Silane-Treated Silicon Negative Active Material for Lithium Batteries
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Solution Overview
Problem
Graphite-based negative active materials in lithium rechargeable batteries have limited lithium occlusion capacity and exhibit reduced cycle-life due to expansion and shrinkage during charge and discharge, necessitating the development of alternative high-capacity metal-based materials.
Innovation Solution
A negative electrode comprising a current collector with a negative active material layer formed from Si, SiOx, or Si-Q alloys, where the active material is treated with a silane coupling agent and a polymer binder, enhancing cycle-life characteristics through improved adherence and network formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal-based negative active material (Si, SiOx) is used to increase lithium occlusion capacity, then capacity is improved, but cycle-life is reduced due to large expansion and shrinkage during charge and discharge
Solution Approach 1:
The patent applies composite materials by combining metal-based active material (Si or SiOx) with a polymer coating layer formed from silane coupling agent and monomer/oligomer. This composite structure allows the inner metal core to provide high lithium occlusion capacity while the outer polymer shell accommodates expansion/shrinkage and maintains structural integrity during cycling, thereby resolving the contradiction between high capacity and long cycle-life
Solution Approach 2:
The patent changes the physical and chemical parameters of the active material surface by treating Si or SiOx with silane coupling agent followed by polymerization. This surface modification alters the mechanical and chemical properties of the material, creating a flexible polymer coating that can withstand volume changes during charge-discharge cycles, thus improving cycle-life while maintaining high capacity
2Reliability
If graphite-based negative active material is used to ensure long cycle-life, then cycle-life is improved, but lithium occlusion capacity is limited to about 372mAh/g
Solution Approach 1:
The patent creates a composite material system that combines the advantages of both graphite and metal-based materials. The core uses metal-based active material (Si/SiOx) for high capacity, while the polymer coating layer provides the structural stability and adhesion characteristics similar to graphite, achieving both high capacity and long cycle-life simultaneously
3Reliability
If silane coupling agent and polymer binder are applied to metal-based active material, then cycle-life and adherence are improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-treating the metal-based active material surface with silane coupling agent before polymerization. This preliminary surface modification creates reactive groups that facilitate subsequent polymer coating, ensuring strong adhesion and stable cycle-life while organizing the manufacturing process into sequential, manageable steps
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 proposed solution significantly improves the cycle-life characteristics of lithium rechargeable batteries by stabilizing the active material layer, maintaining electrode adherence, and enhancing the battery's performance.
Implementation Method 1
mixing a silane coupling agent, a solvent, and water to produce a hydrolysis product
Implementation Method 2
adding an active material to the hydrolysis product to effect a condensation reaction and to produce a condensation product
Implementation Method 3
polymerizing the mixture on the current collector
Data Source
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AI summary
Disclosed are a negative active material of a rechargeable lithium battery and a rechargeable lithium battery including a negative electrode, and the negative electrode includes a negative active material layer including a negative active material represented by the following Chemical Formula 1. X-Ra-Rb In Chemical Formula 1, X is an active material which comprises a metal and whose functional group has been reacted with a silane coupling agent, Ra is a residual group from a silane coupling agent, and Rb is a polymer including a first repeating unit represented by the following Chemical Formula 2a. In Chemical Formula 2a, R10 to R13 are the same or different, and are hydrogen; or a substituted or unsubstituted C1 to C5 alkyl group, and n1 is an integer ranging from 1 to 100000 and * is a chemical bond.