Porous Silicon-Carbon Anode Material to Prevent Expansion Cracks
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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 is deposited inside the pores of carbon-based particles, creating a nested structure where silicon is contained within the carbon matrix. This nesting approach allows silicon to expand within the confined pore space while the carbon shell maintains structural integrity and prevents crack propagation.
Solution Approach 2:
The invention utilizes carbon-based particles with controlled pore sizes (20 nm or less) to accommodate silicon. The porous structure provides expansion space for silicon while maintaining overall structural stability, preventing cracks during charging and discharging cycles.
2Ease of manufacture
If silicon is deposited with large crystallite size, then manufacturing is easier, but power property and lifespan are reduced
Solution Approach 1:
The invention controls the crystallite size of silicon to 7 nm or less by adjusting deposition parameters such as temperature, pressure, and precursor concentration. This parameter control achieves fine-grained silicon structures that provide both adequate manufacturing feasibility and superior battery lifespan through reduced volume expansion and improved structural stability.
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 configuration prevents cracks, maintains high-capacity properties, and improves the lifespan of lithium secondary batteries by reducing volume expansion and increasing the amorphous structure stability.
Implementation Method 1
a silicon-based compound gas is injected to the carbon-based particle. The carbon-based particle is fired together with the silicon-based compound gas to deposit silicon at an inside of the pores of the carbon-based particle or on the surface of the carbon-based particle
Implementation Method 2
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 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
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.