Two-Layer Negative Electrode Plate for Fast-Charging Cycle Life
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Solution Overview
Problem
Secondary batteries face challenges in achieving high energy density, long cycle life, and fast charging performance due to issues such as increased polarization and safety risks from lithium dendrite formation, which are not adequately addressed by existing methods of thickening electrode coatings or using high-capacity active substances.
Innovation Solution
A negative electrode plate with a two-layer structure, where the ratio of gram capacity to thickness of the first and second active substance layers is optimized within specific ranges (3.5 ≤ A/B ≤ 10.0 and 6.5 ≤ C/D ≤ 23.0), allowing for a balance between high energy density, long cycle life, and fast charging performance by adjusting the active substance's crystal structure and layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the coating thickness of the electrode plate is increased to increase capacity per unit area, then energy density is improved, but polarization becomes severe and cycle life deteriorates
Solution Approach 1:
The negative electrode plate is divided into two distinct active substance layers: a first layer with higher gram capacity and a second layer with lower gram capacity. This segmentation allows each layer to perform different functions - the first layer provides high capacity while the second layer facilitates ion transport, thereby resolving the contradiction between increasing capacity and maintaining cycle life.
2Quantity of substance
If an active substance with high gram capacity is used to increase energy density, then energy density is improved, but lithiation/delithiation capability deteriorates and metal lithium precipitates
Solution Approach 1:
Different regions of the negative electrode plate are assigned different properties: the first active substance layer uses materials with high gram capacity (such as graphite) to maximize energy storage, while the second active substance layer uses materials with lower gram capacity but superior ion transport properties to ensure fast lithiation/delithiation. This local differentiation resolves the contradiction between high capacity and fast reaction kinetics.
3Quantity of substance
If the gram capacity of negative graphite material is increased, then energy density is improved, but lithiation/delithiation capability becomes poorer and charging performance deteriorates
Solution Approach 1:
The negative electrode plate employs a composite structure consisting of two different active substances layered together. The first layer comprises high-capacity materials like graphite, while the second layer incorporates materials that facilitate rapid ion exchange. This composite approach enables the electrode to simultaneously achieve high energy density and fast charging capability by combining the advantages of different materials.
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 optimized negative electrode plate design enhances energy density, extends cycle life, and improves high-rate charging capabilities while reducing safety issues related to lithium dendrite formation, achieving a balance that existing technologies struggle to achieve.
Implementation Method 1
a lithiation/delithiation capability of the negative graphite material becomes poorer. If a charging rate is relatively large, lithium ions released from a positive electrode cannot be intercalated into a negative material in a timely manner
Data Source
Figure 1~3
Figure 4~5
AI summary
This application provides a negative electrode plate, a secondary battery (5), a battery module (4), a battery pack (1), and an apparatus. The negative electrode plate includes a negative current collector and a plurality of active substance layers on the negative current collector. 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 gram capacity of the negative active substance of the first active substance layer to thickness of the first active substance layer is 3.5-10.0. Aratio of gram capacity of the negative active substance of the second active substance layer to thickness of the second active substance layer is 6.5-23.0.