Silicon Negative Active Material for Lithium Battery Volume Expansion

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Solution Overview

Problem

Rechargeable lithium batteries face challenges with the cycle-life characteristics and volume expansion of negative active materials, particularly silicon-based ones, which affect the battery's capacity and durability due to severe volume changes during charging and discharging.

Innovation Solution

A composite negative active material is developed, comprising silicon particles, metal particles (such as Ni, Ti, or Sn), and a combination of hard and soft amorphous carbon, where the metal particles are positioned on the surface of the silicon particles, and the amorphous carbon surrounds them, improving electrical conductivity and strength, and reducing volume expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon particles are used as negative active material, then battery capacity is improved, but volume expansion occurs during charging and discharging

Engineering Contradiction:

Improvebattery capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

Metal particles are positioned on the surface of silicon particles, and amorphous carbon surrounds the composite, creating a nested structure where each layer protects and supports the inner components during volume changes

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

A composite structure combining silicon particles, metal particles (Ni, Ti, or Sn), and amorphous carbon is created, where each material component addresses specific issues: silicon provides capacity, metal particles suppress volume expansion, and carbon provides conductivity and structural stability

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon-based negative active material is used, then battery capacity increases, but cycle-life characteristics deteriorate

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle-life characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The composite structure combines silicon with metal particles and amorphous carbon, where the carbon matrix maintains structural integrity over cycles while allowing silicon to expand and contract, thus preserving cycle-life characteristics

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The amorphous carbon layer acts as a flexible shell surrounding the silicon-metal composite, accommodating volume changes during charging and discharging while maintaining electrical contact and preventing structural degradation

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If amorphous carbon surrounds the composite, then electrical conductivity and strength are improved, but device complexity increases

Engineering Contradiction:

Improveelectrical conductivity and strengthVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The amorphous carbon layer performs multiple functions simultaneously: it provides electrical conductivity, mechanical strength, structural stability, and protection against volume expansion, eliminating the need for separate components for each function

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11594722B2Negative active material for rechargeable lithium battery, and rechargeable lithium battery including same

Publication Date: 2023.02.28 SAMSUNG SDI CO LTD

AI summary

A negative active material for a rechargeable lithium battery and a rechargeable lithium battery, the negative active material including a composite including silicon particles, metal particles, and a first amorphous carbon; and a second amorphous carbon surrounding on the composite.