Negative Electrode Layer Segmentation for Battery Output

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Solution Overview

Problem

Existing nonaqueous electrolyte secondary batteries face challenges in improving output characteristics, which are crucial for enhanced performance and efficiency.

Innovation Solution

The negative electrode of the battery incorporates a mixture layer composed of graphite, single wall fibrous carbon, and multiwalled fibrous carbon, with specific distributions and BET specific surface areas in different regions of the layer to optimize conductivity and permeability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a uniform negative electrode mixture layer structure is used, then the manufacturing process is simple, but the output characteristics of the battery are insufficient

Engineering Contradiction:

Improveoutput characteristicsVSAvoidmixture layer structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The negative electrode mixture layer is divided into a first region (40% from the surface) and a second region (40% from the interface with core body), with each region having distinct compositions. The first region contains graphite with smaller BET specific surface area and more single wall fibrous carbon, while the second region contains graphite with larger BET specific surface area and more multiwalled fibrous carbon, optimizing output characteristics through regional differentiation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the mixture layer are assigned different material properties: the first region near the surface uses materials with smaller BET specific surface area for better conductivity, while the second region near the core body uses materials with larger BET specific surface area for enhanced permeability and active material utilization, creating local optimization throughout the layer.

Inventive Principle:

Principle #3Local quality

2Power

If graphite with larger BET specific surface area is used throughout, then permeability is improved, but conductivity is reduced

Engineering Contradiction:

ImproveconductivityVSAvoidpermeability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Graphite with smaller BET specific surface area is concentrated in the first region (40% from surface) to maximize conductivity where electron transport is critical, while graphite with larger BET specific surface area is concentrated in the second region (40% from interface) to maximize permeability where electrolyte access to active material is critical, resolving the conductivity-permeability trade-off through spatial differentiation.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12266784B2Negative electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery

Publication Date: 2025.04.01 TOYOTA JIDOSHA KK

AI summary

A negative electrode for a nonaqueous electrolyte secondary battery comprises a negative electrode core body, and a negative electrode mixture layer. When the range of 40% of the thickness of the negative electrode mixture layer from the surface of the negative electrode mixture layer on the side opposite to the negative electrode core body is defined as a first region and the range of 40% of the thickness of the negative electrode mixture layer from the interface between the negative electrode mixture layer and the negative electrode core body is defined as a second region, the BET specific surface area of the graphite included in the first region is smaller than the BET specific surface area of the graphite included in the second region.