96 g/cm3), where the support layer has a lower density than the metal conductive layer, ensuring good conductivity and mechanical stability, and a tensile strain of 2.5% to prevent sharp resistance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal current collector with conventional thickness (18 μm to 30 μm) is used, then good conductivity and current collection performance are ensured, but the weight increases and energy density decreases
Solution Approach 1:
The current collector is divided into two functional layers: a support layer (polymer or composite material) that provides mechanical strength, and a thin metal conductive layer (300 nm to 2 μm) that provides electrical conductivity. This segmentation allows each layer to be optimized for its specific function, reducing overall weight while maintaining performance.
Solution Approach 2:
The invention uses composite structures combining polymer support layers with metal conductive layers. The support layer can be made of polyolefin, polyester, polyimide, or their composite materials, creating a lightweight yet mechanically stable current collector that maintains good electrical conductivity through the thin metal layer.
2Weight of moving object
If the thickness of the metal conductive layer is reduced to increase energy density, then weight decreases and energy density increases, but sheet resistance increases sharply due to tensile deformation
Solution Approach 1:
The invention optimizes the thickness parameter of the metal conductive layer to be within 300 nm to 2 μm, and controls the density to be 8.0 g/cm³ to 8.96 g/cm³. These parameter changes ensure that the layer is thin enough to reduce weight but thick enough to maintain low sheet resistance growth rate (≤5% at 2.5% tensile strain).
Solution Approach 2:
The support layer acts as an intermediary that provides mechanical support to the thin metal conductive layer, preventing excessive tensile deformation. This mediator allows the metal layer to remain thin for weight reduction while the support layer ensures dimensional stability and limits sheet resistance increase during battery assembly and operation.
Data Source
AI summary
This application discloses a negative current collector, a negative electrode plate, an electrochemical apparatus, a battery module, a battery pack, and a device. The negative current collector includes a support layer and a metal conductive layer that is disposed on at least one of two opposite surfaces of the support layer in a thickness direction of the support layer. A density of the support layer is less than a density of the metal conductive layer; and the density of the metal conductive layer is 8.0 g/cm3 to 8.96 g/cm3. A thickness D1 of the metal conductive layer is 300 nm≤D1≤2 μm. When a tensile strain of the negative current collector is 2.5%, a sheet resistance growth rate T of the metal conductive layer is T≤5%.