Negative Electrode Plate Two-Layer Structure
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Solution Overview
Problem
Rechargeable batteries face challenges in achieving a balance between high energy density and fast charging performance, with existing designs often compromising on either energy density or cycle life due to limitations in active substance particle size and layer thickness.
Innovation Solution
A negative electrode plate with a two-layer structure, where the first active substance layer has a larger particle size for higher capacity and the second active substance layer has a smaller particle size for improved charging performance, satisfying specific ratios of thickness to particle size to optimize energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the particle size of active substance is increased to improve energy density, then the capacity increases, but the charging performance deteriorates
Solution Approach 1:
The negative electrode plate is divided into two distinct active substance layers: a first layer with larger particle size (A) and greater thickness (B) for high energy density, and a second layer with smaller particle size (C) and appropriate thickness (D) for fast charging. This segmentation allows each layer to specialize in one function, resolving the contradiction between energy density and charging performance.
Solution Approach 2:
Different regions of the negative electrode plate have different local properties: the first active substance layer uses larger particles optimized for capacity storage, while the second active substance layer uses smaller particles optimized for ion transport speed. This local quality differentiation enables simultaneous optimization of both energy density and charging performance in different parts of the electrode.
2Quantity of substance
If the thickness of active substance layer is increased to improve energy density, then the capacity increases, but the cycle life deteriorates
Solution Approach 1:
The thick negative electrode is segmented into two layers with different thickness-to-particle-size ratios. The first layer has a higher B/A ratio for energy density, while the second layer has a controlled D/C ratio to ensure ion diffusion pathways remain efficient. This segmentation prevents the cycle life deterioration that would occur in a uniformly thick electrode.
Solution Approach 2:
The negative electrode plate uses a composite structure combining two types of active substance layers with different characteristics. The first layer provides high capacity with larger particles and greater thickness, while the second layer acts as a functional composite that maintains ion transport efficiency, together creating an electrode that achieves both high energy density and long cycle life.
Data Source
AI summary
This application provides a negative electrode plate, a secondary battery, a battery module, a battery pack, and an apparatus. The negative electrode plate includes a negative current collector and a plurality of active substance layers formed on the negative current collector, where the plurality of active substance layers include at least a first active substance layer and a second active substance layer; the first active substance layer includes a first negative active substance, and the second active substance layer includes a second negative active substance; a ratio of thickness of the negative active substance of the first active substance layer to average particle size of the first negative active substance is 2.0 to 4.0; and a ratio of thickness of the second active substance layer to average particle size of the second negative active substance is 2.2 to 5.0.