Silicon-Carbon Anode Composition With Closed-Pore Buffering

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Solution Overview

Problem

Silicon-based negative electrode active materials for rechargeable lithium batteries experience significant volume expansion and contraction during charging and discharging, leading to electrolyte depletion, oxide film growth, and increased resistance, which degrade cycle life and rate characteristics.

Innovation Solution

A composite negative electrode active material comprising silicon and amorphous carbon with a controlled closed pore increase rate of 20% to 100% is developed, mitigating volume expansion and contraction by forming a closed pore buffer, thereby reducing cracking and improving electrical conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but volume expansion during charging and discharging causes electrolyte depletion and oxide film growth

Engineering Contradiction:

Improveenergy densityVSAvoidcycle life

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

An amorphous carbon coating layer is formed on the surface of silicon particles to create a flexible protective shell. This carbon layer accommodates volume expansion and contraction during lithium intercalation and deintercalation, preventing direct contact between silicon and electrolyte, thereby reducing electrolyte depletion and oxide film growth while maintaining high capacity

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

A composite structure is created by combining silicon particles with amorphous carbon material. The silicon provides high capacity while the carbon matrix provides structural stability and conductivity. This composite approach allows the silicon to expand and contract without compromising the overall electrode integrity, resolving the contradiction between high energy density and cycle life

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but volume expansion causes increased resistance due to low conductivity

Engineering Contradiction:

Improveenergy densityVSAvoidrate characteristics

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The composite of silicon and amorphous carbon combines the high capacity advantage of silicon with the excellent conductivity of carbon. The carbon matrix provides continuous conductive pathways that maintain electrical conductivity even during volume changes, improving rate characteristics while preserving high energy density

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If silicon-based negative electrode active material is used to increase capacity, then energy density is improved, but volume expansion and contraction cause cracking and degradation

Engineering Contradiction:

Improveenergy densityVSAvoidstructural integrity

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The amorphous carbon coating layer acts as a flexible shell that can accommodate volume expansion and contraction of the silicon core. This flexible coating prevents cracking of the silicon particles and maintains structural integrity during repeated charging and discharging cycles, resolving the contradiction between high capacity and structural strength

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The carbon coating layer is formed beforehand to provide a cushioning effect during volume changes. This pre-formed protective layer absorbs mechanical stress and prevents direct mechanical failure of the silicon structure, maintaining structural integrity while enabling high capacity operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 composite material provides enhanced lifetime and rate characteristics by absorbing volume changes, minimizing electrolyte depletion, and maintaining electrical conductivity, while maintaining high energy density.

Implementation Method 1

The silicon-based negative electrode active material may have a change in volume due to expansion during charging and discharging

Methodology Applied

Scientific EffectVolume expansion and contraction: Thermal Expansion

Implementation Method 2

an increase in resistance due to low conductivity if silicon is used as a negative electrode active material

Methodology Applied

Scientific EffectElectrical conductivity: Conduction (electrical)

Data Source

PatentUS20250333315A1Negative active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same

Publication Date: 2025.10.30 SAMSUNG SDI CO LTD

AI summary

The present disclosure relates to a negative electrode active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery including the same. The negative electrode active material for a rechargeable lithium battery includes a composite of silicon and amorphous carbon, and a closed pore increase rate according to Equation 1 is in a range of 20% to 100%.Closed⁢ pore⁢ increase⁢ rate=(A-B)×1⁢0⁢0Equation⁢ 1in Equation 1, A denotes a sum of an increase rate of closed pores and an increase rate of open pores of the negative electrode active material according to a first measurement method, and B denotes the increase rate of open pores of the negative electrode active material according to a second measurement method.