Layered Negative Electrode Structure for Fast-Charging Battery Cells
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Solution Overview
Problem
Conventional secondary battery electrode plate designs face a trade-off between energy density and fast charging capability, as reducing coating weight for faster charging leads to lower energy density, and increasing it for higher energy density results in poor charging performance due to thicker electrode plates.
Innovation Solution
A multi-layer electrode plate design is employed, with a lower maximum rebound rate for the first negative electrode active material layer and a higher rebound rate for the second layer, optimizing compacted density and surface porosity to achieve both high energy density and fast charging capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the coating weight is reduced to enhance fast charging capability, then the fast charging capability is improved, but the energy density decreases significantly
Solution Approach 1:
The negative electrode active material layer is divided into two distinct layers: a first layer with lower rebound rate (5-10%) for high compacted density and energy density, and a second layer with higher rebound rate (10-14%) for high porosity and fast ion transport. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between energy density and fast charging capability.
Solution Approach 2:
Different regions of the electrode plate are given different properties: the first negative electrode active material layer (closer to current collector) has lower rebound rate and higher compacted density (1.95-2.20 g/cm³) for energy density, while the second layer (surface layer) has higher rebound rate and higher porosity for fast ion diffusion. This local differentiation of material properties enables simultaneous optimization of both contradictory requirements.
2Quantity of substance
If the coating weight is increased to enhance energy density, then the energy density is improved, but the fast charging capability deteriorates due to thicker electrode plates
Solution Approach 1:
The electrode plate is segmented into two functional layers with different thicknesses and properties. The first layer provides the bulk of the active material for energy density, while the second layer provides the porous structure for fast ion transport. This segmentation allows the electrode to achieve both high energy density and fast charging capability without the trade-off present in uniform single-layer designs.
Solution Approach 2:
The surface region (second layer) is designed with higher rebound rate and porosity to facilitate rapid ion diffusion, while the bulk region (first layer) maintains higher compacted density for energy storage. This local quality differentiation ensures that ion transport speed is optimized at the surface where it matters most for fast charging, while energy density is optimized in the bulk.
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
This design allows for enhanced fast charging performance while maintaining high energy density, as the specific selection of rebound rates and compacted densities in the active material layers ensures efficient ion diffusion and electrolyte penetration.
Implementation Method 1
the first negative electrode active material layer includes a first negative electrode active material, the first negative electrode active material has a maximum rebound rate Ra, the second negative electrode active material layer includes a second negative electrode active material, and the second negative electrode active material has a maximum rebound rate Rb
Implementation Method 2
efficient ion diffusion and electrolyte penetration
Data Source
AI summary
A secondary battery according to this application includes a negative electrode. The negative electrode includes a current collector and a negative electrode active material layer disposed on a surface of the current collector. The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer is disposed between the current collector and the second negative electrode active material layer. The first negative electrode active material layer includes a first negative electrode active material, and the first negative electrode active material has a maximum rebound rate Ra; and the second negative electrode active material layer includes a second negative electrode active material, and the second negative electrode active material has a maximum rebound rate Rb; where 5%≤Ra≤13%, 10%≤Rb≤17%, and Ra<Rb.