Silicon-Lithium Aluminate Anode Particles With Low Porosity

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Solution Overview

Problem

Existing negative electrode active materials for non-aqueous electrolyte secondary batteries, such as LSX, suffer from low alkali resistance, leading to side reactions with Li ions and poor cycle characteristics due to volume changes during charge and discharge.

Innovation Solution

A negative electrode active material comprising composite particles with a lithium aluminate phase and a silicon phase dispersed within, where the porosity inside the particles is controlled to be less than or equal to 25% before the first charge and discharge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Si-containing material is used to increase capacity, then theoretical capacity density is improved, but volume change during charge and discharge causes cracking and breakage

Engineering Contradiction:

Improvecapacity densityVSAvoidparticle integrity

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent uses a composite structure where silicon particles are dispersed in a lithium silicate phase (LSX) matrix. This composite material approach allows the silicon to provide high capacity while the LSX matrix provides structural stability and buffers the volume expansion, preventing particle cracking and breakage during charge-discharge cycles.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The lithium silicate phase acts as a flexible matrix that can accommodate the volume expansion of silicon particles during lithiation. The LSX phase envelops the silicon particles, providing a protective shell that allows volume change without causing particle fracture, thus maintaining particle integrity throughout cycling.

Inventive Principle:

Principle #30Flexible shells and thin films

2Productivity

If lithium silicate phase is used in LSX, then initial charge-discharge efficiency is improved, but alkali resistance is low causing side reactions with Li ions

Engineering Contradiction:

Improveinitial charge-discharge efficiencyVSAvoidalkali resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent modifies the composition parameters of the lithium silicate phase by controlling the SiO2 content to be 1-30 mass% and adjusting the Li/Si ratio. This parameter optimization balances the competing requirements: maintaining enough Li content for high initial efficiency while limiting excess Li that would cause side reactions, thereby improving both efficiency and alkali resistance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates local compositional variations within the LSX phase, with different regions having different Li/Si ratios. The core regions have lower Li content for stability, while surface regions maintain higher Li content for efficient Li ion insertion, achieving both high initial efficiency and good alkali resistance through spatially differentiated composition.

Inventive Principle:

Principle #3Local quality

3Duration of action of stationary object

If porosity is increased to accommodate volume change, then cycle characteristics are improved, but initial charge-discharge efficiency decreases

Engineering Contradiction:

Improvecycle characteristicsVSAvoidinitial charge-discharge efficiency

Core Design Contradiction:

Duration of action of stationary objectVSProductivity

Solution Approach 1:

The patent introduces a controlled porous structure within the LSX matrix, creating void spaces that can accommodate silicon volume expansion during cycling. This porous architecture provides buffer space for volume change without requiring excessive overall porosity, thus maintaining good cycle characteristics while preserving reasonable initial efficiency.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent creates a nested structure where silicon particles are embedded within the LSX phase, which itself is embedded in the electrode matrix. This hierarchical nesting allows the inner silicon to expand into the void space provided by the outer LSX matrix, accommodating volume change while maintaining structural integrity and efficient ion transport pathways.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 proposed solution significantly improves the initial charge-discharge efficiency and cycle characteristics of non-aqueous electrolyte secondary batteries by reducing porosity and inhibiting particle cracking and breakage.

Implementation Method 1

Since the Si-containing material such as LSX causes a large change in volume with charge and discharge, cracking, breakage, and the like easily occur with repeated charge and discharge

Methodology Applied

Scientific EffectVolume change accommodation: Elasticity

Implementation Method 2

LSX has a small irreversible capacity compared with SiOx, and has excellent initial charge-discharge efficiency

Methodology Applied

Scientific EffectIon insertion/extraction: Absorption (physical)

Data Source

PatentUS20250158023A1Negative electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Publication Date: 2025.05.15 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A negative electrode active material for a non-aqueous electrolyte secondary battery according to one example of an embodiment comprises composite particles (30) that include a lithium aluminate phase (31) and a silicon phase (32) dispersed in the lithium aluminate phase (31). The composite particles (30) have an internal porosity of 25% or less before being charged and discharged for the first time.