Grooved Negative Electrode for Fast Electrolyte Impregnation
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Solution Overview
Problem
Conventional methods for forming grooves in electrode surfaces to improve electrolyte impregnation in lithium secondary batteries face challenges such as prolonged penetration time, electrolyte evaporation, stress-induced electrode curvature, and misalignment during winding, leading to reduced productivity and reliability.
Innovation Solution
The electrode group design includes a positive electrode with a double-coated part and a core exposed part, and a negative electrode with a double-coated part, a single-coated part, and a core exposed part, where grooves are formed only on the double-coated part of the negative electrode to enhance electrolyte penetration and prevent curvature, along with a porous protective film made of inorganic oxide for improved insulation and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If grooves are formed in the surface of the negative electrode active material layer to improve electrolyte impregnation, then the impregnation speed is improved, but the electrode may break when wound to form the electrode group
Solution Approach 1:
The groove forming is applied locally only to the double-coated part of the negative electrode, not to the single-coated part. This localized treatment allows electrolyte impregnation enhancement where it is most needed (in the active material regions) while preserving the structural integrity of the single-coated transition region that serves as a stress-distributing bridge during winding.
Solution Approach 2:
The negative electrode is segmented into three distinct regions: double-coated part (with grooves), single-coated part (without grooves), and core exposed part. This segmentation allows different functional treatments in different regions - the double-coated part receives groove treatment for enhanced impregnation, while the single-coated part maintains structural continuity to prevent breakage during winding.
2Quantity of substance
If the filling density of the active material in the electrode is increased to increase battery capacity, then the capacity is improved, but the penetration of nonaqueous electrolyte into the electrode group becomes difficult
Solution Approach 1:
Grooves with specific depth (3-20 μm) and width (10-100 μm) are formed in the active material layer, creating porous channels that facilitate electrolyte penetration. These grooves maintain the high filling density of active material while providing pathways for electrolyte to reach deep into the electrode structure, resolving the contradiction between density and penetration.
Solution Approach 2:
The groove structure introduces a vertical dimension (depth into the electrode) in addition to the horizontal surface area. This three-dimensional groove network allows electrolyte to penetrate through the thickness of the high-density active material layer, enabling both high capacity and effective impregnation.
3Loss of time
If grooves are formed in the surface of the negative electrode to improve impregnation, then the impregnation time is reduced, but the amount of active material is reduced
Solution Approach 1:
The groove dimensions are precisely controlled within specific ranges: depth of 3-20 μm and width of 10-100 μm. These parameter optimizations ensure that the grooves provide sufficient pathways for rapid electrolyte impregnation while removing minimal active material, thus reducing impregnation time without significantly sacrificing capacity.
Solution Approach 2:
Grooves are formed only in the double-coated part of the negative electrode, not in the single-coated part or core exposed part. This partial application of groove forming concentrates the impregnation enhancement where it is most needed (in the thick double-coated region) while preserving active material in other regions.
4Productivity
If grooves are formed in the surface of the negative electrode active material layer, then the electrolyte penetration is improved, but the electrode curvature and misalignment occur during winding
Solution Approach 1:
The single-coated part acts as a local quality transition zone without grooves, providing a smooth, flat surface that maintains structural stability during winding. This localized absence of grooves in the single-coated region prevents the curvature and misalignment issues that would otherwise occur during the winding process.
Solution Approach 2:
The single-coated part serves as a pre-designed cushioning region that compensates for the structural disruption caused by grooves in the double-coated part. During winding, this single-coated transition zone absorbs and distributes tensile forces, preventing the propagation of stress concentrations that would lead to electrode breakage or misalignment.
Data Source
AI summary
A positive electrode 2 includes a positive electrode current collector lead 70 connected to a core exposed part 78 formed at a longitudinal center of a current collector core 72. A negative electrode 3 includes a double-coated part 14 including an active material layer 13 and a porous protective film 28 formed on each surface of a current collector core 12, a core exposed part 18, and a single-coated part 17 which is located between the double-coated part 14 and the core exposed part 18, and includes the active material layer 13 and the porous protective film 28 formed only on one of the surfaces of the current collector core 12. A plurality of grooves 10 are formed in each surface of the double-coated part 14, while the grooves 10 are not formed in the single-coated part 17. A negative electrode current collector lead 20 is connected to the core exposed part 18. The negative electrode 3 is wound in such a manner that the core exposed part 18 constitutes a last wound end.