Si-C Composite Particle Coating to Suppress Oxidation and SiC Formation
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Solution Overview
Problem
Existing silicon-carbon composite materials for negative electrodes in lithium-ion batteries face issues of oxidation and low specific capacity due to improper carbon coating, either at low temperatures leading to insufficient coverage or at high temperatures causing silicon carbide generation.
Innovation Solution
The development of composite particles with a specific amorphous layer coating at low temperatures to prevent silicon carbide formation, using amorphous carbon and metal oxides like lithium titanate or niobium pentoxide to enhance oxidation resistance and specific capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the Si-C composite material is coated with a carbonaceous layer at a low temperature, then the coating process is simple and energy-efficient, but the carbon coverage is low and the Si-C composite material is oxidized over time
Solution Approach 1:
The patent applies composite materials by combining amorphous carbon and metal oxide in the coating layer. The metal oxide component (such as aluminum oxide, silicon oxide, or titanium oxide) provides oxidation resistance while the amorphous carbon provides coverage protection. This composite approach allows low-temperature processing while maintaining both coverage and oxidation resistance properties.
Solution Approach 2:
The patent changes the compositional parameters of the coating layer by incorporating metal oxide alongside amorphous carbon. This parameter change enables the coating to function effectively at lower temperatures while preventing oxidation, resolving the contradiction between low processing temperature and oxidation resistance.
2Manufacturing precision
If the Si-C composite material is coated with a carbonaceous layer at a high temperature, then the carbon coverage is improved, but silicon carbide is generated and the specific capacity decreases
Solution Approach 1:
The patent changes the temperature parameter to low temperature processing while compensating for coverage issues by incorporating metal oxide into the coating composition. This allows achieving adequate coverage without high temperature, thereby preventing silicon carbide formation and maintaining high specific capacity.
Solution Approach 2:
By using a composite coating of amorphous carbon and metal oxide, the patent achieves sufficient protective coverage at low temperatures without requiring the high temperatures that would cause silicon carbide generation, thus preserving the specific capacity of the Si-C composite material.
3Reliability
If a carbonaceous layer is coated on Si-C composite material to prevent oxidation, then the oxidation resistance is improved, but silicon carbide may be generated reducing specific capacity
Solution Approach 1:
The patent uses a composite coating layer containing both amorphous carbon and metal oxide. The metal oxide provides oxidation resistance while the amorphous carbon provides protective coverage. This composite structure achieves oxidation protection without generating silicon carbide, thereby maintaining high specific capacity.
Solution Approach 2:
The patent changes the processing temperature to low temperature and modifies the coating composition to include metal oxide. This parameter change enables oxidation protection to be achieved without the high temperatures that would cause silicon carbide formation and capacity loss.
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 composite particles maintain high specific capacity and oxidation resistance, improving cycle characteristics and initial coulombic efficiency of lithium-ion batteries.
Implementation Method 1
Si-C composite particles coated with a specific amorphous layer can suppress oxidation over time of the Si-C composite particles
Implementation Method 2
coating at a low temperature to suppress the generation of SiC
Data Source
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AI summary
An object of the present invention is to provide composite particles capable of suppressing oxidation over time of a Si-C composite material. Composite particles (B) of the present invention contains composite particles (A) containing carbon and silicon; and amorphous layers coating surfaces thereof, wherein the composite particles (B) have ISi/IG of 0.10 or more and 0.65 or less, and have R value (ID/IG) of 1.00 or more and 1.30 or less, when a peak due to silicon is present at 450 to 495 cm-1, an intensity of the peak is defined as ISi, an intensity of a G band (peak intensity in the vicinity of 1600 cm-1) is defined as IG, and an intensity of a D band (peak intensity in the vicinity of 1360 cm-1) is defined as ID in a Raman spectrum, and wherein the composite particles (B) have a full width at half maximum of a peak of a 111 plane of Si of 3.0 deg. or more using a Cu-Kα ray in an XRD pattern.