Silicon-Dispersed Lithium Silicate Negative Electrode

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Solution Overview

Problem

The existing negative electrodes of non-aqueous electrolyte secondary batteries face issues with cracking of the lithium silicate matrix around silicon particles during charge/discharge, leading to reduced current collecting efficiency and increased side reactions, which compromise cycle characteristics and gas generation.

Innovation Solution

Incorporating a lithium silicate phase with silicon particles and at least one element selected from rare-earth or alkaline-earth metals dispersed within the lithium silicate phase, which enhances structural stability and suppresses side reactions by reducing the area for gas generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If silicon particles are dispersed in a lithium silicate phase to achieve high theoretical capacity density, then energy density is improved, but cracking occurs in the matrix around silicon particles during charge/discharge, reducing current collecting efficiency and promoting side reactions

Engineering Contradiction:

Improveenergy densityVSAvoidcycle characteristics

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the lithium silicate phase by introducing specific metal elements (Mg, Ca, Sr, Ba, or their oxides/carbides/nitrides) to modify the matrix properties. This compositional parameter change increases the hardness and structural stability of the lithium silicate phase, preventing cracking during silicon expansion/contraction while maintaining high capacity density

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite material structure where silicon particles are dispersed within a modified lithium silicate phase matrix containing specific metal elements. This composite structure combines the high capacity advantage of silicon with the structural stability of the metal-element-reinforced lithium silicate matrix, resolving the contradiction between energy density and cycle characteristics

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If a metal compound such as zirconium oxide is dispersed in a lithium silicate phase to suppress cracking, then structural stability is improved, but the suppression is not sufficient and minute cracks still cause side reactions and gas generation

Engineering Contradiction:

Improvestructural stabilityVSAvoidgas generation

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The invention optimizes the hardness parameter of the lithium silicate phase by selecting specific metal elements (Mg, Ca, Sr, Ba) with appropriate atomic sizes and bonding characteristics. These elements increase the matrix hardness more effectively than zirconium oxide alone, creating a more rigid matrix that completely prevents crack formation and eliminates the source of gas-generating side reactions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses abundant, low-cost metal elements (Mg, Ca, Sr, Ba) that are more effective than expensive zirconium oxide for achieving the desired structural stability. These elements provide sufficient crack suppression at lower costs and with better performance, making the matrix more resistant to crack formation that would otherwise lead to gas generation

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If the lithium silicate phase matrix is made firm to suppress cracking, then current collecting efficiency is improved, but side reactions still occur through minute cracks, reducing charging/discharging efficiency

Engineering Contradiction:

Improvecurrent collecting efficiencyVSAvoidirreversible capacity

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention modifies the mechanical properties (hardness, rigidity) of the lithium silicate phase by incorporating specific metal elements. This parameter change creates a sufficiently firm matrix that eliminates minute cracks, preventing side reactions and reducing irreversible capacity loss while maintaining good current collecting efficiency through the stable, crack-free structure

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11271197B2Negative electrode material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Publication Date: 2022.03.08 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

Disclosed is a negative electrode material for a non-aqueous electrolyte secondary battery, including: a lithium silicate phase; silicon particles dispersed in the lithium silicate phase; and at least one element Me dispersed in the lithium silicate phase, and selected from the group consisting of a rare-earth element and an alkaline-earth metal. The composition of the lithium silicate phase is represented, for example, by the formula: Li2zSiO2+z, and satisfies 0<z<2, and the element Me is dispersed in the lithium silicate phase, for example, as an Me oxide.