Silicon-Metal Carbide Anode with Carbon Coating for Volume Change
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Solution Overview
Problem
Current rechargeable batteries face challenges in achieving high energy density and stability due to volume changes in negative electrode active materials during charging and discharging.
Innovation Solution
A negative electrode active material is developed, comprising a core with agglomerated silicon primary particles and metal carbide, coated with an amorphous carbon layer. This material is prepared through pulverization, spray-drying, and heat-treatment processes, optimizing the weight ratio and particle size for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon negative electrode active material is used to achieve high capacity, then energy density is improved, but volume change during charging and discharging worsens structural stability
Solution Approach 1:
The patent applies nesting by placing silicon primary particles inside a protective structure comprising metal carbide and amorphous carbon layers. The silicon particles are nested within the metal carbide matrix, which is further enclosed by the amorphous carbon coating, creating a multi-layer protective structure that accommodates volume changes while maintaining structural stability
Solution Approach 2:
The patent uses composite materials by combining silicon with metal carbide and amorphous carbon to create a composite negative electrode active material. This composite structure leverages the high capacity of silicon while the metal carbide and carbon components provide structural stability and accommodate volume expansion during lithium insertion and extraction
2Speed
If silicon particles are pulverized to reduce particle size, then rate capability is improved, but particle aggregation worsens manufacturing control
Solution Approach 1:
The patent merges pulverized silicon primary particles with metal carbide particles through agglomeration to form secondary particles with controlled size distribution. This combining process prevents aggregation issues while maintaining the fine particle size needed for high rate capability, as the metal carbide acts as a spacer and structural framework
Solution Approach 2:
The patent controls particle size parameters by adjusting pulverization conditions and agglomeration parameters. The full width at half maximum (FWHM) of the (111) diffraction peak is used as a parameter to control and characterize the particle size, with specific ranges (0.5°-2°) established to optimize both rate capability and manufacturing control
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 proposed negative electrode active material exhibits improved high-rate cycle-life characteristics, reduced volume change, and stable capacity retention, effectively addressing the limitations of existing battery technologies.
Implementation Method 1
pulverizing silicon particles and a metal carbide by using a ceramic ball to prepare a pulverized product
Implementation Method 2
spay-drying the dispersed liquid to prepare an agglomerated product
Implementation Method 3
heat-treating the resulting mixture
Data Source
AI summary
A negative electrode active material includes a core including secondary particles in which silicon primary particles and a metal carbide are agglomerated; and an amorphous carbon layer on a surface of the core, wherein the primary particles have a full width at half maximum (FWHM, 111) of greater than about 0.5°.