Double-Layer Composite Anode for Adhesion and Volume Expansion Control
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high energy density due to poor adhesion between carbon-based materials like graphite and lithiophilic materials like silicon, leading to detachment and decreased charge/discharge efficiency, and silicon's large volume expansion during charging and discharging.
Innovation Solution
A composite anode active material is developed with a core of carbon-based particles, a buffer layer of carbide, and a coating layer of lithiophilic material, enhancing adhesion and suppressing silicon crystallization through a controlled chemical vapor deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the surface of carbon-based particles is coated with a coating layer having high energy density, then the energy density of the battery is improved, but the adhesion between the carbon-based particles and the coating layer is poor, leading to detachment during charging and discharging
Solution Approach 1:
An intermediate layer comprising silicon carbide is introduced between the carbon-based particles and the lithiophilic material coating layer. This intermediate layer acts as a mediator that enhances adhesion between the carbon-based particles and the lithiophilic material, preventing detachment during charging and discharging while maintaining high energy density.
Solution Approach 2:
A composite structure is formed with multiple layers: carbon-based particles as the core, silicon carbide intermediate layer, and lithiophilic material coating layer. This composite material structure combines the advantages of each component to achieve both high adhesion and high energy density.
2Use of energy by moving object
If silicon is used as a substitute for graphite to increase theoretical capacity, then the energy density is improved, but the volume change rate reaches up to 300% during charging and discharging
Solution Approach 1:
The crystallite size of the lithiophilic material is controlled within a specific range of 2 nm to 11 nm. By changing this critical parameter, the volume expansion during charging is suppressed while maintaining high theoretical capacity. This parameter optimization allows silicon to function effectively without excessive volume change.
Solution Approach 2:
The lithiophilic material is distributed in a controlled manner with specific crystallite size throughout the coating layer, creating local structural characteristics that accommodate volume changes during lithiation and delithiation processes.
3Ease of manufacture
If the surface of the carbon material is directly coated with the lithiophilic material using chemical vapor deposition, then the coating process is simplified, but a non-uniform coating layer is formed
Solution Approach 1:
The silicon carbide intermediate layer serves as a mediator that facilitates uniform deposition of the lithiophilic material. This intermediate layer provides a suitable surface for controlled chemical vapor deposition, ensuring uniform coating formation while maintaining process simplicity.
4Reliability
If silicon undergoes structural change from amorphous to crystalline during charging, then the lithiophilic property is improved, but large volume expansion occurs
Solution Approach 1:
The crystallite size of the lithiophilic material is precisely controlled within 2 nm to 11 nm to prevent complete crystallization during charging. This parameter control maintains lithiophilic properties while suppressing excessive volume expansion that would occur with full crystallization.
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 anode active material improves charge/discharge efficiency and lifespan by preventing interfacial detachment and uniform volume expansion, maintaining high energy density without crystallization of silicon.
Implementation Method 1
coating the surface of carbon-based particles with a coating layer having high energy density... using chemical vapor deposition
Implementation Method 2
adhesion between graphite and silicon is poor, and thus detachment may occur easily... enhancing adhesion therebetween
Implementation Method 3
silicon has a volume change rate of up to 300% when charging and discharging the battery... suppressing crystallization of silicon during charging
Data Source
AI summary
A composite anode active material including a double layer and a method of manufacturing the same are disclosed. In coating the surface of carbon-based particles with a coating layer having high energy density, a buffer layer is formed between the carbon-based particles and the coating layer. Charge/discharge efficiency of an all-solid-state battery including the anode active material is thereby improved. The anode active material has a core including carbon-based particles, a buffer layer covering at least a portion of a surface of the core and including a carbide, and a coating layer covering at least a portion of a surface of the buffer layer and including a lithiophilic material.