Porous Silicon-Carbon Anode Coating for Crack-Resistant Li Batteries
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Solution Overview
Problem
The silicon-carbon composite anode active material in lithium secondary batteries experiences significant volume expansion differences during charging and discharging, leading to cracks and exposure to electrolyte, which degrades capacity and life-span properties.
Innovation Solution
A composite particle structure is developed with a carbon-based particle containing pores, a silicon-containing coating layer inside and/or on the surface, and a surface oxide layer containing silicon oxide, with controlled oxidation numbers and oxygen content ratios to prevent cracking and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-carbon composite anode active material is used to increase capacity, then the energy density is improved, but the volume expansion difference causes cracks and exposure to electrolyte during repeated charging and discharging
Solution Approach 1:
The patent embeds silicon particles inside porous carbon particles, creating a nested structure where the silicon is contained within the carbon matrix. This nested configuration allows the carbon to constrain the silicon's volume expansion while still accommodating the capacity benefits of silicon, thereby preventing cracks and maintaining structural integrity during charging and discharging cycles.
Solution Approach 2:
The patent employs porous carbon particles as the host matrix for silicon. The porous structure provides void spaces that can accommodate the volume expansion of silicon during lithiation, preventing mechanical stress and crack formation. The pores act as buffer zones that absorb expansion forces, maintaining the overall structural integrity of the anode material.
2Quantity of substance
If the silicon content is increased to improve capacity properties, then the energy density is improved, but the cracks and electrolyte exposure degrade life-span properties
Solution Approach 1:
By nesting silicon particles within porous carbon particles, the patent creates a protective configuration where the carbon matrix surrounds and protects the silicon. This nested structure prevents direct contact between silicon and electrolyte, reducing side reactions and maintaining life-span properties even with high silicon content that improves capacity.
Solution Approach 2:
The porous carbon structure provides a controlled environment for silicon, where the pores accommodate volume changes without compromising the overall structure. This porous configuration allows the material to maintain structural integrity over many cycles, thereby extending life-span while preserving the high capacity benefits of increased silicon content.
3Stability of the object's composition
If a silicon-containing coating layer is formed inside pores and/or on surface to suppress cracks, then the structural stability is improved, but the oxidation number control requires precise manufacturing
Solution Approach 1:
The patent employs oxidation treatments that modify the silicon surface to form a silicon oxide layer with controlled oxidation numbers. By adjusting oxidation parameters such as temperature, time, and oxygen exposure, the patent achieves the desired oxidation number range (0.6 or less) that balances structural stability with manufacturing feasibility. This parameter control approach transforms the manufacturing challenge into a controllable process variable.
Solution Approach 2:
The patent creates a composite structure with multiple layers: porous carbon particle, silicon-containing coating layer, and surface oxide layer. This composite material approach allows each layer to perform its specific function while working together to achieve overall structural stability. The oxidation number control becomes part of the composite material design rather than a standalone manufacturing challenge.
4Reliability
If a surface oxide layer is formed on the silicon-containing coating layer to prevent side reactions, then the chemical stability is improved, but the device complexity increases
Solution Approach 1:
The patent creates a nested multi-layer structure where the surface oxide layer is formed on the silicon-containing coating layer, which itself is inside the porous carbon particle. This nested configuration provides chemical stability through the oxide layer while organizing the complexity in a hierarchical manner that simplifies the overall device architecture. Each nested layer serves a specific function, making the complexity manageable and purposeful.
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 particle structure effectively mitigates volume expansion, reduces cracks, and suppresses side reactions, thereby improving the capacity and life-span properties of the lithium secondary battery.
Implementation Method 1
a surface oxide layer formed on the silicon-containing coating layer. The surface oxide layer contains silicon oxide
Data Source
Figure 1
Figure 2~3
AI summary
An anode active material for a secondary battery according to an embodiment of the present invention includes a plurality of a composite particle. The composite particle includes a carbon-based particle containing pores therein, a silicon-containing coating layer formed at an inside of the pores and/or on a surface of the carbon-based particle, and a surface oxide layer formed on the silicon-containing coating layer. The surface oxide layer contains silicon oxide. A silicon oxidation number ratio defined by Equation 1 of the composite particle is 0.6 or less.