Negative Electrode Current Collector Hardness for Sodium Dendrite Control
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Solution Overview
Problem
Sodium-ion batteries face challenges due to lower energy density, reduced cycle reversibility, and safety issues related to dendritic growth, exacerbated by the flexibility of thin negative electrode current collectors, which complicates processing and reduces yield.
Innovation Solution
A negative electrode current collector with a metal substrate and conductive layer having a Vickers hardness of 400-850 MPa and a thickness of 0.5-6 μm, incorporating conductive particles and binders, enhances hardness and processability while ensuring high capacity, using materials like hard carbon, carbon black, and carbon nanotubes to improve conductivity and deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative electrode current collector and conductive layer are made thinner to pursue higher energy density, then the energy density increases, but the current collector becomes more flexible which complicates processing and reduces yield
Solution Approach 1:
The patent applies composite materials by combining a metal substrate with a conductive layer containing conductive particles (such as carbon black, carbon nanotubes, or graphene) and binder. This composite structure provides both the thin profile needed for high energy density and the mechanical strength required for ease of processing. The conductive particles form a network within the binder that reinforces the thin conductive layer, preventing it from being overly flexible while maintaining electrical conductivity.
Solution Approach 2:
The patent utilizes parameter changes by carefully controlling the thickness of the conductive layer within a specific range (0.5-6 μm) and adjusting the composition ratios of conductive particles to binder. By optimizing these parameters, the current collector achieves a balance between thinness (for energy density) and structural integrity (for processability). The Vickers hardness is controlled within 400-850 MPa to ensure appropriate mechanical properties.
2Ease of manufacture
If the conductive layer thickness is increased to improve hardness and processability, then the processability improves, but the capacity of the battery is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the conductive layer thickness within the optimal range of 0.5-6 μm. This parameter optimization ensures that the layer is thick enough to provide adequate hardness and processability while remaining thin enough to maintain high battery capacity. The Vickers hardness parameter is also controlled within 400-850 MPa to achieve the desired balance.
Solution Approach 2:
The composite material structure with conductive particles dispersed in a binder provides enhanced mechanical strength per unit thickness. This allows the conductive layer to achieve sufficient hardness and processability at thinner thicknesses, thereby avoiding the capacity loss that would result from increasing the thickness.
3Ease of manufacture
If the Vickers hardness is increased beyond 850 MPa to improve processability, then the processability improves, but the current collector becomes susceptible to brittle failure during processing
Solution Approach 1:
The patent applies parameter changes by establishing an optimal upper limit for Vickers hardness at 850 MPa. This parameter control ensures that the current collector has sufficient hardness for good processability while avoiding excessive hardness that would lead to brittleness. The conductive layer thickness is also controlled within 0.5-6 μm to prevent edge collapse and separation issues associated with overly hard structures.
Data Source
AI summary
A negative electrode current collector may comprise a metal substrate and a conductive layer provided on at least one surface of the metal substrate, the negative electrode current collector may have a Vickers hardness of 400 MPa-900 MPa, and the conductive layer may have a thickness of 0.5 μm-6 μm.