Composite Graphite Particles with Dispersed Metal Alloying Agents

Solution Overview

Problem

Existing composite Si-graphite particles for nonaqueous secondary batteries face issues with metal particle aggregation and low dispersion, leading to cycle deterioration and reduced charge-discharge efficiency due to weak bindability and volume expansion during charging and discharging.

Innovation Solution

The development of composite graphite particles with a high degree of metal particle dispersion, where the metal particles are uniformly distributed within the graphite structure, reducing the likelihood of aggregation and enhancing charge-discharge efficiency by minimizing direct contact with the electrolyte and absorbing volume expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If metal particles are added to increase capacity, then battery capacity is improved, but metal particles aggregate and disperse poorly leading to cycle deterioration

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by creating regions with different metal particle concentrations within the graphite particles. The metal particles are selectively distributed in specific zones rather than uniformly throughout, allowing high capacity regions to coexist with regions that maintain structural integrity and prevent aggregation. This localized distribution strategy enables the battery to achieve high capacity while maintaining good cycle characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining graphite with metal particles to create composite graphite particles. This composite structure allows the graphite matrix to provide structural stability and prevent metal particle aggregation, while the metal particles contribute high capacity. The synergistic combination resolves the contradiction between achieving high capacity through metal addition and maintaining cycle reliability by preventing metal particle aggregation.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If metal particles are added to increase capacity, then battery capacity is improved, but charge-discharge efficiency decreases due to volume expansion

Engineering Contradiction:

Improvebattery capacityVSAvoidcharge-discharge efficiency

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The patent applies local quality by creating regions with different metal particle concentrations within the graphite particles. The metal particles are selectively distributed in specific zones rather than uniformly throughout, allowing high capacity regions to coexist with regions that maintain structural integrity and prevent aggregation. This localized distribution strategy enables the battery to achieve high capacity while maintaining good cycle characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining graphite with metal particles to create composite graphite particles. This composite structure allows the graphite matrix to provide structural stability and prevent metal particle aggregation, while the metal particles contribute high capacity. The synergistic combination resolves the contradiction between achieving high capacity through metal addition and maintaining cycle reliability by preventing metal particle aggregation.

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 results in a nonaqueous secondary battery with improved high capacity, high charge-discharge efficiency, and superior discharge characteristics by maintaining the integrity of the composite particles and reducing irreversible Li ion loss.

Implementation Method 1

metal particles capable of alloying with Li

Methodology Applied

Scientific EffectAlloying: Solid Solution Strengthening

Implementation Method 2

graphite and metal particles capable of alloying with Li

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Data Source

PatentUS11605810B2Method to prepare composite graphite particles for nonaqueous secondary battery negative electrode, active material for nonaqueous secondary battery negative electrode, and nonaqueous secondary battery

Publication Date: 2023.03.14 MITSUBISHI CHEM CORP

AI summary

The invention relates to composite graphite particles for a nonaqueous secondary battery negative electrode containing graphite (A) and metal particles (B) capable of alloying with Li, wherein the degree of dispersion of the metal particles (B) in the composite graphite particles is 0.78 or more and the internal void fraction of the composite graphite particles is 3% or more and 40% or less.