Negative Electrode Porosity Layout for Uniform Wound Battery Reactions

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Solution Overview

Problem

Non-aqueous electrolyte secondary batteries face challenges in maintaining uniform charge-discharge reactions between the inner and outer winding sides of the negative electrode, leading to deteriorated high-speed charge cycle characteristics.

Innovation Solution

The battery design incorporates a negative electrode with distinct mixture layers on its inner and outer winding sides, where the inner winding side layer has graphite particles with internal porosity between 6% and 20%, and the outer winding side layer has graphite particles with internal porosity less than or equal to 5%, ensuring appropriate electrolyte retention and charge distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If graphite particles with small internal porosity are distributed on the surface side of the negative electrode mixture layer, then peeling of graphite particles from the current collector is inhibited and high-speed charge cycle characteristics are improved, but charge-discharge reactions do not proceed uniformly on the inner and outer winding sides

Engineering Contradiction:

Improvehigh-speed charge cycle characteristicsVSAvoiduniformity of charge-discharge reactions

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by using graphite particles with different internal porosity values in different regions of the negative electrode. Specifically, the inner winding side uses graphite particles with 5% ≤ internal porosity < 20%, while the outer winding side uses graphite particles with internal porosity < 5%. This regional differentiation ensures that each area has the appropriate electrolyte retention characteristics for its location, achieving uniform charge-discharge reactions across the entire electrode while maintaining high-speed charge cycle performance.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If the amount of electrolyte liquid on the inner winding side is increased to match the outer winding side, then charge-discharge reactions become uniform, but the battery structure becomes more complex

Engineering Contradiction:

Improveuniformity of charge-discharge reactionsVSAvoidnegative electrode structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent changes the physical parameter of graphite particles (internal porosity) to control electrolyte retention in different regions. By selecting graphite particles with specific internal porosity ranges for the inner winding side (5% ≤ internal porosity < 20%) and outer winding side (internal porosity < 5%), the patent achieves uniform electrolyte distribution and uniform charge-discharge reactions without modifying the overall battery structure or adding complex components.

Inventive Principle:

Principle #35Parameter changes

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 design enhances battery capacity and high-speed charge cycle characteristics by ensuring uniform charge-discharge reactions across the negative electrode, thereby improving overall battery performance.

Implementation Method 1

the amount of an electrolyte liquid held on the inner winding side of the negative electrode is smaller than an amount of an electrolyte liquid held on the outer winding side of the negative electrode

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

graphite particles having an internal porosity of greater than or equal to 6% and less than or equal to 20%, the second negative electrode mixture layer includes graphite particles having an internal porosity of less than or equal to 5%

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 3

charge-discharge reactions hardly proceed uniformly on an inner winding side and an outer winding side of a negative electrode in a wound electrode assembly

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentUS20250038207A1Non-aqueous electrolyte secondary battery

Publication Date: 2025.01.30 PANASONIC ENERGY CO LTD

AI summary

A negative electrode of this non-aqueous electrolyte secondary battery has a negative electrode electric current collector, an inner winding side negative electrode mix layer, and an outer winding side negative electrode mix layer. The inner winding side negative electrode mix layer and the outer winding side negative electrode mix layer each has a first negative electrode mix layer facing the negative electrode electric current collector, and a second negative electrode mix layer facing the positive electrode. The first negative electrode mix layer includes graphite particles having an internal porosity of 6-20% and the second negative electrode mix layer includes graphite particles having an internal porosity of 5% or less. In the inner winding side negative electrode mix layer, the thickness t1 of the first negative electrode mix layer and the thickness t2 of the second negative electrode mix layer satisfy the relationship t1/t2<1.