Negative Electrode Graphite Gradient for 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 charge and discharge cycles.
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% to 20%), where graphite particles A are more concentrated near the outer surface and graphite particles B near the collector, along with a rubber binder distribution of 90% to 100% 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 a negative electrode mixture layer with spatially varying composition: graphite particles A (low internal porosity) are concentrated in the outer half region while graphite particles B (higher internal porosity) are concentrated in the inner half region adjacent to the collector. This local differentiation allows the outer region to provide high energy density while the inner region provides effective electrolyte absorption pathways.
2Use of energy by moving object
If graphite particles with low internal porosity are used, then energy density is improved, but rapid charge and discharge cycle characteristics deteriorate
Solution Approach 1:
The patent creates different functional zones within the negative electrode mixture layer: the outer half region with graphite particles A provides high energy density, while the inner half region with graphite particles B provides rapid electrolyte absorption for fast charge/discharge performance. This local quality differentiation resolves the contradiction between energy density and rapid charge/discharge characteristics.
3Ease of manufacture
If uniform distribution of graphite particles is used, then manufacturing simplicity is maintained, but electrolyte absorption capability deteriorates
Solution Approach 1:
The patent implements a non-uniform distribution of graphite particles with different internal porosity values in different regions of the negative electrode mixture layer. Specifically, graphite particles A are concentrated in the outer half region while graphite particles B are concentrated in the inner half region, creating local quality differences that enhance electrolyte absorption capability while maintaining manufacturing feasibility through controlled mixing and coating processes.
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 have an internal porosity of 8% to 20%, and are contained in the half region of the negative electrode mixture layer adjacent to the negative electrode collector in a greater amount than in the half region adjacent to an outer surface
Data Source
Figure 1
Figure 2~3
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.