Silicon-Carbon Core-Shell Negative Electrode for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with electrode expansion and contraction due to electrochemical reactions, leading to damage and reduced performance, especially when using silicon as a high-capacity negative electrode material.
Innovation Solution
A negative electrode active material is developed with secondary particles formed by aggregating primary particles, where the core includes silicon or silicon compounds with a carbon surface layer, optimizing particle size and porosity to enhance lithium ion pathways and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to increase capacity, then battery capacity increases significantly, but electrode expansion and contraction occurs during lithium intercalation and deintercalation
Solution Approach 1:
The patent applies nested structure by placing silicon particles inside carbon particles, forming a core-shell configuration where the inner core contains silicon and the outer shell contains carbon. This nested arrangement allows silicon to provide high capacity while the surrounding carbon shell constrains expansion and provides structural stability during lithium intercalation and deintercalation cycles.
Solution Approach 2:
The patent creates a composite material system combining silicon and carbon in a specific configuration. The composite structure leverages silicon's high lithium capacity and carbon's structural stability and conductivity, achieving both high capacity and mechanical stability through the synergistic combination of different materials with complementary properties.
2Productivity
If primary particles are aggregated to form secondary particles, then lithium ion pathways increase improving output characteristics, but particle size distribution becomes more complex
Solution Approach 1:
The patent divides the negative electrode material into hierarchical levels: primary particles (silicon-carbon composites) are further segmented and aggregated into secondary particles with controlled size distribution. This segmentation approach creates multiple pathways for lithium ion transport while maintaining manageable particle size control at each level of aggregation.
3Speed
If core particle size is reduced to 0.5-20 μm, then lithium ion diffusion distance decreases improving rate capability, but surface area to volume ratio increases potentially increasing reactivity
Solution Approach 1:
The patent applies local quality by creating different zones within the particle structure: the inner core region contains silicon optimized for lithium capacity, while the outer shell region contains carbon optimized for structural stability and controlled surface properties. This spatial differentiation of material properties allows small particle size for fast diffusion while the carbon shell moderates surface reactivity.
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
This configuration improves the output characteristics, initial efficiency, and rate capability of lithium secondary batteries while minimizing electrode damage from repeated lithium intercalation and deintercalation, maintaining high capacity and power performance.
Implementation Method 1
lithium ions coming out of a positive electrode active material and being intercalated into a negative electrode active material
Implementation Method 2
deintercalated again during discharge
Implementation Method 3
a surface layer which is disposed on a surface of the core and contains carbon
Implementation Method 4
charge and discharge are possible due to lithium ions performing a role of transferring energy while travelling back and forth between both electrodes
Data Source
AI summary
The present invention relates to a negative electrode active material including a secondary particle in which primary particles are aggregated, wherein the primary particle includes: a core including one or more of silicon and a silicon compound; and a surface layer which is disposed on a surface of the core and contains carbon, wherein an average particle size D50 of the core is in a range of 0.5 μm to 20 μm, a method of preparing the same, an electrode including the same, and a lithium secondary battery including the same.