Porous Silicon-Carbon Anode Material for Expansion-Induced Crack Control
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Solution Overview
Problem
Lithium secondary batteries face issues with cracks in the anode active material due to volume expansion ratios between silicon and carbon, leading to reduced lifespan and power properties.
Innovation Solution
An anode active material is developed using carbon-based particles with pores of 20 nm or less, where silicon is deposited inside or on the surface, maintaining a crystallite size of 7 nm or less, and an amorphous structure to reduce volume expansion and enhance structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is combined with carbon to form silicon-carbon composite anode active material, then capacity is improved, but cracks occur due to volume expansion ratio difference
Solution Approach 1:
Silicon particles are embedded within the internal pores of carbon-based particles, creating a nested structure where silicon is contained within the carbon matrix. This prevents silicon from expanding outward and causing cracks, while still allowing lithium insertion. The nested configuration resolves the contradiction by containing the volume expansion within the carbon structure.
Solution Approach 2:
The carbon-based particle contains internal pores with specific pore sizes that accommodate silicon particles. The porous structure of carbon provides space for silicon volume expansion during lithiation, preventing crack formation. This resolves the contradiction by providing a buffer volume within the carbon matrix that absorbs expansion stresses.
2Volume of stationary object
If silicon crystallite size is reduced to 7 nm or less, then volume expansion is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges: silicon crystallite size of 7 nm or less, pore size of 20 nm or less, and specific surface area ranges. By controlling these parameters within defined boundaries, the invention achieves reduced volume expansion while maintaining manufacturability. The parameter optimization resolves the contradiction by finding the optimal range that satisfies both performance and manufacturing requirements.
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
This approach prevents cracks and maintains high-capacity properties, improving the lifespan and power efficiency of lithium secondary batteries by reducing volume expansion and increasing the amorphous structure of silicon.
Implementation Method 1
silicon formed at an inside of the pores of the carbon-based particle or on the surface of the carbon-based particle
Implementation Method 2
silicon formed at an inside of the pores of the carbon-based particle or on the surface of the carbon-based particle
Implementation Method 3
Silicon has an amorphous structure or a crystallite size of silicon measured by an X-ray diffraction (XRD) analysis is 7 nm or less
Implementation Method 4
a crystallite size of silicon measured by an X-ray diffraction (XRD) analysis is 7 nm or less
Data Source
AI summary
An anode active material for a lithium secondary battery and a lithium secondary battery are provided. The anode active material includes a carbon-based particle including pores formed in at least one of an inside of the particle and a surface of the particle and having a pore size of the carbon-based particle is 20 nm or less, and silicon formed at an inside of the pores of the carbon-based particle or on the surface of the carbon-based particle. Silicon has an amorphous structure or a crystallite size of silicon measured by an XRD analysis is 7 nm or less. Difference between volume expansion ratios of carbon and silicon can be reduced to improve life-span property of the secondary battery.