Sulfur-Containing Silicon Anode Material for Low-Expansion Cycling
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Solution Overview
Problem
Rechargeable lithium batteries using silicon-based negative electrode active materials face challenges due to large volume changes during lithium intercalation/deintercalation, leading to electrode expansion and contraction, which limits cycle-life characteristics and practical application.
Innovation Solution
A negative electrode active material comprising a spherical core of silicon nanoparticles coated with amorphous carbon and containing sulfur, with a specific span value and sphericity, is prepared through pulverization, spray drying, and carbon coating processes to enhance structural stability and ion/electron transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used to increase battery capacity, then electrochemical capacity is improved, but volume change during lithium intercalation/deintercalation increases causing electrode expansion and contraction
Solution Approach 1:
The patent embeds silicon nanoparticles inside a porous carbon matrix structure, creating a nested configuration where the silicon is contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium intercalation/deintercalation while the outer carbon matrix maintains the overall structural integrity and prevents excessive volume change of the electrode material.
Solution Approach 2:
The patent employs a porous carbon matrix that acts as a flexible shell surrounding the silicon nanoparticles. This carbon shell can accommodate the volume changes of silicon during charging and discharging cycles while maintaining structural stability, effectively managing the expansion and contraction without causing electrode degradation.
2Quantity of substance
If silicon-based active materials are used to increase battery capacity, then electrochemical capacity is improved, but cycle-life characteristics deteriorate due to violent expansion and contraction
Solution Approach 1:
The nested structure of silicon nanoparticles within the porous carbon matrix protects the silicon from mechanical degradation during repeated charging and discharging cycles. The carbon matrix absorbs and distributes the mechanical stress, preventing the silicon from fracturing or losing electrical contact, thereby extending the battery's cycle life.
Solution Approach 2:
The patent creates a composite material combining silicon and carbon in a specific architecture. The silicon provides high capacity while the carbon provides structural stability and conductivity. This composite structure synergistically combines the advantages of both materials, achieving high capacity with improved cycle-life characteristics.
3Volume of moving object
If the structure of silicon-based negative electrode active materials is changed to reduce volume change, then electrode expansion is reduced, but practical application becomes difficult
Solution Approach 1:
The patent applies different structural characteristics to different parts of the electrode material: silicon nanoparticles provide high capacity in the core, while the porous carbon matrix provides structural stability and flexibility in the outer region. This local differentiation allows each component to perform its optimal function while being manufacturable using conventional processes.
Solution Approach 2:
The patent optimizes key parameters including the size of silicon nanoparticles, the porosity and thickness of the carbon matrix, and the overall morphology of the composite particles. By carefully controlling these parameters, the material achieves reduced volume change while maintaining compatibility with existing manufacturing processes and practical application requirements.
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 solution provides improved cycle-life and high capacity by reducing volume expansion, protecting the silicon surface, and enhancing electrical conductivity and ion transfer performance.
Implementation Method 1
silicon-based active materials typically have a large volume change accompanying lithium intercalation/deintercalation
Implementation Method 2
an amorphous carbon coating layer on the surface of the core
Implementation Method 3
the negative electrode active material has a span value, which is the standard deviation around the mean value, determined according to Equation 1 below, in a range of about 1.1 to about 1.6
Data Source
AI summary
Examples of the disclosure include a negative electrode active material including a spherical core including silicon nanoparticles and sulfur, and an amorphous carbon coating layer on the surface of the spherical core, wherein the negative electrode active material has a span value in a range of about 1.1 to about 1.6, and exhibiting high efficiency, high capacity, and long cycle-life characteristics.