Fluorine-Resin-Coated Silicon Anode Material for Cycle Stability

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Solution Overview

Problem

The use of composite particles including silicate and silicon as a negative electrode active material in non-aqueous electrolyte secondary batteries leads to deterioration in charge/discharge cyclic characteristics due to reactions with water and hydroxide ions, causing silicon oxidation and decomposition of the non-aqueous electrolyte and thickener degradation.

Innovation Solution

A composite particle with a silicate and silicon core coated with a fluorine resin surface layer is used to suppress the reaction between the silicate and water, preventing silicon oxidation and thickener decomposition, thereby maintaining the integrity of the non-aqueous electrolyte.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If composite particles including silicate and silicon are used as negative electrode active material, then capacity per unit volume is improved, but charge/discharge cyclic characteristics deteriorate

Engineering Contradiction:

Improvecapacity per unit volumeVSAvoidcharge/discharge cyclic characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A coating layer comprising fluorine-containing polymer is applied on the surface of composite particles including silicate and silicon. This coating layer acts as an intermediary barrier that prevents direct contact between water/hydroxide ions and the silicon particles, thereby suppressing oxidation reactions and electrolyte decomposition while maintaining high capacity per unit volume.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A thin film coating layer made of fluorine-containing polymer is formed on the composite particles. This flexible protective shell provides chemical stability and resistance to water and hydroxide ions, preventing degradation of the underlying silicon particles during charge/discharge cycling while preserving the high capacity characteristics of silicon.

Inventive Principle:

Principle #30Flexible shells and thin films

2Quantity of substance

If silicate and silicon composite particles are used, then ion intercalation capacity is improved, but silicon oxidation occurs due to reaction with water and hydroxide ions

Engineering Contradiction:

Improveion intercalation capacityVSAvoidsilicon oxidation resistance

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The fluorine-containing polymer coating serves as an intermediary protective layer that physically separates water and hydroxide ions from the silicon particles. This prevents the chemical reaction between hydroxide ions and silicon that would otherwise cause oxidation and capacity degradation, while still allowing the silicon to maintain its high ion intercalation capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The fluorine-containing polymer coating creates an inert chemical environment around the silicon particles, protecting them from reactive species in the electrolyte such as water and hydroxide ions. This inert barrier prevents oxidation reactions and maintains the stability of silicon composition during battery operation.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Quantity of substance

If silicate is present in composite particles, then capacity is improved, but thickener decomposition occurs due to reaction with water

Engineering Contradiction:

ImprovecapacityVSAvoidthickener decomposition

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

The fluorine-containing polymer coating acts as a protective intermediary that prevents water from reaching and reacting with the thickener in the electrolyte. By blocking water access to the composite particles surface, the coating prevents hydrolysis and decomposition of the thickener, thereby maintaining electrolyte stability and battery performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 fluorine resin coating effectively inhibits the deterioration of charge/discharge cyclic characteristics by reducing the reactivity of silicon with water and preserving the bindability of the composite particles, thus enhancing the battery's performance.

Implementation Method 1

a surface layer coating the composite particle, and the surface layer includes a fluorine resin... suppress the reaction between the silicate and water, preventing silicon oxidation

Methodology Applied

Scientific EffectChemical resistance barrier:

Implementation Method 2

preserving the bindability of the composite particles, thus enhancing the battery's performance

Methodology Applied

Scientific EffectAdhesion preservation:

Data Source

PatentUS12381209B2Negative electrode active material for nonaqueous electrolyte secondary battery, negative electrode, and nonaqueous electrolyte secondary battery

Publication Date: 2025.08.05 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

In the present invention, negative electrode active material particles for a nonaqueous electrolyte secondary battery which can suppress decrease of charging and discharging cycle characteristics, are each provided with: a composite particle that includes a silicate phase and silicon particles dispersed in the silicate phase; and a surface layer that covers the composite particle, wherein the surface layer includes a fluorine resin.