Silicon-Carbon Composite Anode With Hardness Gradient for Fracture Control
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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, comprising a hollow core with multiple hard coating layers and a soft coating layer, where nano-silicon particles are packed within the hollow core and between the hard coating layers, creating a hardness gradient that prevents fracture and optimizes energy capacity.
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 hollow carbon sphere structure, creating a nested configuration where the silicon is contained within the carbon matrix. This nesting approach allows the silicon to expand into the hollow space during lithiation without causing structural failure, thereby maintaining both high capacity and structural stability.
Solution Approach 2:
The patent employs a carbon coating layer that forms a flexible shell around the silicon particles. This carbon shell can accommodate the volume expansion of silicon during charging cycles while maintaining the overall structural integrity. The flexible nature of the carbon shell prevents fracture and pulverization of the silicon anode material.
2Quantity of substance
If silicon particles are packed densely to increase capacity, then energy capacity is improved, but fracture resistance deteriorates
Solution Approach 1:
The patent creates a non-uniform distribution of silicon particles within the hollow carbon sphere, with higher concentration at certain regions and lower at others. This local quality variation allows dense packing in regions where expansion is accommodated by the hollow space, while maintaining fracture resistance in regions where the carbon matrix provides structural support.
Solution Approach 2:
The patent creates a composite structure combining silicon particles with a carbon matrix framework. The composite material leverages the high capacity of silicon while the carbon matrix provides mechanical strength and fracture resistance. The synergistic combination allows both high energy capacity and structural durability.
3Stability of the object's composition
If multiple coating layers are added to prevent fracture, then structural stability is improved, but device complexity increases
Solution Approach 1:
The patent divides the protective structure into multiple functional layers: an inner carbon coating layer directly contacting the silicon particles, and an outer hollow carbon sphere shell. This segmentation allows each layer to perform its specific function - the inner layer prevents direct silicon fracture while the outer shell provides structural support and accommodates expansion - resulting in a relatively simple yet effective overall structure.
Data Source
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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.