Dual-Layer Lithium Battery Anode for High Loading and Adhesion
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving excellent cycle-life characteristics due to issues with binder distribution and loading levels in the negative electrode active material layers, leading to increased resistance and reduced impregnability of the electrolyte.
Innovation Solution
A negative electrode for lithium secondary batteries is designed with a dual-layer structure, where the first active material layer has a higher binder content and is in direct contact with the current collector, while the second active material layer has a lower binder content and is positioned above the first layer, optimizing binder distribution and loading levels to enhance adhesion and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single-layer negative electrode active material layer is used with high loading level, then the battery capacity increases, but the binder distribution becomes uneven and adhesion to current collector deteriorates
Solution Approach 1:
The negative electrode active material layer is divided into two sub-layers: a first sub-layer in direct contact with the current collector containing a first binder, and a second sub-layer positioned above containing a second binder. This segmentation allows each sub-layer to have optimized binder distribution, ensuring good adhesion at the interface while maintaining overall structural integrity and preventing binder aggregation that would occur in a single high-loading layer.
2Reliability
If binder content is increased to improve adhesion, then the adhesion to current collector improves, but the ionic conductivity decreases and electrolyte impregnability is reduced
Solution Approach 1:
Different binder contents are applied to different regions of the negative electrode active material layer. The first sub-layer in contact with the current collector has a higher binder content (0.5-5 wt%) to ensure strong adhesion, while the second sub-layer has a lower binder content (0.1-3 wt%) to maintain high ionic conductivity and facilitate electrolyte impregnation. This local differentiation resolves the contradiction between adhesion and electrolyte access.
3Quantity of substance
If loading level of active material is increased to enhance capacity, then the energy density increases, but the pores for electrolyte impregnation are reduced
Solution Approach 1:
The problem of pore reduction in high-loading electrodes is addressed by introducing a vertical dimensionality through the two-sub-layer structure. The first sub-layer provides structural foundation and adhesion, while the second sub-layer maintains porosity and facilitates electrolyte distribution from the top surface downward. This dimensional approach allows high overall loading levels while preserving necessary pore structure for electrolyte impregnation.
Data Source
AI summary
A negative electrode for a lithium secondary battery comprises a current collector and a negative electrode active material layer formed on the current collector, wherein the negative electrode active material layer includes a first negative electrode active material and a first binder, and a second active material layer formed on the first active material layer and including a second negative electrode active material and a second binder, a content of the first binder is greater than that of the second binder, a loading level of the negative electrode active material layer is 10 mg/cm2 to 30 mg/cm2, a loading level of the first active material layer is 4 mg/cm2 to 25 mg/cm2, a loading level of the second active material layer is 4 mg/cm2 to 25 mg/cm2, and a loading level of the second active material layer is equal to or higher than that of the first active material layer.