Segmented Negative Electrode Layout to Reduce Lithium Plating
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Solution Overview
Problem
Lithium-ion batteries face challenges in maintaining high energy density and cycle performance due to lithium metal precipitation at the negative electrode, leading to capacity attenuation and safety concerns.
Innovation Solution
The negative electrode design includes a negative current collector with a first negative active material layer on one side of a first portion and a second negative active material layer on both sides of a second portion, with specific weight and compacted density ratios to optimize lithium ion distribution and reduce polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the negative electrode uses a single-layer structure with uniform active material distribution, then the manufacturing process is simple, but lithium metal precipitation occurs due to polarization during cycling
Solution Approach 1:
The negative electrode is segmented into a first negative active material layer and a second negative active material layer with different weight per unit area ratios (0.3≤K≤0.7). This segmentation creates non-uniform lithium ion distribution that reduces polarization and prevents lithium metal precipitation during cycling, thereby improving cycle performance while maintaining manufacturing feasibility.
Solution Approach 2:
Different portions of the negative electrode are given different local qualities through the first and second negative active material layers with distinct weight per unit area characteristics. The first layer has lower weight per unit area while the second layer has higher weight per unit area, creating localized variations that optimize lithium ion distribution and reduce polarization effects during battery cycling.
2Quantity of substance
If the negative electrode increases energy density by using higher capacity active materials, then the energy storage capacity improves, but lithium plating occurs due to increased polarization
Solution Approach 1:
The invention changes the parameter of weight per unit area distribution across different layers of the negative electrode. By setting the ratio K between the first and second layers within 0.3≤K≤0.7, the patent optimizes lithium ion flux distribution, reducing polarization effects that lead to lithium plating while maintaining high energy density through the use of high-capacity active materials.
3Ease of manufacture
If the negative electrode uses uniform active material thickness across the electrode, then the manufacturing process is simple, but current density distribution becomes non-uniform during cycling
Solution Approach 1:
The uniform coating process is segmented into two distinct layers with different target weight per unit area values. The first layer is coated to a lower weight per unit area while the second layer is coated to a higher weight per unit area, with their ratio K controlled within 0.3≤K≤0.7. This segmentation transforms a simple manufacturing process into a two-step process that achieves superior current density uniformity during battery cycling.
Data Source
AI summary
A negative electrode includes a negative current collector, a first negative active material layer and a second negative active material layer. The first negative active material layer is arranged on one side of a first portion of the negative current collector, and the second negative active material layers are arranged on two sides of a second portion, different from the first portion, of the negative current collector. A ratio of a weight per unit area of the first negative active material layer to a weight per unit area of the second negative active material layer on the negative current collector is 0.47 to 0.52, and a ratio of a compacted density of the first negative active material layer to a compacted density of the second negative active material layer is 0.9 to 1.1.