Negative Electrode Density Zoning for Better Electrolyte Impregnation
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving optimal electrolyte impregnation, which affects their cycle-life characteristics, particularly in taller battery designs.
Innovation Solution
A negative electrode structure with distinct regions of varying crystalline carbon active material tapped densities, including a center region with lower density 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 energy storage capability is improved, but the electrolyte impregnation becomes insufficient especially in the center region
Solution Approach 1:
The patent applies local quality by using different crystalline carbon materials with different tapped densities in different regions of the negative electrode. The center region (II region) uses first crystalline carbon material with lower tapped density (0.9-1.2 g/cm³) to facilitate electrolyte impregnation, while the edge regions (I and III regions) use second crystalline carbon material with higher tapped density (1.2-1.5 g/cm³) to maintain structural integrity and electrical conductivity. This regional differentiation resolves the contradiction between battery height/capacity and electrolyte impregnation uniformity.
2Quantity of substance
If the tapped density of crystalline carbon material is increased to improve electrode density, then the energy density is improved, but the electrolyte impregnation capability deteriorates
Solution Approach 1:
The patent implements local quality by spatially differentiating the tapped density of crystalline carbon materials across the electrode. The center region employs lower density material (0.9-1.2 g/cm³) optimized for electrolyte absorption, while edge regions use higher density material (1.2-1.5 g/cm³) optimized for structural support and conductivity. This resolves the contradiction between energy density and electrolyte impregnation capability.
Solution Approach 2:
The patent segments the negative electrode into three distinct regions (I, II, and III) with different material properties. The center region (II) is segmented as having different tapped density characteristics compared to the edge regions (I and III). This segmentation allows each region to be optimized for its specific function, resolving the contradiction between overall energy density and local electrolyte impregnation.
3Quantity of substance
If the battery is designed to be taller for higher capacity, then the energy capacity is improved, but the cycle-life characteristics deteriorate due to poor electrolyte distribution
Solution Approach 1:
The patent applies local quality by using different crystalline carbon materials with different tapped densities in different regions of the negative electrode. The center region (II region) uses first crystalline carbon material with lower tapped density (0.9-1.2 g/cm³) to facilitate electrolyte impregnation, while the edge regions (I and III regions) use second crystalline carbon material with higher tapped density (1.2-1.5 g/cm³) to maintain structural integrity and electrical conductivity. This regional differentiation resolves the contradiction between battery height/capacity and electrolyte impregnation uniformity.
Data Source
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.