Negative Electrode Layer Layout for Battery Electrolyte Absorption
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries used in electric vehicles experience deterioration in rapid charge and discharge cycle characteristics due to the failure of the negative electrode to absorb electrolyte effectively during charging and discharging.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a negative electrode mixture layer with graphite particles A of low internal porosity (5% or less) and graphite particles B of higher internal porosity (8-20%), where particles A are more concentrated near the outer surface and particles B near the collector, and a rubber binder concentrated near the collector, enhancing electrolyte absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If graphite particles with low internal porosity are used to achieve high energy density, then energy density is improved, but electrolyte absorption capability deteriorates
Solution Approach 1:
The patent applies local quality by creating different regions within the negative electrode mixture layer with distinct graphite particle characteristics. The outer surface region contains graphite particles with lower internal porosity (5% or less) for high energy density, while the inner region near the collector contains graphite particles with higher internal porosity (8% to 20%) for enhanced electrolyte absorption. This spatial differentiation of material properties resolves the contradiction between energy density and electrolyte absorption capability.
Solution Approach 2:
The patent segments the negative electrode mixture layer into two distinct half regions based on thickness: an outer surface adjacent half region and an inner region adjacent to the collector. Each segment contains graphite particles with specifically controlled internal porosity characteristics, allowing the electrode to simultaneously achieve high energy density at the outer region and effective electrolyte absorption at the inner region.
2Productivity
If graphite particles with low internal porosity are used, then rapid charge and discharge cycle characteristics are improved through high energy density, but the ability to absorb electrolyte during charging deteriorates
Solution Approach 1:
The patent implements local quality by assigning different graphite particle porosity characteristics to different spatial locations within the negative electrode. The outer surface region uses low porosity graphite (5% or less) to optimize rapid charge and discharge performance, while the inner region uses high porosity graphite (8% to 20%) to ensure sufficient electrolyte absorption during charging cycles.
Solution Approach 2:
The negative electrode mixture layer is segmented into two functional zones: an outer zone optimized for rapid charge and discharge characteristics with low porosity graphite particles, and an inner zone optimized for electrolyte absorption with high porosity graphite particles. This segmentation allows each region to perform its specific function effectively.
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
This configuration significantly increases the electrolyte absorptivity of the negative electrode mixture layer, thereby inhibiting the deterioration of rapid charge and discharge cycle characteristics.
Implementation Method 1
The graphite particles B having an internal porosity of 8% to 20% contribute to electrolyte absorption through capillary forces generated by the porous structure
Implementation Method 2
a rubber binder as a binder... The rubber binder is contained in the half region adjacent to the negative electrode collector in an amount of 90 mass % to 100 mass % of all of the rubber binder contained in the negative electrode mixture layer
Data Source
AI summary
The purpose of the present disclosure is to provide a nonaqueous electrolyte secondary battery which is provided with a negative electrode mixture layer that exhibits excellent electrolyte absorbing properties. A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure is characterized by being provided with a negative electrode having a negative electrode collector and a negative electrode mixture layer that is provided on the surface of the negative electrode collector, and is also characterized in that: the negative electrode mixture layer contains graphite particles A and graphite particles B, which serve as a negative electrode active material, and a rubber binder which serves as a binding agent; the graphite particles A have an internal void fraction of 5% or less; the graphite particles B have an internal void fraction of from 8% to 20%; if the negative electrode mixture layer is divided into two halves in the thickness direction, the outer surface-side half contains more graphite particles A than the negative electrode collector-side half; and from 90% to 100% of the all rubber binder contained in the negative electrode mixture layer is contained in the negative electrode collector-side half.