Porous Silicon-Coated Anode Material for Swelling and Crack Control
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Solution Overview
Problem
Lithium secondary batteries face issues with anode active material cracking due to volume expansion differences between silicon and carbon during charging and discharging, leading to capacity degradation and reduced lifespan.
Innovation Solution
An anode active material is developed with carbon-based particles containing pores and a silicon-containing coating, where the silicon coating is formed inside or on the surface of the carbon-based particles, with controlled crystallinity and amorphous structure to mitigate volume expansion and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-carbon composite is used as an anode active material to increase capacity, then the battery capacity is improved, but the volume expansion difference causes cracks and exposure to electrolyte during charging and discharging
Solution Approach 1:
Silicon particles are embedded within carbon-based particles, creating a core-shell structure where the carbon matrix encapsulates the silicon. This nesting approach allows the high-capacity silicon to be protected by the mechanically stable carbon shell, preventing cracks while maintaining capacity benefits
Solution Approach 2:
A carbon coating layer is formed on the surface of carbon-based particles, creating a flexible protective shell that can accommodate silicon volume expansion during lithiation while preventing direct contact with electrolyte. The carbon shell acts as a buffer that absorbs mechanical stress
2Use of energy by moving object
If silicon content is increased to improve capacity properties, then energy density is improved, but power property deteriorates due to increased volume expansion and cracking
Solution Approach 1:
Silicon is distributed as discrete particles within the carbon matrix rather than as a continuous phase. This local distribution allows high silicon content for energy density while maintaining carbon pathways for electron transport, preserving power properties despite increased silicon content
3Stability of the object's composition
If a carbon coating is formed on silicon particles to suppress cracking, then structural stability is improved, but manufacturing complexity increases due to additional coating steps
Solution Approach 1:
The carbon coating formation is combined with the carbonization of carbon-based particles in a single heat treatment process. By merging these two separate operations into one step, the manufacturing complexity is reduced while still achieving the protective carbon shell on silicon particles
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 solution effectively reduces swelling and cracking of the anode active material, improving the lifespan and capacity retention of lithium secondary batteries by ensuring uniform silicon coating and maintaining power properties.
Implementation Method 1
silicon has a large volume expansion ratio when being lithiated
Implementation Method 2
a plurality of carbon-based particles containing pores therein
Data Source
Figure 1~2
AI summary
An anode active material for a lithium secondary and a lithium second battery including the same are provided. The anode active material includes a plurality of carbon-based particles containing pores therein, and a silicon-containing coating formed at an inside of the pores or on a surface of each of the carbon-based particles. A relative standard deviation of D/G peak intensity ratios of a Raman spectrum measured for 50 different carbon-based particles among the plurality of carbon-based particles is 10 % or less.