Amorphous Carbon-Coated Porous Silicon Anodes for Volume Stability
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Solution Overview
Problem
Silicon-based negative electrode materials experience significant volume changes during charging and discharging, leading to physical peeling and increased contact resistance, which deteriorate the capacity and cycle life of secondary batteries.
Innovation Solution
A negative electrode active material comprising a porous silicon-based core coated with an amorphous carbon layer, where the coating layer satisfies specific Raman spectrum ratios (R1/R2 < 3), is developed to suppress volume change and improve electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode material to achieve high capacity, then capacity per unit mass increases to about 1000 mAh/g or more, but volume change occurs by 300% or more during charging/discharging causing physical peeling and increased contact resistance
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, creating a nested configuration where silicon is contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithiation/delithiation while the surrounding carbon matrix provides structural confinement, preventing physical peeling and maintaining electrical contact.
Solution Approach 2:
The patent employs a porous carbon matrix that acts as a flexible shell surrounding the silicon particles. This carbon shell can accommodate the volume expansion of silicon during charging while maintaining structural integrity, preventing the silicon from physically peeling away from the current collector and reducing contact resistance.
2Stability of the object's composition
If nanosizing silicon into wire form and compositing with carbon material is performed to suppress volume change, then volume stability improves, but initial charge and discharge efficiency, cycle characteristics, and high-rate properties are lowered
Solution Approach 1:
The patent applies local quality by creating a porous carbon matrix with specific pore sizes and distributions that are optimized for different functions: larger pores facilitate electrolyte penetration and ion transport for high rate performance, while the overall carbon structure provides volume constraint. The silicon particles are locally distributed within this matrix, maintaining both structural stability and electrochemical activity.
Solution Approach 2:
The patent utilizes a porous carbon matrix structure that provides multiple benefits: the porosity allows efficient electrolyte penetration and lithium ion transport for high charge/discharge rates, while the carbon walls provide structural support to constrain silicon expansion. The porous structure prevents the density issues associated with nanosized silicon wires while maintaining volume 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
The solution effectively suppresses volume change and enhances cycle life characteristics while maintaining excellent battery capacity by uniformly coating the silicon-based material with amorphous carbon, improving electrical conductivity.
Implementation Method 1
a coating layer including an amorphous carbon coated on a surface of the core... effectively suppressing a volume change of silicon occurring during a charging/discharging process
Implementation Method 2
improving electrical conductivity
Data Source
AI summary
A negative electrode active material comprises: a core which contains a porous silicon-based material; and a coating layer which contains amorphous carbon and coats the surface of the core. The coating layer coating the surface of the core satisfies 1<R1/R2<3, in which R1 indicates the ratio (ID1/IG) of the central peak intensity ID1 of D1 band and the central peak intensity IG of G band, and R2 indicates the ratio (ID3/IG) of the central peak intensity ID3 of D3 band and the central peak intensity IG of the G band, wherein the D1 band has a peak center in the wavenumber range of 1350 20 cm−1, the G band has a peak center in the wavenumber range of 1600 20 cm−1, and the D3 band has a peak center in the wavenumber range of 1500±10 cm−1 in the Raman spectrum.