Dual-Layer Negative Electrode Plate for Lithium Plating Control
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Solution Overview
Problem
Lithium-ion batteries with single negative electrode active material layers suffer from low capacity and rapid cycle attenuation due to non-uniform tortuosity, leading to lithium plating and safety hazards, especially at high charge and discharge rates.
Innovation Solution
A negative electrode plate with a current collector and two sequentially arranged active material layers, where the tortuosity of the first layer is between 1 and 5, and the tortuosity of the second layer is between 1 and 5, with a difference of 0.5 to 3.2, enhancing electrolyte infiltration and maintaining solid phase transport efficiency to prevent lithium plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single negative electrode active material layer is used, then the structure is simple, but the tortuosity is non-uniform leading to low capacity and rapid cycle attenuation
Solution Approach 1:
The single negative electrode active material layer is divided into two sequentially arranged layers: a first negative electrode active material layer adjacent to the current collector and a second negative electrode active material layer away from the current collector. This segmentation allows each layer to have optimized tortuosity characteristics, resolving the contradiction between structural simplicity and cycle stability.
Solution Approach 2:
Different tortuosity values are assigned to different layers: the first layer has tortuosity t1 and the second layer has tortuosity t2, with the constraint 0.5 ≤ t2 - t1 ≤ 3.2. This local differentiation of tortuosity properties enables uniform lithium ion transport throughout the electrode, improving capacity retention and preventing lithium plating while maintaining reasonable structural complexity.
2Quantity of substance
If the negative electrode active material layer is compacted to increase density, then the solid phase transport efficiency improves, but the liquid phase diffusion rate decreases
Solution Approach 1:
The solution moves from a single-layer structure to a two-layer structure with different tortuosity characteristics. The first layer (adjacent to current collector) has lower tortuosity for efficient solid phase transport, while the second layer (away from current collector) has higher tortuosity for enhanced liquid phase diffusion. This dimensional change in structural organization resolves the contradiction between density and diffusion rate.
Solution Approach 2:
The tortuosity parameter is differentiated between layers with the constraint 0.5 ≤ t2 - t1 ≤ 3.2. By controlling the tortuosity difference between layers, the patent achieves both high compacted density (through the first layer) and high liquid phase diffusion rate (through the second layer), eliminating lithium plating and improving capacity retention.
3Power
If high charge and discharge rates are applied, then the power density increases, but lithium plating occurs on the surface
Solution Approach 1:
The two-layer structure with differentiated tortuosity is designed in advance to prevent lithium plating before it occurs. The first layer with lower tortuosity ensures efficient lithium ion transport from the current collector, while the second layer with higher tortuosity provides adequate liquid phase diffusion pathways. This preliminary structural design enables high power density operation without lithium plating, even at high charge and discharge rates.
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 battery achieves high capacity retention and stability at high rates without lithium plating, ensuring consistent lithium insertion and extraction rates and improved energy density.
Implementation Method 1
the lithium ions in the negative electrode active material layer away from the current collector have a relatively low rate of liquid phase diffusion
Implementation Method 2
the second active coating layer with the high tortuosity can provide more hole structures, which is conductive to electrolyte infiltration
Data Source
AI summary
A negative electrode plate is provided, which includes a current collector, and a first negative electrode active material layer and a second negative electrode active material layer sequentially arranged on the current collector. A tortuosity of the first negative electrode active material layer and a tortuosity of the second negative electrode active material layer satisfy: 1<t1≤5, 1<t2≤5, and 0.5≤t2−t1≤3.2; where t1 represents the tortuosity of the first negative electrode active material layer, t2 represents the tortuosity of the second negative electrode active material layer, and t2−t1 represents a difference between the tortuosity of the second negative electrode active material layer and the tortuosity of the first negative electrode active material layer.