Silicon Negative Electrode Composition for Stable Charge Potential

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Solution Overview

Problem

Increasing the silicon content in the negative electrode of nonaqueous electrolyte secondary batteries leads to increased polarization, causing the negative electrode potential to drop below the lithium metal potential, resulting in premature end-of-charge voltage and reduced capacity utilization.

Innovation Solution

Incorporating a second material with a higher lithium reaction potential than silicon in the negative electrode mixture layer, maintaining a silicon content of 10 mass% or more, to stabilize the negative electrode potential and prevent premature end-of-charge voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the silicon content in the negative electrode is increased to achieve high capacity, then the battery capacity increases, but the polarization of the negative electrode increases and the negative electrode potential drops below the lithium metal potential

Engineering Contradiction:

Improvebattery capacityVSAvoidnegative electrode potential stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies composite materials by combining silicon-containing particles (first particles) with carbon-coated particles (second particles) in the negative electrode mixture. The carbon coating on the second particles provides a stable potential reference that prevents the negative electrode potential from dropping below the lithium metal potential, while the silicon content can be increased to achieve high capacity. This composite structure resolves the contradiction between achieving high capacity through increased silicon content and maintaining reliable negative electrode potential stability.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the silicon content is increased to achieve high capacity, then the battery capacity increases, but the end-of-charge voltage is reached earlier than assumed and the positive electrode potential fails to rise sufficiently

Engineering Contradiction:

Improvebattery capacityVSAvoidcapacity utilization rate

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The composite material system consisting of silicon-containing particles and carbon-coated particles controls the negative electrode potential to remain above the lithium metal potential. This prevents premature reaching of the end-of-charge voltage, allowing the positive electrode potential to rise sufficiently and achieving adequate capacity utilization rate while maintaining high battery capacity through high silicon content.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the parameter of negative electrode potential by introducing carbon-coated particles with specific properties. This parameter change ensures that the negative electrode potential stays above the lithium metal potential throughout charging, preventing early end-of-charge voltage occurrence and enabling sufficient positive electrode potential rise for high capacity utilization.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If the silicon content is increased to achieve high capacity, then the battery capacity increases, but the polarization of the negative electrode increases

Engineering Contradiction:

Improvebattery capacityVSAvoidpolarization

Core Design Contradiction:

Quantity of substanceVSStress or pressure

Solution Approach 1:

The composite material system combines silicon-containing particles with carbon-coated particles to manage polarization. The carbon-coated particles provide a stable potential reference that counteracts the increased polarization caused by high silicon content, enabling the negative electrode to achieve high capacity without excessive polarization.

Inventive Principle:

Principle #40Composite materials

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

The solution suppresses the decrease in negative electrode potential during charging, allowing the positive electrode potential to rise sufficiently, thereby improving capacity utilization and preventing early end-of-charge voltage.

Implementation Method 1

a material containing silicon that forms an alloy with lithium has been expected to be utilized as a negative electrode active material having a high theoretical capacity density

Methodology Applied

Scientific EffectAlloy formation:

Implementation Method 2

the negative electrode active material includes a first material containing silicon and a second material having a reaction potential with Li higher than silicon

Methodology Applied

Scientific EffectElectrochemical potential difference:

Data Source

PatentUS20250210623A1Negative electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Publication Date: 2025.06.26 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A negative electrode for a nonaqueous electrolyte secondary battery. The negative electrode has a negative electrode mixture layer containing a negative electrode active material. The negative electrode active material includes a first material containing silicon and a second material having a reaction potential with Li higher than silicon. The content Cs of the silicon in the negative electrode mixture layer is 10 mass % or more.