Silicon-Carbon Composite Anode With Hardness Gradient Shells
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Solution Overview
Problem
Silicon anode materials in lithium-ion batteries face issues with low structural stability due to volume expansion during lithium ion intercalation, leading to fracture, capacity decay, and reduced lifespan, as well as inefficiencies in the solid electrolyte interphase (SEI) layer due to mechanical stress.
Innovation Solution
A silicon carbon composite anode material is developed, featuring a hollow core with multiple hard coating layers and a soft coating layer, where nano-silicon particles are packed, providing structural stability and preventing fracture through a hardness gradient, thereby minimizing volume expansion and maintaining electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon anode material is used to increase energy density, then capacity is improved, but structural stability deteriorates due to volume expansion
Solution Approach 1:
The patent embeds silicon particles inside a porous carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nesting approach allows silicon to expand and contract during lithium ion intercalation while being constrained by the carbon matrix, preventing structural collapse and maintaining stability throughout charge-discharge cycles.
Solution Approach 2:
The patent creates a composite anode material combining silicon and carbon in a specific architecture. The composite structure leverages silicon's high capacity characteristics while utilizing carbon's structural stability and conductivity, achieving a synergistic effect that resolves the contradiction between capacity and stability.
2Quantity of substance
If silicon anode material undergoes volume expansion during lithiation, then lithium ion storage capacity is improved, but mechanical strength deteriorates leading to fracture
Solution Approach 1:
The patent employs a porous carbon matrix that acts as a flexible confining structure around silicon particles. This carbon shell can accommodate volume changes through elastic deformation and structural reconfiguration, maintaining mechanical integrity while allowing silicon to expand during lithiation without fracturing.
Solution Approach 2:
The patent utilizes a porous carbon matrix structure that provides void spaces for silicon expansion. The porous architecture allows the carbon structure to deform and reconfigure during volume changes, absorbing mechanical stress and preventing fracture while maintaining structural continuity and strength.
3Quantity of substance
If silicon particles are used to increase capacity, then energy density is improved, but reliability deteriorates due to pulverization and electrical separation
Solution Approach 1:
The patent creates a composite structure where silicon particles are embedded in a conductive carbon matrix. This composite architecture ensures continuous electrical contact between silicon and current collector throughout cycling, preventing electrical separation and maintaining reliable electron transport pathways even as silicon undergoes repeated expansion and contraction.
Solution Approach 2:
The nested configuration of silicon within porous carbon provides mechanical constraint that prevents pulverization. The carbon matrix acts as a protective cage that maintains structural integrity during repeated charge-discharge cycles, ensuring long-term reliability while preserving high energy density.
4Stability of the object's composition
If hard coating layers are added to prevent fracture, then structural stability is improved, but device complexity increases
Solution Approach 1:
The patent employs a porous carbon matrix structure that provides structural stability through its three-dimensional network architecture rather than through multiple dense coating layers. The porous structure inherently accommodates volume changes while maintaining integrity, achieving stability with a single integrated structure rather than multiple complex coatings.
Solution Approach 2:
The patent uses a composite carbon-silicon structure where the carbon phase provides structural stability and the silicon phase provides capacity. This single composite architecture replaces the need for separate hard coating layers, simplifying the overall structure while maintaining structural stability during lithiation.
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 silicon carbon composite anode material enhances durability, prevents capacity reduction, and maintains high energy density and lifespan by effectively managing volume expansion and SEI layer integrity.
Implementation Method 1
silicon (Si) allows a large volume expansion of 4 to 5 times through reaction of 4.4 lithium ions per silicon to form Li22Si5 alloys
Implementation Method 2
each of the hollow core and the hard coating layers has a higher hardness than the soft coating layer, and the anode material has a hardness sequentially increasing from the hollow core to the outermost hard coating layer
Implementation Method 3
generation of greenhouse gas including carbon dioxide and the like and global temperature rise due to the use of fossil energy
Data Source
AI summary
Disclosed are a silicon carbon composite anode material, a method of preparing the same, and a secondary battery including the same. In one embodiment, the anode material includes: a hollow core having a hollow portion therein; one or more hard coating layers spaced apart from each other in an outward direction from the hollow core; nano-silicon particles packed in the hollow portion and in a separation space defined between the hard coating layers; and a soft coating layer formed on an outer circumferential surface of an outermost hard coating layer, wherein each of the hollow core and the hard coating layers has a higher hardness than the soft coating layer, and the anode material has a hardness sequentially increasing from the hollow core to the outermost hard coating layer.