Silicon Nitride Composite Anode Material for Capacity Retention

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Solution Overview

Problem

Silicon compounds in secondary batteries, such as silicate, tend to be eroded by side reactions, leading to capacity degradation due to the generation of hydrogen fluoride and subsequent impurity deposition at the negative electrode.

Innovation Solution

Incorporating a silicon nitride phase into the silicon compound phase of the negative electrode active material, which includes a silicon oxide or silicate phase, dispersed in a sea-island structure to enhance durability and capacity retention by mitigating erosion and stress from lithium ion storage and release.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based active material is used to achieve high theoretical capacity density, then energy density is improved, but side reactions with hydrogen fluoride erode the material causing impurity deposition and capacity degradation

Engineering Contradiction:

Improvecapacity densityVSAvoidcapacity retention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The silicon nitride phase acts as an intermediary protective component within the composite structure. It does not directly participate in lithium ion storage but serves to protect the silicon-based active material from erosion by hydrogen fluoride. This intermediary phase prevents harmful side reactions while allowing the silicon phase to maintain its high capacity density function, thus resolving the contradiction between achieving high capacity density and maintaining capacity retention.

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 introduction of a silicon nitride phase improves the durability of the silicon compound phase, resulting in enhanced charge and discharge cycle characteristics and increased capacity retention in secondary batteries.

Implementation Method 1

use of a material containing silicon capable of being alloyed with lithium

Methodology Applied

Scientific EffectAlloying:

Implementation Method 2

the silicon compound phase is eroded gradually by side reactions in the battery. For example, in a secondary battery having a nonaqueous electrolyte, hydrogen fluoride (HF) generates. Hydrogen fluoride goes through side reactions with the silicate phase

Methodology Applied

Scientific EffectChemical resistance:

Implementation Method 3

The silicate phase eases the stress from expansion and contraction of the silicon phase involved with charge and discharge

Methodology Applied

Scientific EffectExpansion and contraction: Thermal Expansion

Data Source

PatentUS20240363847A1Negative electrode active material for secondary batteries, and secondary battery

Publication Date: 2024.10.31 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A negative electrode active material for a secondary battery includes Si-containing particles, wherein the Si-containing particles include a silicon compound phase, a silicon phase dispersed in the silicon compound phase, and a silicon nitride phase dispersed in the silicon. compound phase, and the silicon compound phase is at least one of a silicon oxide phase and a silicate phase.