Negative Electrode Layout for Better Electrolyte Impregnation
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving optimal electrolyte impregnation, particularly in larger form factors, which affects cycle-life characteristics.
Innovation Solution
A negative electrode design with distinct regions of varying crystalline carbon active material tapped densities, including a low-tapped density center region to enhance electrolyte impregnation, supported by a current collector and a specific distribution of crystalline carbon materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the battery height is increased to achieve higher capacity, then the capacity is improved, but the electrolyte impregnation becomes insufficient particularly in the center region
Solution Approach 1:
The patent applies local quality by creating distinct regions within the negative electrode active material layer with different tapped densities. The center region (II region) uses first crystalline carbon material with lower tapped density (0.9-1.1 g/cm³) to facilitate electrolyte impregnation, while the edge regions (I and III regions) use second crystalline carbon material with higher tapped density (1.2-1.4 g/cm³) for structural stability. This spatial variation in material properties resolves the contradiction between battery height/capacity and electrolyte impregnation effectiveness.
2Strength
If the negative electrode active material layer is made denser to improve structural integrity, then the structural stability is improved, but the electrolyte impregnation is reduced
Solution Approach 1:
The patent implements local quality by assigning different tapped density characteristics to different spatial regions of the negative electrode. The center region employs lower density material (first crystalline carbon) to enable adequate electrolyte penetration, while the edge regions utilize higher density material (second crystalline carbon) to provide structural support. This regional differentiation allows the electrode to simultaneously achieve both structural integrity and sufficient electrolyte impregnation.
Solution Approach 2:
The patent segments the negative electrode active material layer into three distinct regions (I, II, and III) with different material compositions and tapped densities. This segmentation allows each region to be optimized for its specific functional requirements: edge regions for structural support and center region for electrolyte access, thereby resolving the contradiction between structural integrity and electrolyte impregnation.
Data Source
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AI summary
Examples of the disclosure include a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery. The negative electrode includes a current collector, and a negative electrode active material layer on the current collector. The negative electrode active material layer includes a I region, a II region and a III region which are separated by boundaries extending along a longitudinal direction. The II region includes a first crystalline carbon negative electrode active material, the I region and the III region include a second crystalline carbon negative electrode active material, and a tap density of the first crystalline carbon negative electrode active material is lower than a tap density of the second crystalline carbon negative electrode active material.