SiO2-Si Negative Active Material Coating for Stable Battery Cycling
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in maintaining cycle-life stability and capacity efficiency due to limitations in negative active materials, particularly with carbon-based materials, which often degrade over time and affect battery performance.
Innovation Solution
A negative active material for lithium batteries is developed, comprising a SiO2 matrix with Si grains and a coating layer of SiC and carbon, where the SiC to Si peak area ratio is optimized between 0.01 and 0.5, and the coating layer thickness is between 0.01 μm and 1 μm, enhancing cycle-life characteristics without compromising capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon-based materials are used as negative active material, then capacity is maintained, but cycle-life stability deteriorates due to degradation over time
Solution Approach 1:
The patent employs a composite structure consisting of a SiO2 matrix containing Si grains, where Si provides high capacity and SiO2 provides structural stability. This composite material resolves the contradiction by combining materials with complementary properties to achieve both high capacity and improved cycle-life stability.
Solution Approach 2:
The patent applies a coating layer selectively on the surface of the SiO2 matrix core, creating different functional zones: the inner SiO2 matrix provides structural stability while the outer coating layer prevents degradation. This local differentiation allows the material to simultaneously achieve capacity maintenance and cycle-life improvement.
2Quantity of substance
If Si is used to increase capacity, then capacity efficiency improves, but structural stability deteriorates leading to faster degradation
Solution Approach 1:
The patent embeds Si grains within the SiO2 matrix, creating a nested structure where Si (high capacity) is contained within SiO2 (high stability). This nesting allows the Si grains to provide lithium storage capacity while being protected by the stable SiO2 matrix, resolving the contradiction between capacity and structural stability.
Solution Approach 2:
The SiO2 matrix acts as a protective cushion around the Si grains before degradation occurs. This pre-established protective structure prevents the Si grains from degrading during battery cycling, maintaining both capacity and structural integrity over time.
3Reliability
If coating layer thickness is increased to improve stability, then cycle-life improves, but capacity is compromised due to excessive coating
Solution Approach 1:
The patent applies a coating layer with thickness in the range of 0.01-1 μm, which is sufficient to provide protective function for improving cycle-life characteristics but not excessive to significantly compromise capacity. This optimized partial action resolves the contradiction by finding the optimal thickness that provides adequate protection without over-coating.
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 optimized negative active material significantly improves the cycle-life characteristics of lithium batteries by preventing resistance increase and ensuring effective coating, thereby maintaining battery performance and capacity over multiple cycles.
Implementation Method 1
a coating layer continuously or discontinuously coated on the core. The coating layer includes SiC and C
Implementation Method 2
lithium rechargeable batteries use various carbon-based materials (such as artificial graphite, natural graphite, and hard carbon) that can intercalate and deintercalate lithium ions
Data Source
AI summary
A negative active material for a rechargeable lithium battery includes a core including a SiO2 matrix and a Si grain, and a coating layer continuously or discontinuously coated on the core. The coating layer includes SiC and C, and the peak area ratio of the SiC (111) plane to the Si (111) plane as measured by X-ray diffraction analysis (XRD) using a CuKα ray ranges from about 0.01 to about 0.5.