Layered Silicon-Graphite Anode for Adhesion and Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face low energy density due to the low theoretical capacity of graphite and suffer from deteriorated battery life characteristics due to large volume expansion of Si-based materials, along with increased interfacial resistance and reduced electrode adhesive strength.
Innovation Solution
A negative electrode structure is implemented with a silicon-based active material in a lower layer and a graphite-based active material with a carbon coating in an upper layer, utilizing carbon nanotubes to prevent isolation and maintain electrical conductivity, while optimizing the weight ratio and binder content to enhance adhesive strength and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Si-based material is used to increase theoretical capacity, then energy density is improved, but volume expansion occurs during charge and discharge
Solution Approach 1:
The Si-based active material is encapsulated within a graphite-based active material matrix, creating a nested structure where the high-capacity Si material is protected by the volume-stable graphite shell. This allows the Si material to expand and contract during charge-discharge cycles without causing macroscopic volume changes to the electrode.
Solution Approach 2:
The invention creates a composite active material system combining Si-based material (for high capacity) with graphite-based material (for volume stability). The composite structure leverages the complementary properties of both materials to achieve high energy density while maintaining dimensional stability during electrochemical cycling.
2Use of energy by moving object
If Si-based material is used to increase capacity, then energy density is improved, but battery life characteristic deteriorates
Solution Approach 1:
The Si-based active material is encapsulated within a graphite-based active material matrix, creating a nested structure where the high-capacity Si material is protected by the volume-stable graphite shell. This allows the Si material to expand and contract during charge-discharge cycles without causing macroscopic volume changes to the electrode.
Solution Approach 2:
The invention creates a composite active material system combining Si-based material (for high capacity) with graphite-based material (for volume stability). The composite structure leverages the complementary properties of both materials to achieve high energy density while maintaining dimensional stability during electrochemical cycling.
3Use of energy by moving object
If Si-based material is used to increase capacity, then energy density is improved, but interfacial resistance increases
Solution Approach 1:
The graphite-based active material serves as an intermediary layer between the Si-based material and the electrolyte. This intermediate graphite shell provides stable Li-ion insertion/extraction pathways, reducing direct side reactions between Si and electrolyte, thereby lowering interfacial resistance while preserving the high capacity benefits of Si.
4Use of energy by moving object
If Si-based material is used to increase capacity, then energy density is improved, but electrode adhesive strength is reduced
Solution Approach 1:
The Si-based active material is encapsulated within a graphite-based active material matrix, creating a nested structure where the high-capacity Si material is protected by the volume-stable graphite shell. This allows the Si material to expand and contract during charge-discharge cycles without causing macroscopic volume changes to the electrode.
Solution Approach 2:
The invention creates a composite active material system combining Si-based material (for high capacity) with graphite-based material (for volume stability). The composite structure leverages the complementary properties of both materials to achieve high energy density while maintaining dimensional stability during electrochemical cycling.
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
This configuration improves the adhesive strength between the electrode and current collector, maintains electrical conductivity, and enhances the energy density and life characteristics of the battery by minimizing side reactions and volume expansion effects.
Implementation Method 1
the first graphite-based active material has a carbon coating layer on at least a part of a surface
Implementation Method 2
By using a CNT conductive material for preventing isolation of an active material due to volume expansion of the silicon-based material, a capacity of the entire negative electrode is secured and also an electrochemical path is maintained
Implementation Method 3
a negative electrode for a lithium secondary battery includes: a current collector; a first negative electrode active material layer disposed on the current collector and including a silicon-based active material, a first graphite-based active material
Data Source
AI summary
Provided are a negative electrode for a lithium secondary negative electrode battery including: a current collector; a first negative electrode active material layer disposed on the current collector and including a silicon-based active material, a first graphite-based active material, and a linear conductive material; and a second negative electrode active material layer disposed on the first negative electrode active material layer and including a second graphite-based active material. The first graphite-based active material has a carbon coating layer on at least a part of a surface. Also provided is a lithium secondary battery including the negative electrode.