Yolk-Shell Silicon-Carbon Anode Structure for Volume Expansion
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Solution Overview
Problem
Silicon-based anode active materials in secondary batteries suffer from significant volume expansion during charge and discharge cycles, leading to mechanical instability and deterioration in battery performance.
Innovation Solution
A yolk-shell-structured silicon-carbon composite is prepared using atomic layer deposition to form a uniform inorganic layer on silicon particles, followed by etching to create a carbon thin film with controlled voids, forming a yolk-shell structure that accommodates volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon particles are used as anode active materials to improve capacity, then energy density is improved, but mechanical stability deteriorates due to volume expansion of up to 300% during charge and discharge
Solution Approach 1:
The silicon particle is segmented into a yolk (inner silicon core) and shell (outer porous silicon layer) structure, allowing the inner core to expand independently while the outer shell provides mechanical support and accommodates volume changes through its porous architecture
Solution Approach 2:
A flexible carbon thin film is formed on the surface of the yolk-shell structured silicon particles, providing mechanical flexibility to accommodate volume expansion while maintaining structural integrity and preventing particle fracture during charge-discharge cycles
2Strength
If a carbon thin film is formed on silicon particles to maintain structural integrity, then mechanical stability is improved, but peeling of the carbon film occurs due to volume expansion
Solution Approach 1:
The outer shell is designed with a porous structure that can expand and contract to accommodate silicon volume changes during lithiation and delithiation, preventing stress buildup that would cause carbon film peeling while maintaining structural integrity
Solution Approach 2:
The porous shell structure is pre-designed to accommodate expected volume expansion before it occurs, providing a cushioning effect that prevents stress concentration and subsequent carbon film detachment during actual charge-discharge operations
3Manufacturing precision
If strong acid etching is used to create the yolk-shell structure, then manufacturing precision is improved, but environmental friendliness deteriorates due to use of hydrofluoric acid
Solution Approach 1:
A sacrificial inorganic layer is used as a temporary, disposable structure during manufacturing that can be easily removed by mild etching, replacing the need for harsh hydrofluoric acid while maintaining manufacturing precision for creating uniform yolk-shell structures
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 yolk-shell structure suppresses peeling of the carbon thin film, enhancing battery performance and lifespan by accommodating volume changes and maintaining electrical conductivity.
Implementation Method 1
forming an inorganic layer on the silicon particles by atomic layer deposition (ALD)
Implementation Method 2
removing at least a portion of the inorganic layer from the silicon-inorganic layer-carbon composite
Data Source
Figure 1(a)~2(b)
Figure 3~4(c)
Figure 5~6
AI summary
The present invention relates to a yolk-shell-structured silicon-carbon composite, a preparation method therefor, and an anode active material comprising same. The yolk-shell-structured silicon-carbon composite according to an embodiment of the present invention can be prepared without using strong acids, and can have uniform voids formed using, as a sacrificial layer, an inorganic layer with uniform thickness so as to accommodate, when used as an anode active material , silicon volume expansion, and thus can suppress peeling off, caused thereby, of the outermost carbon thin film. As a result, deterioration in battery performance and lifespan can be suppressed.