Dense Carbon-Coated Composite for Stable Silicon Anodes
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Solution Overview
Problem
Existing carbon coating methods for materials like silicon negative electrodes face challenges in achieving a uniform and dense carbon layer, leading to issues with electrical conductivity, volume expansion, and incomplete coating, which affects the performance and stability of carbon-coated composites, especially in lithium-ion batteries.
Innovation Solution
A method involving a rotary converter with twice vapor deposition of carbon-containing gases, specifically using propylene and methane, to achieve a dense carbon coating layer with a controlled density of 1.0-2.0 g·cm−3 and a core element dissolution of 100 ppm or less, ensuring complete and uniform coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas-phase coating is used to improve coating completeness and avoid particle agglomeration, then coating uniformity is improved, but the coating layer compactness deteriorates leading to leakage or dissolution
Solution Approach 1:
The patent changes the physical state parameter of the carbon source from gas phase to liquid phase, and controls the carbonization temperature parameter (800-1000°C) to achieve both uniform coating and dense structure. The liquid-phase carbonization process allows better control of carbon deposition rate and distribution.
Solution Approach 2:
The patent utilizes phase transition of carbon source from liquid to solid during carbonization. The liquid carbon source is heated to undergo carbonization reaction, transforming into solid carbon coating layer with controlled density and structure through the phase change process.
2Ease of manufacture
If solid-phase carbon coating is used to simplify the process, then ease of manufacture is improved, but coating uniformity deteriorates due to particle agglomeration
Solution Approach 1:
The patent uses liquid-phase carbon source instead of solid-phase, utilizing fluid properties to achieve uniform distribution. The liquid carbon source can flow and coat particles more evenly during the carbonization process, avoiding the agglomeration problems of solid-phase mixing.
3Manufacturing precision
If liquid-phase carbon coating is used to improve coating uniformity, then coating completeness is improved, but process complexity increases due to solvent recovery
Solution Approach 1:
The patent extracts and eliminates the solvent recovery step from the traditional liquid-phase carbon coating process. By using a carbon source that carbonizes directly without requiring solvent removal, the method simplifies the process while maintaining the coating completeness benefits of liquid-phase processing.
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 method results in a carbon-coated composite with improved electrical conductivity, reduced volume changes, and enhanced stability during lithium intercalation, enabling better high-temperature performance and cycling characteristics, while allowing for mass production with a simpler process.
Implementation Method 1
a process in which carbon-containing gas coats the surface of the material to be coated by vapor deposition
Implementation Method 2
the solid carbon source is softened and coats the surfaces of particles of the material to be coated, and can be dehydrogenated to carbon by further increasing the temperature
Data Source
AI summary
A carbon coated composite includes a core and a carbon coating layer coated outside the core. The density of the carbon coating layer is 1.0 g·cm−3≤ρ2≤2.0 g·cm−3. The dissolution amount of a core characteristic element of the carbon coated composite is 100 ppm or less. The D50 of the material to be coated with carbon is 1-40 μm. The particle size distribution span meets 0.5≤(D90−D10)/D50≤2. A specific surface area is 1-5 m2·g−1. A ratio of the specific surface area to the stacked pore volume is 0.5-2 cm−1. The increase of D50 of the composite after coating is 3 μm or less. The shell of the carbon coated composite mitigates the volume change of the core. A complete and uniform carbon layer effectively disperses surface charges to form a more stable electric double layer structure.